Nanotechnology breath analyzer for kidney failure
(Nanowerk Spotlight)
High blood pressure and diabetes, increasingly common signs of the unhealthy lifestyle in most Western societies, often are the cause for chronic kidney disease (or chronic renal disease; CKD). CKD is a long-standing, progressive deterioration of renal function. In its end-stage, the disease is a debilitating medical condition of chronic kidney failure which requires intensive and costly treatments through dialysis or even transplantation. Initially, as renal tissue loses function, there are few abnormalities because the remaining tissue increases its performance. Diagnosis of CKD is mostly based on laboratory testing of renal function such as plasma levels of creatinine and urea, sometimes followed by renal biopsy. Imaging techniques are also applied to detect changes in size, texture, and position of the kidneys. These measurements are performed using ultrasound and are suitable only in patients suffering from progressive renal failure. Presently, renal biopsy remains the most definitive test to specifically diagnose chronic and acute renal failure. This method is invasive and thus comprises the risk of infections and bleeding among other possible complications. "So far, blood tests and urinalysis are the golden standard to identify a decline in kidney filtration, wherein high levels of creatinine and blood urea nitrogen usually reflect renal dysfunction – however, these tests tend to be highly inaccurate and may remain within the normal range even while 65-75% of kidney function is lost." Hossam Haick, senior lecturer in the Faculty of Chemical Engineering and the Russell Berrie Nanotechnology Institute at Technion-Israel Institute of Technology, tells Nanowerk. "Given the difficulties in separating healthy renal function from dysfunction, it is perhaps not too surprising that precise biochemical or clinical criteria for diagnosis of acute renal failure have been elusive. Therefore, there is an unmet need for a noninvasive method for detection of renal failure of various etiologies. Furthermore, the challenge remains to diagnose renal disorders with sufficient sensitivity and specificity to provide a large-scale screening technique, feasible for clinical practice, for people at increased risk of developing renal dysfunction." Haick, Zaid Abassi and coworkers from Technion used an experimental model of end stage renal disease (ESRD) in rats to identify by advanced, yet simple nanotechnology-based approach to discriminate between exhaled breath of healthy states and of ESRD states. The team reported their findings in the April 27, 2009 online edition of ACS Nano ("Sniffing Chronic Renal Failure in Rat Model by an Array of Random Networks of Single-Walled Carbon Nanotubes"). In their work, Haick and his team used gas chromatography/ mass spectroscopy in conjugation with solid phase microextraction of healthy and ESRD breath, collected directly from the trachea of the rats, to identify 15 common volatile organic compounds (VOCs) in all samples of healthy and ESRD states and 27 VOCs that appear in diseased rats but not in healthy states.
Online breath analysis via an array of chemiresistive random network of single walled carbon nanotubes (SWCNTs) coated with organic materials showed excellent discrimination between the various breath states. Furthermore, the analysis shows the adequacy of using representative simulated VOCs to imitate the breath of healthy and ESRD states and, therefore, to train the sensors’ array the pertinent breath signatures. "Using SWCNT networks circumvents the requirement of position and structural control (as is the case in devices based on individual SWCNT) because the devices display the averaged usual properties of many randomly distributed SWCNTs," says Haick. "An additional feature of SWCNT networks is that they can be processed into devices of arbitrary size using conventional microfabrication technology." An important implication of these findings, besides the detection of diseases directly related to the respiratory, cardiovascular, and renal systems, is the fact that VOCs are mainly blood borne and the concentration of biologically relevant substances in exhaled breath closely reflects that in the arterial system. Therefore, breath is predestined for monitoring different processes in the body.
Apart from the odor impression of chronic kidney failure, much about the biochemical processes and the formation of marker substances is already known. Haick notes that analysis of the various breath samples by an array of chemiresistive random network of SWCNTs showed excellent discrimination between the various breath states, while revealing significantly enhanced discriminations at lower humidity levels in the breath. "Furthermore, we show that it is enough to use selected number of simulated VOCs to 'train' the sensors’ array system to discriminate between the electronic patterns of healthy states and chronic failure states," says Haick. "Experiments to distinguish less severe kidney failure (e.g., 35-70% reduction in kidney function) and to distinguish chronic kidney failure from other disease (or patho-physiological) states that have a potential to produce a distorted profile of breath VOCs (e.g., liver failure, systemic infection, pneumonia, heart failure, etc.) are underway and will be published soon." The excellent discrimination between the various breath states obtained in this study provides expectations for future capabilities for diagnosis, detection, and screening various stages of kidney disease, especially in the early stages of the disease, where it is possible to control blood pressure, fat, glucose and protein intake to slow the progression. In terms of the devices, the challenges could be summarized in how to bring the sensing technology to a level that it will be very simple to use, lightweight, low-power, and able to detect diseases in noninvasive way (i.e., via breath samples) in real time.
By Michael Berger.
Nanowerk LLC
Thursday, June 11, 2009
Breath analyzer
Nanotechnology breath analyzer for kidney failure
(Nanowerk Spotlight)
High blood pressure and diabetes, increasingly common signs of the unhealthy lifestyle in most Western societies, often are the cause for chronic kidney disease (or chronic renal disease; CKD). CKD is a long-standing, progressive deterioration of renal function. In its end-stage, the disease is a debilitating medical condition of chronic kidney failure which requires intensive and costly treatments through dialysis or even transplantation. Initially, as renal tissue loses function, there are few abnormalities because the remaining tissue increases its performance. Diagnosis of CKD is mostly based on laboratory testing of renal function such as plasma levels of creatinine and urea, sometimes followed by renal biopsy. Imaging techniques are also applied to detect changes in size, texture, and position of the kidneys. These measurements are performed using ultrasound and are suitable only in patients suffering from progressive renal failure. Presently, renal biopsy remains the most definitive test to specifically diagnose chronic and acute renal failure. This method is invasive and thus comprises the risk of infections and bleeding among other possible complications. "So far, blood tests and urinalysis are the golden standard to identify a decline in kidney filtration, wherein high levels of creatinine and blood urea nitrogen usually reflect renal dysfunction – however, these tests tend to be highly inaccurate and may remain within the normal range even while 65-75% of kidney function is lost." Hossam Haick, senior lecturer in the Faculty of Chemical Engineering and the Russell Berrie Nanotechnology Institute at Technion-Israel Institute of Technology, tells Nanowerk. "Given the difficulties in separating healthy renal function from dysfunction, it is perhaps not too surprising that precise biochemical or clinical criteria for diagnosis of acute renal failure have been elusive. Therefore, there is an unmet need for a noninvasive method for detection of renal failure of various etiologies. Furthermore, the challenge remains to diagnose renal disorders with sufficient sensitivity and specificity to provide a large-scale screening technique, feasible for clinical practice, for people at increased risk of developing renal dysfunction." Haick, Zaid Abassi and coworkers from Technion used an experimental model of end stage renal disease (ESRD) in rats to identify by advanced, yet simple nanotechnology-based approach to discriminate between exhaled breath of healthy states and of ESRD states. The team reported their findings in the April 27, 2009 online edition of ACS Nano ("Sniffing Chronic Renal Failure in Rat Model by an Array of Random Networks of Single-Walled Carbon Nanotubes"). In their work, Haick and his team used gas chromatography/ mass spectroscopy in conjugation with solid phase microextraction of healthy and ESRD breath, collected directly from the trachea of the rats, to identify 15 common volatile organic compounds (VOCs) in all samples of healthy and ESRD states and 27 VOCs that appear in diseased rats but not in healthy states.
Online breath analysis via an array of chemiresistive random network of single walled carbon nanotubes (SWCNTs) coated with organic materials showed excellent discrimination between the various breath states. Furthermore, the analysis shows the adequacy of using representative simulated VOCs to imitate the breath of healthy and ESRD states and, therefore, to train the sensors’ array the pertinent breath signatures. "Using SWCNT networks circumvents the requirement of position and structural control (as is the case in devices based on individual SWCNT) because the devices display the averaged usual properties of many randomly distributed SWCNTs," says Haick. "An additional feature of SWCNT networks is that they can be processed into devices of arbitrary size using conventional microfabrication technology." An important implication of these findings, besides the detection of diseases directly related to the respiratory, cardiovascular, and renal systems, is the fact that VOCs are mainly blood borne and the concentration of biologically relevant substances in exhaled breath closely reflects that in the arterial system. Therefore, breath is predestined for monitoring different processes in the body.
Apart from the odor impression of chronic kidney failure, much about the biochemical processes and the formation of marker substances is already known. Haick notes that analysis of the various breath samples by an array of chemiresistive random network of SWCNTs showed excellent discrimination between the various breath states, while revealing significantly enhanced discriminations at lower humidity levels in the breath. "Furthermore, we show that it is enough to use selected number of simulated VOCs to 'train' the sensors’ array system to discriminate between the electronic patterns of healthy states and chronic failure states," says Haick. "Experiments to distinguish less severe kidney failure (e.g., 35-70% reduction in kidney function) and to distinguish chronic kidney failure from other disease (or patho-physiological) states that have a potential to produce a distorted profile of breath VOCs (e.g., liver failure, systemic infection, pneumonia, heart failure, etc.) are underway and will be published soon." The excellent discrimination between the various breath states obtained in this study provides expectations for future capabilities for diagnosis, detection, and screening various stages of kidney disease, especially in the early stages of the disease, where it is possible to control blood pressure, fat, glucose and protein intake to slow the progression. In terms of the devices, the challenges could be summarized in how to bring the sensing technology to a level that it will be very simple to use, lightweight, low-power, and able to detect diseases in noninvasive way (i.e., via breath samples) in real time.
Online breath analysis via an array of chemiresistive random network of single walled carbon nanotubes (SWCNTs) coated with organic materials showed excellent discrimination between the various breath states. Furthermore, the analysis shows the adequacy of using representative simulated VOCs to imitate the breath of healthy and ESRD states and, therefore, to train the sensors’ array the pertinent breath signatures. "Using SWCNT networks circumvents the requirement of position and structural control (as is the case in devices based on individual SWCNT) because the devices display the averaged usual properties of many randomly distributed SWCNTs," says Haick. "An additional feature of SWCNT networks is that they can be processed into devices of arbitrary size using conventional microfabrication technology." An important implication of these findings, besides the detection of diseases directly related to the respiratory, cardiovascular, and renal systems, is the fact that VOCs are mainly blood borne and the concentration of biologically relevant substances in exhaled breath closely reflects that in the arterial system. Therefore, breath is predestined for monitoring different processes in the body.
Apart from the odor impression of chronic kidney failure, much about the biochemical processes and the formation of marker substances is already known. Haick notes that analysis of the various breath samples by an array of chemiresistive random network of SWCNTs showed excellent discrimination between the various breath states, while revealing significantly enhanced discriminations at lower humidity levels in the breath. "Furthermore, we show that it is enough to use selected number of simulated VOCs to 'train' the sensors’ array system to discriminate between the electronic patterns of healthy states and chronic failure states," says Haick. "Experiments to distinguish less severe kidney failure (e.g., 35-70% reduction in kidney function) and to distinguish chronic kidney failure from other disease (or patho-physiological) states that have a potential to produce a distorted profile of breath VOCs (e.g., liver failure, systemic infection, pneumonia, heart failure, etc.) are underway and will be published soon." The excellent discrimination between the various breath states obtained in this study provides expectations for future capabilities for diagnosis, detection, and screening various stages of kidney disease, especially in the early stages of the disease, where it is possible to control blood pressure, fat, glucose and protein intake to slow the progression. In terms of the devices, the challenges could be summarized in how to bring the sensing technology to a level that it will be very simple to use, lightweight, low-power, and able to detect diseases in noninvasive way (i.e., via breath samples) in real time.
By Michael Berger.
Nanowerk LLC
Biosensing
Nanoparticle Libraries for Biosensing Over the past couple of years, researchers have developed a number of standardized techniques for attaching an antibody or protein to the surface of a nanoparticle in order to create a targeted drug delivery vehicle or imaging agent. This approach works well when trying to target a known cancer biomarker, but the fact is that today, researchers have only a few such markers to choose from, and many types of cancers do not express those few known markers.
In an attempt to overcome this limitation, a team of researchers at the Massachusetts General Hospital has taken a different approach, creating a large library of nanoparticles, each with a different small molecule decorating its surface. They then screen this library to see if any of the nanoparticles will bind to any number of cancer cells while ignoring healthy cells.
Reporting its work in the journal Bioconjugate Chemistry, a team led by Ralph Weissleder, M.D., and Lee Josephson, Ph.D., describes the methods they use for attaching a variety of small organic molecules to the surface of a magnetic and fluorescent nanoparticle. The researchers chose to use small molecules of “nonbiological origin” with an eye on keeping costs and regulatory burdens low should any of these nanoparticles prove clinically useful.
The researchers also worked out a method to ensure that each chemical preparation went as planned. This latter step is critically important in order to distinguish between modified nanoparticles that have no biological activity and those that have no activity because the expected chemical modifications never occurred in the first place. Finally, in order to automate the screening process, the researchers also developed two techniques for “printing” the resulting libraries of modified nanoparticles onto glass slides or for adding each member of the library to the tiny indentations on a standard 96-well assay plate used in a wide variety of screening technologies.
In a demonstration experiment, the investigators prepared a 96-well plate in which each well contained macrophages, a type of immune system cell that has a propensity to engulf nanoparticles. They then added individual members of the library to each well and identified modified nanoparticles that were not taken very effectively by macrophages (see illustration). The macrophage-avoiding nanoparticles may be able to more effectively deliver drugs to tumors since more of them may be able to reach their target rather than be eliminated from the body by macrophages.
This work, which was funded by the National Cancer Institute, is detailed in a paper titled, “Development of nanoparticle libraries for biosensing.” This paper was published online in advance of print publication.
An abstract is available at the journal’s website.
Source>http://www.nanotechwire.com/news.asp?nid=2838
In an attempt to overcome this limitation, a team of researchers at the Massachusetts General Hospital has taken a different approach, creating a large library of nanoparticles, each with a different small molecule decorating its surface. They then screen this library to see if any of the nanoparticles will bind to any number of cancer cells while ignoring healthy cells.
Reporting its work in the journal Bioconjugate Chemistry, a team led by Ralph Weissleder, M.D., and Lee Josephson, Ph.D., describes the methods they use for attaching a variety of small organic molecules to the surface of a magnetic and fluorescent nanoparticle. The researchers chose to use small molecules of “nonbiological origin” with an eye on keeping costs and regulatory burdens low should any of these nanoparticles prove clinically useful.
The researchers also worked out a method to ensure that each chemical preparation went as planned. This latter step is critically important in order to distinguish between modified nanoparticles that have no biological activity and those that have no activity because the expected chemical modifications never occurred in the first place. Finally, in order to automate the screening process, the researchers also developed two techniques for “printing” the resulting libraries of modified nanoparticles onto glass slides or for adding each member of the library to the tiny indentations on a standard 96-well assay plate used in a wide variety of screening technologies.
In a demonstration experiment, the investigators prepared a 96-well plate in which each well contained macrophages, a type of immune system cell that has a propensity to engulf nanoparticles. They then added individual members of the library to each well and identified modified nanoparticles that were not taken very effectively by macrophages (see illustration). The macrophage-avoiding nanoparticles may be able to more effectively deliver drugs to tumors since more of them may be able to reach their target rather than be eliminated from the body by macrophages.
This work, which was funded by the National Cancer Institute, is detailed in a paper titled, “Development of nanoparticle libraries for biosensing.” This paper was published online in advance of print publication.
An abstract is available at the journal’s website.
Source>http://www.nanotechwire.com/news.asp?nid=2838
Nanoparticle
Combining Two Drugs in One Nanoparticle Overcomes Multidrug Resistance
Cancer cells, like bacteria, can develop resistance to drug therapy. In fact, research suggests strongly that multidrug-resistant cancer cells that remain alive after chemotherapy are responsible for the reappearance of tumors and the poor prognosis for patients whose cancer recurs. One new approach that shows promise in overcoming such multidrug resistance is to combine two different anticancer agents in one nanoscale construct, providing a one-two punch that can prove lethal to such resistant cells. This work appears in the journal Molecular Pharmaceutics.
Mansoor Amiji, Ph.D., principal investigator of the National Cancer Institute-funded Nanotherapeutic Strategy for Multidrug Resistant Tumors Platform Partnership at Northeastern University, and postdoctoral fellow Srinivas Ganta, Ph.D., created a nanoemulsion entrapping both paclitaxel and curcumin. The former compound is a widely used anticancer agent, whereas the latter comes from the spice tumeric and has been shown to inhibit several cancer-related processes.
The investigators prepared their nanoformulation by mixing the two drugs with flaxseed oil, the emulsifier lecithin from egg yolks, and the biocompatible polymer polyethylene glycol. To help track this nanoformulation, the investigators also added a fluorescent dye to the mixture. Ultrasonification for 10 minutes produced stable, nanosize droplets that were readily taken up by tumor cells grown in culture. In addition, the nanoformulation had significant anticancer activity that surpassed that of either of the two drugs administered together or separately, particularly in multidrug-resistant cells. Biochemical assays showed that the curcumin component inhibited P-glycoprotein, which tumor cells use to excrete anticancer agents and protect themselves from the effects of those agents. Both drugs also had the effect of triggering apoptosis in the treated cells.
This work, which was detailed in the paper “Coadministration of paclitaxel and curcumin in nanoemulsion formulations to overcome multidrug resistance in tumor cells,” was supported by the NCI Alliance for Nanotechnology in Cancer, a comprehensive initiative designed to accelerate the application of nanotechnology to the prevention, diagnosis, and treatment of cancer.
An abstract is available at the journal’s Web site.
>http://www.nanotechwire.com/news.asp?nid=7861
Cancer cells, like bacteria, can develop resistance to drug therapy. In fact, research suggests strongly that multidrug-resistant cancer cells that remain alive after chemotherapy are responsible for the reappearance of tumors and the poor prognosis for patients whose cancer recurs. One new approach that shows promise in overcoming such multidrug resistance is to combine two different anticancer agents in one nanoscale construct, providing a one-two punch that can prove lethal to such resistant cells. This work appears in the journal Molecular Pharmaceutics.
Mansoor Amiji, Ph.D., principal investigator of the National Cancer Institute-funded Nanotherapeutic Strategy for Multidrug Resistant Tumors Platform Partnership at Northeastern University, and postdoctoral fellow Srinivas Ganta, Ph.D., created a nanoemulsion entrapping both paclitaxel and curcumin. The former compound is a widely used anticancer agent, whereas the latter comes from the spice tumeric and has been shown to inhibit several cancer-related processes.
The investigators prepared their nanoformulation by mixing the two drugs with flaxseed oil, the emulsifier lecithin from egg yolks, and the biocompatible polymer polyethylene glycol. To help track this nanoformulation, the investigators also added a fluorescent dye to the mixture. Ultrasonification for 10 minutes produced stable, nanosize droplets that were readily taken up by tumor cells grown in culture. In addition, the nanoformulation had significant anticancer activity that surpassed that of either of the two drugs administered together or separately, particularly in multidrug-resistant cells. Biochemical assays showed that the curcumin component inhibited P-glycoprotein, which tumor cells use to excrete anticancer agents and protect themselves from the effects of those agents. Both drugs also had the effect of triggering apoptosis in the treated cells.
This work, which was detailed in the paper “Coadministration of paclitaxel and curcumin in nanoemulsion formulations to overcome multidrug resistance in tumor cells,” was supported by the NCI Alliance for Nanotechnology in Cancer, a comprehensive initiative designed to accelerate the application of nanotechnology to the prevention, diagnosis, and treatment of cancer.
An abstract is available at the journal’s Web site.
>http://www.nanotechwire.com/news.asp?nid=7861
Capsules Encapsulated
Drug Deliver With Nanotechnology:
Capsules Encapsulated
When cells cannot carry out the tasks required of them by our bodies, the result is disease. Nanobiotechnology researchers are looking for ways to allow synthetic systems take over simple cellular activities when they are absent from the cell. This requires transport systems that can encapsulate medications and other substances and release them in a controlled fashion at the right moment.
The transporter must be able to interact with the surroundings in order to receive the signal to unload its cargo. A team led by Frank Caruso at the University of Melbourne has now developed a microcontainer that can hold thousands of individual "carrier units"—a "capsosome". These are polymer capsules in which liposomes have been embedded to form subcompartments.
Currently, the primary type of nanotransporter used for drugs is the capsule: Polymer capsules form stable containers that are semipermeable, which allows for communication with the surrounding medium. However, these are not suitable for the transport of small molecules because they can escape. Liposomes are good at protecting small drug molecules; however, they are often unstable and impermeable to substances from the environment. The Australian researchers have now combined the advantages of both systems in their capsosomes.
Capsosomes are produced by several steps. First, a layer of polymer is deposited onto small silica spheres. This polymer contains building blocks modified with cholesterol. Liposomes that have been loaded with an enzyme can be securely anchored to the cholesterol units and thus attached to the polymer film. Subsequently, more polymer layers are added and then cross-linked by disulfide bridges into a gel by means of a specially developed, very gentle cross-linking reaction. In the final step, the silica core is etched away without damaging the sensitive cargo.
Experiments with an enzyme as model cargo demonstrated that the liposomes remain intact and the cargo does not escape. Addition of a detergent releases the enzyme in a functional state. By means of the enzymatic reaction, which causes a color change of the solution, it was possible to determine the number of liposome compartments to be about 8000 per polymer capsule.
"Because the capsosomes are biodegradable and nontoxic", says Brigitte Staedler, a senior researcher in the group, "they would also be suitable for use as resorbable synthetic cell organelles and for the transport of drugs." In addition, the scientists are planning to encapsulate liposomes filled with different enzymes together and to equip them with specific "receivers" which would allow the individual cargo to be released in a targeted fashion. This would make it possible to use enzymatic reaction cascades for catalytic reaction processes.
Frank Caruso. A Microreactor with Thousands of Subcompartments: Enzyme-Loaded Liposomes within Polymer Capsules. Angewandte Chemie International Edition, 2009, 48, No. 24, 4359-4362 DOI: 10.1002/anie.200900386
>http://www.nanotechwire.com/news.asp?nid=7944
Capsules Encapsulated
When cells cannot carry out the tasks required of them by our bodies, the result is disease. Nanobiotechnology researchers are looking for ways to allow synthetic systems take over simple cellular activities when they are absent from the cell. This requires transport systems that can encapsulate medications and other substances and release them in a controlled fashion at the right moment.
The transporter must be able to interact with the surroundings in order to receive the signal to unload its cargo. A team led by Frank Caruso at the University of Melbourne has now developed a microcontainer that can hold thousands of individual "carrier units"—a "capsosome". These are polymer capsules in which liposomes have been embedded to form subcompartments.
Currently, the primary type of nanotransporter used for drugs is the capsule: Polymer capsules form stable containers that are semipermeable, which allows for communication with the surrounding medium. However, these are not suitable for the transport of small molecules because they can escape. Liposomes are good at protecting small drug molecules; however, they are often unstable and impermeable to substances from the environment. The Australian researchers have now combined the advantages of both systems in their capsosomes.
Capsosomes are produced by several steps. First, a layer of polymer is deposited onto small silica spheres. This polymer contains building blocks modified with cholesterol. Liposomes that have been loaded with an enzyme can be securely anchored to the cholesterol units and thus attached to the polymer film. Subsequently, more polymer layers are added and then cross-linked by disulfide bridges into a gel by means of a specially developed, very gentle cross-linking reaction. In the final step, the silica core is etched away without damaging the sensitive cargo.
Experiments with an enzyme as model cargo demonstrated that the liposomes remain intact and the cargo does not escape. Addition of a detergent releases the enzyme in a functional state. By means of the enzymatic reaction, which causes a color change of the solution, it was possible to determine the number of liposome compartments to be about 8000 per polymer capsule.
"Because the capsosomes are biodegradable and nontoxic", says Brigitte Staedler, a senior researcher in the group, "they would also be suitable for use as resorbable synthetic cell organelles and for the transport of drugs." In addition, the scientists are planning to encapsulate liposomes filled with different enzymes together and to equip them with specific "receivers" which would allow the individual cargo to be released in a targeted fashion. This would make it possible to use enzymatic reaction cascades for catalytic reaction processes.
Frank Caruso. A Microreactor with Thousands of Subcompartments: Enzyme-Loaded Liposomes within Polymer Capsules. Angewandte Chemie International Edition, 2009, 48, No. 24, 4359-4362 DOI: 10.1002/anie.200900386
>http://www.nanotechwire.com/news.asp?nid=7944
Dead or alive
Nanotechnology technique tells the difference
(From Nanowerk Spotlight)
A major concern in microbiology is to determine whether a bacterium is dead or alive. This crucial question has major consequences in food industry, water supply or health care. While culture-based tests can determine whether bacteria can proliferate and form colonies, these tests are time-consuming and work poorly with certain slow-growing or non-culturable bacteria. They are not suitable for applications where real-time results are needed, e.g. in industrial manufacturing or food processing. A team of scientists in France has now discovered that living and dead cells can be discriminated with a nanotechnology technique on the basis of their cell wall nanomechanical properties. This finding is totally new and has been made possible thanks to an interdisciplinary approach which mixes physics, biology and chemistry. This work is a key stone in the understanding of bacterial cell wall behavior. "We have developed a method to probe the mechanical properties of living and dead bacteria via atomic force microscope (AFM) indentation experimentations," Aline Cerf tells Nanowerk. ". Indeed, we provide a new way to probe bacterial cell viability based on cell wall nanomechanical properties, independently from cell ability to grow on a medium or to be penetrated by a fluorescent dye." Cerf, a PhD student in the NanoBioSystems group at LAAS-CNRS, is first author of a recent paper in Langmuir ("Nanomechanical Properties of Dead or Alive Single-Patterned Bacteria") where she and collaborators from LAAS-CNRS describe their findings. "We wanted to explore the modifications that could occur in the nanomechanical properties of a single E. coli bacterium, while it is alive and while it is dead," says Etienne Dague, a researcher in the NanoBioSystems group. "To reach this goal, it has been of first importance to immobilize the living bacteria in an aqueous environment to avoid any cell wall modifications due to a drying step." Thus, in developing a technique to probe the mechanical properties of bacteria via AFM indentation experiments, the French team also came up with an immobilization method for bacteria that doesn't require a chemical fixation.
The researchers set up a fast and simple procedure – based on a conventional microcontact printing and a simple incubation technique to generate functionalized patterns so as to induce local bacteria deposition – that allowed them to produce reliable chemical patterns exhibiting different surface properties to induce selective adsorption of individual bacteria in liquid media at registered positions. "We have evidenced a selective adsorption of bacteria on these local chemical patterns, producing highly ordered arrays of single living bacteria with a success rate close to 100%," says Cerf. The team then used this controlled immobilization method to study the mechanical properties of dead or alive bacterial cell in aqueous environment. Using force spectroscopy before and after heating , they measured the Young moduli of the same cell. The cells with a damaged membrane (after heating) present a Young modulus twice as high (6.1 ? 1.5 MPa versus 3.0 ? 0.6 MPa) as that of healthy bacteria. At the same time it has been impossible to evidence a difference between the AFM images of the living and the dead cell. "We have shown that we are capable of engineering large areas with patterns of single bacteria and this will be of major interest for future applications," says Dague. "Indeed, thanks to a periodic arrangement of cells, the process consisting in measuring the nanomechanical properties of cells could possibly be automated and a tool to count live or dead bacteria could be designed."
By Michael Berger.
Nanowerk LLC >http://www.nanowerk.com/spotlight/spotid=10816.php
(From Nanowerk Spotlight)
A major concern in microbiology is to determine whether a bacterium is dead or alive. This crucial question has major consequences in food industry, water supply or health care. While culture-based tests can determine whether bacteria can proliferate and form colonies, these tests are time-consuming and work poorly with certain slow-growing or non-culturable bacteria. They are not suitable for applications where real-time results are needed, e.g. in industrial manufacturing or food processing. A team of scientists in France has now discovered that living and dead cells can be discriminated with a nanotechnology technique on the basis of their cell wall nanomechanical properties. This finding is totally new and has been made possible thanks to an interdisciplinary approach which mixes physics, biology and chemistry. This work is a key stone in the understanding of bacterial cell wall behavior. "We have developed a method to probe the mechanical properties of living and dead bacteria via atomic force microscope (AFM) indentation experimentations," Aline Cerf tells Nanowerk. ". Indeed, we provide a new way to probe bacterial cell viability based on cell wall nanomechanical properties, independently from cell ability to grow on a medium or to be penetrated by a fluorescent dye." Cerf, a PhD student in the NanoBioSystems group at LAAS-CNRS, is first author of a recent paper in Langmuir ("Nanomechanical Properties of Dead or Alive Single-Patterned Bacteria") where she and collaborators from LAAS-CNRS describe their findings. "We wanted to explore the modifications that could occur in the nanomechanical properties of a single E. coli bacterium, while it is alive and while it is dead," says Etienne Dague, a researcher in the NanoBioSystems group. "To reach this goal, it has been of first importance to immobilize the living bacteria in an aqueous environment to avoid any cell wall modifications due to a drying step." Thus, in developing a technique to probe the mechanical properties of bacteria via AFM indentation experiments, the French team also came up with an immobilization method for bacteria that doesn't require a chemical fixation.
The researchers set up a fast and simple procedure – based on a conventional microcontact printing and a simple incubation technique to generate functionalized patterns so as to induce local bacteria deposition – that allowed them to produce reliable chemical patterns exhibiting different surface properties to induce selective adsorption of individual bacteria in liquid media at registered positions. "We have evidenced a selective adsorption of bacteria on these local chemical patterns, producing highly ordered arrays of single living bacteria with a success rate close to 100%," says Cerf. The team then used this controlled immobilization method to study the mechanical properties of dead or alive bacterial cell in aqueous environment. Using force spectroscopy before and after heating , they measured the Young moduli of the same cell. The cells with a damaged membrane (after heating) present a Young modulus twice as high (6.1 ? 1.5 MPa versus 3.0 ? 0.6 MPa) as that of healthy bacteria. At the same time it has been impossible to evidence a difference between the AFM images of the living and the dead cell. "We have shown that we are capable of engineering large areas with patterns of single bacteria and this will be of major interest for future applications," says Dague. "Indeed, thanks to a periodic arrangement of cells, the process consisting in measuring the nanomechanical properties of cells could possibly be automated and a tool to count live or dead bacteria could be designed."
By Michael Berger.
Nanowerk LLC >http://www.nanowerk.com/spotlight/spotid=10816.php
What is nanotechnology?(8)
What is nanotechnology?
(1):> 1. The Significance of the Nanoscale
(2):>2. New Materials: Nanomaterials
(3):>2.1 Nanomaterials
(4):>3. Nanomaterial Science
(5):>3.1 Nanoscale in Two Dimensions
(6):>3.2 Nanoscale in Two Dimensions(cont.)
(7):>3.3 Nanoscale in Three Dimensions(cont.)
(8):>3.4 Nanoscale in Three Dimensions(cont.)
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3.3 Nanoscale in Three Dimensions(cont.)
b) Fullerenes (carbon 60)
Model C60In the mid-1980s a new class of carbon material was discovered called carbon 60 (C60).Harry Kroto and Richard Smalley, the experimental chemists who discovered C60 named it "buckminsterfullerene", in recognition of the architect Buckminster Fuller, who was well-known for building geodesic domes, and the term fullerenes was then given to any closed carbon cage. C60 are spherical molecules about 1nm in diameter, comprising 60 carbon atoms arranged as 20 hexagons and 12 pentagons: the configuration of a football. In 1990, a technique to produce larger quantities of C60 was developed by resistively heating graphite rods in a helium atmosphere. Several applications are envisaged for fullerenes, such as miniature ‘ball bearings’ to lubricate surfaces, drug delivery vehicles and in electronic circuits.
c) DendrimersDendrimers are spherical polymeric molecules, formed through a nanoscale hierarchical self-assembly process. There are many types of dendrimer; the smallest is several nanometres in size. Dendrimers are used in conventional applications such as coatings and inks, but they also have a range of interesting properties which could lead to useful applications. For example, dendrimers can act as nanoscale carrier molecules and as such could be used in drug delivery. Environmental clean-up could be assisted by dendrimers as they can trap metal ions, which could then be filtered out of water with ultra-filtration techniques.
d) Quantum DotsNanoparticles of semiconductors (quantum dots) were theorized in the 1970s and initially created in the early 1980s. If semiconductor particles are made small enough, quantum effects come into play, which limit the energies at which electrons and holes (the absence of an electron) can exist in the particles. As energy is related to wavelength (or colour), this means that the optical properties of the particle can be finely tuned depending on its size. Thus, particles can be made to emit or absorb specific wavelengths (colours) of light, merely by controlling their size. Recently, quantum dots have found applications in composites, solar cells (Gratzel cells) and fluorescent biological labels (for example to trace a biological molecule) which use both the small particle size and tuneable energy levels. Recent advances in chemistry have resulted in the preparation of monolayer-protected, high-quality, monodispersed, crystalline quantum dots as small as 2nm in diameter, which can be conveniently treated and processed as a typical chemical reagent.
(1):> 1. The Significance of the Nanoscale
(2):>2. New Materials: Nanomaterials
(3):>2.1 Nanomaterials
(4):>3. Nanomaterial Science
(5):>3.1 Nanoscale in Two Dimensions
(6):>3.2 Nanoscale in Two Dimensions(cont.)
(7):>3.3 Nanoscale in Three Dimensions(cont.)
(8):>3.4 Nanoscale in Three Dimensions(cont.)
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3.3 Nanoscale in Three Dimensions(cont.)
b) Fullerenes (carbon 60)
Model C60In the mid-1980s a new class of carbon material was discovered called carbon 60 (C60).Harry Kroto and Richard Smalley, the experimental chemists who discovered C60 named it "buckminsterfullerene", in recognition of the architect Buckminster Fuller, who was well-known for building geodesic domes, and the term fullerenes was then given to any closed carbon cage. C60 are spherical molecules about 1nm in diameter, comprising 60 carbon atoms arranged as 20 hexagons and 12 pentagons: the configuration of a football. In 1990, a technique to produce larger quantities of C60 was developed by resistively heating graphite rods in a helium atmosphere. Several applications are envisaged for fullerenes, such as miniature ‘ball bearings’ to lubricate surfaces, drug delivery vehicles and in electronic circuits.
c) DendrimersDendrimers are spherical polymeric molecules, formed through a nanoscale hierarchical self-assembly process. There are many types of dendrimer; the smallest is several nanometres in size. Dendrimers are used in conventional applications such as coatings and inks, but they also have a range of interesting properties which could lead to useful applications. For example, dendrimers can act as nanoscale carrier molecules and as such could be used in drug delivery. Environmental clean-up could be assisted by dendrimers as they can trap metal ions, which could then be filtered out of water with ultra-filtration techniques.
d) Quantum DotsNanoparticles of semiconductors (quantum dots) were theorized in the 1970s and initially created in the early 1980s. If semiconductor particles are made small enough, quantum effects come into play, which limit the energies at which electrons and holes (the absence of an electron) can exist in the particles. As energy is related to wavelength (or colour), this means that the optical properties of the particle can be finely tuned depending on its size. Thus, particles can be made to emit or absorb specific wavelengths (colours) of light, merely by controlling their size. Recently, quantum dots have found applications in composites, solar cells (Gratzel cells) and fluorescent biological labels (for example to trace a biological molecule) which use both the small particle size and tuneable energy levels. Recent advances in chemistry have resulted in the preparation of monolayer-protected, high-quality, monodispersed, crystalline quantum dots as small as 2nm in diameter, which can be conveniently treated and processed as a typical chemical reagent.
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