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Nanotechnology Spotlight

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Posted: Dec 09, 2011

Nanotechnology and microbiology

(Nanowerk Spotlight) Microbiology relates to nanoscience at a number of levels. Many bacterial entities are nano-machines in nature, including molecular motors like flagella and pili. Bacteria also form biofilms by the process of self-assembly (for example the formation of Curli-film by E. coli). The formation of aerial hyphae by bacteria and fungi is also directed by the controlled and ordered assembly of building blocks. Also, the formation of virus capsids is a classical process of molecular recognition and self-assembly at the nano-scale.
Nanotechnology involves creating and manipulating organic and inorganic matter at the nanoscale. It promises to provide the means for designing nanomaterials; materials with tailor-made physical, chemical and biological properties controlled by defined molecular structures and dynamics. The present molecular biology techniques of genetic modification of crops are already forms of what has been termed nanotechnology.
Nanotechnology can provide for the future development of far more precise and effective methods of, and other forms of, manipulation of food polymers and polymeric assemblages to provide tailor-made improvements to food quality and food safety. Nanotechnology promises not only the creation of novel and precisely defined material properties, it also promises that these materials will have self-assembling, self-healing and maintaining properties.
Typical size of nano- and microsized biological objects
Typical size of nano- and microsized biological objects (horizontal axis: log-scale) from left- to right: (a) Hydrogen atom (∼0.1nm) , (b) water molecule (diameter: ∼0.4nm), (c) peptide aptamer (size ∼3nm), (d) lipid bilayer (thickness ∼5nm), (e) protein (size ∼10nm), (f) antibody (size ∼10nm), (g) ribosome (diameter ∼30nm), (h) human papilloma virus (diameter ∼60nm), (i) mitochondrium (length ∼1 µm), (j) Helicobacter pylori (length ∼3µm), (k) nucleus (diameter ∼3µm), (l) erythrocyte (diameter ∼8µm), mammalian cell (diameter ∼20µm). [source]
Nanoscience does have an impact on several areas of microbiology. It allows for the study and visualization at the molecular-assembly levels of a process. It facilitates identification of molecular recognition and self-assembly motifs as well as the assessment of these processes. Specifically, there are three areas where microbiologists use nanotechnologists' techniques:

– Imaging single molecules

– Poking and pulling nanoscale objects (laser traps, optical tweezer)

– Determining spatial organization in living microbes (AFM, near/far field microscope)

Nanotechnology in food microbiology
Detection of very small amounts of a chemical contaminant, virus or bacteria in food systems is another potential application of nanotechnology. The exciting possibility of combining biology and nanoscale technology into sensors holds the potential of increased sensitivity and therefore a significantly reduced response-time to sense potential problems.
Nanosensors that are being developed by researchers at both Purdue and Clemson universities use nanoparticles, which can either be tailor-made to fluoresce different colors or, alternatively, be manufactured out of magnetic materials. These nanoparticles can then selectively attach themselves to any number of food pathogens. Employees, using handheld sensors employing either infrared light or magnetic materials, could then note the presence of even minuscule traces of harmful pathogens. The advantage of such a system is that literally hundreds and potentially thousands of nanoparticles can be placed on a single nanosensor to rapidly, accurately and affordably detect the presence of any number of different bacteria and pathogens. A second advantage of nanosensors is that, given their small size, they can gain access into the tiny crevices where the pathogens often hide.
The application of nanotechnologies on the detection of pathogenic organisms in food and the development of nanosensors for food safety is also studied at the Bioanalytical Microsystems and Biosensors Laboratory at Cornell University. The focus of the research performed at Cornell University is on the development of rapid and portable biosensors for the detection of pathogens in the environment, food and for clinical diagnostics. The bioanalytical microsystems use the same biological principles as were used in the simple biosensors, i.e. RNA recognition via DNA/RNA hybridization and liposome amplification. The bioanalytical microsystems that are studied focus on the very rapid detection of pathogens in routine drinking water testing, food analysis, environmental water testing and in clinical diagnostics (see "Nanotechnology and its applications in the food sector").
Nanotechnology in medical biology – application of nanodiagnostics in infectious diseases
The rapid and sensitive detection of pathogenic bacteria at the point of care is extremely important. Limitations of most of the conventional diagnostic methods are the lack of ultrasensitivity and delay in getting results. A bioconjugated nanoparticle-based bioassay for in situ pathogen quantification can detect a single bacterium within 20 minutes.
Detection of single-molecule hybridization has been achieved by a hybridization-detection method using multicolor oligonucleotide-functionalized QDs as nanoprobes. In the presence of various target sequences, combinatorial self-assembly of the nanoprobes via independent hybridization reactions leads to the generation of discernible sequence specific detection of multiple relevant sequences ("Multiplexed Hybridization detection with multicolor colocalization of quantum dot nanoprobes").
A spectroscopic assay based on SERS using silver nanorods, which significantly amplify the signal, has been developed for rapid detection of trace levels of viruses with a high degree of sensitivity and specificity. The technique measures the change in frequency of a near- infrared laser as it scatters viral DNA or RNA. That change in frequency is as distinct as a fingerprint. This novel SERS assay can detect spectral differences between viruses, viral strains, and viruses with gene deletions in biological media. The method provides rapid diagnostics (60 s) for detection and characterization of viruses generating reproducible spectra without viral manipulation. This method is also inexpensive and easily reproducible (see for instance: "Nanotechnology: A new frontier in virus detection in clinical practice").
The use of nanoparticles as tags or labels allows for the detection of infectious agents in small sample volumes directly in a very sensitive, specific and rapid format at lower costs than current in-use technologies. This advance in early detection enables accurate and prompt treatment.
Quantum dot technology is currently the most widely employed nanotechnology in this area. The recently emerging cantilever technology is the most promising. The technology strengthens and expands the DNA and protein microarray methods and has applications in genomic analysis, proteomics, and molecular diagnostics.
Waveguide technology is an emergent area with many diagnostic applications. Nanosensors are the new contrivance for detection of bioterrorism agents. All these new technologies would have to be evaluated in clinical settings before their full import is appreciated and accepted ("New frontiers in nanotechnology for cancer treatment" and "Cancer nanotechnology: opportunities and challenges").
Nanotechnology in water microbiology – water treatment by detection of microbial pathogens
An adequate supply of safe drinking water is one of the major prerequisites for a healthy life, but waterborne diseases is still a major cause of death in many parts of the world, particularly in young children, the elderly, or those with compromised immune systems. As the epidemiology of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors.
An important challenge is therefore the rapid, specific and sensitive detection of waterborne pathogens. Presently, microbial tests are based essentially on time-consuming culture methods. However, newer enzymatic, immunological and genetic methods are being developed to replace and/or support classical approaches to microbial detection. Moreover, innovations in nanotechnologies and nanosciences are having a significant impact in biodiagnostics, where a number of nanoparticle-based assays and nanodevices have been introduced for biomolecular detection (see for instance: Nanotechnology in Water Treatment Applications and Environmental Microbiology: Current Technology and Water Applications).
By Dr. Arti Goel (agoel2@amity.edu), Lecturer, Amity Institute of Microbial Biotechnology, Amity University, Noida (U.P.).

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