October 13, 2011
(Nanowerk Spotlight) Nanotechnology is an enabling technology that deals with nanometer-sized objects. A decade ago, nanoparticles were studied because of their size-dependent physical and chemical properties (“Synthesis and Characterization of Monodisperse Nanocrystals and Close-Packed Nanocrystal Assemblies”). Now they have entered a commercial exploration period leading to the establishment various novel fields of science – one of them being nanobiotechnology (see for instance:“Commercializing nanotechnology” and “Investing in nanotechnology”).
Understanding of biological processes at the nanoscale level is a strong driving force behind the development of nanobiotechnology. Living organisms are built of cells that are typically 10 µm across. Individual biomolecules are much smaller in the sub-micron size domain. Even smaller are the proteins with a typical size of just 5 nm, which is comparable with the dimensions of the smallest man-made nanoparticles. This simple size comparison suggests that using nanoparticles as nanoprobes would allow us to spy at the cellular machinery without introducing too much interference.
In order to enhance the utilization of nanomaterial in biological systems, it is very important to understand the influence they impart on cellular health and function. Nanomaterials present a research challenge as very little is known about how they behave in relation to micro-organisms, particularly at the cellular and molecular levels.
Most of the nanomaterials reported earlier have demonstrated to be efficient antimicrobial agents against virus, bacteria or fungus (see “Nanotechnology in medicine and antibacterial effect of silver nanoparticles” (pdf) and “Antibacterial Characterization of Silver Nanoparticles against E. Coli ATCC-15224”).
There are scarce research reports on the growth-promoting role of nanomaterials especially with respect to microbes. With the progress of nanotechnology, many laboratories around the world have investigated the fact that nanoparticles possess more surface area than microparticles, which greatly improves the nanoparticles’ physical and chemical characteristics. But very little is known on how their changed characteristics influences the microbial world.
Our recent findings, however, have challenged this concept of antimicrobial activity of nanoparticles. This concept clearly demonstrates the growth-promoting role of the nanoparticles on microbes. The significance of the present observation can be useful in rapid detection of pathogens like N. meningitides, H. pylori, S. pyogenes and many other microbes especially slow growing.
Meningitis is an inflammation of the meninges, the protective membranes covering brain and spinal cord, and may be due to infection by viruses, bacteria, or other microorganisms (“Bacterial meningitis in children”). Bacterial meningitis constitutes a significant global public health problem and can be life-threatening. N. meningitidis and S. pneumoniae are a major cause of bacterial meningitis. Early growth and identification of the type of bacteria responsible in culture is important for selecting the correct antibiotics for adequate treatment to save the life of patient.
We studied the impact of nanomaterials on growth of N. meningitides. For this study we used three types of nanomaterials, Titanium dioxide (TiO2), carbon nanotubes (CNTs) and activated carbon nanotubes (Ac-CNTs). Serial dilutions of standard strain of N. meningitides were prepared in the BHI (Brain Heart Infusion) for inoculum’s preparation. Equal volume of these dilutions was spread on the plates poured with chocolate Agar, chocolate agar added with either TiO2 or CNT or Ac-CNT. Plates were incubated at 37°C in 5% CO2 in humidified chamber and observed after every 2 hrs till 24 hrs for early growth and colonies were counted after 24 hrs.
Figure 1: N. meningitidis interacting with nanomaterials; control chocolate agar (without any nanomaterials), chocolate agar with carbon nanotubes (CNT), chocolate agar with titanium dioxide nanoparticles (TiO2) and chocolate agar with activated carbon nanotubes (Ac-CNTs). These were added to the medium before autoclaving.
The results indicates that colonies of N. meningitidis starts appearing early on media added with nanomaterials (after 12.5 hrs) as compared to plain Chocolate agar (growth after 18-22 hrs). Quantitatively also, the number of colonies were enhanced 3-4 fold in presence of media added with any of these nanomaterials. The numbers of colonies were maximum in case of Ac-CNT followed by TiO2and CNT respectively (Figure1). Addition of Ac-CNT and TiO2 enhanced the growth significantly 67.0 ± 2.89 ( Mean ± SD) and 27.0 ± 5.35 respectively. With addition of CNT also the numbers of colonies were found to be almost double i.e 15.75 ± 1.75 in contrast of 8.5 ± 3.5 colonies in case of control.
It was observed that the stage of nanomaterials inclusion is crucial. The inclusion before wet sterilization showed a positive and stimulating effect on the growth of N. meningitides. The results were in support of our earlier reported work which proved the role of a similar kind of nanomaterial-based media for the growth enhancement of symbiotic fungus (“Role of nanomaterials in symbiotic fungus growth enhancement”; pdf).
The key finding of our recent work is that the addition of nanomaterials can enhance the growth of microbes and help in early identification of pathogens. The results indicate that this may serve as an excellent tool for growth enhancement as well as early diagnosis of slow growing pathogens.
Our results established for the first time that a nanomaterial-based media can enhance the growth of microbes and effectively function in the early diagnosis of diseases.
The data collected indeed is very fascinating for the advancement of science and technology but it leads to many basic questions and also ethical issues. Our research promotes the growth of microbes using nanomaterial leading to new direction for commercialization and medical diagnosis. The moot question is if nanomaterials will alter the metabolism of microbes and/or lead to mutations? How will these materials affect microorganisms at the molecular level, which may affect the further identification of the microbe? Future research needs to address all these questions and how to control all these responses for utilizing maximum beneficial effects of nanomaterials.
By Ramesh Kumar (Amity Institute of Advance Research and Studies (Material & Devices), Amity University, Noida, India, 201303), Bimal Kumar Das (Department of Microbiology, All India Institute of Medical Sciences, New Delhi-110029), V.K. Jain (Amity Institute of Advance Research and Studies (Material & Devices), ) and Suman (Amity Institute of Advance Research and Studies (Material & Devices). All correspondence should be addressed to Dr. Suman: email@example.com