This project includes design, simulation and preliminary tests of a photonic biochip for bacterial killing through the temperature increase caused by the heating of gold nanoparticles . The proposed biochip is made of PolyDiMethylSiloxane (PDMS) in which microfluidic channels, gold nanorods (GNRs) and optical waveguides are combined and integrated. Microfluidic channels and optical waveguides are made on separated substrates then coupled to form a single PDMS chip. GNRs are deposited on the top surface of the substrate which includes the optical waveguides. Microfluidic channels are used to transport a bacterial solution. Optical waveguides confine near infrared light (NIR) at a wavelength of 810 nm with a power of about 0.5 W/cm2. NIR light beams activate the GNRs exciting local plasmon resonances, which determine a temperature increase above 45 °C, able to kill the bacteria flowing in the microfluidic channel.
The solution with bacteria will be introduced in the microfluidic channel by using an inlet micropump and extracted at higher temperature by means of an outlet micropump after photothermal treatment. The output solution will be characterized to check presence of bacteria. To validate the proposed approach, a strain of Escherichia coli (E. coli) has been selected as a representative type of bacteria, having a great impact as it causes severe illness in humans since it is found in the lower intestine of warm-blooded organisms.
The proposed plasmonic integrated microsystem will be thoroughly investigated highlighting the structure-function relation and assessing the antimicrobial activity by means of viability assays.
This proposal is a preliminary step toward developing integrated nanomedicine, for guiding, and optimization of thermal-based laser treatment. The research involves multidisciplinary expertise ranging from photonics, electromagnetism, biology, advanced microscopy, biomedical engineering.
The biophotonic chip which will be developed in this project is unique in his kind. The proposed biochip concept basically opens the possibility to create a low-cost effective approach to kill bacteria by using a portable, biocompatible, microsystem which can be further developed for in-vivo thermal therapy by using a proper different waveguide-MC microsystem. The proposed biochip is a technological platform to test several kinds of bacteria since there are no apparent biological limitations.
The photothermal activation of GNR in microchannels by using confined guided laser beams has not been studied so far. Measurements scheduled in this project will produce interesting results expected to be published in peer-reviewed journals.
This proposal is a preliminary step toward developing integrated nanomedicine, which combines nanotherapeutics with simultaneous nanodiagnostics for guide and optimization of thermal-based laser treatment. PPTT technique is a powerful tool that can monitor thermal and accompanied effects at broad temperature ranges from a few degrees (diagnostics) to several hundred or thousand degrees (therapeutics). We believe this approach may be applicable as a therapeutic strategy for infections caused by other types of bacteria, and potentially viral infections (e.g., hepatitis), since both can be labelled with gold nanoparticles [33,34].
Furthermore, we plan to transit this technology to an in vivo animal study, using the principle of integrated PPTT flow imaging cytometry, which has been used to detect gold nanoparticles in bioflow in vivo [35], or in combination with fluorescence and photoacoustic technique [36] to monitor transportation particles in blood and lymph flow and their accumulation in specific sites.
This project is a step for realizing a new generation of light assisted and on-demand antimicrobial therapies.
Another important innovative potential application of the proposed approach is the purification of water from diluted bacteria in which a proper design of a new kind of nanoparticles whose absorption peak is in the visible wavelengths. This approach would allow to develop nanoparticle assisted bacteria purification by using daylight source as a further evolution of this project.
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