The quantification of human immunodeficiency virus at point of care remains a challenge in resource limited settings. The incorporation of nanotechnology and label free optical biosensing has unlocked promising opportunities in the development of diagnostic tools for infectious diseases. Optical biosensors offer a rapid and sensitive optical method for various biological materials such as cells, biomolecules, and viruses by monitoring the dielectric permittivity changes at the interface of a transducer substrate and the analyte. This work focuses on exploring photonic crystal biosensor efficiency and sensitivity for viral load measurement. Photonic crystal biosensors are a unique class of biosensors that allow for label free analysis as they can control and confine light propagation due to the photonic bandgap. Silane treated photonic crystal was functionalized with anti-HIV-gp120 antibody before the addition of various concentrations of HIV pseudovirus. The samples were analyzed on a custom build transmission spectroscopy that used white light as a light source. The results showed a red shift at different virus concentrations, which demonstrates that photonic crystal biosensors are sensitive enough to detect differences in virus concentrations. Therefore, photonic crystals have a potential in the development of photonic crystal-based biosensors for viral load detection.
A lot of individuals residing in resource limited settings where timely access to medical care is a challenge and healthcare infrastructure is usually poor have no access to laboratory facilities. Disease diagnosis in such sites is dependent on the presence of point-of-care (POC) devices. These POC diagnostics play a key role in ensuring rapid patient care because they are simple to use, inexpensive, portable, instrument independent and do not require a trained technician to operate. In this study, we used a smartphone camera as a spectrometer for measurement of rhodamine at different concentrations. Rhodamine was used as the analyte of choice for proof of concept purposes. The smartphone platform was able to detect the absorption within the visible spectral range from 400 to 700 nm. The results obtained showed that the performance of the smartphone based platform correlates with the conventional microplate reader. From this study, we therefore envision an inexpensive and portable smartphone based devise with connectivity to the internet for POC diagnostics in resource limited settings.
Biological macromolecules such as antibodies, enzymes, proteins and aptamers have good molecular recognition ability which makes them good candidates for biosensing applications. In this study, glass substrates were treated with silane in order to immobilize HIV gp41 antibodies on their surfaces. The HIV pseudovirus was added to the treated substrates followed by addition of antibodies conjugated to nanoparticles. The surfaces were characterised by using water contact angle, atomic force microscopy (AFM) and Raman spectroscopy. Our preliminary data displayed that the antibodies were indeed immobilized on the glass substrates which made it possible for capturing the intact HIV pseudovirus. Further, Raman spectroscopy revealed the presence of disulphide bonds indicating successful conjugation of the HIV gp41 antibodies to the HIV pseudovirus.
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