Studies towards the development of a device for the Raman characterisation of the Sars-CoV-2 antibody

Abstract

Human Civilization is no stranger to infectious diseases, throughout the abundance of time infectious diseases, famine and wars have been a major threat to human existence and progress. These disease are caused by micrometer to nanometer sized microorganisms like bacteria, pathogens, and viruses. They are of various types, with each having its own unique effect on the infected host. It becomes self evident that only early detection, quarantine and treatment of the infected can curtail a possible exonential growth rate of infections and the possibility of mutation of a given virus to a more virulent strain. The emergence of SARS-CoV-2 in december 2019 has brought about a unified global effort to characterise and curtail the virus. This effort has met with some difficulties, the inability to contain the rapid spread of COVID-19 proceeds from the unavailability of simple, reliable, cheap and rapid testing methods. Lab based testing during epidemics cannot cater for the overwhelming number of test to be done. In such a Pandemic situation, an interplay of the above situational dynamics, begs the need for very sensitive and efficient point of care device that simplifies diagnoses of SARs-CoV-2 virus. The WHO stipulates that all such point of care devices should meet with following standards: (i) affordable; (ii)sensitive; (iii) specific; (iv) user-friendly; (v) rapid and robust; (vi)equipment-free;and (vii) deliverable to end-users. In this thesis, an immunoassay based on surface enhanced Raman spectroscopy (SERS) was used to investigate SARs-CoV-2 antibody for its characteristic Raman finger print. Characterization of SERS substrate like Nanoporous gold, gold nanoparticles deposited on topaz and sputtered on borosilicate glass showed a decent enhancement factor of about 10^3 to 10^4 , it was also observed on all SERS substrate that a 1µm height of deposited nanoparticles was sufficient for SERS enhancement. The immobilization of the Genetex SARs-CoV-2 was done using Cysteamine hydrochloride and Lomants reagent, linkage was only possible only after sufficient cleaning was effected on the SERS substrates, the Raman spectrum obtained was same for both protocols, however noise and substrate instability was observed. The presence of Cysteamine Hydrochloride monolayers was confirmed by the Raman peaks 510, 643, 726, 938, 1015, 2557, 2928, and2962cm−1 each respectively assigned to ν(S − S), ν(C − S), ν(C − S), ν(C − C(−N)), ν(C − C(−N)), ν(S − H), νas(CH2) and ν2(CH2) . The characteristic disufide band, Aliphatic and Aromatic bands, Amide I and Amide III bands were identified for both linking protocols and tentatively assigned. since adsorption of the thiol monolayers was from solution a Langmuir growth model is proposed as the means of thiol growth and orientation.