C-MEMS-derived glassy carbon electrochemical biosensors for rapid detection of SARS-CoV-2 spike protein

According to a World Health Organization(WHO)report,the world has experienced more than 766 million cases of positive SARS-CoV-2 infection and more than 6.9 million deaths due to COVID through May 2023.The WHO declared a pandemic due to the rapid spread of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)virus,and the fight against this pandemic is not over yet.Important reasons for virus spread include the lack of detection kits,appropriate detection techniques,delay in detection,asymptomatic cases and failure in mass screening.In the last 3 years,several researchers and medical companies have introduced successful test kits to detect the infection of symptomatic patients in real time,which was necessary to monitor the spread.However,it is also important to have information on asymptomatic cases,which can be obtained by antibody testing for the SARS-CoV-2 virus.In this work,we developed a simple,advantageous immobilization procedure for rapidly detecting the SARS-CoV-2 spike protein.Carbon-MEMS-derived glassy carbon(GC)is used as the sensor electrode,and the detection is based on covalently linking the SARS-CoV-2 antibody to the GC surface.Glutaraldehyde was used as a cross-linker between the antibody and glassy carbon electrode(GCE).The binding was investigated using Fourier transform infrared spectroscopy(FTIR)characterization and cyclic voltammetric(CV)analysis.Electrochemical impedance spectroscopy(EIS)was utilized to measure the change in total impedance before and after incubation of the SARS-CoV-2 antibody with various concentrations of SARS-CoV-2 spike protein.The developed sensor can sense 1 fg/ml to 1µg/ml SARS-CoV-2 spike protein.This detection is label-free,and the chances of false positives are minimal.The calculated LOD was~31 copies of viral RNA/mL.The coefficient of variation(CV)number is calculated from EIS data at 100 Hz,which is found to be 0.398%.The developed sensor may be used for mass screening because it is cost-effective.

Glassy carbon microneedles-new transdermal drug delivery device derived from a scalable C-MEMS process

Because carbon is the basic element of all life forms and has been successfully applied as a material for medical applications,it is desirable to investigate carbon for drug delivery applications,as well.In this work,we report the fabrication of a hollow carbon microneedle array with flow channels using a conventional carbonmicroelectromechanical system(C-MEMS)process.This process utilizes the scalable and irreversible step of pyrolysis,where prepatterned SU-8 microneedles(precursor)are converted to glassy carbon structures in an inert atmosphere at high temperature(900°C)while retaining their original shape upon shrinkage.Once converted to glassy carbon,the microneedles inherit the unique properties of hardness,biocompatibility,and thermal and chemical resistance associated with this material.A comparative study of hardness and Young’s modulus for carbon microneedles and SU-8 microneedles was performed to evaluate the increased strength of the microneedles induced by the C-MEMS process steps.Structural shrinkage of the carbon microneedles upon pyrolysis was observed and estimated.Material characterizations including energy-dispersive X-ray spectroscopy(EDX)and Raman spectroscopy were carried out to estimate the atomic percentage of carbon in the microneedle structure and its crystalline nature,respectively.Our investigations confirm that the microneedles are glassy in nature.Compression and bending tests were also performed to determine the maximum forces that the carbon microneedles can withstand,and it was found that these forces were approximately two orders of magnitude higher than the resistive forces presented by skin.A microneedle array was inserted into mouse skin multiple times and was successfully removed without the breakage of any microneedles.