Alternative platform for COVID-19 diagnosis based on AuNP-modified lab-on-paper.

COVID-19 has caused global health problems, and so rapid diagnosis is crucial to slow spread of the disease. Herein, a novel lab-on-paper screening method for SARS-CoV-2 Omicron BA.2 variant was developed using a gold nanoparticle-based colorimetric biosensor along with sensitive detection of SARS-CoV-2 antigen using laser desorption ionization-mass spectrometry (LDI-MS). As a result of antigen-antibody interaction, in the presence of SARS-CoV-2 antigen the gold nanoparticles undergo aggregation and change color from red to light purple, allowing for rapid determination of SARS-CoV-2 antigen with the naked eye. Furthermore, the lab-on-paper method can be directly applied as a substrate for sensitive quantitation of SARS-CoV-2 antigen in saliva using LDI-MS without the use of a conventional organic matrix and sample preparation. LDI-MS offers early diagnosis with high sensitivity, rapidity without sample preparation and lower cost per test compared with reverse transcriptase-PCR, which is crucial for preventing mortality in patients with underlying conditions. This method showed linearity over 0.01-1 µg mL-1 covering the cut-off value of 0.048 µg mL-1 for COVID-19 detection in human saliva. Moreover, a colorimetric sensor for urea was also fabricated in-parallel, for prediction of COVID-19 severity in patients with chronic kidney disease. The color change upon increasing urea concentration directly reflected kidney damage, which is related to increasing risk of mortality among patients with COVID-19. Hence, this platform might be a potential device for non-invasive diagnosis of SARS-CoV-2 Omicron BA.2 variant, which is the variant of most concern because it is transmitted more rapidly than the original SARS-CoV-2 virus and the Delta variant.

Emerging 3D printing based on polymers and nanomaterial additives: Enhancement of properties and potential applications

Three-dimensional printing (3D printing) has gained tremendous attention from various fields including scientific researchers and commercial industries. Polymers are the most widely used materials since they demonstrate ease of processing and ability to gain the desired properties by adding additives. Nonetheless, there are many challenges including limited printable material, slow printing speed, low resolution, functionality, and suitable property for using in specific applications. The use of nanomaterials with unique properties to improve the polymer properties has been developed leading to increased number of polymer nanocomposites with versatility. The addition of nanomaterials into polymers can significantly alter and enhance mechanical properties, thermal and electrical conductivity, including cell adhesion and proliferation in biomedical application. 3D printing technology coupled with the high-performance polymer nanocomposites can create 3D polymer structures with the precise and complex geometries, and also exhibit multi-functional properties provided by the different properties from polymers and nanomaterials. 3D printing polymer nanocomposites can be applied as the alternative materials for tissue engineering, biomedical devices, sensors, electronics and recently in personal protection during COVID-19 pandemic. The trends of utilization of polymers, well-known materials for 3D printing, coupled with nanotechnology is still continuous growing since variety of applications is rapidly expanded for advanced application, especially in biomedical field.