Prothrombin, or factor II, is vital in blood coagulation, transforming into active thrombin. The prothrombin time test (PTT) measures blood clotting time, crucial for heart disease patients on anticoagulants. Our study introduces a novel approach using refractive index to measure prothrombin time, validated through experimental outcomes. This method leverages light refraction principles, offering rapid results, simplicity, and point-of-care potential. Testing with clinical samples showed strong correlation with traditional PTT methods. Developing a point-of-care device for prothrombin time measurement promises to enhance patient care by enabling real-time monitoring of clotting efficiency, allowing timely adjustments to anticoagulant therapy, thus reducing risks of bleeding or thrombosis. The simplicity and accessibility of this method can revolutionize anticoagulant management, especially in resource-limited settings.
Label-free quantification of polymerization is of significant importance in today's research as recent advancements in the polymer field have sparked numerous applications in the biomedical industry. Poly-((Ethylene Glycol) Methyl Ether)- Methacrylate (POEGMA) has been recognized as a replacement for PNIPAM for biomedical applications due to various factors such as biocompatibility and thermal response rate. With a rapid thermal response, POEGMA allows for a variety of biomedical applications including a potential drug delivery mechanism. In this study, a Photonic Crystal-Total Internal Reflection (PC-TIR) biosensor has been utilized to monitor POEGMA-144, which has been synthesized via an Atom Transfer Radical Polymerization (ATRP) grafting-from approach. Monitoring the optical resonance of this biosensor, it allows for quantification of the growth of a layer of an initiator on the sensor surface as well as the growth of the POEGMA on top of it. In addition, the PC-TIR sensor further allows real-time analysis of the polymer’s thermal responsiveness in an aqueous environment. At a well-defined, molecular weight specific, Lower Critical Solution Temperature (LCST) of 42°C, the POEGMA-144 polymer conformationally changes, becoming hydrophobic and collapsing after expelling any water between its PEG side chains. Using the PC-TIR biosensor, a definitive polymer collapse was observed at the LCST; similarly, a re-swelling of the polymer was observed as the ambient temperature of the polymer was allowed to cool back to room temperature.
Label-Free detection of cardiac biomarkers has become an area of great interest with respect to point of care (POC) analysis of acute myocardial infarction and drug cardiotoxicity assays. DNA aptamers have become a potential replacement to traditional antibody detection of antigens in bioassays. In comparison to antibodies, DNA aptamers provide the advantages of lower cost, high flexibility, high batch-to-batch uniformity, stability at 37°C when immobilized on the sensor surface, and reusability with a regeneration solution. However, aptamer usage requires novel binding pathways that must be explored to ensure efficiency and consistency. Herein, a direct approach for Cardiac Troponin I (cTnI) detection was tested utilizing UV immobilization of Amino- and PolyT-modified aptamers on APTES or MPTMS modified and unmodified sensor surfaces composed of SiO2 for a Photonic Crystal-Total Internal Reflection biosensor (PC-TIR). The detection of aptamer functionalization, and ultimately antigen detection, were monitored with a label-free bioassay system enabled by a PC-TIR sensor. Results from this study indicated that the binding pathways with the highest aptamer immobilization were: Amino modified aptamer on an APTES modified surface and PolyT modified aptamer on an MPTMS surface. Detection of the antigen was dependent on both aptamer secondary structure formation and aptamer immobilization following UV exposure.
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