Nanoplasmonic biosensor for rapid detection of multiple viral variants in human serum.

As viruses constantly change due to mutation, variants are expected to emerge demanding development of sensors capable of detecting multiple variants using one single sensor platform. Herein, we report the integration of a synthetic binder against SARS-CoV-2 with a nanoplasmonic-based sensing technology, which enables the successful detection of spike proteins of Alpha, Beta and Gamma variants of SARS CoV-2. The recognition event is achieved by specific nanostructured molecularly imprinted polymers (nanoMIPs), developed against a region of the receptor binding domain (RBD) of the SARS CoV-2 spike protein. The transduction is based on the principle of localized surface plasmon resonance (LSPR) associated with silver nanostructures. The nanoMIPs-functionalised LSPR sensor allows for the detection of all 3 protein variants with a limit of detection of 9.71 fM, 7.32 fM and 8.81 pM using wavelength shifts respectively for Alpha, Beta and Gamma spike protein variants. This can be achieved within 30 min from the sample collection, both from blood and using nasal swab, thus making this sensor suitable for rapid detection of COVID-19. Additionally, the turnaround time for sensor development and validation can be completed in less than 8 weeks, making it suitable for addressing future pandemic needs without the requirement for biological binding agents, which is one of the bottlenecks to the supply chain in diagnostic devices.

Molecularly Imprinted Polymer Nanoparticles Enable Rapid, Reliable, and Robust Point-of-Care Thermal Detection of SARS-CoV-2.

Rapid antigen tests are currently used for population screening of COVID-19. However, they lack sensitivity and utilize antibodies as receptors, which can only function in narrow temperature and pH ranges. Consequently, molecularly imprinted polymer nanoparticles (nanoMIPs) are synthetized with a fast (2 h) and scalable process using merely a tiny SARS-CoV-2 fragment (∼10 amino acids). The nanoMIPs rival the affinity of SARS-CoV-2 antibodies under standard testing conditions and surpass them at elevated temperatures or in acidic media. Therefore, nanoMIP sensors possess clear advantages over antibody-based assays as they can function in various challenging media. A thermal assay is developed with nanoMIPs electrografted onto screen-printed electrodes to accurately quantify SARS-CoV-2 antigens. Heat transfer-based measurements demonstrate superior detection limits compared to commercial rapid antigen tests and most antigen tests from the literature for both the alpha (∼9.9 fg mL-1) and delta (∼6.1 fg mL-1) variants of the spike protein. A prototype assay is developed, which can rapidly (∼15 min) validate clinical patient samples with excellent sensitivity and specificity. The straightforward epitope imprinting method and high robustness of nanoMIPs produce a SARS-CoV-2 sensor with significant commercial potential for population screening, in addition to the possibility of measurements in diagnostically challenging environments.

Immobilization of Molecularly Imprinted Polymer Nanoparticles onto Surfaces Using Different Strategies: Evaluating the Influence of the Functionalized Interface on the Performance of a Thermal Assay for the Detection of the Cardiac Biomarker Troponin I.

We demonstrate that a novel functionalized interface, where molecularly imprinted polymer nanoparticles (nanoMIPs) are attached to screen-printed graphite electrodes (SPEs), can be utilized for the thermal detection of the cardiac biomarker troponin I (cTnI). The ultrasensitive detection of the unique protein cTnI can be utilized for the early diagnosis of myocardial infraction (i.e., heart attacks), resulting in considerably lower patient mortality and morbidity. Our developed platform presents an innovative route to develop accurate, low-cost, and disposable sensors for the diagnosis of cardiovascular diseases, specifically myocardial infraction. A reproducible and advantageous solid-phase approach was utilized to synthesize high-affinity nanoMIPs (average size = 71 nm) for cTnI, which served as synthetic receptors in a thermal sensing platform. To assess the performance and commercial potential of the sensor platform, various approaches were used to immobilize nanoMIPs onto thermocouples or SPEs: dip coating, drop casting, and a covalent approach relying on electrografting with an organic coupling reaction. Characterization of the nanoMIP-functionalized surfaces was performed with electrochemical impedance spectroscopy, atomic force microscopy, and scanning electron microscopy. Measurements from an in-house designed thermal setup revealed that covalent functionalization of nanoMIPs onto SPEs led to the most reproducible sensing capabilities. The proof of application was provided by measuring buffered solutions spiked with cTnI, which demonstrated that through monitoring changes in heat transfer at the solid-liquid interface, we can measure concentrations as low as 10 pg L-1, resulting in the most sensitive test of this type. Furthermore, preliminary data are presented for a prototype platform, which can detect cTnI with shorter measurement times and smaller sample volumes. The excellent sensor performance, versatility of the nanoMIPs, and reproducible and low-cost nature of the SPEs demonstrate that this sensor platform technology has a clear commercial route with high potential to contribute to sustainable healthcare.

Thermal Detection of Cardiac Biomarkers Heart-Fatty Acid Binding Protein and ST2 Using a Molecularly Imprinted Nanoparticle-Based Multiplex Sensor Platform.

This manuscript describes the production of molecularly imprinted polymer nanoparticles (nanoMIPs) for the cardiac biomarkers heart-fatty acid binding protein (H-FABP) and ST2 by solid-phase synthesis, and their use as synthetic antibodies in a multiplexed sensing platform. Analysis by surface plasmon resonance (SPR) shows that the affinity of the nanoMIPs is similar to that of commercially available antibodies. The particles are coated onto the surface of thermocouples and inserted into 3D-printed flow cells of different multiplexed designs. We demonstrate that it is possible to selectively detect both cardiac biomarkers within the physiologically relevant range. Furthermore, the developed sensor platform is the first example of a multiplex format of this thermal analysis technique which enables simultaneous measurements of two different compounds with minimal cross selectivity. The format where three thermocouples are positioned in parallel exhibits the highest sensitivity, which is explained by modeling the heat flow distribution within the flow cell. This design is used in further experiments and proof-of-application of the sensor platform is provided by measuring spiked fetal bovine serum samples. Because of the high selectivity, short measurement time, and low cost of this array format, it provides an interesting alternative to traditional immunoassays. The use of nanoMIPs enables a multimarker strategy, which has the potential to contribute to sustainable healthcare by improving the reliability of cardiac biomarker testing.

Design and Synthesis of Waterborne Polyurethanes.

Waterborne polyurethanes (WBPUs) have attracted increasing attention in a wide range of industrial applications because of their versatile properties as well as ecofriendly nature. Although extensive research has been carried out on WBPU synthesis, the roles of some of the key synthesis components remain unclear. In this study, through systematically controlling and fine tuning the precursor compositions and reaction conditions, over 300 WBPUs are synthesized. This research enables the roles of several key components that govern WBPU physicochemical properties and ultimately the potential WBPU applications to be identified. Using hair styling as an example, it is demonstrated that only the WBPUs with an optimal range of properties (e.g., Young's modulus >150 MPa, elongation at break: 15-300%, moisture uptake <10%) can achieve strong styling performance. To further improve the natural-feel sensory benefits in the final styling products, a number of fatty acids with different carbon chain lengths or unsaturation levels are incorporated into WBPUs. Among the ten fatty acids studied, linoleic acid is identified as the most preferred additive. Both in vitro and in vivo testing demonstrate that WBPUs with optimal properties are promising materials for developing strong, long-lasting styling products with natural feel.