Utilisation of molecularly imprinting technology for the detection of glucocorticoids for a point of care surface plasmon resonance (SPR) device

Recent Advances on Rapid Detection Methods of Steroid Hormones in Animal Origin Foods

Animal-derived foods constitute a crucial source of nutrients for humans. The judicious application of steroid hormones in the breeding process can serve multiple purposes, including growth promotion, weight gain, and anti-inflammatory effects, among others. However, excessive misuse poses a considerable risk to both food safety and consumer health. Currently, the primary means of detecting steroid hormones involve liquid chromatography, gas chromatography, and their combination with mass spectrometry. These methods necessitate advanced instrumentation, intricate pretreatment procedures, and the expertise of specialized laboratories and technicians. In recent years, the swift evolution of analytical science, technology, and instrumentation has given rise to various rapid detection techniques for steroid hormone residues, providing a robust technical foundation for ensuring food safety. This review commences by delineating the roles of steroid hormones, the associated residue hazards, and the pertinent residue restriction standards. Subsequently, it delves deeply into the analysis of the most recent rapid detection techniques for steroid hormones, ultimately culminating in an assessment of the challenges currently confronting the field, along with an exploration of potential future advancements. We sincerely hope that this review will inspire and provide valuable insights to the pertinent researchers.

Development of molecularly imprinted polymers for the detection of human chorionic gonadotropin

Diagnostic pregnancy tests are the most widely used immunoassays for home-based use. These tests employ the well-established lateral flow assay (LFA) technique, reminiscent of affinity chromatography relying on the dual action of two orthogonal anti-hCG antibodies. Immunoassays suffer from several drawbacks, including challenges in antibody manufacturing, suboptimal accuracy, and sensitivity to adverse storing conditions. Additionally, LFAs are typically designed for single use, as the LFA technique is non-reusable. An alternative to overcome these drawbacks is to leverage molecularly imprinted polymer (MIP) technology to generate polymer-based hCG-receptors and, subsequently, non-bioreceptor-based tests. Here, we report the development of MIP nanogels for hCG detection, exploiting epitopes and magnetic templates for high-yielding dispersed phase imprinting. The resulting nanogels were designed for orthogonal targeting of two immunogenic epitopes (SV and PQ) and were thoroughly characterized with respect to physical properties, binding affinity, specificity, and sensitivity. Molecular dynamics simulations indicated a pronounced conformational overlap between the templates and the epitopes in the native protein, supporting their suitability for templating cavities for hCG recognition. Quartz crystal microbalance (QCM)-based binding tests and kinetic interaction analysis by surface plasmon resonance (SPR) revealed nanomolar dissociation constants for the MIP nanogels and their corresponding template peptides and low uptake of lutenizing hormone (LH), structurally resembling to hCG. Receptor reusability was demonstrated in the multicycle SPR sensing mode using a low pH regeneration buffer. The results suggest the feasibility of using imprinted nanogels as a class of cost-effective, stable alternatives to natural antibodies for hCG detection. We foresee applications of these binders with respect to reusable pregnancy tests and other hCG-related disease diagnostics.

Molecularly imprinted nanogels as synthetic recognition materials for the ultrasensitive detection of periodontal disease biomarkers

Periodontal disease affects supporting dental structures and ranks among one of the top most expensive conditions to treat in the world. Moreover, in recent years, the disease has also been linked to cardiovascular and Alzheimer's diseases. At present, there is a serious lack of accurate diagnostic tools to identify people at severe risk of periodontal disease progression. Porphyromonas gingivalis is often considered one of the most contributing factors towards disease progression. It produces the Arg- and Lys-specific proteases Rgp and Kgp, respectively. Within this work, a short epitope sequence of these proteases is immobilised onto a magnetic nanoparticle platform. These are then used as a template to produce high-affinity, selective molecularly imprinted nanogels, using the common monomers N-tert-butylacrylamide (TBAM), N-isopropyl acrylamide (NIPAM), and N-(3-aminopropyl) methacrylamide hydrochloride (APMA). N,N-Methylene bis(acrylamide) (BIS) was used as a crosslinking monomer to form the interconnected polymeric network. The produced nanogels were immobilised onto a planar gold surface and characterised using the optical technique of surface plasmon resonance. They showed high selectivity and affinity towards their template, with affinity constants of 79.4 and 89.7 nM for the Rgp and Kgp epitope nanogels, respectively. From their calibration curves, the theoretical limit of detection was determined to be 1.27 nM for the Rgp nanogels and 2.00 nM for the Kgp nanogels. Furthermore, they also showed excellent selectivity against bacterial culture supernatants E8 (Rgp knockout), K1A (Kgp knockout), and W50-d (wild-type) strains in complex medium of brain heart infusion (BHI).

A Review Study on Molecularly Imprinting Surface Plasmon Resonance Sensors for Food Analysis

Surface plasmon resonance (SPR) sensors have emerged as a powerful tool in biosensing applications due to their ability to provide sensitive and real-time detection of chemical and biological analytes. This review focuses on the development and application of molecularly imprinted polymer (MIP)-based SPR sensors for food analysis. By combining the high selectivity of molecular imprinting techniques with the sensitivity of SPR, these sensors offer significant advantages in detecting food contaminants and other target molecules. The article covers the basic principles of SPR, the role of MIPs in sensor specificity, recent advancements in this sensor development, and food applications. Furthermore, the potential for these sensors to contribute to food safety and quality control was explored, showcasing their adaptability to complex food matrices. The review concluded the future directions and challenges of SPR-MIP sensors in food analysis, emphasizing their promise in achieving high-throughput, cost-effective, and portable sensing solutions.

Enzyme Activity Inhibition of α-Amylase Using Molecularly Imprinted Polymer (MIP) Hydrogel Microparticles

Molecularly imprinted polymers (MIPs) are a class of synthetic recognition materials that offer a cost-effective and robust alternative to antibodies. While MIPs have found predominant use in biosensing and diagnostic applications, their potential for alternative uses, such as enzyme inhibition, remains unexplored. In this work, we synthesized a range of acrylamide-based hydrogel MIP microparticles (35 μm) specific for the recognition of α-amylase. These MIPs also showed good selectivity toward the target protein with over 96% binding of the target protein, compared with the control nonimprinted polymer (NIP) counterparts. Specificity of the MIPs was determined with the binding of nontarget proteins, trypsin, human serum albumin (HSA), and bovine serum albumin (BSA). The MIPs were further evaluated for their ability to inhibit α-amylase enzymatic activity, showing a significant decrease in activity. These findings highlight the potential of MIPs as enzyme inhibitors, suggesting an innovative application beyond their conventional use.

Maximizing the Accuracy of Equilibrium Dissociation Constants for Affinity Complexes: From Theory to Practical Recommendations

The equilibrium dissociation constant (Kd) is a major characteristic of affinity complexes and one of the most frequently determined physicochemical parameters. Despite its significance, the values of Kd obtained for the same complex under similar conditions often exhibit considerable discrepancies and sometimes vary by orders of magnitude. These inconsistencies highlight the susceptibility of Kd determination to large systematic errors, even when random errors are small. It is imperative to both minimize and quantitatively assess the systematic errors inherent in Kd determination. Traditionally, Kd values are determined through nonlinear regression of binding isotherms. This analysis utilizes three variables: concentrations of two reactants and a fraction R of unbound limiting reactant. The systematic errors in Kd arise directly from systematic errors in these variables. Therefore, to maximize the accuracy of Kd, this study thoroughly analyzes the sources of systematic errors within the three variables, including (i) non-additive signals to calculate R, (ii) mis-calibrated experimental instruments, (iii) inaccurate calibration parameters, (iv) insufficient incubation time, (v) unsaturated binding isotherm, (vi) impurities in the reactants, and (vii) solute adsorption onto surfaces. Through this analysis, we illustrate how each source contributes to inaccuracies in the determination of Kd and propose strategies to minimize these contributions. Additionally, we introduce a method for quantitatively assessing the confidence intervals of systematic errors in concentrations, a crucial step toward quantitatively evaluating the accuracy of Kd. While presenting original findings, this paper also reiterates the fundamentals of Kd determination, hence guiding researchers across all proficiency levels. By shedding light on the sources of systematic errors and offering strategies for their mitigation, our work will help researchers enhance the accuracy of Kd determination, thereby making binding studies more reliable and the conclusions drawn from such studies more robust.

Assessment of Acrylamide Levels by Advanced Molecularly Imprinted Polymer-Imprinted Surface Plasmon Resonance (SPR) Sensor Technology and Sensory Quality in Homemade Fried Potatoes

This study evaluated acrylamide (AA) levels and various quality parameters in homemade fried potatoes prepared in different sizes by integrating principles from the Slow Food Movement with advanced sensor technology. To this aim, a surface plasmon resonance (SPR) sensor based on a molecularly imprinted polymer (MIP) was first developed for the determination of AA in homemade fried potatoes at low levels, and the AA levels in the samples were established. First of all, monolayer formation of allyl mercaptane on the SPR chip surface was carried out to form double bonds that could polymerize on the chip surface. AA-imprinted SPR chip surfaces modified with allyl mercaptane were prepared via UV polymerization using ethylene glycol dimethacrylate (EGDMA) as a cross-linker, N,N'-azobisisobutyronitrile (AIBN) as an initiator, and methacryloylamidoglutamicacid (MAGA) as a monomer. The prepared AA-imprinted and nonimprinted surfaces were characterized by atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy methods. The SPR sensor indicated linearity in the range of 1.0 × 10-9-5.0 × 10-8 M with a detection limit (LOD) of 3.0 × 10-10 M in homemade fried potatoes, and the SPR sensor demonstrated high selectivity and repeatability in terms of AA detection. Additionally, the highest AA level was observed in the potato sample belonging to the T1 group, at 15.37 nM (p < 0.05), and a strong and positive correlation was found between AA levels and sensory parameters, the a* value, the ΔE value, and the browning index (BI) (p < 0.05).

The Amount of Cross-Linker Influences Affinity and Selectivity of NanoMIPs Prepared by Solid-Phase Polymerization Synthesis

The cross-linker methylene-bis-acrylamide is usually present in nanoMIPs obtained by solid-phase polymerization synthesis at 2 mol% concentration, with very few exceptions. Here, we studied the influence of variable amounts of methylene-bis-acrylamide in the range between 0 (no cross-linker) and 50 mol% concentration on the binding properties of rabbit IgG nanoMIPs. The binding parameters were determined by equilibrium binding experiments and the results show that the degree of cross-linking defines three distinct types of nanoMIPs: (i) those with a low degree of cross-linking, including nanoMIPs without cross-linker (0-05 mol%), showing a low binding affinity, high density of binding sites, and low selectivity; (ii) nanoMIPs with a medium degree of cross-linking (1-18 mol%), showing higher binding affinity, low density of binding sites, and high selectivity; (iii) nanoMIPs with a high degree of cross-linking (32-50 mol%), characterized by non-specific nanopolymer-ligand interactions, with low binding affinity, high density of binding sites, and no selectivity. In conclusion, the results are particularly relevant in the synthesis of high-affinity, high-selectivity nanoMIPs as they demonstrate that a significant gain in affinity and selectivity could be achieved with pre-polymerization mixtures containing quantities of cross-linker up to 10-20 mol%, well higher than those normally used in this technique.