Dual Biomimetic Recognition-Driven Plasmonic Nanogap-Enhanced Raman Scattering for Ultrasensitive Protein Fingerprinting and Quantitation

Epitope-imprinted biomaterials with tailor-made molecular targeting for biomedical applications

Molecular imprinting technology (MIT), a synthetic strategy to create tailor-made molecular specificity, has recently achieved significant advancements. Epitope imprinting strategy, an improved MIT by imprinting the epitopes of biomolecules (e.g., proteins and nucleic acids), enables to target the entire molecule through recognizing partial epitopes exposed on it, greatly expanding the applicability and simplifying synthesis process of molecularly imprinted polymers (MIPs). Thus, epitope imprinting strategy offers promising solutions for the fabrication of smart biomaterials with molecular targeting and exhibits wide applications in various biomedical scenarios. This review explores the latest advances in epitope imprinting techniques, emphasizing selection of epitopes and functional monomers. We highlight the significant improvements in specificity, sensitivity, and stability of these materials, which have facilitated their use in bioanalysis, clinical therapy, and pharmaceutical development. Additionally, we discuss the application of epitope-imprinted materials in the recognition and detection of peptides, proteins, and cells. Despite these advancements, challenges such as template complexity, imprinting efficiency, and scalability remain. This review addresses these issues and proposes potential directions for future research to overcome these barriers, thereby enhancing the efficacy and practicality of epitope molecularly imprinting technology in biomedical fields.

PSMA-Targeting Imprinted Nanogels for Prostate Tumor Localization and Imaging

Prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancer cells and tumor vasculature, making it an important biomarker. However, conventional PSMA-targeting agents like antibodies and small molecules have limitations. Antibodies exhibit instability and complex production, while small molecules show lower specificity and higher toxicity. Herein, this work develops a novel PSMA-targeting synthetic antibody to address prior limitations. This work synthesizes fluorescently labelled, N-isopropylacrylamide-based epitope imprinted nanogels (MIP-M) using a dispersion of magnetic nanoparticles as template carriers with a linear epitope from PSMA's extracellular apical domain as the template. MIP-M demonstrates high binding affinities for both the epitope template (apparent KD = 6 × 10-10 м) and PSMA (apparent KD = 2.5 × 10-9 м). Compared to reference peptides and human serum albumin, MIP-M indicates high specificity. Flow cytometry and confocal laser scanning microscopy comparing cell lines displaying normal (PC3) and enhanced (LNCaP) PSMA expression levels, revealed that MIP-M and a PSMA antibody exhibits comparable binding preferences for the latter cell line. Moreover, MIP-M demonstrates selectivity on par with the PSMA antibody for targeting PSMA-positive prostate tumor over normal tissue, enabling discrimination. This MIP-M addresses stability, production, specificity and toxicity limitations of prior targeting agents and offer a promising alternative for PSMA-directed cancer diagnosis and treatment.

Machine learning-assisted label-free colorectal cancer diagnosis using plasmonic needle-endoscopy system

Early and accurate detection of colorectal cancer (CRC) is critical for improving patient outcomes. Existing diagnostic techniques are often invasive and carry risks of complications. Herein, we introduce a plasmonic gold nanopolyhedron (AuNH)-coated needle-based surface-enhanced Raman scattering (SERS) sensor, integrated with endoscopy, for direct mucus sampling and label-free detection of CRC. The thin and flexible stainless-steel needle is coated with polymerized dopamine, which serves as an adhesive layer and simultaneously initiates the nucleation of gold nanoparticle (AuNP) seeds on the needle surface. The AuNP seeds are further grown through a surface-directed reduction using Au ions-hydroxylamine hydrochloride solution, resulting in the formation of dense AuNHs. The formation mechanism of AuNHs and the layered structure of the plasmonic needle-based SERS (PNS) sensor are thoroughly analyzed. Furthermore, a strong field enhancement of the PNS sensor is observed, amplified around the edges of the polyhedral shapes and at nanogap sites between AuNHs. The feasibility of the PNS sensor combined with endoscopy system is further investigated using mouse models for direct colonic mucus sampling and verifying noninvasive label-free classification of CRC from normal controls. A logistic regression-based machine learning method is employed and successfully differentiates CRC and normal mice, achieving 100% sensitivity, 93.33% specificity, and 96.67% accuracy. Moreover, Raman profiling of metabolites and their correlations with Raman signals of mucus samples are analyzed using the Pearson correlation coefficient, offering insights for identifying potential cancer biomarkers. The developed PNS-assisted endoscopy technology is expected to advance the early screening and diagnosis approach of CRC in the future.

Recent advances of biocompatible optical nanobiosensors in liquid biopsy: towards early non-invasive diagnosis

Liquid biopsy is a non-invasive diagnostic method that can reduce the risk of complications and offers exceptional benefits in the dynamic monitoring and acquisition of heterogeneous cell population information. Optical nanomaterials with excellent light absorption, luminescence, and photoelectrochemical properties have accelerated the development of liquid biopsy technologies. Owing to the unique size effect of optical nanomaterials, their improved optical properties enable them to exhibit good sensitivity and specificity for mitigating signal interference from various molecules in body fluids. Nanomaterials with biocompatible and optical sensing properties play a crucial role in advancing the maturity and diversification of liquid biopsy technologies. This article offers a comprehensive review of recent advanced liquid biopsy technologies that utilize novel biocompatible optical nanomaterials, including fluorescence, colorimetric, photoelectrochemical, and Raman broad-spectrum-based biosensors. We focused on liquid biopsy for the most significant early biomarkers in clinical medicine, and specifically reviewed reports on the effectiveness of optical nanosensing technology in the detection of real patient samples, which may provide basic evidence for the transition of optical nanosensing technology from engineering design to clinical practice. Furthermore, we introduced the integration of optical nanosensing-based liquid biopsy with modern devices, such as smartphones, to demonstrate the potential of the technology in portable clinical diagnosis.

Multifunctional Self-Signaling nanoMIP and Its Application for a Washing-Free Assay of Human Angiotensin-Converting Enzyme 2

Molecular imprinting techniques have attracted a lot of attention as a potential biomimetic technology, but there are still challenges in protein imprinting. Herein, multifunctional nanosized molecularly imprinted polymers (nanoMIPs) for human angiotensin-converting enzyme 2 (ACE2) were prepared by epitope imprinting of magnetic nanoparticles-anchored peptide (magNP-P) templates, which were further applied to construct a competitive displacement fluorescence assay toward ACE2. A cysteine-flanked dodecapeptide sequence was elaborately selected as an epitope for ACE2, which was immobilized onto the surface of magnetic nanoparticles and served as a magNP-P template for imprinting. During polymerization, fluorescent monomers were introduced to endow fluorescence responsiveness to the prepared self-signaling nanoMIPs. A competitive displacement fluorescence assay based on the nanoMIPs was established and operated in a washing-free manner, yielding a wide range for ACE2 (0.1-6.0 pg/mL) and a low detection limit (0.081 pg/mL). This approach offers a promising avenue in the preparation of nanoMIPs for macromolecule recognition and expands potential application of an MIP in the detection of proteins as well as peptides.

An outlier removal method based on PCA-DBSCAN for blood-SERS data analysis

Surface-enhanced Raman spectroscopy (SERS) has shown promising potential in cancer screening. In practical applications, Raman spectra are often affected by deviations from the spectrometer, changes in measurement environments, and anomalies in spectrum characteristic peak intensities due to improper sample storage. Previous research has overlooked the presence of outliers in categorical data, leading to significant impacts on model learning outcomes. In this study, we propose a novel method, called Principal Component Analysis and Density Based Spatial Clustering of Applications with Noise (PCA-DBSCAN) to effectively remove outliers. This method employs dimensionality reduction and spectral data clustering to identify and remove outliers. The PCA-DBSCAN method introduces adjustable parameters (Eps and MinPts) to control the clustering effect. The effectiveness of the proposed PCA-DBSCAN method is verified through modeling on outlier-removed datasets. Further refinement of the machine learning model and PCA-DBSCAN parameters resulted in the best cancer screening model, achieving 97.41% macro-average recall and 97.74% macro-average F1-score. This paper introduces a new outlier removal method that significantly improves the performance of the SERS cancer screening model. Moreover, the proposed method serves as inspiration for outlier detection in other fields, such as biomedical research, environmental monitoring, manufacturing, quality control, and hazard prediction.

Research Status in the Use of Surface-Enhanced Raman Scattering (SERS) to Detect Pesticide Residues in Foods and Plant-Derived Chinese Herbal Medicines

Surface-enhanced Raman scattering (SERS) technology has unique advantages in the rapid detection of pesticides in plant-derived foods, leading to reduced detection limits and increased accuracy. Plant-derived Chinese herbal medicines have similar sources to plant-derived foods; however, due to the rough surfaces and complex compositions of herbal medicines, the detection of pesticide residues in this context continues to rely heavily on traditional methods, which are time consuming and laborious and are unable to meet market demands for portability. The application of flexible nanomaterials and SERS technology in this realm would allow rapid and accurate detection in a portable format. Therefore, in this review, we summarize the underlying principles and characteristics of SERS technology, with particular focus on applications of SERS for the analysis of pesticide residues in agricultural products. This paper summarizes recent research progress in the field from three main directions: sample pretreatment, SERS substrates, and data processing. The prospects and limitations of SERS technology are also discussed, in order to provide theoretical support for rapid detection of pesticide residues in Chinese herbal medicines.

A highly selective and sensitive sensor for promethazine based on molecularly imprinted interface coated Au/Sn bimetal nanoclusters functionalized acupuncture needle microelectrode

Promethazine (PMZ) is an effective antihistamine that is used as a nerve tranquilizer to treat mental disorders. However, drug abuse causes harm to the human body and also pollutes the environment to a certain extent. Therefore, it is crucial to develop a highly selective and sensitive biosensor for PMZ determination. An acupuncture needle (AN) was used as an electrode in 2015, and further research on the electrode's essence in electrochemistry is needed. In this work, a sensor based on a surface imprinted film coordinated Au/Sn biometal was first fabricated on AN via electrochemistry. The obtained cavities showed complementary and suitable sites for "N atom" electron transfer through the phenyl ring structure in promethazine, which is rigorous for the configuration near the interface. Under the optimal conditions, MIP/Au/Sn/ANE exhibits a good linear relationship in the range of 0.5 μM-500 μM, and the detection limit (LOD) is 0.14 μM (S/N = 3). The sensor exhibits good repeatability, stability, and selectivity and can be successfully used to analyze and detect PMZ in human serum and environmental water. The findings are scientifically significant for AN electrochemistry and the sensors have potential for in vivo medicamentosus monitoring in the future.

Molecularly imprinted and cladded polymers for constructing a portable plasmonic immunoassay for peptides in biofluids

Using two molecularly imprinted and cladded polymers (cMIPs), an inexpensive, fast and portable plasmonic immuno-sandwich assay (PISA) was rationally developed for high-specificity and ultra-sensitive detection of C-peptide in urine. The dual cMIPs-based PISA allowed healthy individuals to be distinguished from diabetes patients and exhibited several significant merits over existing immunoassays, holding great promise in clinical diagnosis.