Sensing, Imaging, and Therapeutic Strategies Endowing by Conjugate Polymers for Precision Medicine

Conjugated polymers (CPs) have promising applications in biomedical fields, such as disease monitoring, real-time imaging diagnosis, and disease treatment. As a promising luminescent material with tunable emission, high brightness and excellent stability, CPs are widely used as fluorescent probes in biological detection and imaging. Rational molecular design and structural optimization have broadened absorption/emission range of CPs, which are more conductive for disease diagnosis and precision therapy. This review provides a comprehensive overview of recent advances in the application of CPs, aiming to elucidate their structural and functional relationships. The fluorescence properties of CPs and the mechanism of detection signal amplification are first discussed, followed by an elucidation of their emerging applications in biological detection. Subsequently, CPs-based imaging systems and therapeutic strategies are illustrated systematically. Finally, recent advancements in utilizing CPs as electroactive materials for bioelectronic devices are also investigated. Moreover, the challenges and outlooks of CPs for precision medicine are discussed. Through this systematic review, it is hoped to highlight the frontier progress of CPs and promote new breakthroughs in fundamental research and clinical transformation.

A novel β-cyclodextrin-assisted enhancement strategy for portable and sensitive detection of miR-21 in human serum

Benefiting from our discovery that β-cyclodextrin (β-CD) could enhance the catalytic activity of invertase through hydrogen bonding to improve detection sensitivity, a highly sensitive and convenient biosensor for the detection of miR-21 was proposed, which is based on the simplicity of reading signals from a personal glucose meter (PGM), combined with self-assembled signal amplification probes and the performance of β-CD as an enhancer. In the presence of miR-21, magnetic nanoparticle coupled capture DNA (MNPs-cDNA) could capture it and then connect assist DNA/H1-invertase (aDNA/H1) and self-assembled signal amplification probes (H1/H2) in turn. As a result, a "super sandwich" structure was formed. The invertase on MNPs-cDNA could catalyze the hydrolysis of sucrose to glucose and this catalytic process could be enhanced by β-CD. The PGM signal exhibited a linear correlation with miR-21 concentration within the range of 25 pmol L-1 to 3 nmol L-1, and the detection limit was as low as 5 pmol L-1 with high specificity. Moreover, the recoveries were 103.82-124.65% and RSD was 2.59-6.43%. Furthermore, the biosensor was validated for the detection of miR-21 in serum, and the results showed that miR-21 levels in serum samples from patients with Diffuse Large B-Cell Lymphoma (DLBCL) (n = 12) were significantly higher than those from healthy controls (n = 12) (P < 0.001). Therefore, the ingenious combination of PGM-based signal reading, self-assembled signal amplification probes and β-CD as an enhancer successfully constructed a convenient, sensitive and specific biosensing method, which is expected to be applied to clinical diagnosis.

Nanomaterials in electrochemical nanobiosensors of miRNAs

Nanomaterial-based biosensors have received significant attention owing to their unique properties, especially enhanced sensitivity. Recent advancements in biomedical diagnosis have highlighted the role of microRNAs (miRNAs) as sensitive prognostic and diagnostic biomarkers for various diseases. Current diagnostics methods, however, need further improvements with regards to their sensitivity, mainly due to the low concentration levels of miRNAs in the body. The low limit of detection of nanomaterial-based biosensors has turned them into powerful tools for detecting and quantifying these biomarkers. Herein, we assemble an overview of recent developments in the application of different nanomaterials and nanostructures as miRNA electrochemical biosensing platforms, along with their pros and cons. The techniques are categorized based on the nanomaterial used.

Electrostatic assemblies of molecularly imprinted polymers on the surface of electrospun nanofiber membranes for the point-of-care detection of thiodiglycol, a sulfur mustard poisoning metabolic marker

In this study, molecularly imprinted polymers (MIPs) were assembled on the surface of ethylene imine polymer (PEI)/poly(vinyl alcohol) (PVA) electrospun nanofiber membranes for the point-of-care testing (POCT) of thiodiglycol (TDG), a sulfur mustard poisoning metabolic marker, using concentrated gold nanoparticles (AuNPs) as the signal reporting units. The MIPs/PEI/PVA nanofiber membranes could capture TDG specifically through the recognition interaction between MIPs and TDG. Then, AuNPs were adsorbed onto the MIPs/PEI/PVA nanofiber membranes through the Au-S interaction between TDG and AuNPs to produce a visible red color. In order to improve the sensitivity, the silver-enhanced solutions were used to deepen the color of the nanofiber membranes and the software Image J was used to read the gray value as the signal response for subsequent analysis. There was a good linear relationship between the color change of the MIPs/PEI/PVA nanofiber membranes and the TDG concentration from 0.1 ng mL^-1 to 1.0 μg mL^-1, and the limit of detection was 38 pg mL^-1. This method was applied for the selective detection of TDG in urine, showing great potential for the clinical diagnosis of mustard gas poisoning.

Multifunctional Hybrid Nanozymes for Magnetic Enrichment and Bioelectrocatalytic Sensing of Circulating Tumor RNA during Minimal Residual Disease Monitoring

Iron oxide nanozymes are a form of nanomaterial with both superparamagnetic and enzyme-mimicking properties. Ongoing research efforts have been made to create multifunctional iron oxide hybrid nanozymes with auxiliary properties through biomolecular modifications. Such iron oxide hybrid nanozymes can be useful for rapid and cost-effective analysis of circulating tumor nucleic acids (ctNAs) in patient liquid biopsies during minimal residual disease (MRD) monitoring of cancer recurrence. Herein, the use of streptavidin-modified iron oxide hybrid nanozymes is reported for magnetic enrichment and bioelectrocatalytic sensing of three prostate cancer (PCa) ctRNA biomarkers with high detection specificity and sensitivity (10 copies) over an ultrabroad dynamic range (five orders of magnitude). Furthermore, the feasibility of ctRNA analysis for pre- and post-cancer treatment MRD monitoring is demonstrated using PCa urinary liquid biopsy samples.

Graphene-oxide-based bioassay for the fluorometric determination of agrC gene transcription in methicillin-resistant Staphylococcus aureus that uses nicking-enzyme-assisted target recycling and a hybridization chain reaction

Herein, we report the development of a graphene-oxide-based (GO-based) fluorescent bioassay for determining agrC gene transcription (mRNA) in methicillin-resistant Staphylococcus aureus (MRSA). The design is based on nicking-enzyme-assisted (Nb.BbvcI-assisted) target recycling amplification (NATR) and a hybridization chain reaction (HCR). The system consists of a helper probe (HP), a molecular beacon (MB) probe, four hairpins, and endonuclease Nb.BbvcI, which plays a role in target recycling and signal amplification. In the absence of the target, all of the carboxyfluorescein-labeled (FAM-labeled) hairpins are adsorbed through π-stacking interactions onto the surface of GO, resulting in FAM signal quenching. When the target is added, three nucleic acid chains hybridize together to form a triple complex that is recognized by Nb.BbvCI. The MB probe is then cleaved by Nb.BbvCI to generate an HP/target complex and two new DNA fragments; the former is hybridized to another MB probe and enters the next round of reaction. The two newly reproduced DNA fragments induce a HCR with the assistance of hairpins 1-4 to create double-stranded DNA (dsDNA) products. These dsDNA products are repelled by GO and generate strong fluorescence at excitation/emission wavelengths of 480/514 nm. Importantly, synergy between FAM and the dsDNA-SYBR Green I duplex structure led to significantly amplified fluorescence and enhanced sensitivity. The bioassay showed a detection limit of 7.5 fM toward the target and a good linearity in the 10 fM to 100 pM range. The developed method was applied to monitor biofilm formation and study the mechanism of drug action, with satisfactory results obtained.

Engineered G-Quadruplex-Embedded Self-Quenching Probes Regulate Single Probe-Based Multiplex Isothermal Amplification to Light Road Lamp Probes for Sensitized Determination of microRNAs

Design of oligonucleotide probe-based isothermal amplification with the ability to identify miRNA biomarkers is crucial for molecular diagnostics. In this work, we engineered a miRNA-21-responsive G-quadruplex-embedded self-quenching probe (GE-SQP) that can regulate single probe-based multiplex amplifications. The free GE-SQP is tightly locked in a quenching state with no active G-quadruplexes. Introduction of target miRNA to hybridize with GE-SQP would induce a multiplex isothermal amplification to significantly build a lot of one-bulb-contained road lamp probe (OC-RLP) and two-bulb-contained road lamp probe (TC-RLP) using G-quadruplex as the lamp bulb. When lightened by thioflavin T (ThT), beams of fluorescence were emitted to show the presented miRNA-21. Specially, the whole amplification is only a one probe-involved one-step reaction without any wasted species. The mix-to-detection and all-in amplification behavior allows the sensing system a maximally maintained operation simplicity and high assay performance. In such a way, the detection range of miRNA-21 is from 1 fM to 1 nM with a limit of detection of 0.86 fM. The practicability was demonstrated by determining miRNA-21 from serum samples with acceptable results. We expect that this method can open a new avenue for exploring advanced biosensors with improved analytical performances.

Preparation of a molecularly imprinted test strip for point-of-care detection of thiodiglycol, a sulfur mustard poisoning metabolic marker

Conventional methods for the detection of the sulfur mustard poisoning metabolic marker, thiodiglycol (TDG), require expensive instruments and reagents as well as professional operators. To address these problems, a novel test strip based on a molecularly imprinted sensitive membrane (MIM) was developed in this work for point-of-care (POC) detection of TDG. The TDG test strip was prepared conveniently by coating molecular imprinted polymers (MIPs) on a nitrocellulose membrane. When the sample contained TDG, the MIPs could specifically bind with TDG. A great number of AuNPs (AuNPs) could then be adsorbed on the test strip via the formation of an Au-S bond between TDG and AuNPs, giving the test strip the obvious red color of AuNPs. In the absence of TDG, the test strip exhibited much lighter color because it could not adsorb AuNPs. By monitoring the color change of the test strip, TDG could be detected from 1.0 ng/mL to 100.0 μg/mL with a detection limit of 0.23 ng/mL (3σ) under the optimal conditions (the molar ratio of TDG to MAA was 1:2; the eluent was chloroform; the elution time was 50 min; the reaction time between MIPs and TDG was 15 min; the adsorption time of AuNPs was 40 min; the temperature of the reaction system was 35 °C). This method has excellent selectivity and has been used to detect TDG in urine, showing great potential for POC detection of TDG in clinical samples.

Multiple adsorption properties of aptamers on metal-organic frameworks for nucleic acid assay

Enrichment and detection of circulating free nucleic acids in biological samples have gained great attention for disease diagnosis or prognostic evaluation. Nanoscale metal-organic frameworks (NMOFs) have been used for aptamer-based nucleic acid sensing. In this work, different NMOFs, including ZIF-8, MIL-88, MIL-100, MIL-101, as well as Eu-TDA and Tb-TDA [prepared by the coordination of 2,2'-thiodiacetic acid (TDA) and Eu³⁺ or Tb³⁺], were investigated in nucleic acid sensing by employing their aptamer adsorption ability and fluorescence quenching capacity for the labeled dyes. Two types of dye aptamer, FAM-labeled aptamer (FAM-Ap) and TexasRedaptamer (TexasRed-Ap) were designed, and their adsorption properties on NMOFs-were compared. It was found that the TexasRed-Ap can be well used for nucleic acid (miR-21) extraction and sensing by linking with a pH-responsive nucleotide chain (TexasRed-Ap-pH) or with an additional random chain ssDNA-1' (TexasRed-Ap-a). After interacted with the target miR-21 in biosamples, the TexasRed-dsDNA + NMOFs composites can be collected, and the formed TexasRed-dsDNA can be released by changing pH value or addition of ssDNA-1, which is matched with ssDNA-1'. A linear relationship from 0.1 to 200 pM for miR-21 detection was obtained. The results show that the NMOFs can be used as promising platforms for nucleic acid extraction and fluorescent sensing.