Gold-plated magnetic polymers for highly specific enrichment and label-free detection of blood biomarkers under physiological conditions

Amphiphilic Polymer-Mediated Aggregation-Induced Emission Nanoparticles for Highly Sensitive Organophosphorus Pesticide Biosensing

Biosensing applications require signal reporters to be sufficiently stable and biosafe as well as highly efficient. Aggregation-induced emission (AIE) nanoparticles have proven to be capable of cell-imaging and cancer therapy; however, realizing sensitive detection of biomolecules remains a great challenge because of their instability, biotoxicity, and lack of modifiable functional groups. Herein, we report a self-assembling strategy to fabricate AIE nanoparticles (PTDNPs) through the dispersion of amphiphilic polymers (PTDs) in phosphate-buffered saline. The PTDs were prepared through radical copolymerization of N-(1,2,2-triphenylvinyl)-4-acetylaniline and dimethyl diallyl ammonium chloride. We found that the particle size, morphology, functional groups, and fluorescence property of PTDNPs can be fine-tuned. Further, PTDNPs-0.10 were chosen as signal reporters to detect organophosphorus pesticides (OPs) with the aid of gold nanoparticles. Their sensing performance on OPs is superior to that using C-dot/quantum dot/rhodamine B as the signal reporter. This study not only provides new possibilities to fabricate novel AIE nanoparticles with exceptional properties, but also facilitates the AIE nanoparticle's application for target analyte biosensing.

Plasmonic DNA hotspots made from tungsten disulfide nanosheets and gold nanoparticles for ultrasensitive aptamer-based SERS detection of myoglobin

A nanohybrid mediated SERS substrate was prepared by in-situ synthesis and assembly of gold nanoparticles (AuNPs) on exfoliated nanosheets of tungsten disulfide (WS₂) to form plasmonic hotspots. The nanohybrid surface was functionalized with specific aptamers which imparted high selectivity for the cardiac marker myoglobin (Mb). The fabricated aptasensor was read by SERS using a 532 nm laser and demonstrated significant signal enhancement, and this allowed Mb to be determined in the 10 f. mL^-1 to 0.1 μg mL^-1 concentration range. The study presents an approach to synergistically exploit the unique chemical and electromagnetic properties of both WS₂ and AuNPs for many-fold enhancement of SERS signals. Graphical abstract Schematic presentation of a nanohybrid-mediated SERS substrate prepared by in-situ assembly of gold nanoparticles (AuNPs) reduced on exfoliated nanosheets of tungsten disulfide (WS₂) to form plasmonic hot spots. Specific aptamers immobilized on the SERS surface impart high sensitivity and selectivity for the cardiac marker myoglobin (Mb).

Multiplex immunoassays using virus-tethered gold microspheres by DC impedance-based flow cytometry

Bead-based multiplex immunoassays for common use require enhanced sensitivity and effective prevention of non-specific adsorption, as well as miniaturization of the detection device. In this work, we have implemented virus-tethered gold microspheres for multiplex immunoassay applications, employing a DC impedance-based flow cytometer as a detection element. The advantages of virus-tethered gold microspheres, including excellent prevention of non-specific adsorption, are extended to signal enhancement arising from the large quantity of antibody loading on each virion, and to flexible movement of filamentous virus. Individual virus-tethered beads generate their own DC impedance and fluorescence signals, which are simultaneously detected by a chip-based microfluidic flow cytometer. This system successfully realized multiplex immunoassays involving four biomarkers: cardiac troponin I (cTnI), prostate specific antigen (PSA), creatine kinase MB (CK-MB), and myoglobin in undiluted human sera, elevating sensitivity by up to 5.7-fold compared to the beads without virus. Constructive integration between filamentous virus-tethered Au-layered microspheres and use of a microfluidic cytometer suggests a promising strategy for competitive multiplex immunoassay development based on suspension arrays.

Translocation Pathway-Dependent Assembly of Streptavidin- and Antibody-Binding Filamentous Virus-Like Particles

Compared to well-tolerated p3 fusion, the display of fast-folding proteins fused to the minor capsid p7 and the major capsid p8, as well as in vivo biotinylation of biotin acceptor peptide (AP) fused to p7, are found to be markedly inefficient using the filamentous phage. Here, to overcome such limitations, the effect of translocation pathways, amber mutation, and phage and phagemid display systems on p7 and p8 display of antibody-binding domains are examined, while comparing the level of in vivo biotinylation of AP fused to p7 or p3. Interestingly, the in vivo biotinylation of AP occurs only in p3 fusion and the fast-folding antibody-binding scaffolds fused to p7 and p8 are best displayed via a twin-arginine translocation pathway in TG1 cells. The lower the expression level of the wild-type p8 and the smaller the size of the guest protein, the better the display of Z-domain fused to the recombinant p8. The in vivo biotinylated multifunctional filamentous virus-like particles can be vertically immobilized on streptavidin (SAV)-coated microspheres to resemble cellular microvilli-like structures, which reportedly enhance protein-protein interactions due to dramatically expanded flexible surface area.