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In this work, a 3D-framework of functionalized multi-walled carbon nanotubes (fMWCNTs) decorated with molecularly imprinted polymer (MIP), has been fabricated to achieve fast and ultrasensitive electrochemical molecular sensing. The cavity networks of MIP layer from Norfloxacin (NFX) molecules offers simultaneous identification and quantification of NFX; and thus, ensures its high selectivity. The porous structure of fMWCNT 3D-framwork effectively increases the specific surface area, and the copolymer of fMWCNTs and MIP shows synergistic effect for electrocatalytic reaction of NFX at the modified sensor. Under optimized conditions, the fabricated sensors show wide linear detection ranges of 0.003-0.391 μM and 0.391–3.125 μM, low limit of determination (LOD) of 1.58 nM, and excellent selectivity in discriminating NFX according to its structural analogues and possible interferences. Precise and fast quantification of NFX in pharmaceutical formulations (Yunnan Baiyao and Ouyi Pharmaceutical) and rat plasma samples (N = 4) suggests its simplicity and reliability. The recoveries from pharmaceutical formulations ranged from 97.36 to 109.58% with the precisions (relative standard deviations, RSD, n = 3) of 1.74–3.41%; and the recoveries from rat plasma samples ranged from 83.00 to 115.67% with RSDs (n = 3) of 0.45–10.30%. Considering the advantages of easy fabrication, and selective and sensitive detection, such sensors with different types of MIPs would be widely applied in the fields of pharmaceutical analysis, and environmental and clinical therapeutic drug monitoring.

Water-in-water (w/w) emulsions are particularly advantageous for biomedical-related applications, such as cell encapsulation, bioreactors, biocompatible storage, and processing of biomacromolecules. However, due to ultralow interfacial tension, generation and stabilization of uniform w/w droplets are challenging. In this work, we report a strategy of creating stable and size-controllable w/w droplets that can quickly form polyelectrolyte microcapsules (PEMCs) in a microfluidic device. A three-phase (inner, middle, outer) aqueous system was applied to create a stream of inner phase, which could be broken into droplets via a mechanical perturbation frequency, with size determined by the stream diameter and vibration frequency. The interfacial complexation is formed via electrostatic interaction of polycations of poly(diallyldimethylammoniumchloride) with polyanions of polystyrene sodium sulfate in the inner and outer phases. With addition of negatively charged silica nanoparticles, the stability, permeability, and mechanical strength of the PEMC shell could be well manipulated. Prepared PEMCs were verified by encapsulating fluorescein isothiocyanate-labeled dextran molecules and stimuli-triggered release by varying the pH value or osmotic pressure. A model enzyme, trypsin, was successfully encapsulated into PEMCs and released without impairing their catalytic activity. These results highlight its potential applications for efficient encapsulation, storage, delivery, and release of chemical, biological, pharmaceutical, and therapeutic agents.

To achieve an ultrasensitive biosensor, the modified nanomaterials with high specific surface area, proper chemical and electrical/optical properties are highly required. In the present work, we designed a rapid and ultrasensitive label-free electrochemical immunosensor for interleukin-6 (IL-6) detection based on nanoporous mesoporous-carbon (NMC) composite decorated with gold nanoparticles (NMC@AuNPs). The NMC served as the transducer matrix, which is modified on the surface of glassy carbon electrode (GCE), to deposit the gold nanoparticles (AuNPs). NMC is synthesized via a wrinkled SiO2-nanoparticle (wSiO2NP) assisted sacrificing strategy, which displays an interconnected 3D structure to achieve high specific surface area and abundant porous for rapid sample enrichment; meanwhile, the composited hierarchical porous structure promotes the deposition and entanglement of AuNPs to form stable NMC@AuNPs and achieve enhanced electrical conductivity. Specific antibody against IL-6 protein is immobilized onto the surface of AuNPs, based on the antibody-antigen recognition strategy, the constructed immunosensors demonstrate high sensitivity and selectivity for assay of IL-6 with a linear dynamic range of 0.5–1200 pg mL−1 and the ultralow limit of detection (LOD) of 0.14 pg mL−1. Toward the detection of IL-6 in human serum samples, this label-free biosensor with a short detection period (within 60 min, including sample processing and electrochemical measurement). Moreover, the label-free biosensor exhibited an excellent sensitivity and specificity, suggesting it possesses the potential for other biomarkers in point-of-care biosensing application.

Porous carbon-based nanomaterials have attracted much attention because of their specific structure and multifunctionality. We report on a strategy for constructing porous microparticles consisting of carbon nanotubes (CNTs) connected with honeycomb nanopores and their application for electrochemical sensors. The microdroplets containing silica nanoparticles (SiO2NPs) and CNTs are created using a microfluidic device, with droplet size and composition being tunable via the fluidic phases. Solid microparticles consisting of close-packed SiO2NPs and CNTs (SiO2NP-CNT-μPs) are obtained after water evaporation and calcination. Target honeycomb CNT-microparticles (h-CNT-μPs) are achieved after removing SiO2NPs from the SiO2NP-CNT-μPs. The glassy carbon electrodes (GCEs) modified with h-CNT-μPs and Nafion (h-CNT-μPs/Nafion/GCEs) show highly enhanced specific surface area and electrocatalytic activity. Under optimized conditions, h-CNT-μPs/Nafion/GCEs exhibit linear response to methyl parathion (MP) in the concentration ranges of 0.3–20.0 μM and 20.0–150.0 μM with the limit of detection of 0.092 μM (S/N = 3), showing good sensitivity, selectivity, reproducibility and anti-interference. Prepared electrochemical sensors have also been applied for determination of MP in practical samples of tomato and cabbage, showing comparable results to those measured using a high-performance liquid chromatography (HPLC). This proposed strategy is highly efficient for constructing microscale sensor units considering their size, uniformity and compositions, providing a reliable way for monitoring pesticide and other active components in fruits, vegetables and other scenarios of agricultural and industrial production.