Interstitial Fluid Biomarkers’ Minimally Invasive Monitoring Using Microneedle Sensor Arrays

Skin interstitial fluid (ISF) is a biofluid with information-rich biomarkers for disease diagnosis and prognosis. Microneedle (MN) integration of sampling and instant biomarker readout hold great potential in health status monitoring and point-of-care testing (POCT). The present work describes an attractive MN sensor array for minimally invasive monitoring of ISF microRNA (miRNA) and Cu²⁺.

The MN array is made of methacrylated gelatin (GelMA) and methacrylated hyaluronic acid (MeHA), and a further divisionally encapsulated miRNA and Cu²⁺ detection system, and is cross-linked through blue-light irradiation.

The MN patch displays good mechanical properties that enable withstanding more than 0.4 N per needle, and exhibits a high swelling ratio of 700% that facilitates timely extraction of sufficient ISF for biomarker analysis. For proof-of-concept, it realizes detection of miRNAs and Cu²⁺ efficiently and quantitatively in an agarose skin and fresh porcine cadaver skin model. Given the good sampling and in situ monitoring ability, the MN array holds great promise for skin ISF-based applications.

Colorimetric Detection of Organophosphate Pesticides Based on Acetylcholinesterase and Cysteamine Capped Gold Nanoparticles as Nanozyme

Organophosphates (OPs) are neurotoxic agents also used as pesticides that can permanently block the active site of the acetylcholinesterase (AChE). A robust and sensitive detection system of OPs utilising the enzyme mimic potential of the cysteamine capped gold nanoparticles (C-AuNPs) was developed. The detection assay was performed by stepwise addition of AChE, parathion ethyl (PE)-a candidate OP, acetylcholine chloride (ACh), C-AuNPs, and 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the buffer solution.

The whole sensing protocol completes in 30-40 min, including both incubations. The Transmission Electron Microscopy (TEM) results indicated that the NPs are spherical and have an average size of 13.24 nm.

The monomers of C-AuNPs exhibited intense catalytic activity (nanozyme) for the oxidization of TMB, revealed by the production of instant blue colour and confirmed by a sharp peak at 652 nm. The proposed biosensor’s detection limit and linear ranges were 5.8 ng·mL^-1 and 11.6-92.8 ng·mL^-1, respectively, for PE. The results strongly advocate that the suggested facile colorimetric biosensor may provide an excellent platform for on-site monitoring of OPs.

A bovine nucleus pulposus explant culture model