Development of a synthesis strategy for sulfamethoxazole derivatives and their coupling with hydrogel microparticles

Sulfonamides were the first synthetic antibiotics broadly applied in veterinary and human medicine. Their increased use over the last few decades and limited technology to degrade them after entering the sewage system have led to their accumulation in the environment. A new hydrogel microparticle based biosensing application for sulfonamides is developed to overcome existing labour-intensive, and expensive detection methods to analyse and quantify their environmental distribution. This biosensing assay is based on the soft colloidal probe principle and requires microparticle functionalization strategies with target molecules. In this study, we developed a step-wise synthesis approach for sulfamethoxazole (SMX) derivatives in high yield, with SMX being one of the most ubiquitous sulfonamide antibiotics. After de novo synthesis of the SMX derivative, two coupling schemes to poly(ethylene glycol) (PEG) hydrogel microparticles bearing maleimide and thiol groups were investigated. In one approach, we coupled a cysteamine linker to a carboxyl group at the SMX derivative allowing for subsequent binding via the thiol-functionality to the maleimide groups of the microparticles in a mild, high-yielding thiol-ene "click" reaction. In a second approach, an additional 1,11-bis(maleimido)-3,6,9-trioxaundecane linker was coupled to the cysteamine to target the hydrolytically more stable thiol-groups of the microparticles. Successful PEG microparticle functionalization with the SMX derivatives was proven by IR spectroscopy and fluorescence microscopy. SMX-functionalized microparticles will be used in future applications for sulfonamide detection as well as for pull-down assays and screenings for new sulfomethoxazole binding targets.

Multifunctional Gel Films of Marine Polysaccharides Cross-Linked with Poly-Metal Ions for Wound Healing

The development of an efficient and convenient material to improve skin tissue regeneration is a major challenge in healthcare. Inspired by the theory of moist wound healing, portable chitooligosaccharide (COS)/sodium alginate (SA) dual-net gel films containing multiple metal ions were prepared by a casting and in-situ spray method, which can be used to significantly promote wound healing without the use of therapeutic drugs. A variety of divalent cations was introduced in this experiment to improve the advantages of each metal ion by forming metal ion chelates with COS. Moreover, the physicochemical properties and antioxidant properties of nIon²⁺-COS/SA gel films were systematically characterized and evaluated by in vitro experiments. The gel films showed good antibacterial activity against Gram-negative and Gram-positive bacteria. In addition, the gel films showed good cytocompatibility in cellular experiments, and the gel films with Zn²⁺ and Sr²⁺ addition significantly accelerated wound healing in whole skin defect model experiments. Therefore, this nIon²⁺-COS/SA gel film is an ideal candidate material for wound dressing.

Label-free electrochemical microfluidic biosensors: futuristic point-of-care analytical devices for monitoring diseases

The integration of microfluidics with electrochemical analysis has resulted in the development of single miniaturized detection systems, which allows the precise control of sample volume with multianalyte detection capability in a cost- and time-effective manner. Microfluidic electrochemical sensing devices (MESDs) can potentially serve as precise sensing and monitoring systems for the detection of molecular markers in various detrimental diseases. MESDs offer several advantages, including (i) automated sample preparation and detection, (ii) low sample and reagent requirement, (iii) detection of multianalyte in a single run, (iv) multiplex analysis in a single integrated device, and (v) portability with simplicity in application and disposability. Label-free MESDs can serve an affordable real-time detection with a simple analysis in a short processing time, providing point-of-care diagnosis/detection possibilities in precision medicine, and environmental analysis. In the current review, we elaborate on label-free microfluidic biosensors, provide comprehensive insights into electrochemical detection techniques, and discuss the principles of label-free microfluidic-based sensing approaches.