A K+-sensitive photonic crystal hydrogel sensor for efficient visual monitoring of hyperkalemia/hypokalemia

A penicillinase-modified poly(N-isopropylacrylamide-co-acrylamide) smart hydrogel biosensor with superior recyclability for sensitive and colorimetric detection of penicillin G

Antibiotics are widely used for treating bacterial infections. However, excessive or improper use of antibiotics can pose a serious threat to human health and water environments, and thus, developing cost-effective, portable and effective strategies to analyze and detect antibiotics is highly desired. Herein, we reported a responsive photonic hydrogel (RPH)-based optical biosensor (PPNAH) with superior recyclability for sensitive and colorimetric determination of a typical β-lactam antibiotic penicillin G (PG) in water. This sensor was composed of poly(N-isopropylacrylamide-co-acrylamide) smart hydrogel with incorporated penicillinase and Fe3O4@SiO2 colloidal photonic crystals (CPCs). The sensor could translate PG concentration signals into changes in the diffraction wavelength and structural color of the hydrogel. It possessed high sensitivity and selectivity to PG and excellent detection performances for other two typical β-lactam antibiotics. Most importantly, due to the unique thermosensitivity of the poly(N-isopropylacrylamide) moieties in the hydrogel, the PG-responded PPNAH sensor could be facilely regenerated via a simple physical method at least fifty times while without compromising its response performance. Besides, our sensor was suitable for monitoring the PG-contaminated environmental water and displayed satisfactory detection performances. Such a sensor possessed obvious advantages of superior recyclability, highly chemical stability, low production cost, easy fabrication, wide range of visual detection, simple and intuitive operation for PG detection, and environmental-friendliness, which holds great potential in sensitive and colorimetric detection of the PG residues in polluted water.

Multi-stimuli responsive photonic hydrogel based on a novel photonic crystal template containing gold nanorods

Multi-stimuli responsive photonic hydrogels (MRPHs) fabricated by doping nanoparticles into hydrogels show promising potential value in the fields of visual detection and drug delivery. However, complicated surface chemical modification is selected to improve the compatibility between nanoparticles and a pre-gel solution of hydrogel. Herein, we developed a simple and convenient vertical deposition method to prepare a novel photonic crystal (PC) template containing gold nanorods (Au NRs) (Au NRs/PC template), which could respond to near-infrared (NIR) light due to the conversion capability of Au NRs from NIR light to heat. Additionally, carboxyl groups on the surface of polystyrene (PS) colloids endowed the Au NRs/PC template with pH-stimulus responsiveness. Based on the Au NRs/PC template, MRPH film was fabricated by infiltrating the pre-gel solution of poly(N-isopropylacrylamide) (PNIPAM) hydrogel into the gap of a 'sandwich' structure through capillary forces and then polymerizing at 25 °C for 24 h. The obtained MRPH film could respond to NIR light, pH and temperature. Under the irradiation of NIR light, only the irradiated position lost structural color while the film volume had no distinct change. With the increase of ambient temperature, the whole MRPH film completely lost structural color and shrank significantly, which was greatly different from the phenomenon irradiated by NIR light. Besides, the structural color of the MRPH film exhibited a red shift from green to orange-red as the pH increased. Overall, both the Au NRs/PC template and the MRPH film may have potential applications in visual detection, due to their multi-stimuli responsiveness.