Creation of Nanotips on ITO Electrode by Nanoparticle Deposition: An Easy Way to Enhance the Performance of Electrically Responsive Photonic Crystal and Fabricate Electrically Triggered Anticounterfeiting Tags

Electrically responsive photonic crystals (ERPC) are promising materials for electrophoretic displays, smart windows, and tunable optical devices. However, the high working voltage limits the application of most polar ERPCs because it damages color saturation, response stability, and reversibility. Herein, an easy but general method based on the modification of electrodes with nanoparticles is developed to improve ERPC's performance. The deposition of Au, Cu, or Cu₂O nanoparticles created nanotip structures on the electrode, which enhanced the charge injection and local electric field strength, lowered 43% of the working voltage, and increased the color saturation. Meanwhile, the lowered voltage inhibited the electrodeposition of colloidal particles and the electrochemical reaction, which also improved the stability and reversibility of the electrical response. Based on the region-selective modification of the electrode and the resulting asymmetric electrical response, an electrically triggered tag with a “pattern showing/hiding” effect is fabricated for anticounterfeiting purposes.     

Charge Booster Tags for Controlled Release of Therapeutics from a Therapeutic Carrier

Injectable hydrogels are promising delivery vehicles for the sustained release of therapeutic proteins. Electrostatic interactions between proteins and hydrogels often increase affinity to decelerate protein release. However, this approach is not suitable for weakly charged proteins. The current study shows that the genetic fusion of a highly charged protein segment (charge booster tag) with proteins can control their interactions with injectable gels. A positive or negative charge booster tag is introduced into urate oxidase (UOX), a therapeutic protein for gout, to generate UOX variants with varying net charges. When a positively-charged injectable hydrogel is used, both the in vitro release rate and in vivo serum half-life of UOX are correlated with the net negative charge. This modified delivery approach results in a serum half-life of over 106 h for the UOX variant, which is substantially longer than that of free UOX (3.3 h). Hence, charge booster tags can be used as a systematic strategy for controlling the release of therapeutic proteins.     

HaloTag-Based Reporters for Fluorescence Imaging and Biosensing

Visualizing the structure and dynamics of biomolecules is critical to understand biological function, and requires methods to fluorescently label targets of interest in their cellular context. Self-labelling proteins, which combine a genetically encoded tag with a small-molecule fluorophore, have attracted considerable attention for this purpose, as they can overcome limitations of fluorescent proteins. Among them, the HaloTag protein is the most broadly used, showing fast specific labelling with a small, easy to functionalize and cell-permeant ligand. Synthetic chemistry and protein engineering have provided a portfolio of powerful imaging tools exploiting HaloTag, along with general methods to optimize and adapt them to specific applications. Here, we provide an overview of fluorescent reporters based on the HaloTag protein for imaging and biosensing, highlighting engineering strategies and general applications.