Fingerprints are an important kind of material evidence with the key function in personal identification, which are unique and life-long to everyone. Latent (invisible) fingerprints are common at the crime scene, needing to be visualized with proper methods in order to identify sources of the fingerprints in routine forensic practice. Fluorescent imaging of latent fingerprints has the advantage of high contrast, sensitivity, selectivity, and less dependency on instruments. Taking the environment and users' safety into consideration, organic materials for fluorescent imaging of latent fingerprints are reviewed mainly in recent 5 years. New strategies of fingerprint reagents and improved performances established for fingerprint development based on fluorescent organic materials are discussed in the view of forensic practice. In addition, we briefly highlight current challenges of recent fluorescent imaging works based on organic materials for the latent fingerprints development in forensic practice.

Droplet-based microfluidics has been widely applied in enzyme directed evolution (DE), in either cell or cell-free system, due to its low cost and high throughput. As the isolation principles are based on the labeled or label-free characteristics in the droplets, sorting method contributes mostly to the efficiency of the whole system. Fluorescence-activated droplet sorting (FADS) is the mostly applied labeled method but faces challenges of target enzyme scope. Label-free sorting methods show potential to greatly broaden the microfluidic application range. Here, we review the developments of droplet sorting methods through a comprehensive literature survey, including labeled detections [FADS and absorbance-activated droplet sorting (AADS)] and label-free detections [electrochemical-based droplet sorting (ECDS), mass-activated droplet sorting (MADS), Raman-activated droplet sorting (RADS), and nuclear magnetic resonance-based droplet sorting (NMR-DS)]. We highlight recent cases in the last 5 years in which novel enzymes or highly efficient variants are generated by microfluidic DE. In addition, the advantages and challenges of different sorting methods are briefly discussed to provide an outlook for future applications in enzyme DE.

Forensic chemistry deals with the analysis of various types of physical evidences related to crime, corresponding to the detection of target substances or elements in complex matrices. There is a vital need for highly selective, rapid, and sensitive biosensing technologies in heavy metal ions analysis especially those from living persons, autopsy, food, water, soil, and other identified substances at very preliminary stages. Fluorescent materials-based method for heavy metal ions detection is one of the most important analytical methods, resulting in the ability to measure analytes in complex matrices with unsurpassed selectivity and sensitivity. In this mini review, different fluorescent materials-based analytical methods aiming at several heavy metal ions detection are exclusively reviewed through a comprehensive literature survey. In addition, current challenges to achieve integrated evidence analysis process are briefly discussed to provide an outlook for heavy metal ions detection based on fluorescent analytical methods in the forensic chemistry field.

Microneedle (MN)-assisted drug delivery technology has gained increasing attention over the past two decades. Its advantages of self-management and being minimally invasive could allow this technology to be an alternative to hypodermic needles. MNs can penetrate the stratum corneum and deliver active ingredients to the body through the dermal tissue in a controlled and sustained release. Long-acting polymeric MNs can reduce administration frequency to improve patient compliance and therapeutic outcomes, especially in the management of chronic diseases. In addition, long-acting MNs could avoid gastrointestinal reactions and reduce side effects, which has potential value for clinical application. In this paper, advances in design strategies and applications of long-acting polymeric MNs are reviewed. We also discuss the challenges in scale manufacture and regulations of polymeric MN systems. These two aspects will accelerate the effective clinical translation of MN products.

Developing regioisomeric organic fluorescent materials with tunable photophysical properties is particularly important in diverse applications. Here we synthesized three cationic regioisomeric aggregation-induced emission (AIE)-active acrylonitriles (o-TPE-ANPy⁺, m-TPE-ANPy⁺, and p-TPE-ANPy⁺) by conjugation with tetraphenylethylene at different ortho/meta/para positions. The regioisomerism remarkably impacted their photophysical characteristics and solid-state intermolecular interactions. The regioisomeric AIE luminogens (AIEgens) exhibited faint emissions in solution but boosted fluorescence behaviors in the solid state. o-TPE-ANPy⁺ and m-TPE-ANPy⁺ showed similar yellow solid-state emissions with a fluorescence quantum yield (QY) of 14.3% and 1.8%, respectively. However, due to the strong intermolecular charge transfer effect, p-TPE-ANPy⁺ exhibited a red-shifted solid-state emission of 616 nm (QY of 17.2%). In addition, m-TPE-ANPy⁺ and p-TPE-ANPy⁺ exhibited larger fluorescence enhancements toward viscosity than o-TPE-ANPy⁺. Moreover, o-TPE-ANPy⁺ was applied for achieving reversible mechanochromic performance with fluorescence changing from yellow to orange. Further use of these biocompatible AIEgens for wash-free and light-up imaging of mitochondria was successfully demonstrated. These interesting results facilitate a better understanding of the structure–property relationships in fluorescent regioisomers.