Mini Review: Forensic Value of Aquaporines

Forensic pathologists are routinely confronted with unclear causes of death or findings. In some scenarios, it can be difficult to answer the specific questions posed by criminal investigators or prosecutors. Such scenarios may include questions about wound vitality or causes of death when typical or landmark findings are difficult to find. In addition to the usual subsequent examinations to clarify unclear causes of death or special questions, immunohistochemical analysis has become increasingly important since its establishment in the early 40s of the 20th century. Since then, numerous studies have been conducted to determine the usefulness and significance of immunohistochemical investigations on various structures and proteins. These proteins include, for example, aquaporins, which belong to the family of water channels. They enable the transport of water and of small molecules, such as glycerol, through biological channels and so far, 13 classes of aquaporins could have been identified in vertebrates. The classic aquaporin channels 1, 2, 4 and 5 are only permeable to water. The aquaporin channels 3, 7, 9, and 10 are also called aquaglycerolporins since they can also transport glycerol. This mini review discusses the immunohistochemical research on aquaporins, their range of applications, and respective forensic importance, their current limitations, and possible further implementations in the future.

A Facile Strategy for the Ion Current and Fluorescence Dual-Lock in Detection: Naphthalic Anhydride Azide (NAA)-Modified Biomimetic Nanochannel Sensor towards H2S

Inspired by biological channels, the electric signal-based artificial nanochannel system exhibits high sensitivity in various analyses. However, ion current may be affected by many other factors, leading to false-positive signals. For reliable detection, in this work, we apply a facile strategy to combine both current signal and fluorescence. Fluorescent probes were conjugated to the nanochannel surface by covalent bonds. By utilizing the specific reduction of azide groups in the probe to amino groups by H2S, a synchronizing change in fluorescence and nanochannel surface charge was established. As a result, both transmembrane ion current and fluorescence intensity showed significant changes. The photoelectric double-checked locking from temporal and spatial variation validly confirmed the response process and protected detection accuracy. The work may provide new ideas for the development of more sophisticated current and fluorescence dual-index nanochannel systems.

A bibliometric study on biomimetic and bioinspired membranes for water filtration

Insights into the biological channels and synthetic pore-forming assemblies have elucidated many fundamental aspects of selective water and solute transport over the last few decades. This has led to the development of novel technologies with unique selectivity and permeability. In terms of membrane separation technology, this development has proceeded by adapting either of two approaches: (i) one where biological channel proteins are reconstituted in suitable materials mimicking the biological bilayer membrane and (ii) one where selective transport is mimicked in synthetic structures. The development of water filtration membranes in the former approach takes advantage of aquaporin proteins as representative building blocks and that of carbon nanotubes and molecular pore-forming assemblies in the latter approach. The first approach is often referred to as the field dominated by biomimetic membranes and the latter referred to as artificial water channels. In this study, a bibliometric analysis was conducted to investigate trends in these two areas based on growing publication trends, peer-reviewed journal selection, countries, institutions, authors, and collaborative networks. A total of 3199 records available from Scopus between 1962 and 2021 were extracted and analyzed. The results showed strong international collaborations and highlighted leading researchers and hubs of excellence in these two areas. This is very timely considering that the UN climate change conference (COP26) in Glasgow, UK later this year will bring focus to the global need for water treatment technologies. This work can serve as a quick reference for early-career researchers and industries working in the area of membrane development for water purification/filtration.

Water friction in nanofluidic channels made from two-dimensional crystals

Membrane-based applications such as osmotic power generation, desalination and molecular separation would benefit from decreasing water friction in nanoscale channels. However, mechanisms that allow fast water flows are not fully understood yet. Here we report angstrom-scale capillaries made from atomically flat crystals and study the effect of confining walls’ material on water friction. A massive difference is observed between channels made from isostructural graphite and hexagonal boron nitride, which is attributed to different electrostatic and chemical interactions at the solid-liquid interface. Using precision microgravimetry and ion streaming measurements, we evaluate the slip length, a measure of water friction, and investigate its possible links with electrical conductivity, wettability, surface charge and polarity of the confining walls. We also show that water friction can be controlled using hybrid capillaries with different slip lengths at opposing walls. The reported advances extend nanofluidics’ toolkit for designing smart membranes and mimicking manifold machinery of biological channels.

Bioinspired artificial nanochannels: construction and application

Inspired by nature, this review focuses on the construction and applications of biomimetic artificial nanochannels from the perspective of the relationship between biological channels and artificial nanochannels.

Study on the Heat Reduction Effect of Biomimetic Unidirectional Transporting Channels Inspired by Nepenthes alata

Heat control has been a momentous problem in engineering areas which include manufacturing, aeronautics, microchips and so forth for a considerable amount of time. The control of material for thermal deformation, effective cooling are the key components of the aero crafts and compactly laid out microchips are urgently needed for improvement. In a micro-scale, researchers are mainly focused on the mechanism, design, improvement and heat transfer of straight channels other than developing other types of channels. A previous study on the carnivorous plant, Nepenthes alata, indicates that the water can be transported continuously and directionally on the surface of the rim of the pitcher because of its multi-scale structures. Meanwhile, the transporting speed is much higher than what was thought previously. Inspired by this unique phenomenon, the heat management ability of this biological micro channel is investigated in this research. Firstly, based on existing studies, the features of the biological channels are extracted. Then, the unidirectional channels are designed and fabricated by elliptical vibration cutting accordingly. The experimental platform for thermal control was established consequently. Both bio-inspired and straight triangular channels of the same depth and width were set for comparison. Through the comparative experiments, it is concluded preliminarily that the critical point of heat transfer performance of the two channels exists, and the biomimetic structure can improve and strengthen the cooling effects at a large flow rate because of the unique geometric structure. The temperature reduction of the bio-inspired channels can be increased by up to 84 percent compared with straight channels in a single experiment when heated up to 150 centigrade.

A double helix of opposite charges to form channels with unique CO2 selectivity and dynamics

Electrostatic charges patterning along crystalline channels recognize CO2 with high selectivity and promote its fast screwing dynamics through the crystal at one million steps per second, strongly reminiscent of trans-membrane transport in biological channels.