Polymeric Based Hydrogel Membranes for Biomedical Applications

The development of biomedical applications is a transdisciplinary field that in recent years has involved researchers from chemistry, pharmacy, medicine, biology, biophysics, and biomechanical engineering. The fabrication of biomedical devices requires the use of biocompatible materials that do not damage living tissues and have some biomechanical characteristics. The use of polymeric membranes, as materials meeting the above-mentioned requirements, has become increasingly popular in recent years, with outstanding results in tissue engineering, for regeneration and replenishment of tissues constituting internal organs, in wound healing dressings, and in the realization of systems for diagnosis and therapy, through the controlled release of active substances. The biomedical application of hydrogel membranes has had little uptake in the past due to the toxicity of cross-linking agents and to the existing limitations regarding gelation under physiological conditions, but now it is proving to be a very promising field This review presents the important technological innovations that the use of membrane hydrogels has promoted, enabling the resolution of recurrent clinical problems, such as post-transplant rejection crises, haemorrhagic crises due to the adhesion of proteins, bacteria, and platelets on biomedical devices in contact with blood, and poor compliance of patients undergoing long-term drug therapies.

Sodium alginate-hydrogel coatings on extracorporeal membrane oxygenation for anticoagulation

Thromboembolism caused by the use of extracorporeal membrane oxygenation (ECMO) remains common among patients with existing heart diseases and contributes to significant morbidity and mortality during the COVID-19 pandemic. Various surface modification strategies have been proposed, showing that the methacrylated alginate (MA-SA) hydrogel layer is transparent, which aids the observation of the thromboembolism from the inner wall of the tubing. In the combined dynamic and static blood of ECMO tubing inner surface in vitro experiments, it was also demonstrated that the adhesion of blood clots to the surface of vessels was remarkably reduced, and the MA-SA-based hydrogel coating could significantly prolong the activated partial thrombin time and block the endogenous coagulation. The favorable properties of natural polysaccharides of hydrogel coatings make them the best surface material choices to be applied for blood-contacting medical devices and significantly improve anticoagulant performance.

Electron Microscopy Imaging Applications of Room Temperature Ionic Liquids in the Biological Field: A Review

For biological imaging using electron microscopy (EM), the use of room-temperature ionic liquids (RTILs) has been proposed as an alternative to traditional lengthy preparation methods. With their low vapor pressures and conductivity, RTILs can be applied onto hard-to-image soft and/or wet samples without dehydration - allowing for a more representative, hydrated state of material and opening the possibility for visualization of in situ physiological processes using conventional EM systems. However, RTILs have yet to be utilized to their full potential by microscopists and microbiologists alike. To this end, this review aims to provide a comprehensive summary of biological applications of RTILs for EM to bridge the RTIL, in situ microscopy, and biological communities. We outline future research avenues for the use of RTILs for the EM observation of biological samples, notably i) RTIL selection and optimization, ii) applications for live cell processes and iii) electron beam and ionic liquid interaction studies.

Simultaneous Visualization of Wet Cells and Nanostructured Biomaterials in SEM using Ionic Liquids

This work presents a successful methodology to image mammalian cells adhered to nanostructured titanium by using scanning electron microscopy (SEM) operating in low-vacuum mode following ionic liquid treatment. Human osteoblast-like Saos-2 cells were treated with a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate, and subsequently imaged on titanium by SEM. Titanium substrates were modified to create laser-induced periodic surface structures (LIPSS) for visualization at the submicron scale. By using a combination of fluorescence-based cell metabolism along with light microscopy and SEM image analysis, the shape and location of irradiated cells were confirmed to be unchanged after multiple irradiation sessions; the viability of minimally irradiated cells was also unaltered. The wet imaging conditions combined with a rapid facile protocol using ionic liquid allows this technique to fulfill a niche in examining cellular behavior on biomaterials with submicron surface features. The demonstrated method to track observed cell adhesion to submicron surface features by SEM has great implications for understanding cell migration on nanostructured surfaces as well as the exploration of simpler SEM preparation methods for cellular imaging.

Electron microscopy using ionic liquids for life and materials sciences

An ionic liquid (IL) is a salt consisting of only cations and anions, which exists in the liquid state at room temperature. Interestingly ILs combine various favorable physicochemical properties, such as negligible vapor pressure, flame resistance, relatively high ionic conductivity, wide electrochemical window, etc. To take advantage of two specific features of ILs, viz. their nonvolatile and antistatic nature, in 2006, Kuwabata, Torimoto et al. reported a milestone study led to current IL-based electron microscopy techniques. Thereafter, several IL-based electron microscopy techniques have been proposed for life science and materials science applications, e.g. pretreatment of hydrous and/or non-electron conductive specimens and in situ/operando observation of chemical reactions occurring in ILs. In this review, the fundamental approaches for making full use of these techniques and their impact on science and technology are introduced.

A facile ionic-liquid pretreatment method for the examination of archaeological wood by scanning electron microscopy

Wood has been a crucial natural material for human civilization since prehistoric times. In archaeology, the examination of the wood microstructure is important for the study of architecture, musical instruments, sculptures, and so on. Scanning electron microscopy (SEM) examination is sometimes unsuitable for archaeological wood due to the limited amount of precious samples, which may be too small to be cut by microtomes and mounted on holders. Moreover, the conductive coating material cannot be uniformly deposited over uneven wood surfaces. To overcome these issues, a rapid and simple pretreatment method using room-temperature ionic liquids (RTIL) was proposed. Four common RTILs were evaluated for the pretreatment of wood chips for SEM examination. We found that water content, viscosity, density, and hydrophobicity of IL solutions were important factors affecting SEM image quality. A 7.5% solution of 1-butyl-1-methylpyrrolidium dicyanamide (BMP-DCA) in ethanol (v/v) was found to work very well. The IL pretreatment could be performed in a few minutes without special equipment. It is gentle enough to preserve delicate structures such as the torus/margo of pit membranes, even at elevated temperatures, without causing obvious damage or deformation. We successfully imaged hand-cut wood chips from 18^th-century buildings, an 18^th-century European violin, and a Chinese zither over 1000 years old. We therefore conclude that highly hydrophilic ionic liquids with low density and viscosity are suitable for use in SEM examinations of both modern and antique wood specimens.

Monitoring dynamic spiculation in red blood cells with scanning ion conductance microscopy

Phospholipids are critical structural components of the membrane of human erythrocytes and their asymmetric transbilayer distribution is essential for normal cell functions. Phospholipid asymmetry is maintained by transporters that shuttle phospholipids between the inner leaflet and the outer leaflet of the membrane bilayer. When an exogenous, short acyl chain, phosphatidylcholine (PC) or phosphatidylserine (PS) is incorporated into erythrocytes, a discocyte-to-echinocyte shape change is induced. PC treated cells remain echinocytic, while PS treated cells return to discocytes, and eventually stomatocytes, due to the action of an inwardly directed transporter. These morphological changes have been well studied by light microscopy and scanning electron microscopy in the past few decades. However, most of this research is based on the glutaraldehyde fixed cells, which limits the dynamic study in discrete time points instead of continuous single cell measurements. Scanning ion conductance microscopy (SICM) is a scanning probe technique which is ideal for live cell imaging due to high resolution, in situ and non-contact scanning. To better understand these phospholipid-induced morphological changes, SICM was used to scan the morphological change of human erythrocytes after the incorporation of exogenous dilauroylphosphatidylserine (DLPS) and the results revealed single cell dynamic morphological changes and the movement of spicules on the membrane surface.