A Combined Strategy to Surface-Graft Stimuli-Responsive Hydrogels Using Plasma Activation and Supercritical Carbon Dioxide

Green Strategies for Molecularly Imprinted Polymer Development

Molecular imprinting is a powerful technology to create artificial receptors within polymeric matrices. Although it was reported for the first time by Polyakov, eighty-four years ago, it remains, nowadays, a very challenging research area. Molecularly imprinted polymers (MIPs) have been successfully used in several applications where selective binding is a requirement, such as immunoassays, affinity separation, sensors, and catalysis. Conventional methods used on MIP production still use large amounts of organic solvents which, allied with stricter legislation on the use and release of chemicals to the environment and the presence of impurities on final materials, will boost, in our opinion, the use of new cleaner synthetic strategies, in particular, with the application of the principles of green chemistry and engineering. Supercritical carbon dioxide, microwave, ionic liquids, and ultrasound technology are some of the green strategies which have already been applied in MIP production. These strategies can improve MIP properties, such as controlled morphology, homogeneity of the binding sites, and the absence of organic solvents. This review intends to give examples reported in literature on green approaches to MIP development, from nano- to micron-scale applications.

Multi-modulation for self-assemblies of amphiphilic rigid-soft compounds through alteration of solution polarity and temperature

A new class of small molecule-based amphiphilic carbazole-containing compounds has been designed and synthesized. Detailed analysis of the temperature- and solvent-dependent UV-vis absorption spectra has provided insights into the cooperative self-assembly mechanism of the carbazole-containing compounds. Interestingly, the prepared amphiphilic rigid-soft compounds were also found to display a lower critical solution temperature (LCST) behavior in aqueous solution, which is relatively less explored in small molecule-based materials, leading to promising candidates for the design of a new class of thermo-responsive materials.

A discrete amphiphilic organoplatinum(II) metallacycle with tunable lower critical solution temperature behavior

Oligo(ethylene glycol) (OEG)-decorated supramolecular assemblies are distinguished by their neutral character and macroscopic temperature-sensitive phase transition behavior. OEG functionalization is an emerging strategy to obtain thermoresponsive macrocyclic amphiphiles, although known methods organize the hydrophilic and hydrophobic segments by covalent bonding. Coordination-driven self-assembly offers an alternative route for organizing OEG-functionalized precursors into nanoscopic architectures, resulting in well-defined metallacycle cores surrounded by hydrophilic scaffolds to impart overall amphiphilic character. Here a tri(ethylene glycol)-functionalized thermosensitive amphiphilic metallacycle was prepared with high efficiency by means of the directional-bonding approach. The ensembles thus formed showed good lower critical solution temperature behavior with a highly sensitive phase separation and excellent reversibility. Moreover, the clouding point decreased with increasing metallacycle concentration and addition of K(+).

pH-Responsive Supramolecular Control of Polymer Thermoresponsive Behavior by Pillararene-Based Host-Guest Interactions

We demonstrate precise control of the lower critical solution temperature (LCST) behavior of a thermoresponsive polymer in water by pillararene-based host-guest interactions. The LCST value of the polymer increases upon the stepwise addition of either of the two pillararene hosts. On account of the pH-responsiveness of the pillararene-based host-guest interactions, the recovery of the LCST is achieved by treatment with acid, reflecting the pH-responsive supramolecular control of the LCST.

Engineering stem cell fate with biochemical and biomechanical properties of microcarriers

Microcarriers have been widely used for various biotechnology applications because of their high scale-up potential, high reproducibility in regulating cellular behavior, and well-documented compliance with current Good Manufacturing Practices (cGMP). Recently, microcarriers have been emerging as a novel approach for stem cell expansion and differentiation, enabling potential scale-up of stem cell-derived products in large bioreactors. This review summarizes recent advances of using microcarriers in mesenchymal stem cell (MSC) and pluripotent stem cell (PSC) cultures. From the reported data, efficient expansion and differentiation of stem cells on microcarriers rely on their ability to modulate cell shape (i.e. round or spreading) and cell organization (i.e. aggregate size). Nonetheless, current screening of microcarriers remains empirical, and accurate understanding of how stem cells interact with microcarriers still remains unknown. This review suggests that accurate characterization of biochemical and biomechanical properties of microcarriers is required to fully exploit their potential in regulating stem cell fate decision. Due to the variety of microcarriers, such detailed analyses should lead to the rational design of application-specific microcarriers, enabling the exploitation of reproducible effects for large scale biomedical applications.