A Clean and Simple Route to Soft, Biocompatible Nanocapsules via UV-Cross-Linkable Azido-Hyperbranched Polyglycerol

Polyglycerol-Based Hydrogel as Versatile Support Matrix for 3D Multicellular Tumor Spheroid Formation

Hydrogel-based artificial scaffolds are essential for advancing cell culture models from 2D to 3D, enabling a more realistic representation of physiological conditions. These hydrogels can be customized through crosslinking to mimic the extracellular matrix. While the impact of extracellular matrix scaffolds on cell behavior is widely acknowledged, mechanosensing has become a crucial factor in regulating various cellular functions. cancer cells' malignant properties depend on mechanical cues from their microenvironment, including factors like stiffness, shear stress, and pressure. Developing hydrogels capable of modulating stiffness holds great promise for better understanding cell behavior under distinct mechanical stress stimuli. In this study, we aim to 3D culture various cancer cell lines, including MCF-7, HT-29, HeLa, A549, BT-474, and SK-BR-3. We utilize a non-degradable hydrogel formed from alpha acrylate-functionalized dendritic polyglycerol (dPG) and thiol-functionalized 4-arm polyethylene glycol (PEG) via the thiol-Michael click reaction. Due to its high multivalent hydroxy groups and bioinert ether backbone, dPG polymer was an excellent alternative as a crosslinking hub and is highly compatible with living microorganisms. The rheological viscoelasticity of the hydrogels is tailored to achieve a mechanical stiffness of approximately 1 kPa, suitable for cell growth. Cancer cells are in situ encapsulated within these 3D network hydrogels and cultured with cell media. The grown tumor spheroids were characterized by fluorescence and confocal microscopies. The average grown size of all tumoroid types was ca. 150 µm after 25 days of incubation. Besides, the stability of a swollen gel remains constant after 2 months at physiological conditions, highlighting the nondegradable potential. The successful formation of multicellular tumor spheroids (MCTSs) for all cancer cell types demonstrates the versatility of our hydrogel platform in 3D cell growth.

Polymer-Ligated Nanocrystals Enabled by Nonlinear Block Copolymer Nanoreactors: Synthesis, Properties, and Applications

The past several decades have witnessed substantial advances in synthesis and self-assembly of inorganic nanocrystals (NCs) due largely to their size- and shape-dependent properties for use in optics, optoelectronics, catalysis, energy conversion and storage, nanotechnology, and biomedical applications. Among various routes to NCs, the nonlinear block copolymer (BCP) nanoreactor technique has recently emerged as a general yet robust strategy for crafting a rich diversity of NCs of interest with precisely controlled dimensions, compositions, architectures, and surface chemistry. It is notable that nonlinear BCPs are unimolecular micelles, where each block copolymer arm of nonlinear BCP is covalently connected to a central core or polymer backbone. As such, their structures are static and stable, representing a class of functional polymers with complex architecture for directing the synthesis of NCs. In this review, recent progress in synthesizing NCs by capitalizing on two sets of nonlinear BCPs as nanoreactors are discussed. They are star-shaped BCPs for producing 0D spherical nanoparticles, including plain, hollow, and core-shell nanoparticles, and bottlebrush-like BCPs for creating 1D plain and core/shell nanorods (and nanowires) as well as nanotubes. As the surface of these NCs is intimately tethered with the outer blocks of nonlinear BCPs used, they can thus be regarded as polymer-ligated NCs (i.e., hairy NCs). First, the rational design and synthesis of nonlinear BCPs via controlled/living radical polymerizations is introduced. Subsequently, their use as the NC-directing nanoreactors to yield monodisperse nanoparticles and nanorods with judiciously engineered dimensions, compositions, and surface chemistry is examined. Afterward, the intriguing properties of such polymer-ligated NCs, which are found to depend sensitively on their sizes, architectures, and functionalities of surface polymer hairs, are highlighted. Some practical applications of these polymer-ligated NCs for energy conversion and storage and drug delivery are then discussed. Finally, challenges and opportunities in this rapidly evolving field are presented.

Development of visible-light responsive and mechanically enhanced "smart" UCST interpenetrating network hydrogels

An interpenetrating polymer network (IPN), chlorophyllin-incorporated environmentally responsive hydrogel was synthesized and exhibited the following features: enhanced mechanical properties, upper critical solution temperature (UCST) swelling behavior, and promising visible-light responsiveness. Poor mechanical properties are known challenges for hydrogel-based materials. By forming an interpenetrating network between polyacrylamide (PAAm) and poly(acrylic acid) (PAAc) polymer networks, the mechanical properties of the synthesized IPN hydrogels were significantly improved compared to hydrogels made of a single network of each polymer. The formation of the interpenetrating network was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), the analysis of glass transition temperature, and a unique UCST responsive swelling behavior, which is in contrast to the more prevalent lower critical solution temperature (LCST) behaviour of environmentally responsive hydrogels. The visible-light responsiveness of the synthesized hydrogel also demonstrated a positive swelling behavior, and the effect of incorporating chlorophyllin as the chromophore unit was observed to reduce the average pore size and further enhance the mechanical properties of the hydrogel. This interpenetrating network system shows potential to serve as a new route in developing "smart" hydrogels using visible-light as a simple, inexpensive, and remotely controllable stimulus.

Self-assembly and multi-stimuli responsive behavior of PAA-b-PAzoMA-b-PNIPAM triblock copolymers

A PAA-b-PAzoMA-b-PNIPAM triblock copolymer containing pH, photo and temperature sensitive groups could self-assemble into spherical micelles or vesicles with multi-stimuli responsiveness.