Engineering multifunctional dynamic hydrogel for biomedical and tissue regenerative applications

Hydrogels have emerged in various biomedical applications, including tissue engineering and medical devices, due to their ability to imitate the natural extracellular matrix (ECM) of tissues. However, conventional static hydrogels lack the ability to dynamically respond to changes in their surroundings to withstand the robust changes of the biophysical microenvironment and to trigger on-demand functionality such as drug release and mechanical change. In contrast, multifunctional dynamic hydrogels can adapt and respond to external stimuli and have drawn great attention in recent studies. It is realized that the integration of nanomaterials into dynamic hydrogels provides numerous functionalities for a great variety of biomedical applications that cannot be achieved by conventional hydrogels. This review article provides a comprehensive overview of recent advances in designing and fabricating dynamic hydrogels for biomedical applications. We describe different types of dynamic hydrogels based on breakable and reversible covalent bonds as well as noncovalent interactions. These mechanisms are described in detail as a useful reference for designing crosslinking strategies that strongly influence the mechanical properties of the hydrogels. We also discuss the use of dynamic hydrogels and their potential benefits. This review further explores different biomedical applications of dynamic nanocomposite hydrogels, including their use in drug delivery, tissue engineering, bioadhesives, wound healing, cancer treatment, and mechanistic study, as well as multiple-scale biomedical applications. Finally, we discuss the challenges and future perspectives of dynamic hydrogels in the field of biomedical engineering, including the integration of diverse technologies

Preparation and optical properties of novel bioactive photonic crystals obtained from core-shell poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) microspheres

Optical properties of polymer microspheres with polystyrene cores and polyglycidol-enriched shells poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) (P(S/PGL) particles with number average diameters Dn determined by scanning electron microscopy equal 237 and 271 nm), were studied before and after immobilization of ovalbumin. The particles were synthesized by emulsifier-free emulsion copolymerization of styrene and polyglycidol macromonomer (poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol)) initiated with potassium persulfate. Molar fraction of polyglycidol units in the interfacial layer of the microspheres determined by XPS was equal 42.6 and 34.0%, for the particles with Dn equal 137 and 271 nm, respectively. Colloidal crystals from the aforementioned particles were prepared by deposition of particle suspensions on the glass slides and subsequent evaporation of water. It was found that optical properties of colloidal crystals from the P(S/PGL) microspheres strongly depend on modification of their interfacial layer by covalent immobilization of ovalbumin. The coating of particles with ovalbumin resulted in decreasing their refractive index from 1.58 to 1.52

Size-Controlled 3D Colloidal Crystals Formed in an Aqueous Suspension of Polystyrene/Polyglycidol Microspheres with Covalently Bound l‑DOPA

Stable three-dimensional colloidal crystals were fabricated in an aqueous suspension of Tris buffer at pH > 8. The basic building blocks of the crystals were submicron-sized polystyrene–polyglycidol core–shell particles (<i>D</i>_n(SEM) = 270 ± 18 nm) with covalently bound 3,4-dihydroxyphenylalanine (l-DOPA). The growth of the crystals was triggered by a thermodynamically favorable arrangement of particles leading to their close packing and by the formation of covalent cross-links between the individual particles. Under alkaline conditions, molecules of l-DOPA are oxidized, which allows their participation in cross-linking, necessary for the stabilization of the formed colloidal crystals. The average size of the fabricated colloidal crystals is determined by their weight, density of the suspending medium, and the energy of their Brownian motion. Crystals generated during the suspension of particles fall down after reaching the critical weight. Therefore, crystals of similar dimensions are deposited at the bottom of the vessel. The described system is the first example of the formation of stable colloidal crystals in a suspension

Multilayers of poly(styrene/α\alpha-tert-butoxy-ω\omega-vinylbenzyl-polyglycidol) microspheres with core-shell morphology : characterization by AFM, SIMS and XPS

The methods of preparation and characterization of core-shell poly(styrene$\alpha$-tert-butoxy-$\omega$-vinylbenzyl-polyglycidol) particles arranged in colloidal crystals are described. The particles wereprepared via emulsifier free emulsion copolymerization of styrene and alpha-tert-butoxy-omega-vinylbenzyl-polyglycidol macromonomer in aqueous medium, initiated by potassium persulfate. The individualpolymerizations differed in a way of addition of macromonomer to the polymerization mixture. The parti-cles assemblies were characterized by atomic force microscopy, Secondary Ion Mass Spectrometry (SIMS)and X-ray Photoelectron Spectroscopy (XPS). In-depth distribution of chemical states was determined byXPS combined with argon gas cluster ion sputtering (Ar-GCIB). The morphology of microspheres assem-blies reflected the composition of the entire particles. It was found that the method of macromonomeraddition to the polymerization mixture affects the particles size, surface and overall morphology

Gradient Poly(styrene-<i>co</i>-polyglycidol) Grafts via Silicon Surface-Initiated AGET ATRP

Gradient copolymer grafts of styrene and α-<i>tert</i>-butoxy-ω-vinylbenzyl-poly­(glycidol ethoxyethyl ether) (PGLet), a precursor of α-<i>tert</i>-butoxy-ω-vinylbenzyl-polyglycidol macromonomer (PGL), were prepared on silicon wafers via a surface-initiated activator generated by electron transfer radical polymerization (AGET ATRP). Silicon plates with previously attached 2-bromoisobutyrate served as a macroinitiator for the AGET ATRP (activator generated by electron transfer) of styrene and PGLet. The copolymers’ gradient P­(S-<i>co</i>-PPGL) of composition and thickness was obtained by a simple method where the plates were slowly removed from reaction mixture using a step motor. PGLet was added continuously (dropwise) into the reactor during withdrawal of the plates from solution in order to increase the relative concentration of PGLet in polymerization mixture. A range of strategies of making grafts was tested. The plates with copolymers grafts were analyzed by various techniques, like XPS, ellipsometry, and FTIR spectroscopy. The results indicate that the AGET ATRP process is dependent on the styrene/PGLet macromonomer ratio in the polymerization mixture. Under optimal conditions, the addition of PGLet during polymerization and subsequent deprotection of hydroxyl groups of PGLet permit to obtain plates with a novel copolymer layer with composition, thickness, and wettability gradient. Plates with chemical composition of copolymer grafts gradient served as versatile supports with controlled hydrophilic/hydrophobic area and were suitable for tailored deposition of particles

A DSC and XPS characterization of Core-shell Morphology of Block Copolymer Nanoparticles

Self-assembly of amphiphilic block copolymer chains is known to produce core–shell nanoparticles, but imaging techniques have generally failed to provide clear evidence about the multiphase structure. We report herein the advantages and limitations of modulated temperature differential scanning calorimetry (MDSC) and X-ray photoelectron spectroscopy (XPS) for the morphology study of spherical poly(hydroxyethyl acrylate)-b-polystyrene diblock copolymer nanoparticles with an intensity-average diameter of 40 nm. Using lyophilized particles, MDSC is more informative than XPS since it allows the three morphological features of composite latex particles to be distinguished: polystyrene core, poly(hydroxyethyl acrylate) shell, and interface. In MDSC, phase separation is evidenced by two distinct increments of heat capacity (ΔCp) in the glass transition regions of the two blocks. By measuring ΔCp values, an interface weight fraction of 70% is measured that gradually decreases to 50% with annealing time (150 °C, 2 h), indicating a higher extent of phase separation

Highly hydrophilic surfaces from polyglycidol grafts with dual antifouling and specific protein recognition properties.

International audienceHomopolymer grafts from α-tert-butoxy-ω-vinylbenzyl-polyglycidol (PGL) were prepared on gold and stainless steel (SS) substrates modified by 4-benzoyl-phenyl (BP) moieties derived from the electroreduction of the parent salt 4-benzoyl benzene diazonium tetrafluoroborate. The grafted BP aryl groups efficiently served to surface-initiate photopolymerization (SIPP) of PGL. In similar conditions, SIPP of hydroxyethyl methacrylate (HEMA) permitted the production of PHEMA grafts as model surfaces. Water contact angles were found to be 66°, 15°, and 0° for SS-BP, SS-PHEMA, and SS-PPGL, respectively. The spontaneous spreading of water drops on SS-PPGL was invariably observed with 1.5 μL water drops. PPGL thus appears as a superhydrophilic polymer. Resistance to nonspecific adsorption of proteins of PPGL and PHEMA grafts on gold was evaluated by surface plasmon resonance (SPR) using antibovine serum albumin (anti-BSA). The results conclusively show that PPGL-grafts exhibit enhanced resistance to anti-BSA adsorption compared to the well-known hydrophilic PHEMA. PPGL grafts were further modified with BSA through the carbonyldiimidazole activation of the OH groups providing immunosensing surfaces. The so-prepared PPGL-grafted BSA hybrids specifically interacted with anti-BSA in PBS as compared to antimyoglobin. It is clear that the superhydrophilic character of PPGL grafts opens new avenues for biomedical applications where surfaces with dual functionality, namely, specific protein grafting together with resistance to biofouling, are required