Preparation and properties of poly(ethylene glycol)-bpoly( 3-acrylamidophenylboronic acid) glucose responsive particles and their hyaluronic acid-based microneedle patches

To overcome the pain and risk of hypoglycemia in insulin administration,glucose-responsive microneedles have been developed by researchers,which could release insulin according to the blood glucose level.We designed a kind of particles by a reversible addition-fragmentation chain transfer(RAFT)method containing a phenylboronic acid group as the sensor of glucose and carrier of insulin.poly(ethylene glycol)(PEG)-2-(dodecylthio(thiocarbonyl)thio)-2-methylpropionic acid(DDMAT)was synthesized as a macromolecular RAFT agent,which was then reacted with 3-acrylamidophenylboronic acid(AAPBA)to synthesize the block copolymer PEG-b-PAAPBA.Glucose-responsive particles loaded with insulin were prepared by self-assembly based on hydrophilic-hydrophobic interactions.Microneedle patches loaded with glucose-responsive particles were prepared using hyaluronic acid as the substrate.The insulin release behavior of the particles in glucose solutions of 0,100,and 400 mg/dL showed significant glucose responsiveness and good biosafety.The results of blood glucose control experiments in rats indicate that a single microneedle patch can effectively maintain normal blood glucose for over 7 h.

An injectable conductive hydrogel with dual responsive release of rosmarinic acid improves cardiac function and promotes repair after myocardial infarction

Myocardial infarction (MI) causes irreversible damage to the heart muscle, seriously threatening the lives of patients. Injectable hydrogels have attracted extensive attention in the treatment of MI. By promoting the coupling of mechanical and electrical signals between cardiomyocytes, combined with synergistic therapeutic strategies targeting the pathological processes of inflammation, proliferation, and fibrotic remodeling after MI, it is expected to improve the therapeutic effect. In this study, a pH/ROS dual-responsive injectable hydrogel was developed by modifying xanthan gum and gelatin with reversible imine bond and boronic ester bond double crosslinking. By encapsulating polydopamine-rosmarinic acid nanoparticles to achieve on-demand drug release in response to the microenvironment of MI, thereby exerting anti-inflammatory, anti-apoptotic, and anti-fibrosis effects. By adding conductive composites to improve the conductivity and mechanical strength of the hydrogel, restore electrical signal transmission in the infarct area, promote synchronous contraction of cardiomyocytes, avoid induced arrhythmias, and induce angiogenesis. Furthermore, the multifunctional hydrogel promoted the expression of cardiac-specific markers to restore cardiac function after MI. The in vivo and in vitro results demonstrate the effectiveness of this synergistic comprehensive treatment strategy in MI treatment, showing great application potential to promote the repair of infarcted hearts.

Dual-responsive fiber-reinforced hydrogel actuators by direct ion patterning

Nature inspired deformable heterogeneous smart hydrogels have attracted much attention in many fields such as biomedicine devices and soft actuators.However,normal spatial heterogeneous hydrogel structures can only respond to single factor and take one action as set in fabrication.Herein,we report a pre-stretched metal-liganded shape memory hydrogel with fiber reinforced,P(AAc-co-AAm)/CCNFs-Fe3+(CCNFs:carboxylated cellulose nanofibers,AAc:acrylic acid,AAm:acrylamide),which can conduct shape deformation by solvent induction and ultraviolet(UV)light.The deformation pattern could be programmed by the deposing of ferroin ions.Also,the pre-stretched shape memory hydrogels could effectively produce cyclic actuation or complex shape actuation by UV light.More importantly,combining the solvent response with the light response enabled complex reversible actuations,such as simulating the bending and unfolding of fingers.The addition of CCNFs significantly enhanced the mechanical properties of the hydrogels.The hydrogels with 3 wt.%CCNFs showed an elongation at break of about 500%and a significant increase in tensile strength of 8.7-fold to 1.55 MPa after coordination with metal ions,which was able to meet the mechanical requirements of the bionic actuated hydrogels.This work demonstrated that combining light-programmed and light-responsive shape-memory hydrogels,complemented by another independent response property,could achieve complex and reversible programmed actuations.

Multi-bond Network Hydrogels with Robust Mechanical and Self-healable Properties

Multi-bond network（MBN） which contains a single network with hierarchical cross-links is a suggested way to fabricate robust hydrogels. In order to reveal the roles of different cross-links with hierarchical bond energy in the MBN, here we fabricate poly（acrylic acid） physical hydrogels with dual bond network composed of ionic cross-links between carboxylFe3＋ interactions and hydrogen bonds, and compare these dually cross-linked hydrogels with singly and ternarily cross-linked hydrogels. Simple models are employed to predict the tensile property, and the results confirm that the multi-bond network with hierarchical distribution in the bond energy of cross-links endows hydrogel with effective energy-dissipating mechanism. Moreover, the dually cross-linked MBN gels exhibit excellent mechanical properties（tensile strength up to 500 k Pa, elongation at break ~ 2400%） and complete self-healing after being kept at 50 °C for 48 h. The factors on promoting self-healing are deeply explored and the dynamic multi-bonds are regarded to trigger the self-healing along with the mutual diffusion of long polymer chains and ferric ions.

POSS-modified PEG Adhesives for Wound Closure

PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth. In this study, we produced a series of POSS-modified PEG adhesives with high adhesive strength. Introduction of inorganic hydrophobic POSS units decreased the swelling of the adhesives and enhanced cell adhesion and growth. The in vitro cytotoxicity and in vivo inflammatory response experiments clearly demonstrated that the adhesives were nontoxic and possessed excellent biocompatibility. Compared with the sutured wounds, the adhesive-treated wounds showed an accelerated healing process in wounded skin model of the Bama miniature pig, demonstrating that the POSS-modified PEG adhesive is a promising candidate for wound closure.

PREFACE

Hydrogels are classical soft and wet materials that have been extensively studied over the past several decades. Recently, with the development of supramolecular science, nanotechnology and precisely synthetic chemistry, various novel hydrogels have been designed and fabricated, which show emerging applications in tissue engineering, drug delivery, anti-fouling coatings, flexible electronics and soft robotics. Through tailoring their two-dimensional surface structures and three- dimensional networks, unique properties such as ultra-high mechanical strength, responsiveness to various kinds of stimuli, biocompatibility, special wettability and adhesion can be achieved.