pH-Universal Catechol-Amine Chemistry for Versatile Hyaluronic Acid Bioadhesives.

Catechol, a major mussel-inspired underwater adhesive moiety, has been used to develop functional adhesive hydrogels for biomedical applications. However, oxidative catechol chemistry for interpolymer crosslinking and adhesion is exclusively effective under alkaline conditions, with limited applications in non-alkaline conditions. To overcome this limitation, pH-universal catechol-amine chemistry to recapitulate naturally occurring biochemical events induced by pH variation in the mussel foot is suggested. Aldehyde moieties are introduced to hyaluronic acid (HA) by partial oxidation, which enables dual-mode catechol tethering to the HA via both stable amide and reactive secondary amine bonds. Because of the presence of additional reactive amine groups, the resultant aldehyde-modified HA conjugated with catechol (AH-CA) is effectively crosslinked in acidic and neutral pH conditions. The AH-CA hydrogel exhibits not only fast gelation via active crosslinking regardless of pH conditions, but also strong adhesion and excellent biocompatibility. The hydrogel enables rapid and robust wound sealing and hemostasis in neutral and alkaline conditions. The hydrogel also mediates effective therapeutic stem cell and drug delivery even in dynamic and harsh environments, such as a motile heart and acidic stomach. Therefore, the AH-CA hydrogel can serve as a versatile biomaterial in a wide range of pH conditions in vivo.

Pore Diameter of Mesoporous Silica Modulates Oxidation of H2O2-Sensing Chromophore in a Porous Matrix.

Hydrogen peroxide (H2O2) is an attractive chemical because of its bleaching properties in paper and pulp industry and as a disinfectant in the food, water, and medical industries. However, it is important to monitor the residual H2O2 level after its usage and prevent any unintended health problems or chemical reactions. Most H2O2 sensors often utilize fluorophores or electrical circuitry that requires an additional irradiation or a digital display. To this end, this study presents a 3,3',5,5'-tetramethylbenzidine (TMB)/horseradish peroxidase (HRP)-loaded patch that alerts the presence of high H2O2 levels by generating a visible blue color. We hypothesized that water-insoluble TMB immobilized within mesoporous silica particles of proper pore diameter and structure would act as a colorimetric indicator through the H2O2-mediated oxidation within a cross-linked patch. We examined this hypothesis by immobilizing TMB molecules in mesoporous silica particles with 2 and 7 nm diameter cylindrical pores as well as on nonporous silica particles. Then, we loaded these TMB-silica particles and HRP in a porous alginate patch via sequential in situ cross-linking reaction and lyophilization. In the presence of 25-5000 µM H2O2, which simulate H2O2 concentrations found in residual disinfecting fluids, the patch loaded with TMB-mesoporous silica particles with 7 nm diameter pores generated a distinct blue color with varying intensities depending on the H2O2 concentration. The design principles demonstrated in this study should be applicable to a broad array of sensors to be integrated into a moldable, three-dimensional matrix.

Functional Skeletal Muscle Regeneration with Thermally Drawn Porous Fibers and Reprogrammed Muscle Progenitors for Volumetric Muscle Injury.

Skeletal muscle has an inherent capacity for spontaneous regeneration. However, recovery after severe injuries such as volumetric muscle loss (VML) is limited. There is therefore a need to develop interventions to induce functional skeletal muscle restoration. One suggested approach includes tissue-engineered muscle constructs. Tissue-engineering treatments have so far been impeded by the lack of reliable cell sources and the challenges in engineering of suitable tissue scaffolds. To address these challenges, muscle extracellular matrix (MEM) and induced skeletal myogenic progenitor cells (iMPCs) are integrated within thermally drawn fiber based microchannel scaffolds. The microchannel fibers decorated with MEM enhance differentiation and maturation of iMPCs. Furthermore, engraftment of these bioengineered hybrid muscle constructs induce de novo muscle regeneration accompanied with microvessel and neuromuscular junction formation in a VML mouse model, ultimately leading to functional recovery of muscle activity.

Tissue-Adhesive Chondroitin Sulfate Hydrogel for Cartilage Reconstruction.

Chondroitin sulfate (CS), the main component of cartilage extracellular matrix, has attracted attention as a biomaterial for cartilage tissue engineering. However, current CS hydrogel systems still have limitations for application in successful cartilage tissue engineering owing to their unsuitable degradation kinetics, insufficient mechanical similarity, and lack of integration with the native cartilage tissue. In this study, using mussel adhesive-inspired catechol chemistry, we developed a functional CS hydrogel that exhibits tunable physical and mechanical properties as well as excellent tissue adhesion for efficient integration with native tissues. Various properties of the developed catechol-functionalized CS (CS-CA) hydrogel, including swelling, degradation, mechanical properties, and adhesiveness, could be tailored by varying the conjugation ratio of the catechol group to the CS backbone and the concentration of the CS-CA conjugates. CS-CA hydrogels exhibited significantly increased modulus (∼10 kPa) and superior adhesive properties (∼3 N) over conventional CS hydrogels (∼hundreds Pa and ∼0.05 N). In addition, CS-CA hydrogels incorporating decellularized cartilage tissue dice promoted the chondrogenic differentiation of human adipose-derived mesenchymal stem cells by providing a cartilage-like microenvironment. Finally, the transplantation of autologous cartilage dice using tissue-adhesive CS-CA hydrogels enhanced cartilage integration with host tissue and neo-cartilage formation owing to favorable physical, mechanical, and biological properties for cartilage formation. In conclusion, our study demonstrated the potential utility of the CS-CA hydrogel system in cartilage tissue reconstruction.

Diving beetle-like miniaturized plungers with reversible, rapid biofluid capturing for machine learning-based care of skin disease.

Recent advances in bioinspired nano/microstructures have received attention as promising approaches with which to implement smart skin-interfacial devices for personalized health care. In situ skin diagnosis requires adaptable skin adherence and rapid capture of clinical biofluids. Here, we report a simple, all-in-one device consisting of microplungers and hydrogels that can rapidly capture biofluids and conformally attach to skin for stable, real-time monitoring of health. Inspired by the male diving beetle, the microplungers achieve repeatable, enhanced, and multidirectional adhesion to human skin in dry/wet environments, revealing the role of the cavities in these architectures. The hydrogels within the microplungers instantaneously absorb liquids from the epidermis for enhanced adhesiveness and reversibly change color for visual indication of skin pH levels. To realize advanced biomedical technologies for the diagnosis and treatment of skin, our suction-mediated device is integrated with a machine learning framework for accurate and automated colorimetric analysis of pH levels.

A Phenol-Amine Superglue Inspired by Insect Sclerotization Process.

Exoskeletons of insects formed by sclerotization processes exhibit superstrong properties in moduli. Here, it is demonstrated that mimicking the sclerotization process using phenol and polyamine molecules unexpectedly results in a 100% ecofriendly, biocompatible waterborne superglue. Oxygen presented in air and dissolved in water acts as an initiator producing phenolic radical/quinone for superglue curing. Despite synthesis-free uses of water, phenol, and polyamine, its adhesion strength is comparable to commercial epoxy glue showing >6 MPa in lap shear strength. The phenol-amine superglue bonds to various substrates including ceramics, woods, fabrics, plastics, metals, and importantly biological tissues. Due to strong adhesion, the superglue effectively seals wounds within a few seconds, and, due to its waterborne nature, no harmful respiratory effect is observed because of any release of volatile organic compounds. The easy, cost-effective preparation of the phenol-amine superglue can revolutionize varieties of industrial, biomedical, daily life processes.

Evolutionarily conserved sequence motif analysis guides development of chemically defined hydrogels for therapeutic vascularization.

Biologically active ligands (e.g., RGDS from fibronectin) play critical roles in the development of chemically defined biomaterials. However, recent decades have shown only limited progress in discovering novel extracellular matrix-protein-derived ligands for translational applications. Through motif analysis of evolutionarily conserved RGD-containing regions in laminin (LM) and peptide-functionalized hydrogel microarray screening, we identified a peptide (a1) that showed superior supports for endothelial cell (EC) functions. Mechanistic studies attributed the results to the capacity of a1 engaging both LM- and Fn-binding integrins. RNA sequencing of ECs in a1-functionalized hydrogels showed ~60% similarities with Matrigel in "vasculature development" gene ontology terms. Vasculogenesis assays revealed the capacity of a1-formulated hydrogels to improve EC network formation. Injectable alginates functionalized with a1 and MMPQK (a vascular endothelial growth factor-mimetic peptide with a matrix metalloproteinase-degradable linker) increased blood perfusion and functional recovery over decellularized extracellular matrix and (RGDS + MMPQK)-functionalized hydrogels in an ischemic hindlimb model, illustrating the power of this approach.

High-density lipoprotein-mimicking nanodiscs carrying peptide for enhanced therapeutic angiogenesis in diabetic hindlimb ischemia.

Therapeutic strategies using endogenous stem cell mobilizer can provide effective cell-free therapy for addressing various ischemic diseases. In particular, substance P (SP) exhibited therapeutic regeneration by facilitating mobilization of endogenous stem cells from bone marrow to the injured sites. However, its therapeutic effect has been limited due to short half-life and rapid degradation of administered SP peptides in vivo. Here we sought to develop high-density lipoprotein (HDL)-mimicking nanodiscs conjugated with SP (HDL-SP) in order to increase the in vivo half-life, bone marrow targeting, and therapeutic efficacy of SP for the treatment of diabetic peripheral ischemia. Conjugation of SP onto HDL nanodisc led to remarkable ∼3215- and ∼1060-fold increase in the ex vivo and in vivo half-lives of SP, respectively. Accordingly, HDL-SP nanodiscs improved retention of SP in bone marrow after systemic administration, leading to efficient mobilization of stem cells from bone marrow into blood circulation and reduction of systemic inflammation. Consequently, nanodisc based SP peptide delivery promoted blood vessel formation, blood perfusion recovery and markedly improved limb salvage in diabetic hindlimb ischemia model relative to administration of free SP without nanodisc modification. Therefore, HDL-SP nanodisc can provide a novel strategy for the treatment of diabetic ischemia and HDL nanodisc modification could be potentially useful for the extension of plasma circulation of other labile peptides.

Targeting protein and peptide therapeutics to the heart via tannic acid modification.

Systemic injection into blood vessels is the most common method of drug administration. However, targeting drugs to the heart is challenging, owing to its dynamic mechanical motions and large cardiac output. Here, we show that the modification of protein and peptide therapeutics with tannic acid-a flavonoid found in plants that adheres to extracellular matrices, elastins and collagens-improves their ability to specifically target heart tissue. Tannic-acid-modified (TANNylated) proteins do not adsorb on endothelial glycocalyx layers in blood vessels, yet they penetrate the endothelium to thermodynamically bind to myocardium extracellular matrix before being internalized by myoblasts. In a rat model of myocardial ischaemia-reperfusion injury, TANNylated basic fibroblast growth factor significantly reduced infarct size and increased cardiac function. TANNylation of systemically injected therapeutic proteins, peptides or viruses may enhance the treatment of heart diseases.

Galactosylated Lipidoid Nanoparticles for Delivery of Small Interfering RNA to Inhibit Hepatitis C Viral Replication In Vivo.

Small interfering RNA (siRNA) delivery can provide an effective therapy for treating viral diseases by silencing genes involved in viral replication. In this study, a liver-targeting formulation of lipidoid nanoparticle for delivery of siRNA that targets protein kinase C-related kinase 2 (PRK2) to inhibit hepatitis C virus (HCV) replication is reported. The most effective, minimally cytotoxic lipidoid for siRNA delivery to hepatic cells is identified from a small library of alkyl epoxide-polyamine conjugates. In vitro transfection of PRK2 siRNA (siPRK2) using this lipidoid induces significant silencing of PRK2 (≈80%), suppressing HCV replication in human hepatic cells transfected with the HCV subgenomic replicon. Systemic administration of siPRK2 using the lipidoid nanoparticles results in significant reduction of host PRK2 in the mouse liver (≈60%). This treatment significantly suppresses HCV replication in an HCV-xenograft mouse model. siRNA delivery to the liver is further improved via galactosylation of the lipidoid. Compared with the unmodified lipidoid formulation, galactosylated lipidoids induce greater silencing of host PRK2 in mouse livers (≈80%) and more rapid suppression of HCV replication in an HCV-xenograft mouse. This study suggests that galactosylated lipidoid nanoparticles could provide a treatment for hepatitis C by mediating delivery of anti-viral RNA interference therapeutics to the liver.