Soft yet mechanically robust injectable alginate hydrogels with processing versatility based on alginate/hydroxyapatite hybridization.

The salient gelling feature of alginate via forming the egg-box structure with calcium ions has received extensive interests for different applications. Owing to the interfacial incompatibility of rigid inorganic solids with soft polymers, the requirement of overall stereocomplexation with calcium released from uniformly distributed solids in alginate remains a challenge. In this study, a novel alginate-incorporated calcium source was proposed to tackle the intractable dispersion for the preparation of injectable alginate hydrogels. Calcium phosphate synthesis in alginate solution yielded CaP-alginate hybrids as a calcium source. The physicochemical characterization confirmed the CaP-alginate hybrid was a nano-scale alginate-hydroxyapatite complex. The colloidally stable CaP-alginate hybrids were uniformly dispersed in alginate solutions even under centrifugation. The calcium-induced gelling of the CaP-alginate hybrids-loaded alginate solutions formed soft yet tough hydrogels including transparent sheets and knittable threads, confirming the homogeneous gelation of the hydrogel. The gelation time, injectability and mechanical properties of the hydrogels could be adjusted by changing preparation parameters. The prepared hydrogels showed uniform porous structure, excellent swelling, wetting properties and cytocompatibility, showing a great potential for applications in different fields. The present strategy with organic/inorganic hybridization could be exemplarily followed in the future development of functional hydrogels especially associated with the interface integration.

pH-Responsive Carrier-Free Polyphenol Nanoparticles Assembled by Oxidative Polymerization with Enhanced Stability and Antioxidant Activity for Improved Bioaccessibility.

Encapsulation of plant polyphenols with micro-/nano-carriers for enhanced bioavailability has been well documented, but the preparation of these carriers and subsequent loading of polyphenols is a multiple process, which is generally complicated with potentially unexpected negative effects on the bioactivity of the polyphenols. Here, we reported a convenient method to assemble carrier-free polyphenol nanoparticles (NPs) based on oxidative coupling polymerization. The effectiveness was assessed with five different polyphenols including pyrocatechol (PY), catechin (CA), epigallocatechin gallate (EGCG), tannic acid (TA), and proanthocyanidin (PC). The structural characteristics of these assembled nanoparticles (PY NPs, CA NPs, EG NPs, TA NPs, and PC NPs) were systematically analyzed with dynamic light scattering (DLS), transmission electron microscopy (TEM), UV-visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). All NPs were colloidally stable with varying NaCl concentrations from 0 to 300 mM, were acid-resistant and alkali-intolerant, and were suitable for oral administration. An array of antioxidant assays further confirmed the superior antioxidant capabilities of NPs over Trolox and polyphenol monomers, indicating that the oxidative polymerization of polyphenols did not compromise the polyphenol activity of NPs. The in vitro simulated digestion studies validated that these responsive NPs were actually gastrointestinal pH-responsive and applicable to the gastrointestinal physiological environment. The bioaccessibility assessments by using a static in vitro digestion model revealed that better results were achieved with NPs than polyphenol monomers, with TA NPs showing about 1.5-fold higher bioaccessibility than other polyphenol nanoparticles. The present study with five polyphenols demonstrated that the oxidative polymerization of polyphenols provides an effective platform to assemble various carrier-free NPs with enhanced antioxidant activity, favorable stability, and improved bioaccessibility, which could be used promisingly as a functional food ingredient in food matrices or as oral drug delivery candidates for helping to manage human health or treating various gastrointestinal disorders in both the pharmaceutical and nutritional fields.

Collagen Scaffolds Functionalized by Cu2+-Chelated EGCG Nanoparticles with Anti-Inflammatory, Anti-Oxidation, Vascularization, and Anti-Bacterial Activities for Accelerating Wound Healing.

Skin injury is a common health problem worldwide, and the highly complex healing process poses critical challenges for its management. Therefore, wound dressings with salutary effects are urgently needed for wound care. However, traditional wound dressing with a single function often fails to meet the needs of wound repair, and the integration of multiple functions has been required for wound repair. Herein, Cu2+-chelated epigallocatechin gallate nanoparticles (EAC NPs), with radical scavenging, inflammation relieving, bacteria restraining, and vascularization accelerating capacities, are adopted to functionalize collagen scaffold, aiming to promote wound healing. Radical scavenging experiments verify that EAC NPs could efficiently scavenge radicals. Additionally, EAC NPs could effectively remove Escherichia coli and Staphylococcus aureus. H2O2 stimuli-responsive EAC NPs show slow and sustained release properties of Cu2+. Furthermore, EAC NPs exhibit protective effects against H2O2-induced oxidative-stress damage and anti-inflammatory activity in vivo. Physicochemical characterizations show that the introduction of EAC NPs does not disrupt the gelation behavior of collagen, and the composite scaffolds (CS) remain porous structure similar to collagen scaffold. Animal experiments demonstrate that CS could promote wound healing through improving the thickness of renascent epidermis and number of new vessels. CS with multiple salutary functions is a promising dressing for wound care.

Influences of carboxymethyl chitosan upon stabilization and gelation of O/W Pickering emulsions in the presence of inorganic salts.

The objective of this study was to investigate the effects of carboxymethyl chitosan (CMCS) on the stabilization and gelation of oil-in-water (O/W) Pickering emulsions (PEs) with polyphenol-amino acid particles in the presence of inorganic salts. The results revealed that the CMCS-induced depletion interactions contributed to improving the emulsification ability and interfacial adsorption efficiency of polyphenol-amino acid particles as well as constructing the network structures in the continuous phase. These relevant changes collectively resulted in elevating stability, viscosity and moduli of PEs. The additional effects of different inorganic salts with varying additions were further investigated, and the addition-dependent phenomena were observed. At low additions of inorganic salts, the occurrence of the chelation of inorganic salts with CMCS consolidated the constructed network structure, favorable to the gelation of PEs. With increasing additions, this chelation effect became stronger which compromised the CMCS-induced depletion, gradually leading to destabilization of PEs. In terms of ion species, the more pronounced effect on emulsion stability was achieved with calcium ions than with potassium and iron ions. This study expects to provide a new perspective on the extending application of cationic CMCS for improving the stability of O/W PEs in the food industry.

Tea polyphenol carrier-enhanced dexamethasone nanomedicines for inflammation-targeted treatment of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease characterized by synovial inflammation, cartilage damage and bone erosion. In the progression of RA, the inflammatory mediators including ROS, NO, TNF-α, and IL-6 play important roles in the aggravation of inflammation. Hence, reducing the generation and release of inflammatory mediators is of great importance. However, the high dose and frequent administration of clinical anti-inflammatory drugs such as glucocorticoids (GCs) usually lead to severe side effects. The development of nanotechnology provides a promising strategy to overcome these issues. Here, polyphenol-based nanoparticles with inherent anti-oxidative and anti-inflammatory activities were developed and used as a kind of nanocarrier to deliver dexamethasone (Dex). The in vitro experiments confirmed that the nanoparticles and drugs could act synergistically for suppressing inflammatory mediators in the LPS/INF-γ-induced inflammatory cell model. After intravenous administration, the Dex-loaded nanoparticles with good biosafety showed effective accumulation in inflamed joints and improved therapeutic efficacy by inducing anesis of synovial inflammation and cartilage destruction over free Dex in a collagen-induced arthritis (CIA) mouse model. The results demonstrated that polyphenol-based nanoparticles with therapeutic functions may serve as an innovative platform to synergize with chemotherapeutic agents for enhanced treatment of inflammatory diseases.

Biomimetic mineralization by confined diffusion with viscous hyaluronan network: Assembly of hierarchical flower-like supraparticles.

Biomolecules-mediated biomimetic mineralization has been extensively investigated and applied to fabricate nano-assemblies with unique hierarchical architectures and salient properties. The confined-source ion diffusion plays a key role in the biomineralization process, but little investigative efforts have focused on it. Here, we developed a simple method to mimic the in vivo condition by a confined diffusion method, and hydroxyapatite nanoflower assemblies (HNAs) with exquisite hierarchical architectures were obtained. The HNAs were assembled from needle-like hybrid nanocrystals of hydroxyapatite and hyaluronan. The results revealed that the strong interactions between ions and hyaluronan led to the nucleation of hydroxyapatite and the following aggregation. The combination of the external diffusion field and the internal multiple interactions induced the self-assembling processes. Additionally, HNAs with colloid stability and excellent biocompatibility were proved to be a promising cargo carrier for intranuclear delivery. This work presents a novel biomimetic mineralization strategy based on confined diffusion system for fabricating delicate hydroxyapatite, which offers a new perspective for the development of biomimetic strategies.

Biocompatible, bacteria-targeting resveratrol nanoparticles fabricated by Mannich molecular condensation for accelerating infected wound healing.

Excessive reactive oxygen species (ROS) and long-term inflammation can delay wound healing and cause tissue damage, while bacterial infection aggravates the wound environment further. It is impossible to resolve all these thorny problems simultaneously with a wound dressing that has only one function. The antioxidative and anti-inflammatory properties of resveratrol (Res) have been proven. However, the effect of Res is non-selective, and high levels of Res can inhibit cell growth and promote oxidation. Res is also difficult to dissolve and possesses insufficient antibacterial properties, so its role is limited. In this study, Res was assembled via Mannich reaction into nanoparticles and functionalized by phenylboric acid, giving rise to targeting bacteria and solving the water-insoluble dilemma of Res. In comparison with Trolox, the assembled Res NPs performed better at scavenging ABTS and DPPH free radicals. Furthermore, Res NPs that targeted bacteria also showed high biocompatibility at concentrations five times higher than pure Res. The activities of Res NPs were comparable to free Res in downregulating the expression of inflammatory cytokines, and reducing intracellular excessive ROS. The gel embedded with Res NPs accelerated the formation of granulation tissue, collagen deposition, and re-epithelialization, facilitating wound healing. The present study suggests that functionalized polyphenol-based materials are preferably suited to the development of tissue engineering biomaterials.

Engineered fabrication of EGCG-UV absorber conjugated nano-assemblies for antioxidative sunscreens with broad-band absorption.

Applying sunscreen is a common, convenient, and effective measure to protect skin from ultraviolet (UV) damage, but most of UV absorbers in the present commercially available sunscreens are accompanied with the insufficiencies in terms of efficacy and biosafety. The use of nanotechnology to combine conventional UV absorbers with biocompatible natural products is a feasible strategy to combat these deficiencies. Herein, a simple, green and engineering preparation of broad-band sunscreens was demonstrated by the molecular assembly of a UV absorber aminobenzoic acid (ABA) and polyphenol extracted from green tea (EGCG). Spherical and negatively-charged EGCG/ABA nanoparticles (EA NPs) were simply synthesized with a wide range of particle size from 54.6 to 715.1 nm. These NPs had the satisfactory biocompatibility and antioxidative activity, and could protect fibroblasts from oxidative-stress damage. The formulations containing 10 wt% EA NPs further exhibited broad-spectrum UV absorption and lower UV transmittance than commercial sunscreens. It is believed that this study would spur the utilization of natural reproducible sources for developing biosafe sunscreens with strong anti-UV capability. Indeed, this simple nanotechnology aimed at tackling the biosafe risk of conventional UV absorbers provides a feasible solution strategy with green tea extracts.

Injectable oxidized alginate/carboxylmethyl chitosan hydrogels functionalized with nanoparticles for wound repair.

Owing to its simple properties, the application of injectable hydrogel in wound repair is limited. Therefore, the multi-functionalization of injectable hydrogel to improve the therapeutic effect is imperative. Here, keratin nanoparticles (Ker NPs) with facilitating epithelization capability and nanosized-EGCG covered with Ag nanoparticles (AE NPs) with radicals scavenging capability were used to functionalize injectable oxidized alginate/carboxylmethyl chitosan hydrogel (KA hydrogel). The radical scavenging experiments proved the anti-oxidative capacity of AE NPs. Rheological test exhibited that the gelation time and storage modulus of KA hydrogel were about 216 s and 403 Pa. Additionally, wound healing experiment in vivo showed that KA hydrogel could accelerated wound healing, especially in the early stage, and improved the thickness of renascent epidermis by 21 %. In this work, Ker NPs and AE NPs functionalization endowed injectable hydrogels with the capabilities of scavenging radicals and facilitating epithelization, which is promising for the applications in wound repair.

Injectable hyaluronic acid/hydroxyapatite composite hydrogels as cell carriers for bone repair.

The natural polysaccharide/hydroxyapatite hydrogels are of great interest to bone tissue engineering, but the interfacial mismatch between rigid hydroxyapatite and soft polysaccharide phase in these hydrogels remains unsolved, which is unfavorable to achieving uniform dispersion of hydroxyapatite particles in the hydrogel matrices. Herein, hyaluronic acid (Hya), an extracellular matrix constituent, was chosen as the template for biological mineralization to synthesize Hya/hydroxyapatite hybrid particles (HAHs). The oxidized Hya/hydroxyapatite hybrid particles (OHAHs) were obtained by oxidating the Hya in the HAHs. These OHAHs were the ball-flower particles hybridized with ca. 22 % oxidized Hya. Then, different concentrations of OHAHs were introduced to prepare hydroxyapatite composite hydrogels (HCH) via Schiff-base reaction of oxidized Hya and carboxymethyl chitosan. The injectability and self-healing of HCH were evaluated and the introduction of OHAHs significantly increased the storage modulus. The gelation time of HCH showed a negative relation with the concentration of OHAHs while the storage modulus presented a positive correlation. MTT assays and live/dead staining of L929 cells co-cultured with HCH confirmed that the hydrogels had excellent cytocompatibility, and supported the adhesion and proliferation of cells under the three-dimension culture conditions. These injectable self-healing hydrogels suitable for cell encapsulation were potentially useful for bone defect repair.

Size Changeable Nanomedicines Assembled by Noncovalent Interactions of Responsive Small Molecules for Enhancing Tumor Therapy.

The size of nanocarriers strongly affects their performance in biological systems, especially the capacity to overcome various barriers before delivering the payloads to destinations. However, the optimum size varies at different delivery stages in cancer therapy due to the complicated tumor microenvironment. Relatively large particles are favored for long-term circulation in vivo, while smaller particles contribute to deep penetration into tumor tissues. This dilemma in the size of particles stimulates the development of stimuli-responsive size-shrinking nanocarriers. Herein, we report a facile strategy to construct a tumor-triggered tannic acid (TA) nanoassembly with improved drug delivery efficiency. Cystamine (CA), a small molecule with a disulfide bond, is thus used to mediate TA assembling via cooperative noncovalent interactions, which endows the nanoassembly with intrinsic pH/GSH dual-responsiveness. The obtained TA nanoassemblies were systematically investigated. DOX encapsulated nanoassembly labeled TCFD NP shows high drug loading efficiency, pH/GSH-responsiveness and significant size shrinkage from 122 to 10 nm with simultaneous drug release. The in vitro and in vivo experimental results demonstrate the excellent biocompatibility, sufficient intracellular delivery, enhanced tumor retention/penetration, and superior anticancer efficacy of the small-molecule-mediated nanoassembly. This noncovalent strategy provides a simple method to fabricate a tumor-triggered size-changeable delivery platform to overcome biological barriers.

Dual stimuli-responsive nanocarriers based on polyethylene glycol-mediated schiff base interactions for overcoming tumour chemoresistance.

Multifunctional and stimulus-sensitive intelligent nanodrug delivery systems (NDDSs) can significantly optimize the effectiveness of theranostic agents for cancer treatment. In this study, redox and pH dual-responsive nanocarriers (CPNPs) were prepared through molecular assembly by utilizing the Schiff base interactions of cystamine (Cys), PEG-NH2 and formaldehyde (FA) under aqueous conditions with a one-pot, one-step technique. First, the degradation products of CPNPs exhibited good biocompatibility, and the high concentration of intact CPNPs (200 µg/mL) could inhibit the growth of cells. In addition, doxorubicin (DOX) was encapsulated in CPNPs simply by changing the pH (DOX@CPNPs), and pH/GSH-responsive release behaviour was confirmed. In vitro, CPNPs significantly increased the uptake of DOX and enhanced the cytotoxicity of DOX to tumour cells. More importantly, DOX@CPNPs strongly reversed drug resistance in three different types of cancer cells, exhibiting significant anticancer effects. Collectively, this study presents the easy preparation of nanomedicines that respond to multiple stimuli, which highlights the advantages of Schiff base-based nanomedicines for cancer therapy and reversing chemoresistance.

Synthesis and characterization of injectable self-healing hydrogels based on oxidized alginate-hybrid-hydroxyapatite nanoparticles and carboxymethyl chitosan.

Injectable hydrogels are of great interest in tissue engineering, and those incorporating hydroxyapatite (HA) are especially acclaimed in the application of bone repair. Synthetic micro-HA were generally used for this purpose and in some cases, surface modification of HA was further applied to improve the interfacial compatibility of rigid inorganic HA with soft organic matrix. In this study, the injectable hydrogels based on oxidized alginate hybrid HA nanoparticles and carboxymethyl chitosan were achieved via Schiff base reaction. Physicochemical characterization confirmed that oxidized HA/Alg hybrids (OHAH) were successfully prepared. Rheological measurements verified the formation of hydrogels based on the dynamic imine bonding, and the gelation time showed a negative correlation to the concentration and oxidation time of OHAH, while the storage moduli exhibited a positive correlation. The self-healing property of these hydrogels was validated by the splicing experiments and rheological experiments. The lyophilized hydrogels showed porous structures with numerous HA nanoparticles distributed on the surface of pore wall. MTT assays and live/dead staining of cell experiments confirmed the cytocompatibility of these hydrogels. The injectable hydrogels with self-healing and tunable gelling properties were ingeniously prepared with functionalized alginate-mediated HA hybrid nanoparticles, and these hydrogels are promising for applications in bone tissue engineering.

General Nanomedicine Platform by Solvent-Mediated Disassembly/Reassembly of Scalable Natural Polyphenol Colloidal Spheres.

The current strategy using the assembly of medicines and active functional molecules to develop nanomedicines often requires both molecules to have a specific matched chemical molecular structure; however, this is often difficult to predict, execute, and control in practical applications. Herein, we reported a general solvent-mediated disassembly/reassembly strategy for preparing nanomedicines based on epigallocatechin gallate (EGCG) active molecules. The polyphenol colloidal spheres (CSs) were self-assembled from molecular condensed EGCG in aqueous solution but disassembled in organic solvents and reassembled in aqueous solution. The solvent-mediated disassembly and reassembly capability of CSs gave rise to the active binding of condensed EGCG to various hydrophilic and hydrophobic guest molecules. The maximum encapsulation and drug-loading rate of reassembled CSs/DOX were 90 and 44%, respectively, and the nanomedicines could reverse drug resistance of tumor cells and exhibit enhanced therapeutic effects for breast cancer. Last but not least, 37.3 g of polyphenol CSs was massively produced at one time with a yield of 74.6%, laying a solid foundation for the practical applications of reassembled nanomedicines. The present strategy leading to a general nanomedicines platform was concise and highly efficient for both hydrophilic and hydrophobic drugs, making a breakthrough for low loading dilemma of current nanomedicines, and would open up a new direction for the preparation of nanocarriers, nanocomposites, and nanomedicines from natural polyphenols.

Micro-/Nanomechanics Dependence of Biomimetic Matrices upon Collagen-Based Fibrillar Aggregation and Arrangement.

The mechanical and morphological cues of fibrillar extracellular matrices (ECMs) play vital roles in controlling the cellular behaviors. Understanding and regulating the correlation of the mechanics with morphologies, at the micro-/nanoscale are of great relevance to guide the growth and differentiation of stem or progenitor cells into the desired tissues. However, the investigations directed toward acquiring such a kind of correlation are very limited and far from satisfactory. Here, rheological and nanoindentation tests were employed to appraise the mechanical behaviors of biomimetic ECMs assembled from type I collagen solutions containing the equivalent content of alginate but with different molecular weights (MWs). An alginate-molecular-weight-dependent trend was found in the fibrillogenesis process and the fibril aggregation of these collagen-alginate (CA) matrices. The present study revealed that the viscoelasticity and nonlinear elasticity of the CA matrices relied upon their specific fibrillar architectures in which a heterogeneous structure formed with varying alginate MW, including the coexistence of small fibrils and larger fibrillar bundles. The correlation of the mechanical behaviors with the inhomogeneity in the fibrillar structures was further discussed in combination with those of Ca2+ ionically cross-linked CA matrices. This study not only presented the delicate mechanics of fibrillar ECM analogues but also showed that the introduction of affiliative matters such as polysaccharides (alginate with different MWs) is a simple and convenient strategy to achieve biomimetic hydrogels with tunable viscoelastic properties.