4D printed hydrogel scaffold with swelling-stiffening properties and programmable deformation for minimally invasive implantation.

The power of three-dimensional printing in designing personalized scaffolds with precise dimensions and properties is well-known. However, minimally invasive implantation of complex scaffolds is still challenging. Here, we develop amphiphilic dynamic thermoset polyurethanes catering for multi-material four-dimensional printing to fabricate supportive scaffolds with body temperature-triggered shape memory and water-triggered programmable deformation. Shape memory effect enables the two-dimensional printed pattern to be fixed into temporary one-dimensional shape, facilitating transcatheter delivery. Upon implantation, the body temperature triggers shape recovery of the one-dimensional shape to its original two-dimensional pattern. After swelling, the hydrated pattern undergoes programmable morphing into the desired three-dimensional structure because of swelling mismatch. The structure exhibits unusual soft-to-stiff transition due to the water-driven microphase separation formed between hydrophilic and hydrophobic chain segments. The integration of shape memory, programmable deformability, and swelling-stiffening properties makes the developed dynamic thermoset polyurethanes promising supportive void-filling scaffold materials for minimally invasive implantation.

Molecular co-assembled strategy tuning protein conformation for cartilage regeneration.

The assembly of oligopeptide and polypeptide molecules can reconstruct various ordered advanced structures through intermolecular interactions to achieve protein-like biofunction. Here, we develop a "molecular velcro"-inspired peptide and gelatin co-assembly strategy, in which amphiphilic supramolecular tripeptides are attached to the molecular chain of gelatin methacryloyl via intra-/intermolecular interactions. We perform molecular docking and dynamics simulations to demonstrate the feasibility of this strategy and reveal the advanced structural transition of the co-assembled hydrogel, which brings more ordered ß-sheet content and 10-fold or more compressive strength improvement. We conduct transcriptome analysis to reveal the role of co-assembled hydrogel in promoting cell proliferation and chondrogenic differentiation. Subcutaneous implantation evaluation confirms considerably reduced inflammatory responses and immunogenicity in comparison with type I collagen. We demonstrate that bone mesenchymal stem cells-laden co-assembled hydrogel can be stably fixed in rabbit knee joint defects by photocuring, which significantly facilitates hyaline cartilage regeneration after three months. This co-assembly strategy provides an approach for developing cartilage regenerative biomaterials.

Corrigendum to "Bioinspired supramolecular nanofiber hydrogel through self-assembly of biphenyl-tripeptide for tissue engineering" [Bioact. Mater. 8 (2022) 396-408].

[This corrects the article DOI: 10.1016/j.bioactmat.2021.05.054.].

Bioinspired supramolecular nanofiber hydrogel through self-assembly of biphenyl-tripeptide for tissue engineering.

Supramolecular nanofiber peptide assemblies had been used to construct functional hydrogel biomaterials and achieved great progress. Here, a new class of biphenyl-tripeptides with different C-terminal amino acids sequences transposition were developed, which could self-assemble to form robust supramolecular nanofiber hydrogels from 0.7 to 13.8 kPa at ultra-low weight percent (about 0.27 wt%). Using molecular dynamics simulations to interrogate the physicochemical properties of designed biphenyl-tripeptide sequences in atomic detail, reasonable hydrogen bond interactions and "FF" brick (phenylalanine-phenylalanine) promoted the formation of supramolecular fibrous hydrogels. The biomechanical properties and intermolecular interactions were also analyzed by rheology and spectroscopy analysis to optimize amino acid sequence. Enhanced L929 cells adhesion and proliferation demonstrated good biocompatibility of the hydrogels. The storage modulus of BPAA-AFF with 10 nm nanofibers self-assembling was around 13.8 kPa, and the morphology was similar to natural extracellular matrix. These supramolecular nanofiber hydrogels could effectively support chondrocytes spreading and proliferation, and specifically enhance chondrogenic related genes expression and chondrogenic matrix secretion. Such biomimetic supramolecular short peptide biomaterials hold great potential in regenerative medicine as promising innovative matrices because of their simple and regular molecular structure and excellent biological performance.

Stimuli-responsive biphenyl-tripeptide supramolecular hydrogels as biomimetic extracellular matrix scaffolds for cartilage tissue engineering.

Supramolecular hydrogel composed of aromatic short peptide gelator was an attractive biomaterial owing to its simple and convenient synthetic route, nano-fibrillar microstructure resembling natural collagen fibers and intelligent response to external stimulus. Herein, stimuli-responsive biphenyl-tripeptide supramolecular hydrogels was prepared to simulate extracellular matrix scaffolds by temperature switch, ion induction and pH switch. The amino acid arrangement substantially affected gelation behavior, only BPAA-ßAFF and BPAA-FFßA could form nanostructured supramolecular hydrogels with 8-10 nm nanotubes or nanofibers by potential intermolecular hydrogen bond interactions and π-π stacking. The minimum gelation concentration (MGC) and maximum storage modulus were 0.4 mM (0.023 wt%) and around 8.2 KPa. The two supramolecular hydrogels could support adhesion and proliferation of L929 cells. Moreover, the BPAA-ßAFF hydrogel promoted proliferation and ECM secretion of chondrocytes in vitro, and facilitate the phenotype maintenance of hyaline cartilage. All the results demonstrated that BPAA-ßAFF hydrogel hold great potential application prospects in cartilage tissue engineering. STATEMENT OF SIGNIFICANCE: Diphenylalanine was served as a core segment conjugating with 4-biphenylacetic acid (BPAA) to produce biphenyl-tripeptide compounds with transforming amino sequence, and multiple external stimuli was applied to study the gelation properties of the aromatic short peptide gelators. "FF" brick (phenylalanine-phenylalanine) was crucial for formation of fibrous supramolecular hydrogels. Meanwhile, the sequence of amino acids arrangement also had an essential effect on the gelation behavior. Optimal BPAA-ßAFF with ultra-low minimum gelation concentration (0.4 mM, about 0.023 wt%) and similar microstructure to extracellular matrix (ECM) of nature cartilage tissue could promote the proliferation and ECM secretion of chondrocytes in vitro, and facilitate the formation of hyaline cartilage.

Catechol modified quaternized chitosan enhanced wet adhesive and antibacterial properties of injectable thermo-sensitive hydrogel for wound healing.

Wound dressings based on injectable thermo-sensitive hydrogel possess several advantages over preformed conventional dressings such as rapid reversible sol-gel transition behavior and the capacity of filling the irregular wound defect. Nevertheless, its clinical application is hindered by the weak tissue adhesiveness. Therefore, in this study, the catechol modified quaternized chitosan (QCS-C) was fabricated and incorporated into poly(d,l-lactide)-poly(ethylene glycol)-poly(d,l-lactide) (PLEL) hydrogel to develop an injectable hydrogel with the properties of thermo-sensitive, antibacterial and tissue adhesive. QCS-C could lower the LCST of hydrogel for easy gelation at physiological temperature, and significantly enhanced the tissue adhesion. For wound generation, nano-scaled bioactive glass (nBG：80 SiO2, 16 CaO and 4 P2O5; mol%) was loaded into hydrogel to promote angiogenesis. The mice partial laceration experiment showed that PLEL-nBG-QCS-C hydrogel could effectively seal the ruptured skin and significantly accelerate wound healing. Thus, our findings established a new type of clinical treatment technology for complicated wounds.

A shear-thinning adhesive hydrogel reinforced by photo-initiated crosslinking as a fit-to-shape tissue sealant.

Surgical sealants suitable for wounds with non-flat complex geometries are still a challenge to fulfill clinical requirements. Herein, a novel fit-to-shape sealant enhanced by photo-initiated crosslinking was developed utilizing maleic anhydride modified chitosan (MCS), benzaldehyde-terminated PEG (PEGDF) and polyethylene glycol diacrylate (PEGDA). Initially, the shear-thinning hydrogel prepared through the Schiff-base linkage between MCS and PEGDF could be injected into target sites, remolded to conform to a wound with non-flat complex geometry, and remain on the wound, avoiding adverse liquid leakage. Under illumination with ultra-violet (UV) light, the hydrogel was solidified in situ rapidly to adopt the wound contour and enhanced in adhesive strength to seal defects of the tissue. In addition, the hydrogel exhibits stability in extreme pH environments (pH = 1) and has potential to treat wounds inside the stomach with the existence of gastric acid. Moreover, the hydrogel can be applied as adhesive wound dressings through in situ 3D printing. Taken together, the fit-to-shape sealant enhanced by photo-initiated crosslinking can be considered as promising tissue adhesives for wound closure and other biomedical applications.

Bone Targeted Delivery of SDF-1 via Alendronate Functionalized Nanoparticles in Guiding Stem Cell Migration.

Stem cells are well-known for their great capacity for tissue regeneration. This provides a promising source for cell-based therapies in treating various bone degenerative disorders. However, the major hurdles for their application in transplantation are the poor bone marrow homing and engraftment efficiencies. Stromal cell-derived factor 1 (SDF-1) has been identified as a major stem cell homing factor. With the aims of bone targeted SDF-1 delivery and regulating MSCs migration, alendronate modified liposomal nanoparticles (Aln-Lipo) carrying SDF-1 gene were developed in this study. Alendronate modification significantly increased the mineral binding affinity of liposomes, and facilitated the gene delivery to osteoblastic cells. Up-regulated SDF-1 expression in osteoblasts triggered MSCs migration. Systemic infusion of Aln-Lipo-SDF-1 with fluorescence labeling in mice showed the accumulation in osseous tissue by biophotonic imaging. Corresponding to the delivered SDF-1, the transplanted GFP+ MSCs were attracted to bone marrow and contributed to bone regeneration. This study may provide a useful technique in regulating stem cell migration.

Synergistic chemotherapeutic effect of sorafenib-loaded pullulan-Dox conjugate nanoparticles against murine breast carcinoma.

pH-Sensitive pullulan-doxorubicin conjugates encapsulating sorafenib (P-Dox/S) nanoparticles were developed as a synergistic combinatorial delivery system against murine breast carcinoma. The nanoparticles can encapsulate Dox and sorafenib with ultra-high loading capacity (65.34 wt%) through chemical conjugation and physical loading, whereas can remain stable under physiological conditions and gradually release Dox and sorafenib with the decreasing pH. These conjugates can be effectively internalized and clearly suppress 4T1 cell growth in vitro. Furthermore, research data of in vivo animal models revealed that the synergistic combinatorial P-Dox/S nanoparticles heavily accumulated in solid tumor tissue sites to maximize therapeutic efficacy; they also significantly inhibited solid tumor growth, even remarkably reduced solid tumor volume in comparison to the initial volume, and obviously diminished adverse effects. The anti-tumor therapeutic effect obviously outperformed the delivery of combinational chemotherapy of free drugs or single drug-loaded P-Dox nanoparticles at the same concentration. These promising results indicate the high-efficiency synergistic chemotherapeutic effects of these nanoparticles. Combinational chemotherapy using P-Dox/S nanoparticles has important potential in the clinical treatment of malignancy for overcoming drug resistance and heterogeneity.

Localized multidrug co-delivery by injectable self-crosslinking hydrogel for synergistic combinational chemotherapy.

Significant progress has been made in the use of injectable hydrogels as drug carrier systems to treat cancers by the peritumoral-localized co-delivery of multiple drugs with different therapeutic mechanisms. In this study, a novel, injectable self-crosslinking HA-SH hydrogel was able to concurrently encapsulate multiple drugs (sorafenib, doxorubicin, and metformin) to enhance chemotherapy efficacy. The hydrogel was relatively stable under physiological conditions and could quickly and directly release the loaded drugs to the tumor site in a reductive tumor microenvironment. The in vitro antitumor activity and cell-apoptosis assay demonstrated that the hydrogel loaded with multiple drugs (Gel + DS or Gel + DSM) showed obvious synergistic effects against breast cancer cells. The combinational chemotherapy enhanced the sensitivities of tumor cells and promoted tumor cell apoptosis after peritumoral administration. Compared with the single drug-loaded hydrogel, the hydrogel co-loaded with multiple drugs (Gel + DSM) showed the best tumor growth inhibition. Moreover, the monitoring of mice weight and ex vivo histological analysis of the main organs indicated that localized treatment with the hydrogel co-loaded with multiple drugs (Gel + DSM) obviously relieved the systemic toxicity and showed promise for inhibiting tumor metastasis, suggesting the superiority and potential application prospects of the injectable, self-crosslinking hydrogel co-loaded with multiple drugs.

Temperature and ion dual responsive biphenyl-dipeptide supramolecular hydrogels as extracellular matrix mimic-scaffolds for cell culture applications.

Stimuli-responsive supramolecular hydrogels composed of aromatic short peptide gelators have attracted intensive attention in the field of biomedicine because of their stable chemical structure, simple and convenient synthetic route and intelligent response to external stimuli. In this paper, several dipeptides were coupled to biphenylacetic acid (BPAA) to generate aromatic short peptide compounds through the standard solid phase peptide synthesis. These BPAA-dipeptide compounds presented clearly different gelation behaviors from the generally employed Fmoc-dipeptide and Nap-dipeptide compounds, but only BPAA-diphenylalanine was able to form homogeneous and transparent hydrogels through temperature switching or ion induction. Utilizing the biphenyl group not only expanded the scope of aromatic molecules serving as building blocks of aromatic short peptide gelators but also demonstrated the critical role of aromatic molecules in the self-assembling process. Moreover, supramolecular hydrogels initiated by heating-cooling or salt addition could be exploited as extracellular matrix (ECM) mimic scaffolds to support the adhesive growth and proliferation of L929 cells in 2D/3D culture under physiological conditions, demonstrating their potential applications in regenerative medicine.

The self-crosslinking smart hyaluronic acid hydrogels as injectable three-dimensional scaffolds for cells culture.

Although the disulfide bond crosslinked hyaluronic acid hydrogels have been reported by many research groups, the major researches were focused on effectively forming hydrogels. However, few researchers paid attention to the potential significance of controlling the hydrogel formation and degradation, improving biocompatibility, reducing the toxicity of exogenous and providing convenience to the clinical operations later on. In this research, the novel controllable self-crosslinking smart hydrogels with in-situ gelation property was prepared by a single component, the thiolated hyaluronic acid derivative (HA-SH), and applied as a three-dimensional scaffold to mimic native extracellular matrix (ECM) for the culture of fibroblasts cells (L929) and chondrocytes. A series of HA-SH hydrogels were prepared depending on different degrees of thiol substitution (ranging from 10 to 60%) and molecule weights of HA (0.1, 0.3 and 1.0 MDa). The gelation time, swelling property and smart degradation behavior of HA-SH hydrogel were evaluated. The results showed that the gelation and degradation time of hydrogels could be controlled by adjusting the component of HA-SH polymers. The storage modulus of HA-SH hydrogels obtained by dynamic modulus analysis (DMA) could be up to 44.6 kPa. In addition, HA-SH hydrogels were investigated as a three-dimensional scaffold for the culture of fibroblasts cells (L929) and chondrocytes cells in vitro and as an injectable hydrogel for delivering chondrocytes cells in vivo. These results illustrated that HA-SH hydrogels with controllable gelation process, intelligent degradation behavior, excellent biocompatibility and convenient operational characteristics supplied potential clinical application capacity for tissue engineering and regenerative medicine.

Efficient Delivery of DOX to Nuclei of Hepatic Carcinoma Cells in the Subcutaneous Tumor Model Using pH-Sensitive Pullulan-DOX Conjugates.

A series of pullulan-doxorubicin conjugates (Pu-DOXs) were investigated for effectively delivering DOX to nuclei of hepatic carcinoma cells in subcutaneous tumor model. These Pu-DOXs were prepared by conjugating DOX onto pullulan molecule via pH-responsive hydrazone bond using spacers with different alkane chain length. The highest drug loading content of Pu-DOXs went up to nearly 50%, and the diameter of Pu-DOX nanoparticles ranged from 50 to 170 nm, as measured by DLS and TEM. These Pu-DOX nanoparticles could rapidly release DOX in the acidic environment at pH = 5.0 while being kept relatively stable in neural conditions. The in vitro cell coculture experiments revealed that these Pu-DOX nanoparticles were selectively internalized by hepatic carcinoma cells through receptor-mediated endocytosis via asialoglycoprotein receptor on the hepatic carcinoma cell surface. DOX was rapidly released from Pu-DOX nanoparticles in acidic endosome/lysosome, diffused into cell nuclei due to its strong affinity to nucleic acid, inhibited the cell proliferation, and accelerated the cell apoptosis. In the nude mice subcutaneous hepatic carcinoma model, Pu-DOX nanoparticles efficiently accumulated in the tumor site through the enhanced permeation and retention effect. Then DOX was specifically internalized by hepatic carcinoma cells and rapidly diffused into the nuclei of cells. Compared with the control group in in vivo experiments, these Pu-DOX nanoparticles effectively inhibited solid tumor growth, prolonging the lifetime of the experimental animal. These pH sensitive nanoparticles might provide an important clinical implication for targeted hepatic carcinoma therapy with high efficiency and low systematic toxicity.

High drug loading pH-sensitive pullulan-DOX conjugate nanoparticles for hepatic targeting.

pH-sensitive pullulan-doxorubicin (DOX) conjugates were synthesized by attaching DOX onto pullulan derivate through hydrazone bond that was stable under neutral environment but readily cleaved under mildly acidic condition. By changing the feed ratio of DOX to the pullulan derivate, conjugates with drug-loading content up to 30 wt % were obtained. In aqueous solution, the conjugates spontaneously formed uniform core-shell structured nanoparticles with DOX as core and pullulan as shell. The diameters of the nanoparticles ranged from 50 to 110 nm according to the drug-loading content. In vitro releasing experiments showed that more than 75% DOX released within 2 h at pH 5.0, while less than 15% DOX released after 12 h at pH 7.4. This pH-responsive manner of DOX release might assist the quick diffusion of DOX from the acidic endosome/lysosome and the intracellular transfer into the nucleus. Pullulan on the nanoparticles surface provided the nanoparticles with active targeting property to hepatic cells through specific interaction with asialoglycoprotein receptors on the membrane of hepatic cells, without the necessity of introducing any extra ligand. These pullulan-DOX conjugate nanoparticles were expected to be promising drug delivery system for liver targeting antitumor chemotherapy.

Reduction breakable cholesteryl pullulan nanoparticles for targeted hepatocellular carcinoma chemotherapy.

In this study, a novel nanoparticulate drug delivery platform with inherent targeting ability to hepatic carcinoma cells and reduction-triggered drug release property was developed based on reducible cholesterol-modified pullulan (rCHP). The nanoparticle characteristics and antitumor effects were investigated in vitro and in vivo. The results revealed that drug-loaded rCHP nanoparticles were spherical and their diameter ranged between 80 and 160 nm with a change of molecular structure and drug loading content. rCHP nanoparticles with pullulan shells could anchor to human hepatocellular carcinoma cells (HepG2) due to specific recognition of asialoglycoprotein receptors (ASGPRs) overexpressing at the cytomembrane, reduction-sensitively release doxorubicin (DOX) in tumor cells, and effectively suppress the growth of HepG2 in vitro. In a hepatoma-bearing nude mouse model, attributed to their uncharged pullulan surface layer, the nanoparticles efficiently accumulated in the tumor site and were internalized by tumor cells. After cellular uptake, DOX release triggered by the reductive circumstance of tumor cells was achieved benefiting from the reduction-sensitive DOX release property. These nanoparticles showed significantly better antitumor effect and biosafety than DOX·HCl in the nude mice bearing hepatocellular carcinoma tumor.

Reduction-degradable PEG-b-PAA-b-PEG triblock copolymer micelles incorporated with MTX for cancer chemotherapy.

Reduction-breakable core-shell type polymeric micelles from reduction-degradable amphiphilic polyethylene glycol-b-polyamide amine-b-polyethylene glycol triblock copolymers (PEG-b-PAA-b-PEG) were prepared as new drug carriers of methotrexate (MTX) for cancer chemotherapy. The PEG-b-PAA-b-PEG copolymers were synthesized in a simple one-step process under mild condition through Michael addition. Spherical micelles with diameters ranging from 65 to 123nm were successfully fabricated from the copolymers. These micelles could effectively encapsulate the anti-cancer drug MTX in the core with drug loading content around 13%. The incorporation of MTX resulted in a little size increase but did not influence the morphology of micelles. The drug was hardly released from the micelles in normal condition without DDT as the reductant, but fast released up to 100% within 24h when the structure of micelle core was broken in the presence of DTT, thus provided a potential tool for tumor targeting delivery of MTX using the higher concentration of reductant in tumor tissues. The proliferation inhibition experiments demonstrate that MTX-encapsulated micelles show significant cytotoxicity to KB, HepG2 and 4T1 tumor cells, especiallythe 4T1 cells.

Bioreducible PAA-g-PEG graft micelles with high doxorubicin loading for targeted antitumor effect against mouse breast carcinoma.

Nanomaterials have demonstrated to be promising to deliver a chemotherapeutic drug deeply into the tumor for improving the anticancer efficacy. In this study, eight kinds of bioreducible PAA-g-PEG graft copolymeric micelles were prepared, and the anticancer drug DOX was stably encapsulated in the micelles. Benefited by the hydrophobic interaction and π-π stacking between aromatic structure of DOX and phenyl of PAA in the micelle core, high drug loading content more than 50 wt/wt % could be achieved. Drugs released from micelles in a reduction-sensitive manner, and effectively inhibit the growth of 4T1 mouse breast cancer cells in vitro. In the 4T1 tumor-bearing nude mice breast carcinoma subcutaneous model, the DOX-incorporated micelles showed much stronger accumulation in tumor than DOX·HCl, and reduced distribution in other main organs. The antitumor effect of the micelles was significantly better than DOX·HCl, as confirmed by tumor volume and body weight changes of the tumor-bearing Balb/c mice, as well as survive study. Encapsulation of DOX in the micelles improved the bioavailability of the drugs through the accumulation in tumor by passive targeting, greatly decreased organ damage due to cancer cell wild growth and metastasis, and depressed the toxicity of DOX on the heart and other organs.

Porous collagen scaffold reinforced with surfaced activated PLLA nanoparticles.

Porous collagen scaffold is integrated with surface activated PLLA nanoparticles fabricated by lyophilizing and crosslinking via EDC treatment. In order to prepare surface-modified PLLA nanoparticles, PLLA was firstly grafted with poly (acrylic acid) (PAA) through surface-initiated polymerization of acrylic acid. Nanoparticles of average diameter 316 nm and zeta potential -39.88 mV were obtained from the such-treated PLLA by dialysis method. Porous collagen scaffold were fabricated by mixing PLLA nanoparticles with collagen solution, freeze drying, and crosslinking with EDC. SEM observation revealed that nanoparticles were homogeneously dispersed in collagen matrix, forming interconnected porous structure with pore size ranging from 150 to 200 µm, irrespective of the amount of nanoparticles. The porosity of the scaffolds kept almost unchanged with the increment of the nanoparticles, whereas the mechanical property was obviously improved, and the degradation was effectively retarded. In vitro L929 mouse fibroblast cells seeding and culture studies revealed that cells infiltrated into the scaffolds and were distributed homogeneously. Compared with the pure collagen sponge, the number of cells in hybrid scaffolds greatly increased with the increment of incorporated nanoparticles. These results manifested that the surface-activated PLLA nanoparticles effectively reinforced the porous collagen scaffold and promoted the cells penetrating into the scaffold, and proliferation.