Peptides as multifunctional players in cancer therapy.

Peptides exhibit lower affinity and a shorter half-life in the body than antibodies. Conversely, peptides demonstrate higher efficiency in tissue penetration and cell internalization than antibodies. Regardless of the pros and cons of peptides, they have been used as tumor-homing ligands for delivering carriers (such as nanoparticles, extracellular vesicles, and cells) and cargoes (such as cytotoxic peptides and radioisotopes) to tumors. Additionally, tumor-homing peptides have been conjugated with cargoes such as small-molecule or chemotherapeutic drugs via linkers to synthesize peptide-drug conjugates. In addition, peptides selectively bind to cell surface receptors and proteins, such as immune checkpoints, receptor kinases, and hormone receptors, subsequently blocking their biological activity or serving as hormone analogs. Furthermore, peptides internalized into cells bind to intracellular proteins and interfere with protein-protein interactions. Thus, peptides demonstrate great application potential as multifunctional players in cancer therapy.

Identification of novel CD44v6-binding peptides that block CD44v6 and deliver a pro-apoptotic peptide to tumors to inhibit tumor growth and metastasis in mice.

CD44v6, a splice variant of the cell surface glycoprotein CD44, acts as a co-receptor for c-Met and is upregulated in tumors with high metastatic potential. Methods: We screened a phage-displayed peptide library for peptides that selectively bind to CD44v6-overexpressing cells and exploited them to block CD44v6 and deliver a pro-apoptotic peptide to tumors for cancer therapy. Results: CNLNTIDTC (NLN) and CNEWQLKSC (NEW) peptides bound preferentially to CD44v6-high cells than to CD44v6-low cells. The binding affinities of NLN and NEW to CD44v6 protein were 253 ± 79 and 85 ± 18 nM, respectively. Peptide binding to CD44v6-high cells was inhibited by the knockdown of CD44v6 gene expression and competition with an anti-CD44v6 antibody. A pull-down assay with biotin-labeled peptides enriched CD44v6 from cell lysates. NLN and NEW induced CD44v6 internalization and inhibited hepatocyte growth factor-induced c-Met internalization, c-Met and Erk phosphorylation, and cell migration and invasion. In mice harboring tumors, intravenously administered NLN and NEW homed to the tumors and inhibited metastasis to the lungs. When combined with crizotinib, a c-Met inhibitor, treatment with each peptide inhibited metastatic growth more efficiently than each peptide or crizotinib alone. In addition, KLAKLAKKLAKLAK pro-apoptotic peptide guided by NLN (NLN-KLA) or NEW (NEW-KLA) killed tumor cells and inhibited tumor growth and metastasis. No significant systemic side effects were observed after treatments. Conclusions: These results suggest that NLN and NEW are promising metastasis-inhibiting peptide therapeutics and targeting moieties for CD44v6-expressing metastases.

Calcium peroxide-mediated in situ formation of multifunctional hydrogels with enhanced mesenchymal stem cell behaviors and antibacterial properties.

Injectable hydrogels can serve as therapeutic vehicles and implants for the treatment of various diseases as well as for tissue repair/regeneration. In particular, the horseradish peroxidase (HRP) and hydrogen peroxide (H2O2)-catalyzed hydrogelation system has attracted much attention, due to its ease of handling and controllable gel properties. In this study, we introduce calcium peroxide (CaO2) as a H2O2-generating reagent to gradually supply a radical source for the HRP-catalyzed crosslinking reaction. This novel therapy can create stiff hydrogels without compromising the cytocompatibility of the hydrogels due to the use of initially high concentrations of H2O2. The physico-chemical properties of the hydrogels can be controlled by varying the concentrations of HRP and CaO2. In addition, the controlled and sustained release of bioactive molecules, including H2O2, O2, and Ca2+ ions, from the hydrogels could stimulate the cellular behaviors (attachment, migration, and differentiation) of human mesenchymal stem cells. Moreover, the hydrogels exhibited killing efficacy against both Gram-negative and Gram-positive bacteria, dependent on the H2O2 and Ca2+ release amounts. These positive results suggest that hydrogels formed by HRP/CaO2 can be used as potential matrices for a wide range of biomedical applications, such as bone regeneration and infection treatment.

In situ forming and reactive oxygen species-scavenging gelatin hydrogels for enhancing wound healing efficacy.

The overexpression of reactive oxygen species (ROS) contributes to the pathogenesis of numerous diseases such as atherosclerosis, myocardial infarction, cancer, and chronic inflammation. Therefore, the development of materials that can locally control the adverse effects resulting from excessive ROS generation is of great significance. In this study, the antioxidant gallic acid-conjugated gelatin (GGA) was introduced into gelatin-hydroxyphenyl propionic (GH) hydrogels to create an injectable hydrogel with enhanced free radical scavenging properties compared to pure GH hydrogels. The modified hydrogels were rapidly formed by an HRP-catalyzed cross-linking reaction with high mechanical strength and biodegradability. The resulting GH/GGA hydrogels effectively scavenged the hydroxyl radicals and DPPH radicals, and the scavenging capacity could be modulated by varying GGA concentrations. Moreover, in an in vitro H2O2-induced ROS microenvironment, GH/GGA hydrogels significantly suppressed the oxidative damage of human dermal fibroblast (hDFBs) and preserved their viability by reducing intracellular ROS production. More importantly, the ROS scavenging hydrogel efficiently accelerated the wound healing process with unexpected regenerative healing characteristics, shown by hair follicle formation; promoted neovascularization; and highly ordered the alignment of collagen fiber in a full-thickness skin defect model. Therefore, we expect that injectable GH/GGA hydrogels can serve as promising biomaterials for tissue regeneration applications, including wound treatment and other tissue repair related to ROS overexpression. STATEMENT OF SIGNIFICANCE: Recently, many researchers have endeavored to develop injectable hydrogel matrices that can modulate the ROS level to normal physiological processes for the treatment of various diseases. Here, we designed an injectable gelatin hydrogel in which gallic acid, an antioxidant compound, was conjugated onto a gelatin polymer backbone. The hydrogels showed tunable properties and could scavenge the free radicals in a controllable manner. Because of the ROS scavenging properties, the hydrogels protected the cells from the oxidative damage of ROS microenvironment and effectively accelerated the wound healing process with high quality of healed skin. We believe that this injectable ROS scavenging hydrogel has great potential for wound treatment and tissue regeneration, where oxidative damage by ROS contributes to the pathogenesis.

Tonsil-derived mesenchymal stem cell-embedded in situ crosslinkable gelatin hydrogel therapy recovers postmenopausal osteoporosis through bone regeneration.

We investigated therapeutic potential of human tonsil-derived mesenchymal stem cells (TMSC) subcutaneously delivered to ovariectomized (OVX) mice for developing more safe and effective therapy for osteoporosis. TMSC were isolated from tonsil tissues of children undergoing tonsillectomy, and TMSC-embedded in situ crosslinkable gelatin-hydroxyphenyl propionic acid hydrogel (TMSC-GHH) or TMSC alone were delivered subcutaneously to the dorsa of OVX mice. After 3 months, three-dimensionally reconstructed micro-computed tomographic images revealed better recovery of the femoral heads in OVX mice treated with TMSC-GHH. Serum osteocalcin and alkaline phosphatase were also recovered, indicating bone formation only in TMSC-GHH-treated mice, and absence in hypercalcemia or other severe macroscopic deformities showed biocompatibility of TMSC-GHH. Additionally, visceral fat reduction effects by TMSC-GHH further supported their therapeutic potential. TMSC provided therapeutic benefits toward osteoporosis only when embedded in GHH, and showed potential as a supplement or alternative to current therapies.

Hydrogen Peroxide-Releasing Hydrogels for Enhanced Endothelial Cell Activities and Neovascularization.

Reactive oxygen species (ROS) have been implicated as a critical modulator for various therapeutic applications such as treatment of vascular disorders, wound healing, and cancer treatment. Specifically, growing evidence has recently demonstrated that transient or low levels of hydrogen peroxide (H2O2) facilitates tissue regeneration and wound repair through acute oxidative stress that can evaluate intracellular ROS levels in cells or tissues. Herein, we report a gelatin-based H2O2-releasing hydrogel formed by dual enzyme-mediated reaction using horseradish peroxidase and glucose oxidase (GO x). The release behavior of H2O2 from the hydrogel matrices can be precisely controlled by varying the GO x concentrations. We demonstrate that H2O2-releasing hydrogels with the optimal condition increase transient upregulation of intracellular ROS levels in the endothelial cells (ECs), enhance proliferative activities of ECs in vitro, and facilitate neovascularization in ovo. We suggest that our H2O2-releasing hydrogels hold great potential as an injectable and dynamic matrix for the treatment of vascular disorders as well as in tissue regenerative medicine.

Aging Donor-Derived Human Mesenchymal Stem Cells Exhibit Reduced Reactive Oxygen Species Loads and Increased Differentiation Potential Following Serial Expansion on a PEG-PCL Copolymer Substrate.

Human mesenchymal stem cells (hMSCs) have been widely studied for therapeutic development in tissue engineering and regenerative medicine. They can be harvested from human donors via tissue biopsies, such as bone marrow aspiration, and cultured to reach clinically relevant cell numbers. However, an unmet issue lies in the fact that the hMSC donors for regenerative therapies are more likely to be of advanced age. Their stem cells are not as potent compared to those of young donors, and continue to lose healthy, stemness-related activities when the hMSCs are serially passaged in tissue culture plates. Here, we have developed a cheap, scalable, and effective copolymer film to culture hMSCs obtained from aged human donors over several passages without loss of reactive oxygen species (ROS) handling or differentiation capacity. Assays of cell morphology, reactive oxygen species load, and differentiation potential demonstrate the effectiveness of copolymer culture on reduction in senescence-related activities of aging donor-derived hMSCs that could hinder the therapeutic potential of autologous stem cell therapies.

Sustained release of parathyroid hormone via in situ cross-linking gelatin hydrogels improves the therapeutic potential of tonsil-derived mesenchymal stem cells for hypoparathyroidism.

Biomimetic parathyroid regeneration with sustained release of parathyroid hormone (PTH) into the blood stream is a considerable challenge in hypoparathyroidism treatment. We recently reported that tonsil-derived mesenchymal stem cells (TMSCs), if these cells were both differentiated in vitro before implantation and incorporated into a scaffold Matrigel, are a good cell source for parathyroid regeneration in a parathyroidectomized (PTX) animal model. Here, we present a new strategy for improved clinical application that enhances the sustained release of PTH by controlling mechanical stiffness using in situ-forming gelatin-hydroxyphenyl propionic acid (GH) hydrogels (GHH). Differentiated TMSCs (dTMSCs) embedded in a GHH with a strength of 4.4 kPa exhibited the best sustained release of PTH and were the most effective in hypoparathyroidism treatment, showing improved blood calcium homeostasis compared with Matrigel-embedded dTMSCs. Interestingly, undifferentiated control TMSCs (cTMSCs) also released PTH in a sustained manner if incorporated into GHH. Collectively, these findings may establish a new paradigm for parathyroid regeneration that could ultimately evolve into an improved clinical application. Copyright © 2017 John Wiley & Sons, Ltd.

A novel calcium-accumulating peptide/gelatin in situ forming hydrogel for enhanced bone regeneration.

Bioactive agents, including proteins and peptides, can be loaded into hydrogels to improve bone regenerative capacity with their controlled release. However, the current loading method has focused on physical mixing, which has limited release control. Therefore, alternative conjugation of bioactive agents with hydrogels is highly recommended. Direct chemical conjugation of synthetic peptides containing a functional moiety with a hydrogel would be ideal. Here, we synthesized a bioactive calcium accumulating peptide (CAP) containing a collagen binding motif, which can induce osteogenic differentiation. A tyrosine residue in CAP was used to directly chemically conjugate the peptide with a gelatin-based enzymatically crosslinked hydroxyphenyl propionic acid hydrogel under H2 O2 /Horse radish peroxidase conditions. To test the acceleration of bone formation, human periodontal ligament stem cells (PDLSCs) were loaded into a chemically conjugated CAP hydrogel. The CAP hydrogel induced bone mineralization around the PDLSCs and increased osteogenic marker expressions in vitro. It also recovered a bone layer in a calvarial defect 4 weeks postimplantation. In summary, an injectable CAP hydrogel scaffold system was developed as a potentially useful engineered microenvironment to enhance bone restoration, and it could be utilized as a vehicle for bioactive delivery of stem cells in tissue regenerative therapy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 531-542, 2018.

Heparin-functionalized polymer graft surface eluting MK2 inhibitory peptide to improve hemocompatibility and anti-neointimal activity.

The leading cause of synthetic graft failure includes thrombotic occlusion and intimal hyperplasia at the site of vascular anastomosis. Herein, we report a co-immobilization strategy of heparin and potent anti-neointimal drug (Mitogen Activated Protein Kinase II inhibitory peptide; MK2i) by using a tyrosinase-catalyzed oxidative reaction for preventing thrombotic occlusion and neointimal formation of synthetic vascular grafts. The binding of heparin-tyramine polymer (HT) onto the polycarprolactone (PCL) surface enhanced blood compatibility with significantly reduced protein absorption (64.7% decrease) and platelet adhesion (85.6% decrease) compared to bare PCL surface. When loading MK2i, 1) the HT depot surface gained high MK2i-loading efficiency through charge-charge interaction, and 2) this depot platform enabled long-term, controlled release over 4weeks (92-272µg/mL of MK2i). The released MK2i showed significant inhibitory effects on VSMC migration through down-regulated phosphorylation of target proteins (HSP27 and CREB) associated with intimal hyperplasia. In addition, it was found that the released MK2i infiltrated into the tissue with a cumulative manner in ex vivo human saphenous vein (HSV) model. This present study demonstrates that enzymatically HT-coated surface modification is an effective strategy to induce long-term MK2i release as well as hemocompatibility, thereby improving anti-neointimal activity of synthetic vascular grafts.

A hydrogel matrix prolongs persistence and promotes specific localization of an oncolytic adenovirus in a tumor by restricting nonspecific shedding and an antiviral immune response.

Currently, intratumoral injection of an oncolytic adenovirus (Ad) is the conventional administration route in clinical trials. Nonetheless, the locally administered Ad disseminates to the surrounding nontarget tissues and has short biological activity due to immunogenicity of Ad, thus necessitating multiple injections to achieve a sufficient therapeutic index. In the present study, a tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-expressing oncolytic Ad (oAd-TRAIL) was encapsulated in a gelatin hydrogel (oAd-TRAIL/gel) to enhance and prolong antitumor efficacy of the virus after a single intratumoral injection. oAd-TRAIL/gel showed greater antitumor efficacy than naked oAd-TRAIL did due to enhanced and prolonged intratumoral accumulation of Ad up to a 20-day period, showing potent induction of apoptosis and inhibition of tumor cell proliferation. Furthermore, the gel system effectively prevented shedding of oncolytic Ad from the injection site to hepatic and other healthy tissues. oAd-TRAIL/gel treatment resulted in a markedly weaker antiviral immune response against Ad relative to naked oAd-TRAIL, further contributing to prolonged persistence of the oncolytic Ad in tumor tissue. Moreover, the hydrogel matrix preserved oAd-TRAIL's ability to induce an antitumor immune response, resulting in higher intratumoral infiltration by CD4+/CD8+ T cells. Taken together, these findings show that single intratumoral administration of the Ad/hydrogel modality may prolong and potentiate the therapeutic efficacy of Ad, modulate the immune reaction in favor of the virotherapy, and enhance intratumoral localization of the virus, ultimately overcoming limitations of oncolytic virotherapy revealed in recent clinical trials.

Zwitterionic sulfobetaine polymer-immobilized surface by simple tyrosinase-mediated grafting for enhanced antifouling property.

Introducing antifouling property to biomaterial surfaces has been considered an effective method for preventing the failure of implanted devices. In order to achieve this, the immobilization of zwitterions on biomaterial surfaces has been proven to be an excellent way of improving anti-adhesive potency. In this study, poly(sulfobetaine-co-tyramine), a tyramine-conjugated sulfobetaine polymer, was synthesized and simply grafted onto the surface of polyurethane via a tyrosinase-mediated reaction. Surface characterization by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy demonstrated that the zwitterionic polymer was successfully introduced onto the surface of polyurethane and remained stable for 7days. In vitro studies revealed that poly(sulfobetaine-co-tyramine)-coated surfaces dramatically reduced the adhesion of fibrinogen, platelets, fibroblasts, and S. aureus by over 90% in comparison with bare surfaces. These results proved that polyurethane surfaces grafted with poly(sulfobetaine-co-tyramine) via a tyrosinase-catalyzed reaction could be promising candidates for an implantable medical device with excellent bioinert abilities. STATEMENT OF SIGNIFICANCE: Antifouling surface modification is one of the key strategy to prevent the thrombus formation or infection which occurs on the surface of biomaterial after transplantation. Although there are many methods to modify the surface have been reported, necessity of simple modification technique still exists to apply for practical applications. The purpose of this study is to modify the biomaterial's surface by simply immobilizing antifouling zwitterion polymer via enzyme tyrosinase-mediated reaction which could modify versatile substrates in mild aqueous condition within fast time period. After modification, pSBTA grafted surface becomes resistant to various biological factors including proteins, cells, and bacterias. This approach appears to be a promising method to impart antifouling property on biomaterial surfaces.

In Situ Forming Gelatin Hydrogels-Directed Angiogenic Differentiation and Activity of Patient-Derived Human Mesenchymal Stem Cells.

Directing angiogenic differentiation of mesenchymal stem cells (MSCs) still remains challenging for successful tissue engineering. Without blood vessel formation, stem cell-based approaches are unable to fully regenerate damaged tissues due to limited support for cell viability and desired tissue/organ functionality. Herein, we report in situ cross-linkable gelatin-hydroxyphenyl propionic acid (GH) hydrogels that can induce pro-angiogenic profiles of MSCs via purely material-driven effects. This hydrogel directed endothelial differentiation of mouse and human patient-derived MSCs through integrin-mediated interactions at the cell-material interface, thereby promoting perfusable blood vessel formation in vitro and in vivo. The causative roles of specific integrin types (α1 and αvß3) in directing endothelial differentiation were verified by blocking the integrin functions with chemical inhibitors. In addition, to verify the material-driven effect is not species-specific, we confirmed in vitro endothelial differentiation and in vivo blood vessel formation of patient-derived human MSCs by this hydrogel. These findings provide new insight into how purely material-driven effects can direct endothelial differentiation of MSCs, thereby promoting vascularization of scaffolds towards tissue engineering and regenerative medicine applications in humans.

Multi-layered nanogels with MMP-sheddable PEG masks: Preparation and promotion of tumor cell uptake by controlling surface characteristics.

We describe a facile and effective poly(ethylene glycol) (PEG) coating method that has not been used previously for decoration of nanogels. Layer-by-layer (LbL) assembly was the technique of choice to introduce PEG onto the surface of multi-layered nanogels (MLNGs). Pegylated MLNGs were prepared simply by sequentially dispersing nanogels in solutions of cationic polymer, anionic polymer, and modified PEGs, and each coating step was validated by measuring changes in size and surface charge. Particularly, a peptide linker that is cleavable by matrix metalloproteinase-2 (MMP-2) in the tumor microenvironment was introduced between PEG layer and nanogels because it is known that PEG reduces the uptake of nanoparticles in tumor cells due to its high mobility. In vitro cell studies demonstrated that MLNGs with MMP-cleavable PEGs enhanced the particle uptake up to 3 times in tumor cells due to unmasking of PEG brushes as compared to pegylated MLNGs without MMP-sensitive peptide linkers.

Optimized biodegradable polymeric reservoir-mediated local and sustained co-delivery of dendritic cells and oncolytic adenovirus co-expressing IL-12 and GM-CSF for cancer immunotherapy.

Administration of dendritic cells (DCs) combined with oncolytic adenovirus (Ad) expressing antitumor cytokines induces a potent antitumor effect and antitumor immunity by ameliorating the immunosuppressive tumor microenvironment. However, this combination therapy has significant limitations due to rapid dissemination and inactivation of the therapeutics at the tumor site, necessitating multiple injections of both therapeutics. To overcome these limitations, we have utilized gelatin-based hydrogel to co-deliver oncolytic Ad co-expressing interleukin (IL)-12 and granulocyte-macrophage colony-stimulating factor (GM-CSF) (oAd) and DCs for sustained release of both therapeutics. The injectable and biodegradable hydrogels were prepared by mixing the polymer solutions containing horseradish peroxidase and hydrogen peroxide. Gel matrix enabled sustained release of both oAd and DCs while preserving their biological activity over a considerable time period, leading to efficient retention of both therapeutics in tumor tissue. Further, tumors treated with oAd- and DC-loaded gel (oAd+DC/gel) showed a significantly greater expression level of IL-12, GM-CSF, and interferon-γ (IFN-γ) than either single treatment (oAd or DC) or oAd in combination with DC (oAd+DC), resulting in efficient activation of both endogenous and exogenous DCs, migration of DCs to draining lymph nodes, and tumor infiltration of CD4+ and CD8+ T cells. Moreover, oAd+DC/gel resulted in a significantly higher number of tumor-specific IFN-γ-secreting immune cells compared with oAd+DC. Lastly, oAd+DC/gel significantly attenuated tumor-mediated thymic atrophy, which is associated with immunosuppression in the tumor microenvironment, compared with oAd+DC. Taken together, these results demonstrate that gelatin gel-mediated co-delivery of oncolytic Ad and DCs might be a promising strategy to efficiently retain both therapeutics in tumor tissue and induce a potent antitumor immune response for an extended time period via a single administration.

Hierarchical self-assembly of magnetic nanoclusters for theranostics: Tunable size, enhanced magnetic resonance imagability, and controlled and targeted drug delivery.

Nanoparticle-based imaging and therapy are of interest for theranostic nanomedicine. In particular, superparamagnetic iron oxide (SPIO) nanoparticles (NPs) have attracted much attention in cancer imaging, diagnostics, and treatment because of their superior imagability and biocompatibility (approved by the Food and Drug Administration). Here, we developed SPIO nanoparticles (NPs) that self-assembled into magnetic nanoclusters (SAMNs) in aqueous environments as a theranostic nano-system. To generate multi-functional SPIO NPs, we covalently conjugated ß-cyclodextrin (ß-CD) to SPIO NPs using metal-adhesive dopamine groups. Polyethylene glycol (PEG) and paclitaxel (PTX) were hosted in the ß-CD cavity through high affinity complexation. The core-shell structure of the magnetic nanoclusters was elucidated based on the condensed SPIO core and a PEG shell using electron microscopy and the composition was analyzed by thermogravimetric analysis (TGA). Our results indicate that nanocluster size could be readily controlled by changing the SPIO/PEG ratio in the assemblies. Interestingly, we observed a significant enhancement in magnetic resonance contrast due to the large cluster size and dense iron oxide core. In addition, tethering a tumor-targeting peptide to the SAMNs enhanced their uptake into tumor cells. PTX was efficiently loaded into ß-CDs and released in a controlled manner when exposed to competitive guest molecules. These results strongly indicate that the SAMNs developed in this study possess great potential for application in image-guided cancer chemotherapy. STATEMENT OF SIGNIFICANCE: In this study, we developed multi-functional SPIO NPs that self-assembled into magnetic nanoclusters (SAMNs) in aqueous conditions as a theranostic nano-system. The beta-cyclodextrin (ß-CD) was immobilized on the surfaces of SPIO NPs and RGD-conjugated polyethylene glycol (PEG) and paclitaxel (PTX) were hosted in the ß-CD cavity through high affinity complexation. We found that nanocluster size could be readily controlled by varying the SPIO/PEG ratio in the assemblies, and also demonstrated significant improvement of the functional nanoparticles for theranostic systems; enhanced magnetic resonance, improved cellular uptake, and efficient PTX loading and sustained release at the desired time point. These results strongly indicate that the SAMNs developed in this study possess great potential for application in image-guided cancer chemotherapy.

Enhanced Cellular Activity in Gelatin-Poly(Ethylene Glycol) Hydrogels without Compromising Gel Stiffness.

Adhesion and proliferation of cells are often suppressed in rigid hydrogels as gel stiffness induces mechanical stress to embedded cells. Herein, the composite hydrogel systems to facilitate high cellular activities are described, while maintaining relatively high gel stiffness. This unusual property is obtained by harmonizing gelatin-poly(ethylene glycol)-tyramine (GPT, semisynthetic polymer) and gelatin-hydroxyphenyl propionic acid conjugates (GH, natural polymer) into hydrogels. A minimum GH concentration of 50% is necessary for cells to be proliferative. GPT is utilized to improve biological stability (>1 week) and gelation time (<20 s) of the hydrogels. These results suggest that deficiency in cellular activity driven by gel stiffness could be overcome by finely tuning the material properties in the microenvironments.

Targeted doxorubicin nanotherapy strongly suppressing growth of multidrug resistant tumor in mice.

The rational design of nanomedicine to treat multidrug resistant (MDR) tumors in vivo is described in the study. We prepared multifunctionalized Pluronic micelles that are already well-established to be responsive to low pH and redox in order to systemically deliver doxorubicin (DOX) to MDR tumors. Folic acids (FAs) were introduced on the micelle surface as tumor-targeting molecules. In vitro, the DOX-loaded micelles exerted high cytotoxicity in the DOX-resistant cells by bypassing MDR efflux. Cellular uptake studies clearly demonstrated that FA-conjugated DOX micelles (FA/DOX micelles) were efficiently internalized and accumulated in the MDR cells. In vivo studies indicated significant efficacy of FA/DOX micelles for MDR tumors in mice, and that the volume of tumors was 3 times smaller in this group than that of tumors in the free DOX group, and 8 times smaller than the tumors in the saline group. To the best of our knowledge, this methodology has been recognized to have significantly high efficacy, compared to previously reported DOX nanoparticle formulations. This superior anti-tumor efficacy of FA/DOX micelles in MDR tumor-bearing mice can be attributed to FA-targeted and -mediated endocytosis, inhibition of MDR effect, and subsequent DOX release triggered by dual stimuli (low pH and redox) inside the tumor. Given the promise of the multifunctional micelle mediated delivery on inhibition of MDR tumor growth, FA/DOX micelle platform is a much sought after goal for cancer chemotherapy, especially for cancers resistant to anticancer drugs.

Injectable and mechanically robust 4-arm PPO-PEO/graphene oxide composite hydrogels for biomedical applications.

Graphene-based nanomaterials with different oxidation degrees were incorporated into Tetronic-tyramine (Tet-TA) hydrogels via enzymatic cross-linking. The molecular oxidation of graphene in combination with amphiphilic Tet-TA significantly improved the water dispersibility of graphene oxide (GO), resulting in a significant reinforcement of Tet-TA/GO composite hydrogels that can be used as an injectable biomaterial platform.

Horseradish peroxidase-catalysed in situ-forming hydrogels for tissue-engineering applications.

In situ-forming hydrogels are an attractive class of implantable biomaterials that are used for biomedical applications. These injectable hydrogels are versatile and provide a convenient platform for delivering cells and drugs via minimally invasive surgery. Although several crosslinking methods for preparing in situ forming hydrogels have been developed over the past two decades, most hydrogels are not sufficiently versatile for use in a wide variety of tissue-engineering applications. In recent years, enzyme-catalysed crosslinking approaches have been emerged as a new approach for developing in situ-forming hydrogels. In particular, the horseradish peroxidase (HRP)-catalysed crosslinking approach has received increasing interest, due to its highly improved and tunable capacity to obtain hydrogels with desirable properties. The HRP-catalysed crosslinking reaction immediately occurs upon mixing phenol-rich polymers with HRP and hydrogen peroxide (H2O2) in aqueous media. Based on this unique gel-forming feature, recent studies have shown that various properties of formed hydrogels, such as gelation time, stiffness and degradation rate, can be easily manipulated by varying the concentrations of HRP and H2O2. In this review, we outline the versatile properties of HRP-catalysed in situ-forming hydrogels, with a brief introduction to the crosslinking mechanisms involved. In addition, the recent biomedical applications of HRP-catalysed in situ-forming hydrogels for tissue regeneration are described.