Dual Growth Factor Delivery Using Photo-Cross-Linkable Gelatin Hydrogels for Effectively Reinforced Regeneration of the Rotator Cuff Tendon.

Rotator cuff tears are currently treated with drugs (steroids and nonsteroidal anti-inflammatory drugs) and surgery. However, the damaged rotator cuff requires a considerable amount of time to regenerate, and the regenerated tissue cannot restore the same level of function as that before the damage. Although growth factors can accelerate regeneration, they are difficult to be used alone because of the risk of degradation and the difficulties in ensuring their sustained release. Thus, hydrogels such as gelatin are used, together with growth factors. Gelatin is a biocompatible and biodegradable hydrogel derived from collagen; therefore, it closely resembles the components of native tissues and can retain water and release drugs continuously, while also showing easily tunable mechanical properties by simple modifications. Moreover, gelatin is a natural biopolymer that possesses the ability to form hydrogels of varying compositions, thereby facilitating effective cross-linking. Therefore, gelatin can be considered to be suitable for rotator-to-tendon healing. In this study, we designed photo-cross-linkable gelatin hydrogels to enhance spacing and adhesive effects for rotator cuff repair. We mixed a ruthenium complex (Ru(II)bpy32+) and sodium persulfate into gelatin-based hydrogels and exposed them to blue light to induce gelation. Basic fibroblast growth factor and bone morphogenetic protein-12 were encapsulated in the gelatin hydrogel for localized and sustained release into the wound, thereby enhancing the cell proliferation. The effects of these dual growth factor-loaded hydrogels on cell cytotoxicity and tendon regeneration in rotator cuff tear models were evaluated using mechanical and histological assessments. The findings confirmed that the gelatin hydrogel was biocompatible and that treatment with the dual growth factor-loaded hydrogels in in vivo rotator cuff tear models promoted regeneration and functional restoration in comparison with the findings in the nontreated group. Therefore, growth factor-loaded gelatin-based hydrogels may be suitable for the treatment of rotator cuff tears.

Bionic artificial skin with a fully implantable wireless tactile sensory system for wound healing and restoring skin tactile function.

Tactile function is essential for human life as it enables us to recognize texture and respond to external stimuli, including potential threats with sharp objects that may result in punctures or lacerations. Severe skin damage caused by severe burns, skin cancer, chemical accidents, and industrial accidents damage the structure of the skin tissue as well as the nerve system, resulting in permanent tactile sensory dysfunction, which significantly impacts an individual's daily life. Here, we introduce a fully-implantable wireless powered tactile sensory system embedded artificial skin (WTSA), with stable operation, to restore permanently damaged tactile function and promote wound healing for regenerating severely damaged skin. The fabricated WTSA facilitates (i) replacement of severely damaged tactile sensory with broad biocompatibility, (ii) promoting of skin wound healing and regeneration through collagen and fibrin-based artificial skin (CFAS), and (iii) minimization of foreign body reaction via hydrogel coating on neural interface electrodes. Furthermore, the WTSA shows a stable operation as a sensory system as evidenced by the quantitative analysis of leg movement angle and electromyogram (EMG) signals in response to varying intensities of applied pressures.

Predicting response to anti-EGFR antibody, cetuximab, therapy by monitoring receptor internalization and degradation.

Anti-epidermal growth factor receptor (EGFR) antibody, cetuximab, therapy has significantly improved the clinical outcomes of patients with colorectal cancer, but the response to cetuximab can vary widely among individuals. We thus need strategies for predicting the response to this therapy. However, the current methods are unsatisfactory in their predictive power. Cetuximab can promote the internalization and degradation of EGFR, and its therapeutic efficacy is significantly correlated with the degree of EGFR degradation. Here, we present a new approach to predict the response to anti-EGFR therapy, cetuximab by evaluating the degree of EGFR internalization and degradation of colorectal cancer cells in vitro and in vivo. Our newly developed fluorogenic cetuximab-conjugated probe (Cetux-probe) was confirmed to undergo EGFR binding, internalization, and lysosomal degradation to yield fluorescence activation; it thus shares the action mechanism by which cetuximab exerts its anti-tumor effects. Cetux-probe-activated fluorescence could be used to gauge EGFR degradation and showed a strong linear correlation with the cytotoxicity of cetuximab in colorectal cancer cells and tumor-bearing mice. The predictive ability of Cetux-probe-activated fluorescence was much higher than those of EGFR expression or KRAS mutation status. The Cetux-probes may become useful tools for predicting the response to cetuximab therapy by assessing EGFR degradation.

Enhancing adoptive T-cell therapy with fucoidan-based IL-2 delivery microcapsules.

Adoptive cell therapy (ACT) with antigen-specific T cells is a promising treatment approach for solid cancers. Interleukin-2 (IL-2) has been utilized in boosting the efficacy of ACT. However, the clinical applications of IL-2 in combination with ACT is greatly limited by short exposure and high toxicities. Herein, a complex coacervate was designed to intratumorally deliver IL-2 in a sustained manner and protect against proteolysis. The complex coacervate consisted of fucoidan, a specific IL-2 binding glycosaminoglycan, and poly-l-lysine, a cationic counterpart (FPC2). IL-2-laden FPC2 exhibited a preferential bioactivity in ex vivo expansion of CD8+T cells over Treg cells. Additionally, FPC2 was embedded in pH modulating injectable gel (FPC2-IG) to endure the acidic tumor microenvironment. A single intratumoral administration of FPC2-IG-IL-2 increased expansion of tumor-infiltrating cytotoxic lymphocytes and reduced frequencies of myeloid populations. Notably, the activation and persistency of tumor-reactive T cells were observed only in the tumor site, not in the spleen, confirming a localized effect of FPC2-IG-IL-2. The immune-favorable tumor microenvironment induced by FPC2-IG-IL-2 enabled adoptively transferred TCR-engineered T cells to effectively eradicate tumors. FPC2-IG delivery system is a promising strategy for T-cell-based immunotherapies.

The Regeneration of Large-Sized and Vascularized Adipose Tissue Using a Tailored Elastic Scaffold and dECM Hydrogels.

A dome-shaped elastic poly(l-lactide-co-caprolactone) (PLCL) scaffold with a channel and pore structure was fabricated by a combinative method of 3D printing technology and the gel pressing method (13 mm in diameter and 6.5 mm in thickness) for patient-specific regeneration. The PLCL scaffold was combined with adipose decellularized extracellular matrix (adECM) and heart decellularized extracellular matrix (hdECM) hydrogels and human adipose-derived stem cells (hADSCs) to promote adipogenesis and angiogenesis. These scaffolds had mechanical properties similar to those of native adipose tissue for improved tissue regeneration. The results of the in vitro real-time PCR showed that the dECM hydrogel mixture induces adipogenesis. In addition, the in vivo study at 12 weeks demonstrated that the tissue-engineered PLCL scaffolds containing the hydrogel mixture (hdECM/adECM (80:20)) and hADSCs promoted angiogenesis and adipose tissue formation, and suppressed apoptosis. Therefore, we expect that our constructs will be clinically applicable as material for the regeneration of patient-specific large-sized adipose tissue.

Detection of Lysyl Oxidase Activity in Tumor Extracellular Matrix Using Peptide-Functionalized Gold Nanoprobes.

High LOX levels in the tumor microenvironment causes the cross-linking of extracellular matrix components and increases the stiffness of tumor tissue. Thus, LOX plays an important role in tumorigenesis and in lowering the tumor response to anticancer drugs. Despite comprehensive efforts to identify the roles of LOX in the tumor microenvironment, sensitive and accurate detection methods have not yet been established. Here, we suggest the use of gold nanoparticles functionalized with LOX-sensitive peptides (LS-AuNPs) that aggregate upon exposure to LOX, resulting in a visual color change. LOX-sensitive peptides (LS-peptides) contain lysine residues that are converted to allysine in the presence of LOX, which is highly reactive and binds to adjacent allysine, resulting in the aggregation of the AuNPs. We demonstrated that the synthesized LS-AuNPs are capable of detecting LOX sensitively, specifically both in vitro and in the tissue extract. Moreover, the suggested LS-AuNP-based assay is more sensitive than commonly employed assays or commercially available kits. Therefore, the LS-AuNPs developed in this study can be used to detect LOX levels and can be further used to predict the stiffness or the anticancer drug resistance of the tumor.

Three-Dimensional Vascularized Lung Cancer-on-a-Chip with Lung Extracellular Matrix Hydrogels for In Vitro Screening.

Recent advances in immunotherapies and molecularly targeted therapies have led to an increased interest in exploring the field of in vitro tumor mimetic platforms. An increasing need to understand the mechanisms of anti-cancer therapies has led to the development of natural tumor tissue-like in vitro platforms capable of simulating the tumor microenvironment. The incorporation of vascular structures into the in vitro platforms could be a crucial factor for functional investigation of most anti-cancer therapies, including immunotherapies, which are closely related to the circulatory system. Decellularized lung extracellular matrix (ldECM), comprised of ECM components and pro-angiogenic factors, can initiate vascularization and is ideal for mimicking the natural microenvironment. In this study, we used a ldECM-based hydrogel to develop a 3D vascularized lung cancer-on-a-chip (VLCC). We specifically encapsulated tri-cellular spheroids made from A549 cells, HUVECs, and human lung fibroblasts, for simulating solid type lung cancer. Additionally, two channels were incorporated in the hydrogel construct to mimic perfusable vessel structures that resemble arterioles or venules. Our study highlights how a more effective dose-dependent action of the anti-cancer drug Doxorubicin was observed using a VLCC over 2D screening. This observation confirmed the potential of the VLCC as a 3D in vitro drug screening tool.

Stereocomplex Polylactide for Drug Delivery and Biomedical Applications: A Review.

Polylactide (PLA) is among the most common biodegradable polymers, with applications in various fields, such as renewable and biomedical industries. PLA features poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) enantiomers, which form stereocomplex crystals through racemic blending. PLA emerged as a promising material owing to its sustainable, eco-friendly, and fully biodegradable properties. Nevertheless, PLA still has a low applicability for drug delivery as a carrier and scaffold. Stereocomplex PLA (sc-PLA) exhibits substantially improved mechanical and physical strength compared to the homopolymer, overcoming these limitations. Recently, numerous studies have reported the use of sc-PLA as a drug carrier through encapsulation of various drugs, proteins, and secondary molecules by various processes including micelle formation, self-assembly, emulsion, and inkjet printing. However, concerns such as low loading capacity, weak stability of hydrophilic contents, and non-sustainable release behavior remain. This review focuses on various strategies to overcome the current challenges of sc-PLA in drug delivery systems and biomedical applications in three critical fields, namely anti-cancer therapy, tissue engineering, and anti-microbial activity. Furthermore, the excellent potential of sc-PLA as a next-generation polymeric material is discussed.

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.

Combinatorial Inhibition of Cell Surface Receptors Using Dual Aptamer-Functionalized Nanoconstructs for Cancer Treatment.

Membrane receptors overexpressed in diseased states are considered novel therapeutic targets. However, the single targeting approach faces several fundamental issues, such as poor efficacy, resistance, and toxicity. Here, we report a dual-targeting strategy to enhance anti-cancer efficacy via synergistic proximity interactions between therapeutics and two receptor proteins. Importantly, we report the first finding of an interaction between c-Met and nucleolin and demonstrate the therapeutic value of targeting the interaction between them. Bispecific nanocarriers densely grafted with anti-c-Met and -nucleolin aptamer increased the local concentration of aptamers at the target sites, in addition to inducing target receptor clustering. It was also demonstrated that the simultaneous targeting of c-Met and nucleolin inhibited the cellular functions of the receptors and increased anti-cancer efficacy by altering the cell cycle. Our findings pave the way for the development of an effective combinatorial treatment based on nanoconstruct-mediated interaction between receptors.

The effect of Substance P/Heparin conjugated PLCL polymer coating of bioinert ePTFE vascular grafts on the recruitment of both ECs and SMCs for accelerated regeneration.

Artificial vascular grafts consisting of ePTFE have been mainly used in clinics for the treatment of cardiovascular disease. However, artificial grafts can become clogged after a long time due to thrombosis, as graft maturation by endothelialization is limited. The strategy introduced in this study is to induce graft remodeling through interaction between the bioinert graft and the body. The Substance P (SP) and heparin were covalently conjugated with PLCL, an elastic biocompatible copolymer and the Substance P-conjugated PLCL (SP-PLCL) and/or heparin-conjugated PLCL (Hep-PLCL) were vacuum-coated onto ePTFE vascular grafts. To assess the effectiveness of the coating, coated samples were evaluated by implanting them subcutaneously into SD-Rats. Coatings allow grafts to be remodeled by creating a microenvironment where cells can grow by infiltrating into the grafts while also greatly enhancing angiogenesis. In particular, a double coating of Hep-PLCL and SP-PLCL (Hep/SP-PLCL) at four weeks showed markedly improved vascular remodeling through the recruitment of mesenchymal stem cells (MSCs), vascular cells (ECs, SMCs) and M2 macrophages. Based on these results, it is expected that when the Hep/SP-PLCL-coated ePTFE vascular grafts are implanted in situ, long-term patency will be assured due to the appropriate formation of an endothelial layer and smooth muscle cells in the grafts like native vessels.

Extracellular pH modulating injectable gel for enhancing immune checkpoint inhibitor therapy.

Clinical data from diverse cancer types shows that the increased T cell infiltration in tumors correlates with improved patient prognosis. Acidic extracellular pH is a major attribute of the tumor microenvironment (TME) that promotes immune evasion and tumor progression. Therefore, antagonizing tumor acidity can be a powerful approach in cancer immunotherapy. Here, Pluronic F-127 is used as a NaHCO3 releasing carrier to focally alleviate extracellular tumor acidity. In a mouse tumor model, intratumoral treatment with pH modulating injectable gel (pHe-MIG) generates immune-favorable TME, as evidenced by the decrease of immune-suppressive cells and increase of tumor infiltrating CD8+T cells. The combination of pHe-MIG with immune checkpoint inhibitors, anti-PD-1 and anti-TIGIT antibodies, increases intratumoral T cell function, which leads to tumor clearance. Mechanistically, extracellular acidity was shown to upregulate co-inhibitory immune checkpoint receptors and inhibit mTOR signaling pathways in memory CD8+T cells, which impaired effector functions. Furthermore, an acidic pH environment increased the expression and engagement of TIGIT and its ligand CD155, which suggested that the extracellular pH can regulate the suppressive function of TIGIT pathway. Collectively, these findings suggest that pHe-MIG holds potential as a new TME modulator for effective immune checkpoint inhibitor therapies.

Vascularization of PLGA-based bio-artificial beds by hypoxia-preconditioned mesenchymal stem cells for subcutaneous xenogeneic islet transplantation.

BACKGROUND: Subcutaneous tissue is an attractive extra-hepatic heterotopic site for islet transplantation; however, poor oxygen tension and blood supply during early engraftment of implanted islets have limited the use of this site in clinical applications. METHODS: This study investigated the vascularization potential of hypoxia-preconditioned mesenchymal stem cells (3% O2 ; hypo-MSCs) in PLGA-based bio-artificial beds for subsequent subcutaneous islet transplantation. Sheet-typed polymeric PLGA scaffolds coated with hypo-MSCs or normo-MSCs (MSCs cultured under normoxia conditions, 21% O2 ) were implanted subcutaneously in mice. RESULTS: Compared to normo-MSCs, hypo-MSCs significantly enhanced vasculogenesis, both on the interior and exterior surfaces of the implanted PLGA devices, which peaked 4 weeks after implantation. Further, infusion of porcine islets inside the prevascularized PLGA bed restored normal glycemic control in 6 of 6 STZ-induced diabetic mice. The mass of the marginal islet was approximately 2000 IEQs, which is comparable to that required for the renal subcapsular space, a highly vascularized site. CONCLUSIONS: Therefore, PLGA-based bio-artificial devices prevascularized with hypo-MSCs could be a useful modality for successful subcutaneous islet transplantation, which is of high clinical relevance.

On-Demand Drug Release from Gold Nanoturf for a Thermo- and Chemotherapeutic Esophageal Stent.

Stimuli-responsive delivery systems for cancer therapy have been increasingly used to promote the on-demand therapeutic efficacy of anticancer drugs and, in some cases, simultaneously generate heat in response to a stimulus, resulting in hyperthermia. However, their application is still limited due to the systemic drawbacks of intravenous delivery, such as rapid clearance from the bloodstream and the repeat injections required for sustained safe dosage, which can cause overdosing. Here, we propose a gold (Au)-coated nanoturf structure as an implantable therapeutic interface for near-infrared (NIR)-mediated on-demand hyperthermia chemotherapy. The Au nanoturf possessed long-lasting doxorubicin (DOX) duration, which helps facilitate drug release in a sustained and prolonged manner. Moreover, the Au-coated nanoturf provides reproducible hyperthermia induced by localized surface plasmon resonances under NIR irradiation. Simultaneously, the NIR-mediated temperature increase can promote on-demand drug release at desired time points. For in vivo analysis, the Au nanoturf structure was applied on an esophageal stent, which needs sustained anticancer treatment to prevent tumor recurrence on the implanted surface. This thermo- and chemo-esophageal stent induced significant cancer cell death with released drug and hyperthermia. These phenomena were also confirmed by theoretical analysis. The proposed strategy provides a solution to achieve enhanced thermo-/chemotherapy and has broad applications in sustained cancer treatments.

Skin Regeneration with a Scaffold of Predefined Shape and Bioactive Peptide Hydrogels.

We developed a highly elastic customized scaffold for soft tissue regeneration and combined them with bioactive hydrogels with stem cell-inducing ability. This was done to mimic mechanical properties of native soft tissues and improve the viability of transplanted cells as well as efficiency of tissue regeneration. The proposed study was aimed at evaluating various characteristics of scaffolds and investigating their tissue-regenerating ability. Finger-shaped porous scaffolds were successfully fabricated by an indirect 3D printing of poly (L-lactide-co-ɛ-caprolactone) (PLCL), which provides high elasticity for soft tissue engineering. In addition, a self-assembling peptide hydrogel coupled with substance P (RARADADARARADADA/RARADADARARADADA-substance P, RADA16/RADA16-SP) was used to accelerate angiogenesis and recruit intrinsic mesenchymal stem cells (MSCs). This study included three kinds of groups: Group I = PLCL scaffold with human dermal fibroblasts (HDFs) (P+C), Group II = PLCL scaffold with HDFs and RADA16 (P+C+R), and Group III = PLCL scaffold with HDFs, RADA16, and RADA16-SP (P+C+R+S). The samples were implanted into immunodeficient mice subcutaneously and harvested at 1 and 4 weeks. Tissue regeneration was evaluated by histological analysis with hematoxylin and eosin (H&E) and Masson's trichrome (MT) staining. The images showed that a large number of cells were recruited into the scaffolds, and collagen was deposited in the constructs of the P+C+R+S group. Additionally, recruitment of MSCs, angiogenesis, and collagen were observed by immunofluorescence staining. The results show that the P+C+R+S group had more type I and type III collagen, which are formed in soft tissues, and were deposited on the scaffold compared with the other groups. Moreover, more blood vessels and MSCs were induced in the P+C+R+S group than in those of the P + C and P+C+R groups. Consequently, the results suggest that the construct of the customized porous PLCL scaffold and RADA16/RADA16-SP hydrogel could be a good treatment modality to treat skin defects.

Development and characterization of various osteoarthritis models for tissue engineering.

Osteoarthritis (OA) is characterized by a progressive loss of articular cartilage, subchondral bone sclerosis and synovial inflammation and is the most common chronic condition worldwide today. However, most treatments have focused on pain relief and OA symptoms. For these reasons, many ongoing studies are currently trying to develop efficient and successful therapies based on its pathology. Animal models that mimic the histopathology and symptoms of OA have a critical role in OA research and make it possible to investigate both secondary osteoarthritic changes due to a precedent event such as traumatic injury and naturally occurring changes for the development of therapeutics which can be tested in preclinical and clinical OA trials. We induced OA in various animal models including rats, rabbits and guinea pigs by chemical, surgical and naturally occurring methods. In particular, the Dunkin-Hartley guinea pig is very attractive as an OA animal model because OA slowly progresses which is similar to human primary OA. Thus, this animal model mimics the pathophysiological process and environment of human primary OA. Besides the spontaneous OA model, anterior cruciate ligament transection (ACLT) with medial meniscectomy and bilateral ovariectomy (OVX) as well as a chemical technique using sodium monoiodoacetate (MIA) were used to induce OA. We found that ACLT in the rat model induced OA changes in the histology and micro-CT image compared to OVX. The osteoarthritic change significantly increased following ACLT surgery in the rabbit model. Furthermore, we identified that OA pathogenic changes occurred in a time-dependent manner in spontaneous Dunkin-Hartley guinea pigs. The MIA injection model is a rapid and minimally invasive method for inducing OA in animal models, whereas the spontaneous OA model has a slow and gradual progression of OA similar to human primary OA. We observed that histological OA change was extraordinarily increased at 9 ½ months in the spontaneous OA model, and thus, the grade was similar with that of the MIA model. Therefore, this study reports on OA pathology using various animal models as well as the spontaneous results naturally occurring in an OA animal model which had developed cartilage lesions and progressive osteoarthritic changes.

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.

Decellularized heart ECM hydrogel using supercritical carbon dioxide for improved angiogenesis.

Initial angiogenesis within the first 3 days is critical for healing ischemic diseases such as myocardial infarction. Recently, decellularized extracellular matrix (dECM) has been reported to provide tissue-derived ECM components and can be used as a scaffold for cell delivery for angiogenesis in tissue engineering. Decellularization by various detergents such as sodium dodecyl sulfate (SDS) and triton X-100 can remove the cell nuclei in tissue organs. However, this leads to ECM structure denaturation, decreased presence of various ECM proteins and cytokines, and loss of mechanical properties. To overcome these limitations, in this study, we developed a supercritical carbon dioxide and ethanol co-solvent (scCO2-EtOH) decellularization method, which is a detergent-free system that prevents ECM structure disruption and retains various angiogenic proteins in the heart dECM, and tested on rat heart tissues. The heart tissue was placed into the scCO2 reactor and decellularized at 37 °C and 350 bar. After scCO2-EtOH treatment, the effects were evaluated by DNA, collagen, and glycosaminoglycan (GAG) quantification and hematoxylin and eosin and immunofluorescence staining to determine the absence of nucleic acids and preservation of heart ECM components. Similar to the native group, the scCO2-EtOH group contained more ECM components such as collagen, GAGs, collagen I, laminin, and fibronectin and angiogenic factors including vascular endothelial growth factor, fibroblast growth factor, and platelet-derived growth factor and others in comparison to the detergent group. In addition, to estimate angiogenesis of the dECM hydrogels, the neutralized dECM solution was injected in a rat subcutaneous layer (n = 6 in each group: collagen, scCO2-EOH, and detergent group), after which the solution naturally formed gelation in the subcutaneous layer. After 3 days, the gels were harvested and estimated by immunofluorescence staining and the ImageJ program for angiogenesis analysis. Consequently, blood vessel formation and density of vWF and α-SMA in the scCO2-EtOH group were significantly greater than that in the collagen group. Here we suggest that heart-derived decellularized extracellular matrix (dECM) with scCO2-EtOH treatment is a highly promising angiogenic material for healing in ischemic disease. STATEMENT OF SIGNIFICANCE: Supercritical carbon dioxide (scCO2) in a supercritical phase has low viscosity and high diffusivity between gas and liquid properties and is known to be affordable, non-toxic, and eco-friendly. Therefore, scCO2 extraction technology has been extensively used in commercial and industrial fields. Recently, decellularized extracellular matrix (dECM) was applied to tissue engineering and regenerative medicine as a scaffold, therapeutic material, and bio-ink for 3D printing. Moreover, the general decellularization method using detergents has limitations including eliminating tissue-derived ECM components and disrupting their structures after decellularization. To overcome these limitations, heart tissues were treated with scCO2-EtOH for decellularization, resulting in preserving of tissue due to the various ECM and angiogenic factors derived. In addition, initiation of angiogenesis was highly induced even after 3 days of injection.

Skin Regeneration with Self-Assembled Peptide Hydrogels Conjugated with Substance P in a Diabetic Rat Model.

The wound healing process requires enough blood to supply nutrients and various growth factors to the wound area. However, chronic wounds such as diabetic skin ulcers have limited regeneration due to a lack of cellular and molecular signals because of a deficient blood flow. Mesenchymal stem cells (MSCs) are known to provide various factors, including growth factors, cytokines, and angiogenic mediators. Although MSCs have great therapeutic potential, their transplantation has many obstacles, including the time required to culture the cells, the invasiveness of the procedure, and limited stem cell sources. In this study, we induced a diabetic 1 model in rats aged 7 weeks by injecting streptozotocin and citrate buffer solution. After confirming that diabetes was induced in the rats, we created critical sized wounds on the dorsal area of the rats and then injected hydrogels. We performed the experiments with four groups (defect model for the control, self-assembled peptides (SAPs), SAP with soluble substance P, and SAP conjugated with substance P) to treat the wound defect. Tissues were harvested at 1, 2, and 3 weeks after injection and examined for the wound closure, histological analysis, quantitative real-time polymerase chain reaction analysis, and quantification of collagen deposits to investigate stem cell recruitment and full recovery of wounds at an accelerated time period. As our results show, the wounds treated with SAP and substance P exhibited significantly accelerated wound closure, enhanced collagen deposition, and increased angiogenesis. Furthermore, we confirmed the ability of SAP with substance P to promote the recruitment and homing of cells by immunofluorescence staining of a MSC marker. In addition, it was observed that substance P remained in the wound area up to 3 weeks after the injection of SAP with substance P. It is believed that the endogenous MSCs mobilized by substance P had therapeutic effects through their proper differentiation and release of paracrine factors into the wound sites. In conclusion, this study shows that SAP with substance P can promote wound healing to enhance skin regeneration without cell transplantation in a diabetic model.

Thae use of microfluic spinning fiber as an ophthalmology suture showing the good anastomotic strength control.

Adjusting the mechanical strength of a biomaterial to suit its intended application is very important for realizing beneficial outcomes. Microfluidic spinning fiber have been attracting attention recently due to their various advantages, but their mechanical strength has unfortunately not been a subject of concentrated research, and this lack of research has severely limited their applications. In the current work, we showed the mechanical properties of microfibers can be tuned easily and provided a mathematical explanation for how the microfluidic spinning method intrinsically controls the mechanical properties of a microfluidic spinning fiber. But we were also able to adjust the mechanical properties of such fibers in various other ways, including by using biomolecules to coat the fiber or mixing the biomolecules with the primary component of the fiber and by using a customized twisting machine to change the number of single microfiber strands forming the fiber. We used the bundle fiber as an ophthalmology suture that resulted in a porcine eye with a smoother post-operative surface than did a nylon suture. The results showed the possibility that the proposed method can solve current problems of the microfibers in practical applications, and can thus extend the range of applications of these microfibers.