Joo Young Son

Synthesis and Characterizations of In Situ Cross-Linkable Gelatin and 4-Arm-PPO-PEO Hybrid Hydrogels via Enzymatic Reaction for Tissue Regenerative Medicine

In situ cross-linkable hybrid hydrogels composed of gelatin and 4-arm-polypropylene oxide-polyethylene oxide (Tetronic) was developed as an injectable scaffold for tissue regeneration. The gelatin was modified by hydroxyphenyl propionic acid (HPA) and the Tetronic was conjugated with tyramines (Tet-TA). The hydrogels were rapidly formed by mixing the polymer solutions containing horseradish peroxidase (HRP) and hydrogen peroxide (H(2)O(2)). The gelation time and mechanical properties of the hydrogels could be controlled by varying the HRP and H(2)O(2) concentrations. In vitro degradation study of the hybrid hydrogels was carried out using collagenase and the prolonged proteolytic degradation was obtained due to the presence of the Tetronic. Human dermal fibroblast (hDFB) was cultured in the hydrogel matrices to evaluate the cyto-compatibility. The encapsulated cells were shown to be highly viable and spread over the gel matrices, suggesting that the hybrid hydrogels have an excellent cyto-compatibility. The hydrogels were also subcutaneously injected in the back of mice and the results demonstrated that the hydrogels were rapidly formed at the injected site. From these results, we demonstrate that the in situ cross-linkable hydrogels formed by hybridization of gelatin and Tetronic via enzyme-mediated reactions hold great promise for use as injectable matrices for tissue regenerative medicine due to their tunable physico-chemical properties and excellent bioactivity.

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.

Macro/Nano-gel composite as an injectable and bioactive bulking material for the treatment of urinary incontinence.

Many women around the world are suffering from urinary incontinence, defined as the unintentional leakage of urine by external abnormal pressure. Although various kinds of materials have been utilized to treat this disease, therapies that are more effective are still needed for the treatment of urinary incontinence. Here, we present a macro/nanogel composed of in situ forming gelatin-based macrogels and self-assembled heparin-based nanogels, which can serve as an injectable and bioactive bulking material for the treatment of urinary incontinence. The hybrid hydrogels were prepared via enzymatic reaction in the presence of horseradish peroxidase and hydrogen peroxide. Incorporating a growth factor (GF)-loaded heparin nanogel into a gelatin gel matrix enabled the hybrid gel matrix to release GF continuously up to 28 days. Moreover, we demonstrated that the hydrogel composites stimulated the regeneration of the urethral muscle tissue surrounding the urethral wall and promoted the recovery of their biological function when injected in vivo. Thus, the macro/nanohydrogels may provide an advanced therapeutic technique for the treatment of urinary incontinence as well as an application for regenerative medicine.

Heparin nanogel-containing liposomes for intracellular RNase delivery

AbstractLiposomes containing nanogels (liponanogels) were fabricated by sonicating heparin-Pluronic (HP) nanogels with pegylated lipids for ribonuclease (RNase) delivery. Liponanogels with an average diameter of 316 nm were obtained and their spherical morphology was elucidated by atomic force microscopy (AFM). Confocal laser scanning microscopy (CLSM) revealed the core-shell structure of the liponanogels using two different fluorescent dyes, showing that HP nanogels were localized in the core of the liposomes. Interestingly, the hybridization of these two systems remedies the drawbacks of each system while they hold their strengths called “WIN-WIN effect”. When HP nanogels were used to encapsulate RNase in liponanogels, the loading of RNase was almost doubled as compared with the loading in liposomes without nanogels. Due to the presence of a lipid bilayer on the nanogels, the release of RNase was prolonged over 4 days whereas it was much faster (82% after 21 h) for bare HP nanogels. The cytotoxicity of the RNase-loaded liponanogels was much higher than that of free RNase because of the endocytic cellular uptake of the particles. We believe that these hybrid liponanogel systems can potentially be utilized for the hereditary diseases and targeted cancer therapy since they can efficiently load RNases and sustainly release in target cells.

Dual Enzyme-Triggered In Situ Crosslinkable Gelatin Hydrogels for Artificial Cellular Microenvironments

Horseradish peroxidase (HRP) and hydrogen peroxide (H2 O2 )-mediated crosslinking reaction has become an attractive method to create in situ forming hydrogels. While the crosslinking system has been widely utilized, there are certain issues require improvement to extend their biomedical applications, including creation of stiff hydrogels without compromising cytocompatibility due to initially high concentrations of H2 O2 . A gelatin-based hydrogels formed through a dual enzyme-mediated crosslinking reaction using HRP and glucose oxidase (GOx) as an H2 O2 -generating enzyme to gradually supply a radical source in HRP-mediated crosslinking reaction is reported. The physicochemical properties can be controlled by varying enzyme concentrations. Furthermore the hydrogel matrices provide 3D microenvironments for supporting the growth and spreading of human dermal fibroblasts with minimized cytotoxicity, despite the cells being encapsulated within stiff hydrogels. These hydrogels formed with HRP/GOx have great potential as artificial microenvironments for a wide range of biomedical applications.

Synthesis and characterization of in situ gellable poly(glycerol sebacate)- co -poly(ethylene glycol) polymers

Hydrogels are widely used as implantable scaffolds and drug delivery carriers for biomedical applications. In particular, in situ cross-linkable hydrogels synthesized via enzyme-mediated reaction have received great attention in the field of injectable biomedical research as they have applications in minimally invasive procedures and have easily controllable physicochemical properties (e.g., gelation time, mechanical properties, etc.) under mild conditions. In this study, we synthesized poly(ethylene glycol) (PEG)-co-polymerized poly(glycerol sebacate) (PGS) polymers (PEG-co-PGS) capable of dissolving in aqueous environments and developed injectable hydrogel platforms via a horseradish peroxidase (HRP)-catalyzed cross-linking reaction. To induce in situ gelling, HRP-reactive phenol moieties (tyramine) were covalently conjugated to the PEG-co-PGS polymers, and hydrogel networks were formed in the presence of HRP and hydrogen peroxide (H2O2). The chemical structures of synthesized polymers were confirmed by 1H NMR spectroscopy, and the physicochemical properties of the hydrogels were assessed under varying concentrations of HRP and H2O2 solutions. The gelation time of PEG-co-PGS hydrogels ranged from 12 s to 237 s based on the HRP concentration (0.02-0.25 mg/mL), and the elastic modulus (16-41 Pa) depended on H2O2 concentration. In vitro cytocompatibility studies in human dermal fibroblasts revealed that PEG-co-PGS hydrogels were highly cytocompatible, with no negative effects on cell morphology and viability. In conclusion, our results suggest that PGS-based injectable hydrogels with multi-tunable properties and good cytocompatibility have tremendous potential as injectable scaffolds for tissue engineering applications.

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.

dual growth factor incorporated heparin-pluronic hydrogel/gelatin-poly-tyramine hydrogel

The number of cases of erectile dysfunction (ED) caused after radical prostatectomy (RP) prostate cancer treatment is increasing steadily. Although various studies have been conducted for treatment of post-RP ED, there is still a need for more effective methods. A dual growth factor incorporated heparin-pluronic/gelatin-poly(ethylene glycol)-tyramine (HP/GPT) hydrogel, which consists of a basic fibroblast growth factor (bFGF)-loaded HP hydrogel and nerve growth factor (NGF)-loaded GPT hydrogel, can control dose and rate of growth factor release. In this study, we demonstrated that dual growth factor incorporated HP/GPT hydrogel could further improve erectile function in a rat model of bilateral cavernous nerve injury (BCNI). We showed that erectile function was decreased after BCNI, but it was further improved by treatment with a dual growth factor incorporated HP/GPT hydrogel compared with groups treated with single growth factor in a rat model of cavernous nerve injury. Also, we observed an increase in cyclic guanosine monophosphate (cGMP) levels in the dual growth factor group when compared with the groups treated with single growth factor. This effect was associated with greater upregulation of nitric oxide synthase and endothelial nitric oxide synthase expression in the penile tissue of the group treated with dual growth factor incorporated HP/GPT than in the other experimental groups. Apoptosis in the penile tissue treated with the dual growth factor incorporated HP/GPT hydrogel was lower than those treated singly with either bFGF or NGF incorporated GPT hydrogel. Both α-smooth muscle actin and CD31 expression increased in the group treated with dual growth factor incorporated HP/GPT hydrogel when compared to in the other experimental groups. Altogether, our results proved that the sequential and continuous release of growth factors from dual growth factor incorporated HP/GPT hydrogel prevented fibrosis and nerve damage induced by BCNI in the corpus cavernosum, and promoted the recovery of erectile function. Dual growth factor incorporated HP/GPT hydrogel may be a potent clinical application for the treatment of post-RP ED and could potentially be used various biomedical application in tissue regnerative medicine.