Chang Yang Gong

Biodegradable in situ gel‐forming controlled drug delivery system based on thermosensitive PCL–PEG–PCL hydrogel: Part 1—synthesis, characterization, and acute toxicity evaluation

In this work, biodegradable PCL-PEG-PCL (PCEC) triblock copolymers were successfully synthesized at one-step. Aqueous solution of PCEC copolymer displayed thermosensitive sol-gel-sol transition behavior, which is flowing sol at low temperature and turns into non-flowing gel at body temperature. The cytotoxicity of PCEC copolymer was evaluated by cell viability assay using HEK293 and WISH cells. In vivo gel-formation, degradation test, acute toxicity tests, and histopathological study of PCEC hydrogels were performed in BALB/c mice by subcutaneous administration. In acute toxicity test, the mice were observed continuously for 21 days. For histopathologic study, samples including heart, liver, spleen, lung, kidneys, and tissue of injection site were histochemical prepared and stained with hematoxylin-eosin. No mortality or significant signs of acute toxicity was observed during the whole observation period and there is no significant lesion to be shown in histopathologic study of major organs and tissue of injection site. The maximum tolerance dose (MTD) of PCEC hydrogel (20 wt%) by subcutaneous administration was calculated to be higher than 25 g/kg b.w. The results indicated that the obtained PCEC hydrogel was non-toxic after subcutaneous administration, and could be a safe candidate for in situ gel-forming controlled drug delivery system.

Thermosensitive PEG–PCL–PEG hydrogel controlled drug delivery system: Sol–gel–sol transition and in vitro drug release study

In this article, biodegradable and low molecular weight poly(ethylene glycol)-poly(epsilon-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) triblock copolymers were successfully synthesized. Aqueous solution of the obtained PECE copolymers underwent sol-gel-sol transition as temperature increased which was flowing sol at room temperature and then turned into nonflowing gel at body temperature. Sol-gel-sol phase transition behaviors of aqueous PECE solutions were studied using rheometry and test tube-inverting method, which were affected by many factors, including the heating/cooling procedure and different additives in copolymers aqueous solution. In vitro drug release behavior was studied using bovine serum albumin (BSA) and Vitamin B(12) (VB(12)) as model drugs, and the PECE hydrogel could protect BSA from acidic degradation for 1 week at least. Therefore, PECE hydrogel is believed to be promising for injectable in situ gel-forming controlled drug delivery system due to their great thermosensitivity and biodegradability.

In vitro drug release behavior from a novel thermosensitive composite hydrogel based on Pluronic f127 and poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) copolymer

BackgroundMost conventional methods for delivering chemotherapeutic agents fail to achieve therapeutic concentrations of drugs, despite reaching toxic systemic levels. Novel controlled drug delivery systems are designed to deliver drugs at predetermined rates for predefined periods at the target organ and overcome the shortcomings of conventional drug formulations therefore could diminish the side effects and improve the life quality of the patients. Thus, a suitable controlled drug delivery system is extremely important for chemotherapy.ResultsA novel biodegradable thermosensitive composite hydrogel, based on poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) and Pluronic F127 copolymer, was successfully prepared in this work, which underwent thermosensitive sol-gel-sol transition. And it was flowing sol at ambient temperature but became non-flowing gel at body temperature. By varying the composition, sol-gel-sol transition and in vitro drug release behavior of the composite hydrogel could be adjusted. Cytotoxicity of the composite hydrogel was conducted by cell viability assay using human HEK293 cells. The 293 cell viability of composite hydrogel copolymers were yet higher than 71.4%, even when the input copolymers were 500 μg per well. Vitamin B12 (VB12), honokiol (HK), and bovine serum albumin (BSA) were used as model drugs to investigate the in vitro release behavior of hydrophilic small molecular drug, hydrophobic small molecular drug, and protein drug from the composite hydrogel respectively. All the above-mentioned drugs in this work could be released slowly from composite hydrogel in an extended period. Chemical composition of composite hydrogel, initial drug loading, and hydrogel concentration substantially affected the drug release behavior. The higher Pluronic F127 content, lower initial drug loading amount, or lower hydrogel concentration resulted in higher cumulative release rate.ConclusionThe results showed that composite hydrogel prepared in this paper were biocompatible with low cell cytotoxicity, and the drugs in this work could be released slowly from composite hydrogel in an extended period, which suggested that the composite hydrogel might have great potential applications in biomedical fields.

Acute toxicity evaluation of biodegradable in situ gel-forming controlled drug delivery system based on thermosensitive PEG-PCL-PEG hydrogel

In this work, a biodegradable poly(ethylene glycol)-poly(epsilon-caprolactone)-poly (ethylene glycol) (PEG-PCL-PEG, PECE) triblock copolymer was successfully synthesized. The aqueous solution of such PECE copolymer displayed special sol-gel-sol transition as temperature increase, which is a flowing sol at low-temperature and turns into a nonflowing gel at body temperature. The cytotoxicity of PECE copolymer was evaluated by cell viability assay using HEK 293 cells. In vivo gel formation and degradation test based on intraperitoneal and subcutaneous administration was conducted, respectively. The acute toxicity test and histopathological study were performed in BALB/c mice by intrapleural, intraperitoneal, or subcutaneous administration of PECE hydrogel (30 Wt %), respectively. The dose of intrapleural, intraperitoneal, or subcutaneous administration was up to 10 g/kg body weight (b.w.), 25 g/kg b.w., and 25 g/kg b.w., respectively, and the mice were observed continuously for 14 days. For histopathologic study, samples including heart, liver, lung, kidneys, spleen, stomach, intestine, and tissue of injection site were prepared for histochemical analysis and were stained with hematoxylin-eosin. No mortality or significant signs of acute toxicity was observed during the whole observation period and there is no significant lesion to be shown in histopathologic study of major organs. Therefore, the maximum tolerance dose of PECE hydrogel by intrapleural, intraperitoneal, or subcutaneous administration was calculated to be higher than 10 g/kg b.w., 25 g/kg b.w., and 25 g/kg b.w., respectively. The results indicated that the prepared PECE hydrogel was nontoxic after intrapleural, intraperitoneal, or subcutaneous administration, and it could be a safe candidate for in situ gel-forming controlled drug delivery system.

AAV-mediated human PEDF inhibits tumor growth and metastasis in murine colorectal peritoneal carcinomatosis model

BackgroundAngiogenesis plays an important role in tumor growth and metastasis, therefore antiangiogenic therapy was widely investigated as a promising approach for cancer therapy. Recently, pigment epithelium-derived factor (PEDF) has been shown to be the most potent inhibitor of angiogenesis. Adeno-associated virus (AAV) vectors have been intensively studied due to their wide tropisms, nonpathogenicity, and long-term transgene expression in vivo. The objective of this work was to evaluate the ability of AAV-mediated human PEDF (hPEDF) as a potent tumor suppressor and a potential candidate for cancer gene therapy.MethodsRecombinant AAV2 encoding hPEDF (rAAV2-hPEDF) was constructed and produced, and then was assigned for in vitro and in vivo experiments. Conditioned medium from cells infected with rAAV2-hPEDF was used for cell proliferation and tube formation tests of human umbilical vein endothelial cells (HUVECs). Subsequently, colorectal peritoneal carcinomatosis (CRPC) mouse model was established and treated with rAAV2-hPEDF. Therapeutic efficacy of rAAV2-hPEDF were investigated, including tumor growth and metastasis, survival time, microvessel density (MVD) and apoptosis index of tumor tissues, and hPEDF levels in serum and ascites.ResultsrAAV2-hPEDF was successfully constructed, and transmission electron microscope (TEM) showed that rAAV2-hPEDF particles were non-enveloped icosahedral shape with a diameter of approximately 20 nm. rAAV2-hPEDF-infected cells expressed hPEDF protein, and the conditioned medium from infected cells inhibited proliferation and tube-formation of HUVECs in vitro. Furthermore, in CRPC mouse model, rAAV2-hPEDF significantly suppressed tumor growth and metastasis, and prolonged survival time of treated mice. Immunofluorescence studies indicated that rAAV2-hPEDF could inhibit angiogenesis and induce apoptosis in tumor tissues. Besides, hPEDF levels in serum and ascites of rAAV2-hPEDF-treated mice were significant higher than those in rAAV2-null or normal saline (NS) groups.ConclusionsThus, our results suggest that rAAV2-hPEDF may be a potential candidate as an antiangiogenic therapy agent.

Prevention of abdominal adhesion formation by thermosensitive PECE‐hydrogel in a rat uterine horn model

In this work, we investigated the efficacy of PECE-hydrogel in preventing postsurgical peritoneal adhesions in the rat uterine horn model. Standardized surgical traumas were applied to the peritoneum of the abdominal wall and the uterine horns. PECE hydrogel was applied to the two wound surfaces. Animals were euthanized at different times after surgery, and the gross necropsy findings were documented. Adhesion formation was assessed according to adhesion extent and adhesion severity, and the hydrogel degradation and healing of peritoneal wounds were observed. The remesothelialization was dynamically observed by scanning electron microscope. The results showed that none of the animals in the hydrogel-treated group (n = 12) developed adhesion. In contrast, all untreated animals (n = 12) had adhesions that could only be separated by sharp dissection (p < 0.001). The hydrogel could adhere to the peritoneal wounds and gradually disappear from the wounds within 7-9 days and transformed into viscous fluid being completely absorbed within 12 days. The injured parietal and visceral peritoneum was remesothelialized in about 7 and 9 days, respectively. This work confirmed that PECE hydrogel holds promise as a novel absorbable biomaterial for the reduction of postoperative adhesions after laparotomy.

Acute toxicity evaluation of in situ gel-forming controlled drug delivery system based on biodegradable poly(ε-caprolactone)–poly(ethylene glycol)–poly(ε-caprolactone) copolymer

In this paper, biodegradable poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL) triblock copolymer was synthesized, and was characterized by FTIR, 1H-NMR and GPC. The PCL-PEG-PCL/dimethyl sulfoxide (DMSO) solution displayed in situ gelling behavior when subcutaneously injected into the body. Toxicity tests and a histopathological study were performed in BALB/c mice. We focused mainly on acute organ toxicity of BALB/c mice by subcutaneous injection. In the acute toxicity test, the dose of subcutaneous injection was 5 g/kg body weight (b.w.), and the mice were observed continuously for 14 days. For the histopathological study, samples including heart, lung, liver, kidneys, spleen, stomach and intestine were histochemically prepared and stained with hematoxylin-eosin for histopathological examination. No mortality or significant signs of toxicity were observed during the whole observation period, and there is no significant lesion to be shown in histopathological study of major organs in the mice. Therefore, the maximal tolerance dose of dimethyl sulfoxide (DMSO) solution of PCL-PEG-PCL copolymer by subcutaneous injection was calculated to be higher than 5 g/kg b.w. Therefore, the PCL-PEG-PCL/DMSO system was thought to be non-toxic after subcutaneous injection, and it might be a candidate for an in situ gelling controlled drug delivery system.

A novel vaccine delivery system: Biodegradable nanoparticles in thermosensitive hydrogel

In this work, a novel vaccine delivery system, biodegradable nanoparticles (NPs) in thermosensitive hydrogel, was investigated. Human basic fibroblast growth factor (bFGF)-loaded NPs (bFGF-NPs) were prepared, and then bFGF-NPs were incorporated into thermosensitive hydrogel to form bFGF-NPs in a hydrogel composite (bFGF-NPs/hydrogel). bFGF-NPs/hydrogel was an injectable sol at ambient temperature, but was converted into a non-flowing gel at body temperature. The in vitro release profile showed that bFGF could be released from bFGF-NPs or bFGF-NPs/hydrogel at an extended period, but the release rate of bFGF-NPs/hydrogel was much lower. In vivo experiments suggested that immunogenicity of bFGF improved significantly after being incorporated into the NPs/hydrogel composite, and strong humoral immunity was maintained for longer than 12 weeks. Furthermore, an in vivo protective anti-tumor immunity assay indicated that immunization with bFGF-NPs/hydrogel could induce significant suppression of the growth and metastases of tumors. Thus, the NPs/hydrogel composite may have great potential application as a novel vaccine delivery system.