Papers by Author: Jeong Ok Lim

Abstract: The release behavior of the basic fibroblast growth factor (bFGF) from copolymer hydrogels of N-isopropyl acrylamide (NIPAAm) and sodium methacrylate (SMA) was investigated in relation to the volume phase transition temperatures, which was increased by the incorporation of SMA. In the case of the copolymer hydrogels, a higher volume phase transition temperature was obtained when poly(ethylene glycol) diacrylate (PEGDA) was used as the crosslinking agent, suggesting that the chain length of the crosslinking agent has a significant affect on the volume phase transition temperature of a P(NIPAAm-co-SMA) hydrogel. The concentration of bFGF released from the hydrogels with PEGDA increased relative to the water content, thereby showing a dependence on the volume phase transition temperature. Hence, the release behavior of bFGF from the PNIPAAm and P(NIPAAm-co-SMA) hydrogels was found to be affected by the volume phase transition temperature, which can be easily controlled by changing the comonomer, monomer feed ratio, and crosslinking agent.

Abstract: A different range of vancomycin was incorporated into a poly dl-lactide-co-glycolide) [PLGA] disc matrix using the hot compression method. The disc was placed in phosphate buffered saline (PBS) and incubated at 37oC. The PBS was changed periodically, and the removed solution was analyzed using high performance liquid chromatography. The sensitivity of the antibiotic-polymer matrix was evaluated using cultured-human-ear methicillin-resistant staphylococcus aureus (MRSA). The MRSA growth was inhibited proportionally to the incorporated vancomycin concentration in the disc matrix. A disc incorporating 400 µg of antibiotics inhibited the growth of MRSA 10 times longer than the disc containing 30 µg as a control. It was found that the biodegradable polymer matrix enabled the control-release of an antibiotic, and the release profile was observed as zero order.

Abstract: Intrathecal implants of adrenal medullary chromaffin cells relieve chronic pain by secreting catecholamines, opioids and other neuroactive substances. Recently, macrocapsules with hollow fibers were employed to isolate immunologically xenogeneic chromaffin cells, but the poor viability in vivo of the encapsulated chromaffin cells limited the usefulness of this method. In this study, we used microencapsulation technology to increase the viability of chromaffin cells. Bovine adrenal chromaffin cells were microencapsulated with alginate and poly-L-lysine and implanted intrathecally in a rat using the neuropathic pain model. Intrathecal implants of microencapsulated cells relieved cold allodynia, which is the most prominent symptom of the neuropathic pain model in a rat. Furthermore, the microencapsulated chromaffin cells were morphologically normal and retained their functionality. These findings suggest that the intrathecal implant of microencapsulated chromaffin cells might be a useful method for treating chronic pain.

Abstract: The control of intractable pain through transplanted of chromaffin cells has been recently reported where the analgesic effects are principally due to the production of opioid peptides and catecholamines (CAs) by the chromaffin cells. Currently many cancer patients receive general opioids or local anesthetics, such as bupivacaine. Therefore, the present study investigated the effect of morphine or bupivacaine on the secretion of nicotine-induced CAs from encapsulated chromaffin cells over a period of 180 min. As such, bovine chromaffin cells were isolated and encapsulated with alginate–poly–L–lysine–alginate (APA) biomaterials to prevent immunorejection. The capsules were then pre-incubated with nicotine for 5 min prior to morphine or bupivacaine stimulation, and the quantity of CAs analyzed using a high performance liquid chromatography (HPLC) analysis system. The resulting data showed that the encapsulated chromaffin cells retained the ability of their parent chromaffin cells when responding to opioids by suppressing the release of CAs. In contrast, bupivacaine did not have any statistically significant affect on the basal and nicotine-induced CA release from the encapsulated chromaffin cells.

Abstract: To replace a poly(2-hydroxyethyl methacrylate) (PHEMA) sponge, which has limited applications as an implant material, PHEMA and poly(2-hydroxyethyl methacrylate-co-sodium methacrylate) (P(HEMA-co-SMA)) hydrogels with enhanced biocompatibility were prepared based on the copolymerization of 2-hydroxyethyl methacrylate (HEMA) and sodium methacrylate (SMA) at a high monomer concentration. When the cytotoxicity, cell adhesion, and in vivo tissue reaction of the resulting hydrogels were investigated, the results suggest that hydrogels prepared by the copolymerization of HEMA and SMA at a high monomer concentration have great potential as implant materials with an excellent biocompatibility.

Abstract: Various concentrations of either lidocaine or tetracaine, plus combinations of lidocaine and tetracaine were formulated into liposomes to improve topical anesthesia. The topical anesthetic effects of these liposomal mixtures of local anesthetics (Lipo-MLA) were then compared with those of EMLA (Eutectic Mixture of Local Anesthetics) and single local anesthetic liposomes using a pinprick test on healthy adult volunteers. The Lipo-MLA exhibited significantly improved anesthetic effects compared to the EMLA and single local anesthetic liposomes with a faster onset time of approximately thirty minutes and duration of at least four hours. A dermal toxicity study using rats revealed that Lipo-MLA was safe at greater than 2,000 mg/kg bodyweight.