Preparation of High-Payload, Prolonged-Release Biodegradable Poly(lactic-co-glycolic acid)-Based Tacrolimus Microspheres Using the Single-Jet Electrospray Method.

Tacrolimus-loaded poly(lactic-co-glycolic acid) microspheres (TAC-PLGA-M) can be administered for the long-term survival of transplanted organs due to their immunosuppressive activity. The purpose of our study was to optimize the parameters of the electrospray method, and to prepare TAC-PLGA-M with a high payload and desirable release properties. TAC-PLGA-M were prepared using the electrospray method. In vitro characterization and evaluation were performed using scanning electron microscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy. Drug-loading efficiency was greater than 80% in all formulations with a maximum loading capacity of 16.81±0.37%. XRD and DSC studies suggested that the drug was incorporated in an amorphous state or was molecularly dispersed in the microspheres. The in vitro release study showed prolonged release patterns. TAC-PLGA-M with enhanced drug loading and prolonged-release patterns were successfully prepared using the electrospray method.

Magnetic resonance imaging of pancreatic islets using tissue-adhesive particles containing iron oxide nanoparticles.

Post-transplantation tracking of pancreatic islets is a prerequisite for advancing cell therapy to treat type 1 diabetes. Magnetic resonance imaging (MRI) has emerged as a safe and non-invasive technique for visualizing cells in clinical applications. In this study, we proposed a novel MRI contrast agent formulation by encapsulating iron oxide nanoparticles (IONPs) in poly(lactic-co-glycolic acid) (PLGA) particles functionalized with a tissue adhesive polydopamine (PD) layer (IONP-PLGA-PD MS). Intriguingly, our particles facilitated efficient and robust labeling through a one-step process, allowing for the incorporation of a substantial amount of IONPs without detrimental impacts on the viability and functionality of pancreatic islets. The MRI signals emanating from islets labeled using our particles were found to be stable over 30 days in vitro and 60 days when transplanted under kidney capsules of diabetic mice. These results suggest that our approach provides a potential platform for monitoring the fate of pancreatic islets after transplantation.

Prolongation of graft survival via layer-by-layer assembly of collagen and immunosuppressive particles on pancreatic islets.

Pancreatic islet transplantation holds great potential as a curative therapy for treating type 1 diabetes. However, the need for lifelong systemic immunosuppression with inevitable side effects is an obstacle to clinical success. Here we devised a strategy for the site-specific delivery of an immunosuppressant (tacrolimus) using layer-by-layer assembly of polymeric particles and collagen on the islet surface. This approach aims to provide a continuous and sustained supply of tacrolimus in the vicinity of transplanted cells while avoiding systemic drug exposure. The dose and release rate of tacrolimus can be tunable to achieve therapeutic windows by varying layer-by-layer construction and chemistry of polymers. Transplanting 400 IEQ of pancreatic islets coated with particles containing ∼3 µg of TAC per recipient provided controlled drug release and rectified diabetes for up to 5 months in a xenogeneic rodent model of type 1 diabetes. We anticipate that the findings of this study will be found useful by those developing local immunomodulation strategies aimed at improving the outcomes and safety of cell therapies for curing type 1 diabetes.

Local release of NECA (5'-(N-ethylcarboxamido)adenosine) from implantable polymeric sheets for enhanced islet revascularization in extrahepatic transplantation site.

Clinical intraportal pancreatic islet infusion is popular for treating type I diabetes. However, multiple doses of islets and anti-rejection protocols are needed to compensate for early large cell losses post-infusion due to the harsh hepatic environment. Thus, extrahepatic sites are utilized to enable efficient islet engraftment and reduce islet mass. Here, we reported an effective islet revascularization protocol that was based on the co-implantation of islet/fibrin gel construct with poly(lactic-co-glycolic) acid sheet releasing NECA (5'-(N-ethylcarboxamido) adenosine; a potent agonist of adenosine) into mouse epididymal fat pad. Thin, flexible sheets (d = 4 mm) prepared by simple casting exhibited sustained NECA release for up to 21 days, which effectively improved early islet engraftment with a median diabetic reversal time of 18.5 days. Western blotting revealed the facilitative effect of NECA on VEGF expression from islets in vitro and from grafts in vivo. In addition, NECA directly promoted the angiogenic activities of islet-derived endothelial cells by enhancing their proliferation and vessel-like tube formation. As a result, neovasculatures were effectively formed in the engrafted islet vicinity, as evidenced by vasculature imaging and immunofluorescence. Taken together, we suggest NECA-releasing PLGA sheets offer a safe and effective drug delivery system that enhances islet engraftment while reducing islet mass at extrahepatic sites for clinical relevance.

Polydopamine-tailored paclitaxel-loaded polymeric microspheres with adhered NIR-controllable gold nanoparticles for chemo-phototherapy of pancreatic cancer.

Chemotherapeutic drugs often used as a first-line treatment of pancreatic cancer (PC) exhibit challenges due to resistance development, lack of selectivity, and tumor heterogeneity. Currently, combination chemo-photothermal therapy is known to enhance the therapeutic efficacy of chemotherapeutic drugs in PC. In this study, we develop adherent gold nanoparticles (GNPs) and paclitaxel (PTX)-loaded PLGA microspheres for the treatment of PC. Polydopamine (pD) was used as a linker to adhere GNPs to the surface of PLGA-Ms and characterized using TEM. Short-term cytotoxicity of GNPs-pD-PTX-PLGA-Ms with or without NIR treatment was evaluated using CCK-8 assays. ROS and western blot assay were performed to determine the intensity of ROS following the treatment of GNPs-pD-PTX-PLGA-Ms with or without NIR in Panc-1 cell line. Successful adhesion of GNPs on the microspheres was confirmed by TEM. CCK-8 assay revealed that GNPs-pD-PTX-PLGA-Ms with NIR showed three-fold higher cytotoxicity, compared to the group without NIR. Furthermore, ROS and western blot assay suggest that GNPs-pD-PTX-PLGA-Ms with NIR showed more ROS generation, followed by downregulation of the expression levels of antioxidant enzyme (SOD2 and CATALASE). These results suggest that the GNPs-pD-PTX-PLGA-Ms in combination with NIR irradiation can provide a synergistic chemo-photothermal therapy for the treatment of PC.

Immunoisolation of pancreatic islets via thin-layer surface modification.

Islet transplantation is an alternative method of replacing exogenous insulin to treat type 1 diabetes. However, transplantation of allo- or xenograft islets causes the activation of host's immune reaction, which leads to the failure of the transplanted grafts. Immunosuppressive-sparing strategies have been introduced to avoid adverse effects associated with a long-term use of the immunosuppressive drugs. In this regard, macro/microencapsulation, surface camouflage, and surface modification with immune-privileged cells have been performed to protect the transplanted islets against instant blood-mediated inflammatory reactions or immune reactions. However, the increased size of the encapsulated islets after transplantation leads to insufficient oxygen and nutrients for the islets, causing most of them to undergo apoptosis. Therefore, recent studies have aimed at reducing the capsule thickness while maintaining immunoprotective ability of encapsulated islets. In this review, we discuss several techniques of thin-layer surface coating of pancreatic islets using a variety of polymers, therapeutic agents (TA), TA-loaded nano or microparticles, and living cells.

Engineering "cell-particle hybrids" of pancreatic islets and bioadhesive FK506-loaded polymeric microspheres for local immunomodulation in xenogeneic islet transplantation.

Host immune response remains an obstacle in cell-replacement therapy for treating type I diabetes. Long-term systemic immunosuppression results in suboptimal efficacy and adverse reactions. Thus, "cell-particle hybrids" of pancreatic islets and tissue-adhesive, polydopamine-coated, FK506-loaded biodegradable microspheres (PD-FK506-MS) were developed to locally modulate the immune response at the transplantation site. Coating of FK506-MS with PD enabled the rapid formation of stable cell-particle hybrids without significant changes in islet viability and functionality. Extremely low quantities of FK506 (approximately 600 ng per recipient) sustainably released from cell-particle hybrids effectively prolonged survival of xenogeneic islet graft. Interestingly, FK506 exhibited extended bioavailability in the grafts but was undetectable in systemic circulation and other tissues. Moreover, mRNA expression of inflammatory cytokines was significantly inhibited in the PD-FK506-MS-containing grafts but not in lymphoid organs. This study presents a promising platform that facilitates the translation of local immunomodulation towards an effective strategy with improved safety profiles for treating type I diabetes.

Tissue adhesive FK506-loaded polymeric nanoparticles for multi-layered nano-shielding of pancreatic islets to enhance xenograft survival in a diabetic mouse model.

This study aims to develop a novel surface modification technology to prolong the survival time of pancreatic islets in a xenogenic transplantation model, using 3,4-dihydroxyphenethylamine (DOPA) conjugated poly(lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) nanoparticles (DOPA-NPs) carrying immunosuppressant FK506 (FK506/DOPA-NPs). The functionalized DOPA-NPs formed a versatile coating layer for antigen camouflage without interfering the viability and functionality of islets. The coating layer effectively preserved the morphology and viability of islets in a co-culture condition with xenogenic lymphocytes for 7 days. Interestingly, the mean survival time of islets coated with FK506/DOPA-NPs was significantly higher as compared with that of islets coated with DOPA-NPs (without FK506) and control. This study demonstrated that the combination of surface camouflage and localized low dose of immunosuppressant could be an effective approach in prolonging the survival of transplanted islets. This newly developed platform might be useful for immobilizing various types of small molecules on therapeutic cells and biomaterial surface to improve the therapeutic efficacy in cell therapy and regenerative medicine.

Incorporation of chemotherapeutic agent and photosensitizer in a low temperature-sensitive liposome for effective chemo-hyperthermic anticancer activity.

OBJECTIVES: In this study, we combined chemo- and hyperthermia therapy in a low temperature-sensitive liposome (LTSL) for potential cancer treatment. METHODS: Docetaxel (DOC) and indocyanine green (ICG) as a therapeutic agent and photosensitizer, respectively, were incorporated in a low temperature-sensitive liposome (LTSL/DI). Nanoparticles were evaluated for the physicochemical characterizations, in vitro uptake and cytotoxicity, and furthermore in vivo anticancer activity. RESULTS: The particle size of LTSL/DI was 130.8 ± 2.3 nm, and its drug release profile was pH- and temperature-dependent, which are effective for tumor targeting. The in vitro anticancer activity of LTSL/DI was significantly enhanced compared with free DOC in SCC-7 and MCF-7 cell lines. Interestingly, near-infrared laser irradiation after the treatment resulted in better anticancer activity than in the non-irradiated condition. The in vivo tumor regression effect of LTSL/DI in combination with NIR irradiation was much greater compared with the control group in SCC-7 tumor-bearing mice. After intratumoral injection of LTSL/DI, local heat induced by NIR irradiation and the localized docetaxel burst release could completely ablate the tumor, and inhibit its recurrence. CONCLUSIONS: These results suggest LTSL/DI formulation as a potential therapeutic strategy with effectively localized anti-tumor activity and low risk of side effect to non-target organs.