Improved survival of anchorage-dependent cells in core-shell hydrogel microcapsules via co-encapsulation with cell-friendly microspheres.

In this study, we investigated the effect of intracapsular environment on the survival of anchorage-dependent cells (ADCs) encapsulated in alginate microcapsules with three different core structures, i.e. liquid, semi-liquid and microsphere-encapsulating semi-liquid core, using NIH 3T3 fibroblasts as an ADC model. For the latter, we fabricated poly (ɛ-caprolactone) microspheres and co-encapsulated them with the cells, to establish cell-substrate interactions in the capsule. The fibroblast cells co-encapsulated with the microspheres exhibited higher survival and growth than those without. This study provides a "proof of concept" for employing microspheres as a cell-friendly surface to establish intracapsular cell-substrate interactions thus prolonging the survival of encapsulated therapeutic ADCs.

Sustained exenatide delivery via intracapsular microspheres for improved survival and function of microencapsulated porcine islets.

The ability of glucagon-like peptide-1 analogs to enhance glucose-dependent insulin secretion and to inhibit ß cell apoptosis could be of potential benefit for islet transplantation. In this study, we investigated the effect of sustained local delivery of exenatide, a synthetic exendin-4, on the in vitro viability and function of encapsulated porcine islets. Prior to encapsulation, we fabricated exenatide-loaded poly(latic-co-glycolic acid) microspheres, and investigated their release behavior with different initial drug-loading amounts. Exenatide-loaded microspheres, exhibiting a sustained release over 21 days, were subsequently chosen and co-encapsulated with porcine islets in alginate microcapsules. During the 21-day period, the islets co-encapsulated with the exenatide-loaded microspheres exhibited improved survival and glucose-stimulated insulin secretion, compared to those without. This suggested that the intracapsular sustained delivery of exenatide via microspheres could be a promising strategy for improving survival and function of microencapsulated porcine islets for islet xenotransplantation.

Uniform biodegradable hydrogel microspheres fabricated by a surfactant-free electric-field-assisted method.

Uniform biodegradable hydrogel microspheres (HMS) with precisely controlled size have been fabricated using an electric-field-assisted precision particle fabrication technique. Particle agglomeration was prevented by charging the hydrogel drops and allowing Coulomb repulsion to separate them. As a result, surfactant-free and non-toxic particle fabrication was possible and the resulting microspheres were most suitable for biomedical and food-related applications. Due to the size uniformity, the present HMS may serve as a convenient yet most accurate vehicle for controlled delivery of therapeutic agents and other active ingredients.

Biodegradable gelatin microspheres enhance the neuroprotective potency of osteopontin via quick and sustained release in the post-ischemic brain.

Gelatin microspheres (GMSs) are widely used as drug carriers owing to their excellent biocompatibilities and toxicologically safe degradation products. The drug release profile is easily tailored by controlling the cross-linking density and surface-to-volume ratio, i.e. size, of the GMS. In this study, we employed GMSs which are 25 µm in diameter and cross-linked with 0.03125% glutaraldehyde, to enable rapid initial and a subsequent sustained release. Therapeutic potency of human recombinant osteopontin (rhOPN) with or without encapsulation into GMSs was investigated after administrating them to rat stroke model (Sprague-Dawley; middle cerebral artery occlusion, MCAO). The administration of rhOPN/GMS (100 ng/100 µg) at 1h post-MCAO reduced the mean infarct volume by 81.8% of that of the untreated MCAO control and extended the therapeutic window at least to 12h post-MCAO, demonstrating a markedly enhanced therapeutic potency for the use of OPN in the post-ischemic brain. Scanning electron microscopy micrographs revealed that GMSs maintained the three-dimensional shape for more than 5 days in normal brain but were degraded rapidly in the post-ischemic brain, presumably due to high levels of gelatinase induction. After encapsulation with GMS, the duration of OPN release was markedly extended; from the period of 2 days to 5 days in normal brain, and from 2 days to 4 days in the post-ischemic brain; these encompass the critical period for recovery processes, such as vascularization, and controlling inflammation. Together, these results indicate that GMS-mediated drug delivery has huge potential when it was used in the hyperacute period in the post-ischemic brain.

In vitro and in vivo imaging of peptide-encapsulated polymer nanoparticles for cancer biomarker activated drug delivery.

Gelatin nanoparticles coated with Cathepsin D-specific peptides were developed as a vehicle for the targeted delivery of the cancer drug doxorubicin (DOX) to treat breast malignancy. Cathepsin D, a breast cancer cell secretion enzyme, triggered the release of DOX by digesting the protective peptide-coating layer of nanoparticles. Fabricated nanoparticles were successfully detected with ultrasound imaging in both in vitro conditions and in vivo mouse cancer models. Cell viability experiments were conducted to determine the efficacy of biomarker activation specific to breast cancer cell lines. These experimental results were compared with the outcome of a viability experiment conducted on noncancerous cells. Viability decreased in human MCF7 mammary adenocarcinoma and mouse 4T1 mammary carcinoma cells, while that of noncancerous 3T3 fibroblast cells remained unaffected. Next, a real-time video of nanoparticle flow in mouse models was obtained using in vivo ultrasound imaging. The fluorescent profile of DOX was used as a means to examine nanoparticle localization in vivo. Results show the distribution of nanoparticles concentrated primarily within bladder and tumor sites of subject mice bodies. These findings support the use of biomarker coated nanoparticles in target specific therapy for breast cancer treatment.

The effect of biodegradable gelatin microspheres on the neuroprotective effects of high mobility group box 1 A box in the postischemic brain.

High mobility group box 1 (HMGB1) is a family of endogenous molecules that is released by necrotic cells and causes neuronal damages by triggering inflammatory processes. In the cerebral ischemic brain, sustained and regulated suppression of HMGB1 has been emerged as a therapeutic means to grant neuroprotection. HMGB1 consists of two HMG boxes (A and B) and an acidic C-terminal tail, and the A box peptide antagonistically competes with HMGB1 for its receptors. In the middle cerebral artery occlusion (MCAO) in rats, a murine model of transient cerebral ischemia, administration of HMGB1 A box intraparenchymally, after encapsulated in biodegradable gelatin microspheres (GMS), which enhances the stability of peptide inside and allows its sustained delivery, at 1 h, 3 h, or 6 h after MCAO, reduced mean infarct volumes by, respectively, 81.3%, 42.6% and 30.7% of the untreated MCAO-brain, along with remarkable improvement of neurological deficits. Furthermore, the administration of HMGB1 A box/GMS suppressed proinflammatory cytokine inductions more strongly than the injection of non-encapsulated HMGB1 A box. Given that insulted brains-like ischemia have enhanced gelatinase activity than the normal brain, our results suggest that GMS-mediated delivery of therapeutic peptides is a promising means to provide efficient neuroprotection in the postischemic brain.