RESUMO
Polyelectrolyte complexes formed between laccase and polyvinylamine with grafted TEMPO moieties, PVAm-T, adsorb onto cellulose, causing oxidation. All evidence supports the view that aldehyde groups on oxidized cellulose condense with primary amine groups, giving a grafted layer of PVAm-T complexed with laccase. The grafted PVAm-T serves as a primer layer promoting wet cellulose-to-cellulose adhesion in the presence of PVAm adhesive. The cellulose modification occurs at ambient temperatures and pH 5. The adhesion improvements with mixtures of PVAm-T and laccase are remarkable because both components are macromolecular, which should inhibit the ability of the TEMPO to act as a shuttle between the enzyme and the primary hydroxyl groups on cellulose. It is proposed that PVAm-bound oxoammonium ions exchange with neighboring TEMPO moieties, providing a mechanism for the transfer of oxidation activity from immobilized enzyme to the cellulose surfaces.
Assuntos
Celulose/química , Óxidos N-Cíclicos/química , Proteínas Fúngicas/química , Lacase/química , Oxidantes/química , Polivinil/química , Adesivos/química , Adsorção , Concentração de Íons de Hidrogênio , Fenômenos Mecânicos , Oxirredução , Oxigênio/química , Trametes/enzimologiaRESUMO
Therapeutic delivery to the brain is limited by the blood-brain barrier and is exacerbated by off-target effects associated with systemic delivery, thereby precluding many potential therapies from even being tested. Given the systemic side effects of cyclosporine and erythropoietin, systemic administration would be precluded in the context of stroke, leaving only the possibility of local delivery. We wondered if direct delivery to the brain would allow new reparative therapeutics, such as these, to be identified for stroke. Using a rodent model of stroke, we employed an injectable drug delivery hydrogel strategy to circumvent the blood-brain barrier and thereby achieved, for the first time, local and sustained co-release to the brain of cyclosporine and erythropoietin. Both drugs diffused to the sub-cortical neural stem and progenitor cell (NSPC) niche and were present in the brain for at least 32 days post-stroke. Each drug had a different outcome on brain tissue: cyclosporine increased plasticity in the striatum while erythropoietin stimulated endogenous NSPCs. Only their co-delivery, but not either drug alone, accelerated functional recovery and improved tissue repair. This platform opens avenues for hitherto untested therapeutic combinations to promote regeneration and repair after stroke.
Assuntos
Eritropoetina , Acidente Vascular Cerebral , Animais , Encéfalo , Ciclosporina , Hidrogéis , Ratos , Acidente Vascular Cerebral/tratamento farmacológicoRESUMO
IMPACT STATEMENT: We developed a biocomposite that can be mixed with brain-derived neurotrophic factor (BDNF) and dispensed onto the surface of the brain to provide sustained, local release of the protein using a procedure that avoids additional damage to neural tissue. The composite is simple to fabricate, and provides sustained release without nanoparticle encapsulation of BDNF, preserving material and protein bioactivity. We demonstrate that when delivered epicortically to a rat model of stroke, this composite allows BDNF to diffuse into the brain, resulting in enhanced behavioral recovery and synaptic plasticity in the contralesional hemisphere.
Assuntos
Comportamento Animal , Fator Neurotrófico Derivado do Encéfalo/farmacologia , Sistemas de Liberação de Medicamentos , Recuperação de Função Fisiológica , Acidente Vascular Cerebral/fisiopatologia , Animais , Comportamento Animal/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Encéfalo/fisiopatologia , Membro Posterior/efeitos dos fármacos , Membro Posterior/patologia , Membro Posterior/fisiopatologia , Ácido Hialurônico/química , Masculino , Metilcelulose/química , Neurônios/efeitos dos fármacos , Neurônios/patologia , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/química , Ratos Sprague-Dawley , Recuperação de Função Fisiológica/efeitos dos fármacos , Acidente Vascular Cerebral/patologia , Sinaptofisina/metabolismoRESUMO
Ischemic stroke results in a loss of neurons for which there are no available clinical strategies to stimulate regeneration. While preclinical studies have demonstrated that functional recovery can be obtained by transplanting an exogenous source of neural progenitors into the brain, it remains unknown at which stage of neuronal maturity cells will provide the most benefit. We investigated the role of neuronal maturity on cell survival, differentiation, and long-term sensorimotor recovery in stroke-injured rats using a population of human cortically-specified neuroepithelial progenitor cells (cNEPs) delivered in a biocompatible, bioresorbable hyaluronan/methylcellulose hydrogel. We demonstrate that transplantation of immature cNEPs result in the greatest tissue and functional repair, relative to transplantation of more mature neurons. The transplantation process itself resulted in the least cell death and phenotypic changes in the immature cNEPs, and the greatest acute cell death in the mature cells. The latter negatively impacted host tissue and negated any potential positive effects associated with cell maturity and the hydrogel vehicle, which itself showed some functional and tissue benefit. Moreover, we show that more mature cell populations are drastically altered during the transplantation process itself. The phenotype of the cells before and after transplantation had an enormous impact on their survival and the consequent tissue and behavioral response, emphasizing the importance of characterizing injected cells in transplantation studies more broadly.
Assuntos
Ácido Hialurônico/química , Hidrogéis/química , Células-Tronco Neurais/transplante , Células Neuroepiteliais/transplante , Acidente Vascular Cerebral/terapia , Animais , Células Cultivadas , Humanos , Masculino , Células-Tronco Neurais/citologia , Células Neuroepiteliais/citologia , Neurogênese , Ratos , Ratos Sprague-Dawley , Recuperação de Função Fisiológica , Alicerces Teciduais/químicaRESUMO
Encapsulation of therapeutic molecules within polymer particles is a well-established method for achieving controlled release, yet challenges such as low loading, poor encapsulation efficiency, and loss of protein activity limit clinical translation. Despite this, the paradigm for the use of polymer particles in drug delivery has remained essentially unchanged for several decades. By taking advantage of the adsorption of protein therapeutics to poly(lactic-co-glycolic acid) (PLGA) nanoparticles, we demonstrate controlled release without encapsulation. In fact, we obtain identical, burst-free, extended-release profiles for three different protein therapeutics with and without encapsulation in PLGA nanoparticles embedded within a hydrogel. Using both positively and negatively charged proteins, we show that short-range electrostatic interactions between the proteins and the PLGA nanoparticles are the underlying mechanism for controlled release. Moreover, we demonstrate tunable release by modifying nanoparticle concentration, nanoparticle size, or environmental pH. These new insights obviate the need for encapsulation and offer promising, translatable strategies for a more effective delivery of therapeutic biomolecules.