Progress technology in microencapsulation methods for cell therapy

Abstract

Cell encapsulation in microcapsules allows the in situ delivery of secreted proteins to treat different pathological conditions. Spherical microcapsules offer optimal surface-to-volume ratio for protein and nutrient diffusion, and thus, cell viability. This technology permits cell survival along with protein secretion activity upon appropriate host stimuli without the deleterious effects of immunosuppressant drugs. Microcapsules can be classified in 3 categories: matrix-core/shell microcapsules, liquid-core/shell microcapsules, and cells-core/shell microcapsules (or conformal coating). Many preparation techniques using natural or synthetic polymers as well as inorganic compounds have been reported. Matrix-core/shell microcapsules in which cells are hydrogel-embedded, exemplified by alginates capsule, is by far the most studied method. Numerous refinement of the technique have been proposed over the years such as better material characterization and purification, improvements in microbead generation methods, and new microbeads coating techniques. Other approaches, based on liquid-core capsules showed improved protein production and increased cell survival. But aside those more traditional techniques, new techniques are emerging in response to shortcomings of existing methods. More recently, direct cell aggregate coating have been proposed to minimize membrane thickness and implants size. Microcapsule performances are largely dictated by the physicochemical properties of the materials and the preparation techniques employed. Despite numerous promising pre-clinical results, at the present time each methods proposed need further improvements before reaching the clinical phase.

Microparticles for cell encapsulation and colonic delivery produced by membrane emulsification

“…Thus, the process of particle formation has to be carefully selected. Droplet production can essentially be classified in to two types: single or series drop formation techniques (extrusion-laminar jet break-up [15]; microfluidic devices [21]), and bulk or parallel techniques (stirring [7,36]; Membrane Emulsification (ME) [20])). To-date, Song et al [20] is the only work reported for the encapsulation of cells using an SPG membrane.…”

Device design and materials optimization of conformal coating for islets of Langerhans

“…Among these technologies are PEGylation (22), layer-by-layer (23)(24)(25)(26)(27), and conformal coating (28)(29)(30)(31)(32), which are based on chemically reacting hydrogels directly to the cell surface (21,33,34), as well as the development of ALG derivatives with enhanced performance (35). Although successful in vitro, most technologies have not achieved success as immune barriers in preclinical and clinical models, still requiring systemic immunosuppression (36).…”

Nanomedicine and epigenome. Possible health risks

“…the immobilization of cells within polymeric microspheres or microcapsules, has permitted the transplantation of cells into human and animal subjects without the need for immunosuppressants, while allowing the bidirectional diffusion of nutrients, oxygen and waste (Murua et al, 2008). Microencapsulation materials have comprised natural or synthetic polymers or blends, including alginate, collagen, gelatin, fibrin, polyphosphazenes, poly(acrylic acids), poly(methacrylic acids), copolymers of acrylic acid and methacrylic acid, poly(alkylene oxides), poly(vinyl acetate), polyvinylpyrrolidone, PEG, polyethersulfone, polysaccharides such as agarose, cellulose sulfate, chondroitin sulfate, chitosan, hyaluronan, and copolymers, and blends of each (Rabanel et al, 2009). The first implantable alginatepoly(L-lysine) microcapsules for the treatment of diabetes were presented by Lim and Sun, (1980).…”