Effects of poly(methylene-co-guanidine) on microbial growth in an alginate/cellulose sulphate–CaCl2/poly(methylene-co-guanidine) capsule system

Materials for Cell Surface Engineering

Cell therapies are emerging as a promising new therapeutic modality in medicine, generating effective treatments for previously incurable diseases. Clinical success of cell therapies has energized the field of cellular engineering, spurring further exploration of novel approaches to improve their therapeutic performance. Engineering of cell surfaces using natural and synthetic materials has emerged as a valuable tool in this endeavor. This review summarizes recent advances in the development of technologies for decorating cell surfaces with various materials including nanoparticles, microparticles, and polymeric coatings, focusing on the ways in which surface decorations enhance carrier cells and therapeutic effects. Key benefits of surface-modified cells include protecting the carrier cell, reducing particle clearance, enhancing cell trafficking, masking cell-surface antigens, modulating inflammatory phenotype of carrier cells, and delivering therapeutic agents to target tissues. While most of these technologies are still in the proof-of-concept stage, the promising therapeutic efficacy of these constructs from in vitro and in vivo preclinical studies has laid a strong foundation for eventual clinical translation. Cell surface engineering with materials can imbue a diverse range of advantages for cell therapy, creating opportunities for innovative functionalities, for improved therapeutic efficacy, and transforming the fundamental and translational landscape of cell therapies.

Contribution of polymeric materials to progress in xenotransplantation of microencapsulated cells: a review

Cell microencapsulation and subsequent transplantation of the microencapsulated cells require multidisciplinary approaches. Physical, chemical, biological, engineering, and medical expertise has to be combined. Several natural and synthetic polymeric materials and different technologies have been reported for the preparation of hydrogels, which are suitable to protect cells by microencapsulation. However, owing to the frequent lack of adequate characterization of the hydrogels and their components as well as incomplete description of the technology, many results of in vitro and in vivo studies appear contradictory or cannot reliably be reproduced. This review addresses the state of the art in cell microencapsulation with special focus on microencapsulated cells intended for xenotransplantation cell therapies. The choice of materials, the design and fabrication of the microspheres, as well as the conditions to be met during the cell microencapsulation process, are summarized and discussed prior to presenting research results of in vitro and in vivo studies. Overall, this review will serve to sensitize medically educated specialists for materials and technological aspects of cell microencapsulation.

Insulin encapsulation in reinforced alginate microspheres prepared by internal gelation

Insulin-loaded alginate microspheres prepared by emulsification/internal gelation were reinforced by blending with polyanionic additive polymers and/or chitosan-coating in order to increase the protection of insulin at simulated gastric pH and obtain a sustained release at simulated intestinal pH. Polyanionic additive polymers blended with alginate were cellulose acetate phtalate (CAP), Eudragit L100 (EL100), sodium carboxymethylcellulose (CMC), polyphosphate (PP), dextran sulfate (DS) and cellulose sulfate (CS). Chitosan-coating was applied by using a one-stage procedure. The influence of additive polymers and chitosan-coating on the size distribution of microspheres, encapsulation efficiency and release profile of insulin in simulated gastrointestinal pH conditions was studied. The mean diameter of blended microspheres ranged from 65 to 106 microm and encapsulation efficiency of insulin varied from 14 to 100%, reaching a maximum value when CS and DS were incorporated in the alginate matrix. Insulin release, at pH 1.2, was almost prevented by the incorporation of PP, DS and CS. When uncoated microspheres were transferred to pH 6.8, a fast dissolution occurred, independently of the additive polymer blended with alginate, and insulin was completely released. Increasing the additive polymer concentration in the alginate matrix and/or chitosan-coating the blended alginate microspheres did not promote a sustained release of insulin from microspheres at pH 6.8.

Preparation and characterization of NaCS–CMC/PDMDAAC capsules

A novel capsule system composed of sodium cellulose sulfate (NaCS), carboxymethyl cellulose (CMC) and poly[dimethyl(diallyl)ammonium chloride] (PDMDAAC) was prepared for improving the properties of NaCS/PDMDAAC capsules. The process parameters, such as CMC concentration (0, 2, 4, 6 and 8 g/L), NaCS concentration (20, 25, 30, 35 and 40 g/L), PDMDAAC concentration (20, 30, 40, 50, 60, 70 and 80 g/L), reaction time and temperature were investigated to understand their effects on the diameter, membrane thickness and mechanical strength of capsules. The optimum operation conditions for preparing NaCS-CMC/PDMDAAC capsules were determined as 6-8 g/L CMC, 35-40 g/L NaCS, 60 g/L PDMDAAC and polymerization for 30-40 min. Diffusion of substances with low molecular weight into capsules was investigated, and diffusion coefficients were calculated according to the developed model. The yeast of Candida krusei was chosen as representative cell to evaluate the effects of different cell loading on capsule mechanical strength. Meanwhile the encapsulated osmophilic C. krusei cells were cultured in 250 mL shaking flasks for 72 h to determine the cell leaking properties in short and long term.