Alginate−Poly(ethylene glycol) Hybrid Microspheres with Adjustable Physical Properties

Abstract

A one-step extrusion process under physiological conditions yielded calcium alginate-poly(ethylene glycol) hybrid microspheres (Alg-PEG-M), for which the physical properties were adjustable by the macromolecular characteristics of the components, their concentration as well as the process conditions. A solution containing a mixture of sodium alginate (Naalg) and multiarm vinyl sulfone-terminated PEG (PEG-VS) was extruded into a receiving bath providing calcium ions and a thiol cross-linker. Covalent cross-linking of PEG-VS occurred in the rapidly gelled spherical calcium alginate (Caalg) matrix. After liquefaction of the Caalg, the cross-linked PEG remained spherical. The stoichiometric ratio thiol/VS was decisive for the PEG gel stability. The permeability of the hydrogels could be tuned by adequate choice of the arm length of PEG-VS, while the swelling behavior was influenced by its concentration, the quality of the storage solvent, and the presence or absence of the Caalg matrix. Only slight differences of the mechanical resistance were observed after the dissolution of Caalg.

Microencapsulated human mesenchymal stem cells decrease liver fibrosis in mice

“…The mixture was extruded through a 400 lm needle into the sterile gelation bath prepared by dissolving CaCl 2 and DTT, in DMEM (special formulation as indicated above) with osmolality adjusted to 300 mOs/kg (80 ± 5 mM CaCl 2 ). The receiving bath was incubated in a shaker (80 rpm) at 37°C for 3 h to achieve optimal cross-coupling [27]. Microspheres were collected by filtration and cultured in IMDM 10% FCS.…”

Effect of polysaccharide nanocrystals on structure, properties, and drug release kinetics of alginate-based microspheres

“…To improve the properties of alginate-based microspheres and to cover shortages of drug transporters, many different materials have been proposed to mix with alginate, including both synthetic [9][10][11][12] and natural polymers [13][14][15][16][17][18][19]. The attempts utilized in these studies however, could either not combine effective reinforcement of the structural strength of microspheres with biocompatibility [20], or they involved the use of organic solvent or organic crosslinking agents [21][22][23].…”

Current status of hepatocyte xenotransplantation

“…1): hence, immunosuppression with its intrinsic adverse effects can be reduced or eliminated. The passage of cytokines and inflammatory mediators is dependent on the size of these proteins and the permeability of the microspheres: for instance, for microspheres based on alginate and poly(ethylene glycol) of different molar weight and prepared using different ratios, the permeability can be adjusted between 70 and 150 kDa [44].…”

“…Based on the advantages of both alginate (biocompatibility) and poly(ethylene glycol) (mechanical resistance), novel types of hydrogel microspheres have been designed [44,59,60]. These combine ionotropic interaction of alginate molecules with chemical crosslinking of vinyl sulfone-terminated multi-arm poly(ethylene glycol) molecules.…”

“…These combine ionotropic interaction of alginate molecules with chemical crosslinking of vinyl sulfone-terminated multi-arm poly(ethylene glycol) molecules. These hydrogels allow adaptation of physical properties in a controllable manner, like permeability and swelling, and also offer excellent biocompatibility, mechanical resistance, and stability [44]. Of note, xenografted cells maintained their viability for up to six months in these microspheres [60].…”