A method for fabricating arrays of microcapsules covalently immobilized onto chemically patterned substrates was developed.The core-shell microparticles with poly(allylamine hydrochloride)(PAH) as the outermost layer were obtained by layer-by-layer (LbL) assembly,which were further treated with glutaraldehyde to endow the particles with abundant aldehyde groups on their surfaces.The particles were then covalently coupled to the chemically patterned regions with amino groups created by microcontact printing (μCP).After dissolution of the core particles,arrays of the hollow microcapsules with unchanged structures were obtained.These arrays could stand rigorous environmental conditions of higher ionic strength,and lower and higher pH values.Thus,the technique could be possibly applied to exploiting chips of microcontainers or microreactors in sensing technology.
Alginate,low mole mass heparin-chitosan-alginate,low mole mass heparin microcapsules(ALCAL) with good mechanical stability were made from the high voltage pulsing microcapsule shaping device.ALCAL was made of low-mole-mass heparin(LMWH),alginate(ALG)and chitosan(CS)by supramolecular layer upon layer self-assembled technique.It was found from the microscopic observation that the microcapsules had smooth surface and a porous structure with interconnected pores.The results of the permeability experiment of microcapsules using fluorescein isothiocyanate-bovine serum albumin(FITC-BSA)and fluorescein isothiocyanate-immunoglobulin G(FITC-IgG)showed that the ALCAL membrane could provide cell immuno-isolation;meanwhile,the ALCAL membrane had good biocompatibility.The potential of ALCAL microcapsules for the encapsulation of liver cells had been investigated and showed that the ALCAL membrane supports the survival,proliferation and protein secretion on encapsulating hepatocytes.The ALCAL microcapsule had several advantages compared to more widely used alginate-chitosan-alginate(ACA)microcapsules for the application of cell therapy.
Microarrays of spherical vessel-like colloids such as liposomes, polymerized vesicles and polyelec-trolyte capsules may find diverse applications in bioanalysis, biosensing, and combinatorial chemistry, for their capabilities in encapsulating chemical species such as drugs, biomolecules, probes, polymers and nanoparticles. This review reports the advances on methods for fabricating microarrays of the various hollow colloids. Related strategies are described in detail, including patterning techniques, surface modification methods, and tethering approaches such as oligonucleotide hybridization, receptor-ligand binding, covalent coupling and electrostatic interaction. The preliminary developments of functionalities of these arrays serving as sensor chips, microcarriers and microreactors are summarized as well.
