Processing and characterization of chitosan microspheres to be used as templates for layer-by-layer assembly

Abstract

Chitosan (Ch) microspheres have been developed by precipitation method, cross-linked with glutaraldehyde and used as a template for layer-by-layer (LBL) deposition of two natural polyelectrolytes. Using a LBL methodology, Ch microspheres were alternately coated with hyaluronic acid (HA) and Ch under mild conditions. The roughness of the Ch-based crosslinked microspheres was characterized by atomic force microscopy (AFM). Morphological characterization was performed by environmental scanning electron microscopy (ESEM), scanning electron microscopy (SEM) and stereolight microscopy. The swelling behaviour of the microspheres demonstrated that the ones with more bilayers presented the highest water uptake and the uncoated cross-linked Ch microspheres showed the lowest uptake capability. Microspheres presented spherical shape with sizes ranging from 510 to 840 mum. ESEM demonstrated that a rougher surface with voids is formed in multilayered microspheres caused by the irregular stacking of the layers. A short term mechanical stability assay was also performed, showing that the LBL procedure with more than five bilayers of HA/Ch over Ch cross-linked microspheres provide higher mechanical stability.

Nanostructured Hollow Tubes Based on Chitosan and Alginate Multilayers

“…The most employed LbL protocols are based on the build‐up of PEMs with tunable thickness, chemical and physical properties onto flat surfaces . Nowadays, more complex structures prepared with LbL have been reported, including freestanding films, capsules, and porous scaffolds . Porous scaffolds were obtained by coating free‐packet of leachable spherical templates or by beads agglomeration .…”

“…Here, we report the proof‐of‐concept for the fabrication of hollow tubes composed by PEMs of chitosan (CHIT) and alginate (ALG). CHIT and ALG are often successfully applied in LbL due to their biocompatibility, non‐cytotoxic character, and structural characteristics similar to glycosaminoglycans (GAG's) . Polysaccharides PEMs often lack stability in physiological conditions, exhibiting low stiffness and poor cell adhesion due to high hydration .…”

Dual‐responsive semi‐interpenetrating network beads based on calcium alginate/poly(N‐isopropylacrylamide)/poly(sodium acrylate) for sustained drug release

“…All of the bead samples were exposed to both oscillation and osmotic swelling pressure to evaluate the mechanical stability in PBS (pH 7.4) under oscillation (50 rpm) 28, 29. Figure 4 shows three digital photographs, where the shapes of sample beads in each cylinder can be observed.…”

“…All of the bead samples were exposed to both oscillation and osmotic swelling pressure to evaluate the mechanical stability in PBS (pH 7.4) under oscillation (50 rpm). 28,29 Figure 4 shows three digital photographs, where the shapes of sample beads in each cylinder can be observed. Only NANBs ruptured after 4 h at 45 C, 12 h at 37 C, and 48 h at 25 C; this indicated that SANB-1 and SANB-2 provided higher mechanical resistance, even with a small amount of PAANa.…”

Biomaterials from Marine‐Origin Biopolymers

“…These types of particulate systems may also promote growth of bonelike apatite, after a calcium silicate treatment, according to Leonor et al [184]. A technique employed to enhance the mechanical properties of microspheres is to develop multilayer particles, using the LbL technique [185].…”