Incorporation Of Alginate Research Articles

Bioactive polymeric–ceramic hybrid 3D scaffold for application in bone tissue regeneration

The regeneration of large bone defects remains a challenging scenario from a therapeutic point of view. In fact, the currently available bone substitutes are often limited by poor tissue integration and severe host inflammatory responses, which eventually lead to surgical removal. In an attempt to address these issues, herein we evaluated the importance of alginate incorporation in the production of improved and tunable β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) three-dimensional (3D) porous scaffolds to be used as temporary templates for bone regeneration. Different bioceramic combinations were tested in order to investigate optimal scaffold architectures. Additionally, 3D β-TCP/HA vacuum-coated with alginate, presented improved compressive strength, fracture toughness and Young's modulus, to values similar to those of native bone. The hybrid 3D polymeric–bioceramic scaffolds also supported osteoblast adhesion, maturation and proliferation, as demonstrated by fluorescence microscopy. To the best of our knowledge this is the first time that a 3D scaffold produced with this combination of biomaterials is described. Altogether, our results emphasize that this hybrid scaffold presents promising characteristics for its future application in bone regeneration.

Anionic carbohydrate-containing chitosan scaffolds for bone regeneration

Scaffolds derived from naturally occurring polysaccharides have attracted significant interest in bone tissue engineering due to their excellent biocompatibility and hydrophilic nature favorable for cell attachment. In this study, we developed composite chitosan (CH) scaffolds containing anionic carbohydrate, such as chondroitin 4-sulfate (CS) or alginate (AG), with biomimetic apatite layer on their surfaces, and investigate their capacity to deliver progenitor cells (bone marrow stromal cells, BMSC) and model proteins with net-positive (histone) and net-negative charge (bovine serum albumin, BSA). The incorporation of CS or AG in CH scaffolds increased compressive modulus of the scaffolds and enhanced apatite formation. Initial burst release of histone was significantly higher than that of BSA from CH scaffold, while the addition of CS or AG in the scaffolds significantly reduced the initial burst release of histone, indicating strong electrostatic interaction between histone and negatively charged CS or AG. The apatite layer created on scaffold surfaces significantly reduced the initial burst release of both BSA and histone. Furthermore, apatite-coated scaffolds enhanced spreading, proliferation, and osteogenic differentiation of BMSC seeded on the scaffolds compared to non-coated scaffolds as assessed by live/dead and alamarBlue assays, scanning electron microscopy (SEM), alkaline phosphatase (ALP) activity, and Picrosirius red staining. This study suggests that apatite-coated CH/CS composite scaffolds have the potential as a promising osteogenic system for bone tissue engineering applications.

One-step fabrication of core-shell structured alginate-PLGA/PLLA microparticles as a novel drug delivery system for water soluble drugs.

Current focus on particulate drug delivery entails the need for increased drug loading and sustained release of water soluble drugs. Commonly studied biodegradable polyesters, such as poly(lactide-co-glycolide) (PLGA) and poly(l-lactide) (PLLA), are lacking in terms of loading efficiency of these drugs and a stable encapsulation environment for proteins. While hydrogels could enable higher loading of hydrophilic drugs, they are limited in terms of controlled and sustained release. With this in mind, the aim was to develop microparticles with a hydrophilic drug-loaded hydrogel core encapsulated within a biodegradable polyester shell that can improve hydrophilic drug loading, while providing controlled and sustained release. Herein, we report a single step method of fabricating microparticles via a concurrent ionotropic gelation and solvent extraction. Microparticles fabricated possess a core-shell structure of alginate, encapsulated in a shell constructed of either PLGA or PLLA. The cross-sectional morphology of particles was evaluated via scanning electron microscopy, calcium alginate core dissolution, FT-IR microscopy and Raman mapping. The incorporation of alginate within PLGA or PLLA was shown to increase encapsulation efficiency of a model hydrophilic drug metoclopramide HCl (MCA). The findings showed that the shell served as a membrane in controlling the release of drugs. Such gel-core hydrophobic-shell microparticles thus allow for improved loading and release of water soluble drugs.

Properties of pullulan-based blend films as affected by alginate content and relative humidity.

Pullulan-sodium alginate blend films were prepared and characterized as a function of water activity (aw). At low aw, the incorporation of alginate into pullulan film increased the tensile strength and elastic modulus, but decreased the elongation at break of the composite films; the opposite trends were observed at elevated aw. Above 0.43 aw, water exerted a typical plasticization effect upon the biopolymer blends. As aw increased from 0.23 to 0.43, an anti-plasticization effect was observed as tensile strength and elastic modulus increased. The glass transition temperature of all samples decreased substantially as aw increased from 0.23 to 0.84 due to the plasticization effect of water. Within this aw range, one transition temperature was observed for all film specimens. The stretching vibration band of O-H was investigated using attenuated total reflection Fourier transform infrared spectroscopy to identify the various species of water interacting with the polysaccharide films.

Enhancing immunogenicity to PLGA microparticulate systems by incorporation of alginate and RGD-modified alginate

Poly-lactide-co-glycolide acid (PLGA) and alginate represent two different families of polymers widely used for microencapsulation application, even more, for vaccination purposes as particulate delivery/adjuvant systems. Combination of these polymers has been previously considered for tissue engineering and drug delivery, however there is currently no report regarding their combination for vaccine application. In the present work, a w/o/w solvent extraction technique was developed to prepare novel 1 μm microparticles (MP) composed of PLGA and a small percentage of alginate (PLGA-alg MP). In addition, RGD-modified alginate was also employed as biofunctionalized material favoring MP–cell interaction (PLGA-alg-RGD MP). Two malaria synthetic peptides, SPf66 and S3, were microencapsulated into PLGA, PLGA-alg and PLGA-alg-RGD MP. The diverse MP formulations resulted very similar in terms of size and morphology, although the addition of alginate improved encapsulation efficiency and reduced the amount of surface adsorbed peptide. Immunization studies in Balb/c mice by intradermal route demonstrated that incorporation of alginate elicited higher humoral and cellular immune responses leading to more balanced Th1/Th2 responses. Furthermore, administration of MP containing RGD-modified alginate showed evidence of cell targeting by enhancing immunogenicity of microparticles, in particular with regard to cellular responses such as IFN-γ secretion and lymphoproliferation.

Alginate combined calcium phosphate cements: mechanical properties and in vitro rat bone marrow stromal cell responses

Here, we prepared self-setting calcium phosphate cements (CPCs) based on α-tricalcium phosphate with the incorporation of sodium alginate, and their mechanical properties and in vitro cellular responses were investigated. The addition of alginate enhanced the hardening reaction of CPCs showing shorter setting times within a range of powder-to-liquid ratios. When immersed in a body simulating fluid the alginate-CPCs fully induced a formation of an apatite crystalline phase similar to that of bare CPCs. The compressive and tensile strengths of the CPCs were found to greatly improve during immersion in the fluid, and this improvement was more pronounced in the alginate-CPCs. As a result, the alginate-CPCs retained significantly higher strength values than the bare CPCs after 3-7 days of immersion. The rat bone marrow derived stromal cells (rBMSCs) cultured on the alginate-CPCs initially adhered to and then spread well on the cements surface, showed an on-going increase in the population with culture time, and differentiated into osteoblasts expressing bone-associated genes (collagen type I, osteopontin and bone sialoprotein) and synthesizing alkaline phosphatase. However, the stimulated level of osteogenic differentiation was not confirmative with the incorporation of alginate into the CPC composition based on the results. One merit of the use of alginate was its usefulness in forming CPCs into a variety of scaffold shapes including microspheres and fibers, which is associated with the cross-link of alginate under the calcium-containing solution.

Design and preparation of bionanocomposites based on layered solids with functional and structural properties

Biopolymers such as chitosan, pectin, alginate, ı-carrageenan and gelatin, can be assembled to layered solids by direct intercalation via ion exchange in the case of smectites or a 'co-organised assembly' method in the case of layered double hydroxides (LDHs). Layered perovskites can be delaminated and combined with the biopolymers following a delamination/restacking procedure. The starting cationic exchange ability of smectites such as montmorillonite is turned into an anionic exchange capacity due to the intercalated chitosan excess, while an opposite effect is observed in the case of the LDHs after incorporation of alginate, pectin or ı-carrageenan. This fact, combined with the good mechanical properties of these bionanocomposites, allows their use as the sensing phase of potentiometric sensors applied to the recognition of cationic or anionic species in aqueous solution. Besides, perovskite–gelatin bionanocomposites can be processed as robust translucent films with highly oriented two-dimensional particles exhibiting elevated dielectric permittivity values.