Fabrication and Characterization of PLLA/Chitosan/Nano Calcium Phosphate Scaffolds by Freeze-Casting Technique

Advancement in "Garbage In Biomaterials Out (GIBO)" concept to develop biomaterials from agricultural waste for tissue engineering and biomedical applications

Presently on a global scale, one of the major concerns is to find effective strategies to manage the agricultural waste to protect the environment. One strategy that has been drawing attention among the researchers is the development of biocompatible materials from agricultural waste. This strategy implies successful conversion of agricultural waste products (e.g.: cellulose, eggshell etc.) into building blocks for biomaterial development. Some of these wastes contain even bioactive compounds having biomedical applications. The replacement and augmentation of human tissue with biomaterials as alternative to traditional method not only bypasses immune-rejection, donor scarcity, and maintenance; but also provides long term solution to damaged or malfunctioning organs. Biomaterials development as one of the key challenges in tissue engineering approach, resourced from natural origin imparts better biocompatibility due to closely mimicking composition with cellular microenvironment. The "Garbage In, Biomaterials Out (GIBO)" concept, not only recycles the agricultural wastes, but also adds to biomaterial raw products for further product development in tissue regeneration. This paper reviews the conversion of garbage agricultural by-products to the biocompatible materials for various biomedical applications.

Graphical abstract

The agro-waste biomass processed, purified, modified, and further utilized for the fabrication of biomaterials-based support system for tissue engineering applications to grow living body parts in vitro or in vivo.

Recent Trends in the Development of Bone Regenerative Biomaterials

The goal of a biomaterial is to support the bone tissue regeneration process at the defect site and eventually degrade in situ and get replaced with the newly generated bone tissue. Biomaterials that enhance bone regeneration have a wealth of potential clinical applications from the treatment of non-union fractures to spinal fusion. The use of bone regenerative biomaterials from bioceramics and polymeric components to support bone cell and tissue growth is a longstanding area of interest. Recently, various forms of bone repair materials such as hydrogel, nanofiber scaffolds, and 3D printing composite scaffolds are emerging. Current challenges include the engineering of biomaterials that can match both the mechanical and biological context of bone tissue matrix and support the vascularization of large tissue constructs. Biomaterials with new levels of biofunctionality that attempt to recreate nanoscale topographical, biofactor, and gene delivery cues from the extracellular environment are emerging as interesting candidate bone regenerative biomaterials. This review has been sculptured around a case-by-case basis of current research that is being undertaken in the field of bone regeneration engineering. We will highlight the current progress in the development of physicochemical properties and applications of bone defect repair materials and their perspectives in bone regeneration.

Recent progress in preparation and applications of chitosan/calcium phosphate composite materials

Studying the development of unique materials from sustainable and renewable resources has gained increasing concern due to the depletion of fossil resources. Chitosan and its derivatives have been considered as versatile candidates for preparing attractive materials. The fabrication of chitosan/calcium phosphate composite compounds has received much attention for the development of numerous promising products in different fields. In this short review, recent preparation strategies for chitosan/calcium phosphate composites such as freeze casting, vacuum-assisted filtration, and biomimetic mineralization were discussed. The review presented their advances for diverse applications such as bone tissue engineering implants, drug delivery, wound healing, dental caries, as well adsorption of organic and heavy metals from polluted water. The challenges and future perspectives for the application of chitosan/calcium phosphate materials in biomedical and environmental applications were also involved in this review article.

Mussel-inspired polydopamine induced the osteoinductivity to ice-templating PLGA-gelatin matrix for bone tissue engineering application

In this study, poly(lactic-co-glycolic acid) (PLGA)-gelatin scaffolds were fabricated using the freeze-casting technique. Polydopamine (PDA) coating was applied on the surface of scaffolds to enhance the hydrophilicity, bioactivity, and cellular behavior of the composite constructs. Further, the synergistic effect of PDA coating and lamellar microstructure of scaffolds was evaluated on the promotion of properties. Based on morphological observations, freeze-casting constructs showed lamellar pore channels while the uniformity and pore size were slightly affected by deposition of PDA. The hydrophilicity and swelling capacity of the scaffolds were assessed using contact angle measurement and phosphate buffered saline absorption ratio. The results indicated a significant increment in water-matrix interactions following surface modification. The evaluation of the biodegradation ratio revealed the higher degree of degradation in PDA-coated samples owing to the presence of hydrophilic functional groups in the chemical structure of PDA. On the other hand, the bioactivity potential of PDA in the simulated body fluid solution confirmed the possibility of using coated constructs as a bone reconstructive substitute. The improvement of cellular attachment and filopodia formation in PDA-contained matrixes was the other benefit of the coating process. Furthermore, cellular proliferation and ALP activity were enhanced after PDA coating. The suggested PDA-coated PLGA-gelatin scaffolds can be applied in bone tissue regeneration.

Agarose-based biomaterials for tissue engineering

Agarose is a natural polysaccharide polymer having unique characteristics that give reason to consider it for tissue engineering applications. Special characteristics of agarose such as its excellent biocompatibility, thermo-reversible gelation behavior and physiochemical features support its use as a biomaterial for cell growth and/or controlled/localized drug delivery. The resemblance of this natural carbohydrate polymer to the extracellular matrix results in attractive features that bring about a strong interest in its usage in the field. The scope of this review is to summarize the extensive researches addressing agarose-based biomaterials in order to provide an in-depth understanding of its tissue engineering-related applications.

Design and evaluation of chitosan/poly(l-lactide)/pectin based composite scaffolds for cartilage tissue regeneration

Poor regenerative potential of cartilage tissue due to the avascular nature and lack of supplementation of reparative cells impose an important challenge in recent medical practice towards development of artificial extracellular matrix with enhanced neo-cartilage tissue regeneration potential. Chitosan (CH), poly (l-lactide) (PLLA), and pectin (PC) compositions were tailored to generate polyelectrolyte complex based porous scaffolds using freeze drying method and crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), N-hydroxysuccinimide (NHS) solution containing chondroitin sulfate (CS) to mimic the composition as well as architecture of the cartilage extracellular matrix (ECM). The physical, chemical, thermal, and mechanical behaviors of developed scaffolds were done. The scaffolds were porous with homogeneous pore structure with pore size 49-170μm and porosities in the range of 79 to 84%. Fourier transform infrared study confirmed the presence of polymers (CH, PLLA and PC) within the scaffolds. The crystallinity of the scaffold was examined by the X-ray diffraction studies. Furthermore, scaffold shows suitable swelling property, moderate biodegradation and hemocompatibility in nature and possess suitable mechanical strength for cartilage tissue regeneration. MTT assay, GAG content, and attachment of chondrocyte confirmed the regenerative potential of the cell seeded scaffold. The histopathological analysis defines the suitability of scaffold for cartilage tissue regeneration.

Synthesis and characterization of nanocrystalline forsterite coated poly(L-lactide-co-β-malic acid) scaffolds for bone tissue engineering applications

In this research, after synthesizing poly(L-lactide-co-β-malic acid) (PLMA) copolymer, hybrid particles of ice and nanocrystalline forsterite (NF) as coating carriers were used to prepare NF-coated PLMA scaffolds. The porous NF-coated scaffolds were directly fabricated by a combined technique using porogen leaching and freeze-drying methods. The obtained results indicate that the scaffolds were structurally porous with NF particles on their surfaces. When compared to the uncoated scaffolds, the NF coating improved both mechanical properties as well as enhanced bioactivity of the scaffolds. In addition, in vitro biological response of the rat bone marrow stromal cells indicated that NF significantly increased the biocompatibility of NF-coated scaffolds compared with PLMA.

Polymer coated phosphate glass/hydroxyapatite composite scaffolds for bone tissue engineering applications

Biopolymer coated PG/HA composite scaffolds were prepared with enhanced mechanical properties for bone tissue engineering applications.

Bone tissue engineering via nanostructured calcium phosphate biomaterials and stem cells

Tissue engineering is promising to meet the increasing need for bone regeneration. Nanostructured calcium phosphate (CaP) biomaterials/scaffolds are of special interest as they share chemical/crystallographic similarities to inorganic components of bone. Three applications of nano-CaP are discussed in this review: nanostructured calcium phosphate cement (CPC); nano-CaP composites; and nano-CaP coatings. The interactions between stem cells and nano-CaP are highlighted, including cell attachment, orientation/morphology, differentiation and in vivo bone regeneration. Several trends can be seen: (i) nano-CaP biomaterials support stem cell attachment/proliferation and induce osteogenic differentiation, in some cases even without osteogenic supplements; (ii) the influence of nano-CaP surface patterns on cell alignment is not prominent due to non-uniform distribution of nano-crystals; (iii) nano-CaP can achieve better bone regeneration than conventional CaP biomaterials; (iv) combining stem cells with nano-CaP accelerates bone regeneration, the effect of which can be further enhanced by growth factors; and (v) cell microencapsulation in nano-CaP scaffolds is promising for bone tissue engineering. These understandings would help researchers to further uncover the underlying mechanisms and interactions in nano-CaP stem cell constructs in vitro and in vivo, tailor nano-CaP composite construct design and stem cell type selection to enhance cell function and bone regeneration, and translate laboratory findings to clinical treatments.

The effect of hyaluronic acid on biofunctionality of gelatin-collagen intestine tissue engineering scaffolds

The creation of engineered intestinal tissue has recently stimulated new endeavors with the ultimate goal of intestinal replacement for massive resections of bowel. In this context, we investigated the effect of hyaluronic acid (HA) on the physicochemical characteristics of gelatin-collagen scaffolds and its cytocompatibilty to the human intestinal epithelial Caco-2 cell line in vitro. Gelatin/collagen hybrid scaffolds with different concentrations of HA were prepared by solvent casting and freeze-drying techniques and subsequent chemical crosslinking by genipin. The morphologies of the scaffolds were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. In vitro tests were carried out in phosphate-buffered saline (PBS) solution to study the swelling ratio and the biostability of the scaffolds. It was found that the porous structure of the scaffolds could be tailored by further addition of HA. Moreover, both the swelling ratio and the degradation rate of the scaffold increased by addition of HA. A resazurin-based cell viability assay was employed to determine the viability and estimate the number of scaffold-adherent Caco-2 cells. The assay indicated that the scaffolds were all cytocompatible. We concluded that addition of less than 15% HA to scaffolds with a composition of 9:1 gelatin:collagen results only in incremental improvement in the structural characteristics and cytocompatibility of the gelatin-collagen scaffolds. However, the scaffolds with 25% HA exhibited remarkable enhancement in physicochemical characteristics of the scaffolds including cell viability, growth, and attachment as well as their physical structure.

Synthesis and characterization of poly(lactic-co-glycolic) acid nanoparticles-loaded chitosan/bioactive glass scaffolds as a localized delivery system in the bone defects

The functionality of tissue engineering scaffolds can be enhanced by localized delivery of appropriate biological macromolecules incorporated within biodegradable nanoparticles. In this research, chitosan/58 S-bioactive glass (58 S-BG) containing poly(lactic-co-glycolic) acid (PLGA) nanoparticles has been prepared and then characterized. The effects of further addition of 58 S-BG on the structure of scaffolds have been investigated to optimize the characteristics of the scaffolds for bone tissue engineering applications. The results showed that the scaffolds had high porosity with open pores. It was also shown that the porosity decreased with increasing 58 S-BG content. Furthermore, the PLGA nanoparticles were homogenously distributed within the scaffolds. According to the obtained results, the nanocomposites could be considered as highly bioactive bone tissue engineering scaffolds with the potential of localized delivery of biological macromolecules.