Macroporous Calcium Phosphate/Chitosan Composites Prepared via Unidirectional Ice Segregation and Subsequent Freeze-Drying

Porous biomaterials for tissue engineering: a review

The field of biomaterials has grown rapidly over the past decades. Within this field, porous biomaterials have played a remarkable role in: (i) enabling the manufacture of complex three-dimensional structures; (ii) recreating mechanical properties close to those of the host tissues; (iii) facilitating interconnected structures for the transport of macromolecules and cells; and (iv) behaving as biocompatible inserts, tailored to either interact or not with the host body. This review outlines a brief history of the development of biomaterials, before discussing current materials proposed for use as porous biomaterials and exploring the state-of-the-art in their manufacture. The wide clinical applications of these materials are extensively discussed, drawing on specific examples of how the porous features of such biomaterials impact their behaviours, as well as the advantages and challenges faced, for each class of the materials.

Dicalcium Phosphate Dihydrate Mineral Loaded Freeze-Dried Scaffolds for Potential Synthetic Bone Applications

Dicalcium Phosphate Dihydrate (DCPD) mineral scaffolds alone do not possess the mechanical flexibility, ease of physicochemical properties' tuneability or suitable porosity required for regenerative bone scaffolds. Herein, we fabricated highly porous freeze-dried chitosan scaffolds embedded with different concentrations of Dicalcium Phosphate Dihydrate (DCPD) minerals, i.e., 0, 20, 30, 40 and 50 (wt)%. Increasing DCPD mineral concentration led to increased scaffold crystallinity, where the % crystallinity for CH, 20, 30, 40, and 50-DCPD scaffolds was determined to be 0.1, 20.6, 29.4, 38.8 and 69.9%, respectively. Reduction in scaffold pore size distributions was observed with increasing DCPD concentrations of 0 to 40 (wt)%; coalescence and close-ended pore formation were observed for 50-DCPD scaffolds. 50-DCPD scaffolds presented five times greater mechanical strength than the DCPD mineral-free scaffolds (CH). DCPD mineral enhanced cell proliferation for the 20, 30 and 40-DCPD scaffolds. 50-DCPD scaffolds presented reduced pore interconnectivity due to the coalescence of many pores in addition to the creation of closed-ended pores, which were found to hinder osteoblast cell proliferation.

Mineral-induced bubbling effect and biomineralization as strategies to create highly porous and bioactive scaffolds for dentin tissue engineering

The objective of the study was to assess the biological and mechanical characteristics of chitosan-based scaffolds enriched by mineral phases and biomineralized in simulated body fluid (SBF) as a possible biomaterial for dentin regeneration. Thus, porous chitosan scaffolds were prepared by the mineral-induced bubbling-effect technique and subjected to biomineralization to create biomimetic scaffolds for dentin tissue engineering. Suspensions containing calcium hydroxide, nanohydroxyapatite, or β-tricalcium phosphate were added to the chitosan (CH) solution and subjected to gradual freezing and freeze-drying to obtain CHCa, CHnHA, and CHβTCP porous scaffolds, respectively, by the bubbling effect. Then, scaffolds were incubated in SBF for 5 days at 37°C, under constant stirring, to promote calcium-phosphate (CaP) biomineralization. Scanning electron microscopy revealed increased pore size and porosity degree on mineral-containing scaffolds, with CHCa and CHnHA presenting as round, well-distributed, and with an interconnected pore network. Nevertheless, incubation in SBF disrupted the porous architecture, except for CHCa_SBF , leading to the deposition of CaP coverage, confirmed by Fourier Transform Infrared Spectroscopy analyses. All mineral-containing and SBF-treated formulations presented controlled degradation profiles and released calcium throughout 28 days. When human dental pulp cells (HDPCs) were seeded onto scaffold structures, the porous and interconnected architecture of CHCa, CHnHA, and CHCa_SBF allowed cells to infiltrate and spread throughout the scaffold structure, whereas in other formulations cells were dispersed or agglomerated. It was possible to determine a positive effect on cell proliferation and odontogenic differentiation for mineral-containing formulations, intensely improved by biomineralization. A significant increase in mineralized matrix deposition (by 8.4 to 18.9 times) was observed for CHCa_SBF , CHnHA_SBF , and CHβTCP_SBF in comparison with plain CH. The bioactive effect on odontoblastic marker expression (ALP activity and mineralized matrix) was also observed for HDPCs continuously cultivated with conditioned medium obtained from scaffolds. Therefore, biomineralization of chitosan scaffolds containing different mineral phases was responsible for increasing the capacity for mineralized matrix deposition by pulpal cells, with potential for use in dentin tissue engineering.

Biomaterial-Assisted Regenerative Medicine

This review aims to show case recent regenerative medicine based on biomaterial technologies. Regenerative medicine has arousing substantial interest throughout the world, with “The enhancement of cell activity” one of the essential concepts for the development of regenerative medicine. For example, drug research on drug screening is an important field of regenerative medicine, with the purpose of efficient evaluation of drug effects. It is crucial to enhance cell activity in the body for drug research because the difference in cell condition between in vitro and in vivo leads to a gap in drug evaluation. Biomaterial technology is essential for the further development of regenerative medicine because biomaterials effectively support cell culture or cell transplantation with high cell viability or activity. For example, biomaterial-based cell culture and drug screening could obtain information similar to preclinical or clinical studies. In the case of in vivo studies, biomaterials can assist cell activity, such as natural healing potential, leading to efficient tissue repair of damaged tissue. Therefore, regenerative medicine combined with biomaterials has been noted. For the research of biomaterial-based regenerative medicine, the research objective of regenerative medicine should link to the properties of the biomaterial used in the study. This review introduces regenerative medicine with biomaterial.

Chitosan based bioactive materials in tissue engineering applications-A review

In recent years, there have been increasingly rapid advances of using bioactive materials in tissue engineering applications. Bioactive materials constitute many different structures based upon ceramic, metallic or polymeric materials, and can elicit specific tissue responses. However, most of them are relatively brittle, stiff, and difficult to form into complex shapes. Hence, there has been a growing demand for preparing materials with tailored physical, biological, and mechanical properties, as well as predictable degradation behavior. Chitosan-based materials have been shown to be ideal bioactive materials due to their outstanding properties such as formability into different structures, and fabricability with a wide range of bioactive materials, in addition to their biocompatibility and biodegradability. This review highlights scientific findings concerning the use of innovative chitosan-based bioactive materials in the fields of tissue engineering, with an outlook into their future applications. It also covers latest developments in terms of constituents, fabrication technologies, structural, and bioactive properties of these materials that may represent an effective solution for tissue engineering materials, making them a realistic clinical alternative in the near future.

Characterization of novel calcium hydroxide-mediated highly porous chitosan-calcium scaffolds for potential application in dentin tissue engineering

The aim of this study was to develop a highly porous calcium-containing chitosan scaffold suitable for dentin regeneration. A calcium hydroxide (Ca[OH]₂ ) suspension was used to modulate the degree of porosity and chemical composition of chitosan scaffolds. The chitosan solution concentration and freezing protocol were adjusted to optimize the porous architecture using the phase-separation technique. Scanning electron microscopy/energy-dispersive spectroscopy demonstrated the fabrication of a highly porous calcium-linked chitosan scaffold (CH-Ca), with a well-organized and interconnected porous network. Scaffolds were cross-linked on glutaraldehyde (GA) vapor. Following a 28-day incubation in water, cross-linked CH scaffold had no changes on humid mass, and CH-Ca featured a controlled degradability profile since the significant humid mass loss was observed only after 21 (26.0%) and 28 days (42.2%). Fourier-transform infrared spectroscopy indicated the establishment of Schiff base on cross-linked scaffolds, along with calcium complexation for CH-Ca. Cross-linked CH-Ca scaffold featured a sustained Ca²⁺ release up to 21 days in a humid environment. This porous and stable architecture allowed for human dental pulp cells (HDPCs) to spread throughout the scaffold, with cells exhibiting a widely stretched cytoplasm; whereas, the cells seeded onto CH scaffold were organized in clusters. HDPCs seeded onto CH-Ca featured significantly higher ALP activity, and gene expressions for ALP, Col1, DMP-1, and DSPP in comparison to CH, leading to a significant 3.5 times increase in calcium-rich matrix deposition. In sum, our findings suggest that CH-Ca scaffolds are attractive candidates for creating a highly porous and bioactive substrate for dentin tissue engineering.