Chitosan fibers modified with HAp/β-TCP nanoparticles

Novel 3D-Printed Dressings of Chitosan-Vanillin-Modified Chitosan Blends Loaded with Fluticasone Propionate for Treatment of Atopic Dermatitis

In the present study, the blends of CS and Vanillin-CS derivative (VACS) were utilized for the preparation of printable inks for their application in three-dimensional (3D) printing procedures. Despite the synergic interaction between the blends, the addition of ι-carrageenan (iCR) as a thickening agent was mandatory. Their viscosity analysis was conducted for the evaluation of the optimum CS/VACS ratio. The shear thinning behavior along with the effect of the temperature on viscosity values were evident. Further characterization of the 3D-printed structures was conducted. The effect of the CS/VACS ratio was established through swelling and contact angle measurements. An increasing amount of VACS resulted in lower swelling ability along with higher hydrophobicity. Fluticasone propionate (FLU), a crystalline synthetic corticosteroid, was loaded into the CS/VACS samples. The drug was loaded in its amorphous state, and consequently, its in vitro release was significantly enhanced. An initial burst release, followed by a sustained release profile, was observed.

Evaluation of Polysaccharide-Peptide Conjugates Containing the RGD Motif for Potential Use in Muscle Tissue Regeneration

New scaffold materials composed of biodegradable components are of great interest in regenerative medicine. These materials should be: stable, nontoxic, and biodegrade slowly and steadily, allowing the stable release of biodegradable and biologically active substances. We analyzed peptide-polysaccharide conjugates derived from peptides containing RGD motif (H-RGDS-OH (1), H-GRGDS-NH₂ (2), and cyclo(RGDfC) (3)) and polysaccharides as scaffolds to select the most appropriate biomaterials for application in regenerative medicine. Based on the results of MTT and Ki-67 assays, we can state that the conjugates containing calcium alginate and the ternary nonwoven material were the most supportive of muscle tissue regeneration. Scanning electron microscopy imaging and light microscopy studies with hematoxylin-eosin staining showed that C2C12 cells were able to interact with the tested peptide-polysaccharide conjugates. The release factor (Q) varied depending on both the peptide and the structure of the polysaccharide matrix. LDH, Alamarblue^®, Ki-67, and cell cycle assays indicated that peptides 1 and 2 were characterized by the best biological properties. Conjugates containing chitosan and the ternary polysaccharide nonwoven with peptide 1 exhibited very high antibacterial activity against Staphylococcus aureus and Klebsiella pneumoniae. Overall, the results of the study suggested that polysaccharide conjugates with peptides 1 and 2 can be potentially used in regenerative medicine.

Conjugates of Chitosan and Calcium Alginate with Oligoproline and Oligohydroxyproline Derivatives for Potential Use in Regenerative Medicine

New materials that are as similar as possible in terms of structure and biology to the extracellular matrix (external environment) of cells are of great interest for regenerative medicine. Oligoproline and oligohydroxyproline derivatives (peptides 2-5) are potential mimetics of collagen fragments. Peptides 2-5 have been shown to be similar to the model collagen fragment (H-Gly-Hyp-Pro-Ala-Hyp-Pro-OH, 1) in terms of both their spatial structure and biological activity. In this study, peptides 2-5 were covalently bound to nonwovens based on chitosan and calcium alginate. Incorporation of the peptides was confirmed by Fourier transform -infrared (FT-IR) and zeta potential measurements. Biological studies (cell metabolic activity by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and Live/Dead assay) proved that the obtained peptide-polysaccharide conjugates were not toxic to the endothelial cell line EA.hy 926. In many cases, the conjugates had a highly affirmative influence on cell proliferation. The results of this study show that conjugates of chitosan and calcium alginate with oligoproline and oligohydroxyproline derivatives have potential for use in regenerative medicine.

Development of Amoxicillin-Loaded Electrospun Polyurethane/Chitosan/ $\beta$ -Tricalcium Phosphate Scaffold for Bone Tissue Regeneration

Biocompatible nanocomposite electrospun fibers containing Polyurethane/Chitosan/ $\beta $ -Tri calcium phosphate with diverse concentrations were designed and produced through the electrospinning process for bone tissue engineering applications. After the production process, density measurement, viscosity, electrical conductivity, and tensile strength measurement tests were carried out as physical analyses of blended solutions. The chemical structural characterization was scrutinized using Fourier transform infrared spectrometer (FTIR), and scanning electron microscopy (SEM) was used to observe the morphological details of developed electrospun scaffolds. Cell viability, attachment, and proliferation were performed using a L929 fibroblast cell line. Based on the physical, SEM, FTIR analysis, and cell culture studies, preferable nanofiber composition was selected for further studies. Amoxicillin (AMX) was loaded to that selected nanofiber composition for examination of the drug release. In comparison with other studies on similar AMX controlled products, higher drug loading and encapsulation efficiencies were obtained. It has been clearly found that the developed nanofiber composites have potential for bone tissue engineering applications.

Synthesis and Characterization of β-Tricalcium Phosphate Derived From Haliotis sp. Shells

PURPOSE

To develop a methodology for the synthesis of β-tricalcium phosphate (β-TCP, Ca3(PO4)2) from the shell of Haliotis sp. (abalone shell) and to verify its characterization and biocompatibility.

MATERIALS AND METHODS

Calcium oxide (CaO) was synthesized from abalone shell by sintering and was suspended in distilled water to prepare calcium hydroxide (Ca(OH)2). For the synthesis of calcium carbonate (CaCO3), carbon dioxide was used to infuse Ca(OH)2 at pH 7.4. CaCO3 was reacted with phosphoric acid at pH 6.0 to obtain dicalcium phosphate (CaHPO4). Subsequently, β-TCP was synthesized by a chemical reaction between CaHPO4 and CaO at 950°C to 1100°C for 3 hours. Fourier transform infrared spectroscopy (FT-IR) and x-ray diffraction (XRD) was performed to verify the physiochemical characteristics of the composite synthesized from abalone shell.

RESULTS

FT-IR and XRD results showed that β-TCP was successfully synthesized from abalone shell. The synthesized β-TCP did not affect cell viability of either normal human oral keratinocytes or osteoblastic MG-63 cells. These data indicate that β-TCP synthesized from abalone shell is biologically safe.

CONCLUSIONS

β-TCP (Ca3(PO4)2) synthesized from abalone shell can be used as a potential source of bone grafting material.

Keratin: dissolution, extraction and biomedical application

Keratinous materials such as wool, feathers and hooves are tough unique biological co-products that usually have high sulfur and protein contents. A high cystine content (7-13%) differentiates keratins from other structural proteins, such as collagen and elastin. Dissolution and extraction of keratin is a difficult process compared to other natural polymers, such as chitosan, starch, collagen, and a large-scale use of keratin depends on employing a relatively fast, cost-effective and time efficient extraction method. Keratin has some inherent ability to facilitate cell adhesion, proliferation, and regeneration of the tissue, therefore keratin biomaterials can provide a biocompatible matrix for regrowth and regeneration of the defective tissue. Additionally, due to its amino acid constituents, keratin can be tailored and finely tuned to meet the exact requirement of degradation, drug release or incorporation of different hydrophobic or hydrophilic tails. This review discusses the various methods available for the dissolution and extraction of keratin with emphasis on their advantages and limitations. The impacts of various methods and chemicals used on the structure and the properties of keratin are discussed with the aim of highlighting options available toward commercial keratin production. This review also reports the properties of various keratin-based biomaterials and critically examines how these materials are influenced by the keratin extraction procedure, discussing the features that make them effective as biomedical applications, as well as some of the mechanisms of action and physiological roles of keratin. Particular attention is given to the practical application of keratin biomaterials, namely addressing the advantages and limitations on the use of keratin films, 3D composite scaffolds and keratin hydrogels for tissue engineering, wound healing, hemostatic and controlled drug release.

Hydroxyapatite-chitosan based bioactive hybrid biomaterials with improved mechanical strength

Composites consisting of hydroxyapatite (HA) and chitosan (CTS) have recently been intensively studied. In this work, a novel inorganic-organic (I/O) HA/CTS materials in the form of granules were prepared through a simple solution-based chemical method. During the synthesis of these hybrids, the electrostatic complexes between positively charged, protonated amine groups of chitosan and the negative phosphate species (HPO₄^2- and H₂PO₄^-) were formed. Our biocomposites belong to the class I of hybrids, which was confirmed by FTIR studies. XRD analysis revealed that the obtained materials consisted of hydroxyapatite as the only crystalline phase. Homogeneous dispersion of the components in HA/CTS composites was confirmed. The use of 17wt% and 23wt% of chitosan resulted in approximately 12-fold and 16-fold increase in the compressive strength of HA/CTS as compared to the non-modified HA material. During incubation of the studied materials in SBF, pH of the solution remained close to the physiological one. Formation of apatite layer on their surfaces indicated bioactive nature of the developed biomaterials.

Poly(D,L-Lactide-Co-Glycolide) Tubes With Multifilament Chitosan Yarn or Chitosan Sponge Core in Nerve Regeneration

PURPOSE

The influence of different kinds of nerve guidance conduits on regeneration of totally transected rat sciatic nerves through a 7-mm gap was examined.

MATERIALS AND METHODS

Five different types of conduits made of chitosan and poly(D,L-lactide-co-glycolide) (PLGA) were constructed and tested in vivo. We divided 50 animals into equal groups of 10, with a different type of conduit implanted in each group: chitosan sponge core with an average molecular mass of polymer (Mv) of 287 kDa with 7 channels in a PLGA sleeve, chitosan sponge core with an Mv of 423 kDa with 7 channels in a PLGA sleeve, chitosan sponge core (Mv, 423 kDa) with 13 channels in a PLGA sleeve, chitosan multifilament yarn in a PLGA sleeve, and a PLGA sleeve only. Seven weeks after the operation, we examined the distance covered by regenerating nerve fibers, growing of nerves into the conduit's core, and intensity and type of inflammatory reaction in the conduit, as well as autotomy behavior (reflecting neuropathic pain intensity) in the animals.

RESULTS

Two types of conduits were allowing nerve outgrowth through the gap with minor autotomy and minor inflammatory reactions. These were the conduits with chitosan multifilament yarn in a PLGA sleeve and the conduits with 13-channel microcrystalline chitosan sponge in a PLGA sleeve.

CONCLUSIONS

The type of chitosan used to build the nerve guidance conduit influences the intensity and character of inflammatory reaction present during nerve regeneration, which in turn affects the distance crossed by regenerating nerve fibers, growing of the nerve fibers into the conduit's core, and the intensity of autotomy in the animals.

Competitive adsorption and selectivity sequence of heavy metals by chicken bone-derived biochar: Batch and column experiment

The objective of this research was to evaluate adsorption of heavy metals in single- and ternary-metal forms onto chicken bone biochar (CBB). Competitive sorption of heavy metals by CBB has never been reported previously. The maximum adsorption capacities of metals by CBB were in the order of Cu (130 mg g(-1)) > Cd (109 mg g(-1)) > Zn (93 mg g(-1)) in the single-metal adsorption isotherm and Cu (108 mg g(-1)) >> Cd (54 mg g(-1)) ≥ Zn (44 mg g(-1)) in the ternary-metal adsorption isotherm. Cu was the most retained cation, whereas Zn could be easily exchanged and substituted by Cu. Batch experimental data best fit the Langmuir model rather than the Freundlich isotherms. In the column experiments, the total adsorbed amounts of the metals were in the following order of Cu (210 mg g(-1)) > Cd (192 mg g(-1)) > Zn (178) in single-metal conditions, and Cu (156) > Cd (123) > Zn (92) in ternary-metal conditions. Results from both the batch and column experiments indicate that competitive adsorption among metals increases the mobility of these metals. Especially, Zn in single-metal conditions lost it adsorption capacity most significantly. Based on the 3D simulation graphs of heavy metals, adsorption patterns under single adsorption condition were different than under competitive adsorption condition. Results from both the batch and column experiments show that competitive adsorption among metals increases the mobility of these metals. The maximum metal adsorption capacity of the metals in the column experiments was higher than that in the batch experiment indicating other metal retention mechanisms rather than adsorption may be involved. Therefore, both column and batch experiments are needed for estimating retention capacities and removal efficiencies of metals in CBB.

Biodegradation study of microcrystalline chitosan and microcrystalline chitosan/β-TCP complex composites

Bone repair or regeneration is a common and complicated clinical problem in orthopedic surgery. The importance of natural polymers, such as microcrystalline chitosan, and minerals such as HAp and β-TCP, has grown significantly over the last two decades due to their renewable and biodegradable source, increasing the knowledge and functionality of composites in technological and biomedical applications. This study compares the biodegradation process, bioactivity, structure, morphology, and mechanical properties of microcrystalline chitosan and microcrystalline chitosan/β-TCP complex; the latter according to the new method of preparation. The complex showed a homogeneous network structure with regular pores, good bioactivity, even after 60 days of conducting the hydrolytic and enzymatic degradation process, showing a bacteriostatic and bactericidal activity. The complex indicates that it could be used successfully as a base for implants and scaffolds production in orthopedic surgery.