Alginate gels with a combination of calcium and chitosan oligomer mixtures as crosslinkers

EDTA-chitosan is a feasible conditioning agent for dentin bonding

OBJECTIVES

The bonding effects of EDTA-chitosan, phosphoric acid, and SE-Bond were compared.

MATERIALS AND METHODS

Material synthesis, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, laser confocal microscopy, microtensile bond strength, stereomicroscope observation section, CCK8 cytotoxicity assay, and microfluidic experiments were applied.

RESULTS

EDTA-chitosan was synthesized, and it was found by transmission electron microscopy that the application of EDTA-chitosan to dentin can extrafibrillarly demineralize collagen fibers. Scanning electron microscopy provided evidence for the retention of smear plugs in dentin conditioned with 1 wt% EDTA-chitosan. Mixed layer and long resin protrusions can be formed after bonding under a laser confocal microscope. The microtensile strength test found that the bonding strength and the durability obtained by applying the chelating agent EDTA-chitosan to dentin were equivalent to SE-Bond and better than the phosphoric acid wet bonding commonly used clinically (P < 0.05). The cytotoxicity of EDTA-chitosan was lower than that of phosphoric acid and SE-Bond in the CCK-8 assay and lower than that of phosphoric acid in the microfluidics experiment.

CONCLUSIONS

Taken together, the EDTA-chitosan extrafibrillar demineralization strategy retains intrafibrillar minerals and provides better bonding strength and durability with lower cytotoxicity.

CLINICAL RELEVANCE

EDTA-chitosan has the potential to be applied to dentin resin for direct bonding restoration and has good clinical application prospects.

The use of chitosan as a skin-regeneration agent in burns injuries: A review

Chitosan is an amino-polysaccharide, traditionally obtained by the partial deacetylation of chitin from exoskeletons of crustaceans. Properties such as biocompatibility, hemostasis, and the ability to absorb physiological fluids are attributed to this biopolymer. Chitosan’s biological properties are regulated by its origin, polymerization degree, and molecular weight. In addition, it possesses antibacterial and antifungal activities. It also has been used to prepare films, hydrogels, coatings, nanofibers, and absorbent sponges, all utilized for the healing of skin wounds. In in vivo studies with second-degree burns, healing has been achieved in at least 80% of the cases between the ninth and twelfth day of treatment with chitosan coatings. The crucial steps in the treatment of severe burns are the early excision of damaged tissue and adequate coverage to minimize the risk of infection. So far, partial-thickness autografting is considered the gold standard for the treatment of full-thickness burns. However, the limitations of donor sites have led to the development of skin substitutes. Therefore, the need for an appropriate dermal equivalent that functions as a regeneration template for the growth and deposition of new skin tissue has been recognized. This review describes the properties of chitosan that validate its potential in the treatment of skin burns.

Synthesis and characterization of electroconductive hydrogels based on oxidized alginate and polypyrrole-grafted gelatin as tissue scaffolds

Electroconductive biocompatible hydrogels with tunable properties have extensively been taken into account in tissue engineering applications due to their potential to provide suitable microenvironmental responses for the cells. In the present study, novel electroconductive hydrogels are designed and synthesized by reacting oxidized alginate with polypyrrole-grafted gelatin copolymer (PPy-g-gelatin) via formation of a Schiff-base linkage. The influence of the composition and the concentration of the components on the compressive modulus and functional performance of the hydrogels is investigated. The conductivity of the hydrogels measured by a two-probe method increased by increasing the level of polypyrrole-grafted gelatin, and a conductivity of 0.7753 S m^-1 was exhibited by the hydrogel composed of 8% w/v polypyrrole-grafted gelatin (oxidized alginate:gelatin:polypyrrole-grafted gelatin; 30 : 35 : 35% v/v). The hydrogel compressive modulus was shown to be enhanced by increasing the total concentration of hydrogel. The characteristic features of the prepared hydrogels, including swelling ratio, volume fraction, cross-link density, and mesh size, are also studied and analyzed. Besides, the conductive hydrogels have a smaller mesh size and higher cross-link density than the non-conductive hydrogels. However, the hydrogels with high cross-link density, small mesh size, and large pore size presented higher electroconductivity as a result of easier movement of the ions throughout the hydrogel. These conductive hydrogels exhibited electrical conductivity and biodegradability with cell viability, implying potential as scaffolds for tissue engineering.

Alginate gels crosslinked with chitosan oligomers - a systematic investigation into alginate block structure and chitosan oligomer interaction

Three alginates with fundamentally different block structures, poly-M, poly-G, and poly-MG, have been investigated upon ionic crosslinking with chitosan oligosaccharides (CHOS), using circular dichroism (CD), rheology, and computer simulations, supporting the previously proposed gelling principle of poly-M forming zipper-like junction zones with chitosan (match in charge distance along the two polyelectrolytes) and revealing a unique high gel strength poly-MG chitosan gelling system. CD spectroscopy revealed an increased chiroptical activity exclusively for the poly-M chitosan gelling system, indicative of induced conformational changes and higher ordered structures. Rheological measurement revealed gel strengths (G' < 900 Pa) for poly-MG (1%) CHOS (0.3%) hydrogels, magnitudes of order greater than displayed by its poly-M analogue. Furthermore, the ionically crosslinked poly-MG chitosan hydrogel increased in gel strength upon the addition of salt (G' < 1600 at 50 mM NaCl), suggesting a stabilization of the junction zones through hydrophobic interactions and/or a phase separation. Molecular dynamics simulations have been used to further investigate these findings, comparing interaction energies, charge distances and chain alignments. These alginates are displaying high gel strengths, are known to be fully biocompatible and have revealed a broad range of tolerance to salt concentrations present in biological systems, proving high relevance for biomedical applications.

Co-delivery of minocycline and paclitaxel from injectable hydrogel for treatment of spinal cord injury

Spinal cord injury (SCI) induces pathological and inflammatory responses that create an inhibitory environment at the site of trauma, resulting in axonal degeneration and functional disability. Combination therapies targeting multiple aspects of the injury, will likely be more effective than single therapies to facilitate tissue regeneration after SCI. In this study, we designed a dual-delivery system consisting of a neuroprotective drug, minocycline hydrochloride (MH), and a neuroregenerative drug, paclitaxel (PTX), to enhance tissue regeneration in a rat hemisection model of SCI. For this purpose, PTX-encapsulated poly (lactic-co-glycolic acid) PLGA microspheres along with MH were incorporated into the alginate hydrogel. A prolonged and sustained release of MH and PTX from the alginate hydrogel was obtained over eight weeks. The obtained hydrogels loaded with a combination of both drugs or each of them alone, along with the blank hydrogel (devoid of any drugs) were injected into the lesion site after SCI (at the acute phase). Histological assessments showed that the dual-drug treatment reduced inflammation after seven days. Moreover, a decrease in the scar tissue, as well as an increase in neuronal regeneration was observed after 28 days in rats treated with dual-drug delivery system. Over time, a fast and sustained functional improvement was achieved in animals that received dual-drug treatment compared with other experimental groups. This study provides a novel dual-drug delivery system that can be developed to test for a variety of SCI models or neurological disorders.

Stability improvement and characterization of bioprinted pectin-based scaffold

Purpose:

Bioprinting is an alternative method for constructing tissues/organs for transplantation. This study investigated the cross-linker influence and post-printing modification using oligochitosan and chitosan for stability improvement.

Methods:

Oligochitosan was tested as a novel cross-linker to replace Ca2+ for pectin-based bio-ink. Oligochitosan (2 kD) and different molecular weight of chitosan were used to modify the bioprinted scaffold. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to characterize the scaffolds.

Results:

Oligochitosan failed to serve as a viable cross-linker. Successful post-printing modification was confirmed by FTIR and SEM analyses.

Conclusion:

Regarding post-modification, chitosan-treated scaffolds showed enhanced stability compared to untreated scaffolds. In particular, scaffolds modified with 150 kD chitosan exhibited the highest stability.

Construction of Chitosan-Zn-Based Electrochemical Biosensing Platform for Rapid and Accurate Assay of Actin

This work reports a study on the development of a sensitive immunosensor for the assay of actin, which is fabricated using sensing material chitosan-Zn nanoparticles (NPs) and anti-actin modified on glassy carbon electrode respectively. The prepared materials were characterized using transmission electron microscope (TEM), fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) spectra, and circular dichroism (CD) techniques. Meanwhile, the electrochemical properties were studied by linear sweep voltammetric (LSV), electrochemical impedance spectra (EIS), and differential pulse voltammetry (DPV). According to the experiments, under the optimum conditions, the linear fitting equation was I (μA) = −17.31 + 78.97c (R² = 0.9948). The linear range was from 0.0001 to 0.1 mg/mL and the detection limit (LOD, S/N = 3) was 21.52 ng/mL. The interference studies were also performed for checking the sensors’ selectivity to actin. With better properties of the chitosan-Zn NPs, the modified electrode is considered as a better candidate than Western blot or immunohistochemical method for real-time usability. The detection limit reported is the lowest till date and this method provides a new approach for quality evaluation.

Electrospinning pectin-based nanofibers: a parametric and cross-linker study

Pectin, a natural biopolymer mainly derived from citrus fruits and apple peels, shows excellent biodegradable and biocompatible properties. This study investigated the electrospinning of pectin-based nanofibers. The parameters, pectin:PEO (polyethylene oxide) ratio, surfactant concentration, voltage, and flow rate, were studied to optimize the electrospinning process for generating the pectin-based nanofibers. Oligochitosan, as a novel and nonionic cross-liker of pectin, was also researched. Nanofibers were characterized by using AFM, SEM, and FTIR spectroscopy. The results showed that oligochitosan was preferred over Ca2+ because it cross-linked pectin molecules without negatively affecting the nanofiber morphology. Moreover, oligochitosan treatment produced a positive surface charge of nanofibers, determined by zeta potential measurement, which is desired for tissue engineering applications.

Engineered basement membranes: from in vivo considerations to cell-based assays

Engineered basement membranes are required to mimic in vivo properties within cell-based assays.