In vitro cytocompatibility evaluation of alginate dialdehyde for biological tissue fixation

The alginate dialdehyde crosslinking on curcumin-loaded zein nanofibers for controllable release

In this study, electrospun zein/alginate dialdehyde (AD) nanofibers were prepared by green crosslinking. The degree of crosslinking could reach 50.72 %, and the diameter of electrospun fibers ranged from 446.2 to 541.8 nm. The generation of AD and the bonding of crosslinking were further confirmed by the changes on characteristic peaks and conformational ratios in the infrared spectroscopy and secondary structure analysis. High concentrations of AD led to improved thermal stabilities, mechanical properties, and hydrophobicity. And the highly crosslinked nanofibers (Z-8) owned the highest elastic modulus (24.92 MPa), tensile strength (0.28 MPa), and elongation at break (8.14 %) among five samples. Moreover, Z-8 possessed a high swelling ratio of 5.45 g/g, and a low weight loss of 6.09 %. The samples could encapsulate curcumin efficiently and show controllable release behaviors based on different AD addition. And the oxidation resistance of nanofibers gradually improved, consistent with the release performances. This study indicated AD crosslinking favored the preparation and application of zein nanofibers, and the oxidized polysaccharide acted as the green crosslinking agent, which provided reference value for the application of polysaccharides in food-related electrospun materials.

Origin of critical nature and stability enhancement in collagen matrix based biomaterials: Comprehensive modification technologies

Collagen is the most abundant protein in animals and one of the most important extracellular matrices that chronically plays an important role in biomaterials. However, the major concern about native collagen is the lack of its thermal stability and weak resistance to proteolytic degradation. Currently, a series of modification technologies have been explored for critical nature and stability enhancement in collagen matrix-based biomaterials, and prosperously large-scale progress has been achieved. The establishment of covalent bonds among collagen noumenon has been verified assuringly to have pregnant influences on its physicochemical properties and biological properties, enlightening to discuss the disparate modification technologies on specific effects on the multihierarchical structures and pivotal performances of collagen. In this review, various existing modification methods were classified from a new perspective, scilicet whether to introduce exogenous substances, to reveal the basic scientific theories of collagen modification. Understanding the role of modification technologies in the enhancement of collagen performance is crucial for developing novel collagen-based biomaterials. Moreover, the different modification effects caused by the interaction sites between the modifier and collagen, and the structure-activity relationship between the structure of the modifier and the properties of collagen were reviewed.

Advances on the modification and biomedical applications of acellular dermal matrices

Acellular dermal matrix (ADM) is derived from natural skin by removing the entire epidermis and the cell components of dermis, but retaining the collagen components of dermis. It can be used as a therapeutic alternative to “gold standard” tissue grafts and has been widely used in many surgical fields, since it possesses affluent predominant physicochemical and biological characteristics that have attracted the attention of researchers. Herein, the basic science of biologics with a focus on ADMs is comprehensively described, the modification principles and technologies of ADM are discussed, and the characteristics of ADMs and the evidence behind their use for a variety of reconstructive and prosthetic purposes are reviewed. In addition, the advances in biomedical applications of ADMs and the common indications for use in reconstructing and repairing wounds, maintaining homeostasis in the filling of a tissue defect, guiding tissue regeneration, and delivering cells via grafts in surgical applications are thoroughly analyzed. This review expectedly promotes and inspires the emergence of natural raw collagen-based materials as an advanced substitute biomaterial to autologous tissue transplantation.

Graphical Abstract

A promising potential candidate for vascular replacement materials with anti-inflammatory action, good hemocompatibility and endotheliocyte-cytocompatibility: phytic acid-fixed amniotic membrane

Due to its excellent biocompatibility and anti-inflammatory activity, amniotic membrane (AM) has attracted much attention from scholars. However, its clinical application in vascular reconstruction was limited for poor processability, rapid biodegradation, and insufficient hemocompatibility. A naturally extracted substance with good cytocompatibility, phytic acid (PA), which can quickly form strong and stable hydrogen bonds on the tissue surface, was used to crosslink decellularized AM (DAM) to prepare a novel vascular replacement material. The results showed that PA-fixed AM had excellent mechanical strength and resistance to enzymatic degradation as well as appropriate surface hydrophilicity. Among all samples, 2% PA-fixed specimen showed excellent human umbilical vein endothelial cells (HUVECs)-cytocompatibility and hemocompatibility. It could also stimulate the secretion of vascular endothelial growth factor and endothelin-1 from seeded HUVECs, indicating that PA might promote neovascularization after implantation of PA-fixed specimens. Also, 2% PA-fixed specimen could inhibit the secretion of tumor necrosis factor-αfrom co-cultured macrophages, thus might reduce the inflammatory response after sample implantation. Finally, the results ofex vivoblood test andin vivoexperiments confirmed our deduction that PA might promote neovascularization after implantation. All the results indicated that prepared PA-fixed DAM could be considered as a promising small-diameter vascular replacement material.

A riboflavin–ultraviolet light A-crosslinked decellularized heart valve for improved biomechanical properties, stability, and biocompatibility

Riboflavin–ultraviolet light A could effectively crosslink a decellularized heart valve to improve its biomechanical properties, stability and biocompatibility.

Chitosan⁻Carboxymethylcellulose-Based Polyelectrolyte Complexation and Microcapsule Shell Formulation

Chitosan (CH)–carboxymethyl cellulose sodium salt (NaCMC) microcapsules containing paraffin oil were synthesized by complex formation, and crosslinked with glutaraldehyde (GTA). The electrostatic deposition of NaCMC onto the CH-coated paraffin oil emulsion droplets was demonstrated by zeta potential and optical microscopy. The optimal process conditions were identified in terms of pH of the aqueous solution (5.5) and CH/NaCMC mass ratio (1:1). Encapsulation of paraffin oil and microcapsule morphology were analyzed by ATR-FTIR and SEM, respectively. The effect of GTA crosslinking on paraffin oil latent heat was investigated by DSC and combined with the values of encapsulation efficiency and core content, supporting the compact shell formation.

Effect of Baicalein on Matrix Metalloproteinases and Durability of Resin-Dentin Bonding

OBJECTIVE

In an attempt to increase resin-dentin bonding quality, this study used baicalein as a preconditioner in an etch-and-rinse adhesive to evaluate its effect on matrix metalloproteinases (MMPs) and adhesive durability.

METHODS

As a MMP inhibitor and potential collagen cross-linking agent, baicalein was used as a preconditioner in an etch-and-rinse adhesive system. The degree of conversion was evaluated by Fourier-transform infrared spectroscopy. EnzChek gelatinase/collagenase assay kits were then used to detect the MMP inhibitory effect of different concentrations of baicalein (0.1, 0.5, 2.5, and 5.0 μg/mL) on dentin powders. During in vitro bonding procedures, flat dentin surfaces on sound third molars were preconditioned with 2.5 μg/mL baicalein after being acid-etched; this step was followed by continuation of adhesive processes and build-up of resin composite. After resin-dentin stick preparation, bonding strength, failure mode, and interface nanoleakage were respectively evaluated via microtensile testing, stereomicroscopy, and field emission scanning electron microscopy either immediately or after storage in artificial saliva for three or six months. Data were analyzed by two-way analysis of variance and Tukey test (α=0.05).

RESULTS

Baicalein at a concentration of 0-5.0 μg/mL did not influence the conversion of adhesives. However, it inhibited the activities of dentin-bond gelatinase and collagenase, especially at a concentration of 2.5 μg/mL, while effectively increasing microtensile bonding strength and decreasing nanoleakage in vitro, both immediately and after aging.

CONCLUSIONS

Baicalein used as preconditioner in an etch-and-rinse adhesive system has an anti-MMP function and effectively improves resin-dentin bonding durability in vitro, which has potential value in clinical bonding procedures.

Preparation and investigation of novel SrCl2/DCMC-modified (via DOPA) decellularized arteries with excellent physicochemical properties and cytocompatibility for vascular scaffolds

A new method of fabricating vascular scaffolds was designed in this article by crosslinking the porcine arteries using dialdehyde carboxymethyl (DCMC) and further introducing the Sr element on the surface of modified arteries using DOPA. DCMC had been selected as an ideal crosslinking reagent for its excellent cytobiocompatibility and suitable chemical reactivity. Unfortunately, the endothelialization of biological vascular scaffolds fixed by DCMC was unsatisfactory. To overcome this deficiency, the Sr element was introduced onto arteries to improve the endothelialization of fixed arteries due to the Sr element being able to promote the expression of vascular endothelial growth factor (VEGF) being crucial for growth and proliferation of HUVECs. After modifying and crosslinking, their chemical structures, mechanical properties, stability, and cytocompatibility were examined. Our findings demonstrated that DCMC could improve the mechanical properties of animal-derived materials successfully and possess suitable biocompatibility compared with glutaraldehyde (GA). The Sr element can easily be introduced onto the surface of DCMC modified arteries by DOPA. Compared with purely DCMC-crosslinked ones, SrCl₂/DCMC modification has no significant effect on the mechanical strength of fixed arteries, but a slight tendancy to improve the stability of fixed samples in D-Hanks solution. MTT assay and fluorescence tests implied that SrCl₂/DCMC modification could effectively stimulate HUVECs' adhesion and proliferation, and thus promote the endothelialization process of fixed arteries. SrCl₂/DCMC-modified arteries with excellent physicochemical properties and appealing HUVEC-cytocompatibility should be promising materials for fabricating vascular scaffolds.

A new method of fabricating vascular scaffolds was designed in this article by crosslinking the porcine arteries using dialdehyde carboxymethyl (DCMC) and further introducing the Sr element on the surface of modified arteries using DOPA.

Atelocollagen-based Hydrogels Crosslinked with Oxidised Polysaccharides as Cell Encapsulation Matrix for Engineered Bioactive Stromal Tissue

Tissue stroma is responsible for extracellular matrix (ECM) formation and secretion of factors that coordinate the behaviour of the surrounding cells through the microenvironment created. It's inability to spontaneously regenerate makes it a good candidate for research studies such as testing various tissue engineered products capable of replacing the stroma in order to assure normal tissue regeneration and function. In this study, a bioactive stroma was obtained considering two main components: 1) the artificial ECM formed using atelocollagen-oxidized polysaccharides hydrogels in which the polysaccharide compound (oxidised gellan or pullulan) has the role of crosslinker and 2) encapsulated stromal cells (dermal fibroblasts, ovarian theca-interstitial and granulosa cells). The cell-hosting ability of the hydrogels is demonstrated by a good diffusion of globular proteins (albumin) while the fibrillar morphology proves to be optimal for cell adhesion. These structural properties and cytocompatibility of the components maintain good cell viability and cell encapsulation for more than 12 days. Nevertheless, the results indicate some differences favouring the gellan crosslinked hydrogels. Ovarian stromal cells functionality was maintained as indicated by hormone secretion, confirming cell-cell signalling in encapsulated and co-culture conditions. In vivo implantation shows the regenerative potential of the cell-populated hydrogels as they are integrated into the natural tissue. The possibility of cryopreserving the hydrogel-cell system, while maintaining both cell viability and hydrogel structural integrity underlines the potential of these ready-to-use hydrogels as bioactive stroma for multipurpose tissue regeneration.

Collagen cross-linkers on dentin bonding: Stability of the adhesive interfaces, degree of conversion of the adhesive, cytotoxicity and in situ MMP inhibition

OBJECTIVE

To investigate the effect of collagen cross-links on the stability of adhesive properties, the degree of conversion within the hybrid layer, cytotoxicity and the inhibition potential of the MMPs' activity.

METHODS

The dentin surfaces of human molars were acid-etched and treated with primers containing: 6.5wt% proanthocyanidin, UVA-activated 0.1wt% riboflavin, 5wt% glutaraldehyde and distilled water for 60s. Following, dentin was bonded with Adper Single Bond Plus and Tetric N-Bond; and restored with resin composite. The samples were sectioned into resin-dentin "sticks" and tested for microtensile bond strength (μTBS) after immediate (IM) and 18-month (18M) periods. Bonded sticks at each period were used to evaluate nanoleakage and the degree of conversion (DC) under micro-Raman spectroscopy. The enzimatic activity (P1L10 cross-linkers, P1L22 MMPs' activities) in the hybrid layer was evaluated under confocal microscopy. The culture cell (NIH 3T3 fibroblast cell line) and MTT assay were performed to transdentinal cytotoxicity evaluation. Data from all tests were submitted to appropriate statistical analysis (α=0.05).

RESULTS

All cross-linking primers reduced the degradation of μTBS compared with the control group after 18M (p>0.05). The DC was not affected (p>0.213). The NL increased after 18M for all experimental groups, except for proanthocyanidin with Single Bond Plus (p>0.05). All of the cross-link agents reduced the MMPs' activity, although this inhibition was more pronounced by PA. The cytotoxicity assay revealed reduced cell viability only for glutaraldehyde (p<0.001).

SIGNIFICANCE

Cross-linking primers used in clinically relevant minimized the time degradation of the μTBS without jeopardizing the adhesive polymerization, as well as reduced the collagenolytic activity of MMPs. Glutaraldeyde reduced cell viability significantly and should be avoided for clinical use.

Effects of pH on the alginate dialdehyde (ADA)-crosslinking of natural biological tissues and in vitro study of the endothelial cell compatibility of ADA-crosslinked biological tissues

Investigating the optimal pH-environment for ADA fixation and the HUVECs compatibility of the ADA-fixed biological vascular scaffolds.

Biological properties of dialdehyde carboxymethyl cellulose crosslinked gelatin-PEG composite hydrogel fibers for wound dressings

Gelatin-based composite hydrogel fibers were prepared by gel-spinning with PEG6000 as the modifier. Dialdehyde carboxymethyl cellulose (DCMC), as an ideal crosslinking reagent for protein, was used to fix the composite hydrogel fibers. Then the biological properties of the hydrogel fibers for wound dressings were evaluated. The results indicate that the hydrogen bond interactions and CN linkages between gelatin and DCMC can be formed. The addition of DCMC can efficiently improve the mechanical properties, enzymatic stability and blood compatibility of the hydrogel fibers. Crosslinking with DCMC can reduce the degree of swelling of the hydrogel fibers, which is beneficial for hydrogel fibers to avoid undesired reduction in mechanical properties. Moreover, the composite hydrogel fibers present three-dimensional structure, porous networks and low cytotoxicity. The study suggests that DCMC is an effective crosslinking reagent for biomaterials fixation. The developed composite hydrogel fibers can be well-suited for biomedical applications such as wound dressings.

Crosslinking effect of dialdehyde starch (DAS) on decellularized porcine aortas for tissue engineering

Biological tissue-derived biomaterials must be chemically modified to avoid immediate degradation and immune response before being implanted in human body to replace malfunctioning organs. DAS with active aldehyde groups was employed to replace glutaraldehyde (GA), a most common synthetic crosslinking reagent in clinical practice, to fix bioprostheses for lower cytotoxicity. The aim of this research was to evaluate fixation effect of DAS. The tensile strength, crosslinking stability, cytotoxicity especially the anti-calcification capability of DAS-fixed tissues were investigated. The tensile strength and resistance to enzymatic degradation of samples were increased after DAS fixation, the values maintained stably in D-Hanks solution for several days. Meanwhile, ultrastructure of samples preserved well and the anti-calcification capability of samples were improved, the amount of positive staining points in the whole visual field of 15% DAS-fixed samples was only 0.576 times to GA-fixed ones. Moreover, both unreacted DAS and its hydrolytic products were nontoxic in cytotoxicity study. The results demonstrated DAS might be an effective crosslinking reagent to fix biological tissue-derived biomaterials in tissue engineering.

Preparation and characterization of galactosylated alginate-chitosan oligomer microcapsule for hepatocytes microencapsulation

Galactosylated alginate (GA)-chitosan oligomer microcapsule was prepared to provide a sufficient mechanical stability, a selective permeability and an appropriate three-dimensional (3D) microenvironment for hepatocytes microencapsulation. The microcapsule has a unique asymmetric membrane structure, with a dense layer located in the inner surface and gradually decreasing toward the outside surface. The stable microcapsule was obtained when GA lower than 50%, while the permeability was increased with increasing of GA. A balance between mechanical stability and permeability was achieved through modulating membrane porosity and thickness. The optimal microcapsule displays a selective permeability allowing efficient transport of human serum albumin while effectively blocking immunoglobulin G. Hepatocytes exhibited high and long term viability (>92%), proliferability, multicellular spheroid morphology, and enhancement of liver-specific functions in the microcapsule wherein galactose moieties present chemical cues to support cell-matrix interactions while the 3D structure of the microcapsule behaves physical cues to facilitate cell-cell interactions.

Dose- and time-dependent effects of genipin crosslinking on cell viability and tissue mechanics - toward clinical application for tendon repair

The crosslinking agent genipin is increasingly invoked for the mechanical augmentation of collagen tissues and implants, and has previously been demonstrated to arrest mechanical damage accumulation in various tissues. This study established an in vitro dose-response baseline for the effects of genipin treatment on tendon cells and their matrix, with a view to in vivo application to the repair of partial tendon tears. Regression models based on a broad range of experimental data were used to delineate the range of concentrations that are likely to achieve functionally effective crosslinking, and predict the corresponding degree of cell loss and diminished metabolic activity that can be expected. On these data, it was concluded that rapid mechanical augmentation of tissue properties can only be achieved by accepting some degree of cytotoxicity, yet that post-treatment cell survival may be adequate to eventually repopulate and stabilize the tissue. On this basis, development of delivery strategies and subsequent in vivo study seems warranted.