Journal of Biomaterials Applications

In this study, an injectable dopamine-modified alginate hydrogel combined with nano-hydroxyapatite or strontium hydroxyapatite was cross-linked via the in situ slow release of divalent ions from the hydrolysis of D-glucono-δ-lactone (GDL). The cross-linking mechanism involved the chelation of an alginate with divalent ions and the hydrogen-bonding interaction between alginate and catechol groups. As the GDL concentration at 0.5% (w/v) regulated the release of the divalent ions, which enhanced the chelation effect, it was investigated, and inorganic nanoparticles were homogeneously distributed into the hydrogel system to improve the mechanical properties and stabilize the hydrogel network. Furthermore, the effects of dopamine on the improvement of the mechanical properties were investigated. Results demonstrated that the compressive strength of this injectable hydrogel is enhanced by 4.6 times compared with that of the hydrogel without the addition of GDL, and the compressive strength is enhanced by 4.0 times compared with that of the unmodified alginate hydrogel at strain values ranging from 10% to 50%. The hydrogels combined with strontium hydroxyapatite exhibited a more compact, suitable pore size, with a three-dimensional network structure, and the particle size was 50–100 μm; this range of values is considered as optimal for the growth of bone tissues. In addition, the gelation time can be adjusted from a few minutes to a few seconds by adjusting experiment variables. Our study provides a potential method for improving the mechanical properties of bone tissue engineering materials. ¹HNMR, FTIR, and UV–vis spectroscopy measurements; XRD and SEM; and pH, ion release, and mechanical tests were carried out.

Medical pure titanium (Ti) exhibits excellent mechanical properties and chemical stability in clinical use, but its initial osteointegration period is often postponed due to the bioinert nature of the Ti surface. Roughening and bioactive material coating of Ti implant surfaces are considered effective to enhance the bioactivity of Ti implants. In this study, we evaluated the effects of surface roughening and calcite (CaCO₃) coating of Ti substrates on osteoblastic cell differentiation and growth. We roughened the Ti substrate surface by acid etching, followed by coating with calcite by thermal decomposition of Ca(NO₃)₂ to CaO followed by thermal carbonation of CaO to CaCO₃. The surface topography of roughened Ti substrates (rough Ti) fluctuated, and the arithmetic average of surface roughness (Ra) was 2.2 µm. The rough topography was retained even after calcite coating of rough Ti, and the calcite-coated Ti (calcite-Ti) has an Ra of 2.0 µm. The tensile adhesive and shear adhesive strengths between calcite coating and Ti surface in calcite–Ti were 56.6 ± 16.1 and 10.1 ± 1.39 MPa, respectively. The biological properties and response of calcite–Ti were evaluated in vitro using a pre-osteoblastic cell line (MC3T3-E1). Observation of cell morphology by scanning electron microscopy and immunofluorescence staining revealed that MC3T3-E1 cells attached favorably to the surface with polygonal and filopodial extensions on calcite–Ti. The combination of roughening and calcite coating of the Ti substrate surface significantly increased cell proliferation at 1, 3, and 7 days of incubation. Furthermore, the relative alkaline phosphatase activity of calcite–Ti was higher than that of untreated Ti substrates (smooth Ti) and rough Ti after incubation for 7 days. Thus, the combined surface roughening and calcite coating of Ti substrates promoted MC3T3-E1 differentiation, whereas roughening alone was not effective.

Nanocellulose has recently attracted a great deal of attention for numerous biomedical applications due to its superior mechanical properties, high surface area, tailorable surface chemistry, good biocompatibility, renewable nature, and cost-effectiveness. The objective of this study was to investigate the long-term in vivo biocompatibility of three kinds of nanocellulose, namely, cellulose nanocrystal (CNC), cellulose nanofiber (CNF), and TEMPO-oxidized cellulose nanofiber (TOCNF). The morphological features of these nanocellulose materials were examined by transmission electron microscopy. In vivo biocompatibility of all nanocellulose materials was investigated using a subcutaneous rat model for 1, 2, 4, and 12 weeks of implantation. The average diameters of prepared homogenous CNC, CNF, and TOCNF were ∼6 nm, ∼8 nm, and ∼5 nm respectively, as depicted by micrographs obtained by using transmission electron microscopy. TOCNF showed highest in vitro biocompatibility with respect to CNC and CNF in response to L929 fibroblast cells. In vivo studies revealed that all nanocellulose materials exhibited no foreign body reaction up to two-week post-injection. Subcutaneous implantation at 12 weeks showed lowest inflammation and better tissue repair for TOCNF compared to CNC and CNF. The results suggest that the long-term biocompatibility profile follows the sequence: TOCNF > CNC > CNF.

Different types of siRNA delivery vehicles including nanoparticles have been synthesized and utilized for prostate cancer gene therapy. However, one of the most common limitations being faced is the toxicity of cationic polymers toward the cells. In the current study, magnetic nanoparticles were prepared and conjugated with cationic polymer, polyethylenimine. Then polyethylene glycol was conjugated with polyethylenimine to improve the biocompatibility of nanoparticles. The transmission electron microscopy size of nanoparticles was found to be 15.82 (±9.07) nm, while hydrodynamic size was about 79.20 (±0.68) nm. Zeta potential analysis of polyethylenimine and polyethylene glycol-coated nanoparticles was +31.4 (±0.62) and +5.65 (±0.76) mV, respectively. Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance confirmed the presence of polyethylene glycol and polyethylenimine polymers in magnetic nanoparticles. Cell viability test in mouse fibroblast NIH 3T3 and prostate cancer PC3 cells showed an increased in biocompatibility of functionally modified polyethylene glycol–polyethylenimine–Fe₃O₄ nanoparticles. siRNA targeting a disintegrin and metalloproteinase 10 (ADAM10) was successfully loaded into the polyethylene glycol–polyethylenimine–Fe₃O₄ nanoparticles and delivered to PC3 cells. The results clearly demonstrated a significant decrease in cell viability, which increased within a certain siRNA concentration. The inhibitory concentration (IC50) value for ADAM10 siRNA was calculated to be 15.83 nM after 72 h. Confocal microscopy confirmed the delivery of siRNA-loaded nanoparticles intracellularly to the tumor cells cytosol. This magnetic system can be used as a powerful platform to inhibit cancer cells progression.

Poly (ethylene glycol) (PEG) has been paid much attention to its applications in tissue engineering. However, the studies on poly (ethylene glycol) in tissue applications were currently far from enough. To investigate the crosslinking effects of poly (ethylene glycol) in mechanical properties, anti-enzymatic ability and cytocompatibility, in this study, the poly (ethylene glycol) was crosslinked to decellularized lung scaffolds from rats. In order to obtain the PEGylated decellularized lung scaffold, the N-succinimidyl S-acetylthioacetate was first used to modify the decellularized lung scaffold, and a four-arm- poly (ethylene glycol) containing four acrylate groups was then crosslinked to the decellularized lung scaffold by the Michael addition reaction between acrylate group and sulfhydryl group. The results showed that the optimal concentration of poly (ethylene glycol) and reaction time of PEGylation of decellularized lung scaffold was 40 mg/mL and 4 h, respectively. Histological examinations, SEM and quantification of tissue morphology by septal thickness consistently indicated no differences between PEGylated and normal decellularized lung scaffold in morphology. Compared with native lung and normal decellularized lung scaffold, the Young's modulus and stiffness of PEGylated decellularized lung scaffold increased significantly, whereas enzymatic degradation rate of PEGylated decellularized lung scaffold decreased significantly, suggesting that poly (ethylene glycol) significantly enhanced the biomechanical property and anti-enzymatic stability of decellularized lung scaffold. Further, no significant differences in cell viability were found between PEGylated and normal decellularized lung scaffold, suggesting no toxicity introduction of poly (ethylene glycol) into decellularized lung scaffold by the crosslinking. These findings may provide useful information for further applications of poly (ethylene glycol) in tissue engineering.

Adequate mechanical properties to withstand the surgical procedure and decoration with bioactive molecules promoting tissue regeneration are crucial aspects in the development of successful matrices for cardiac tissue engineering. The aim of this work was the development of a novel cardiac patch based on a blend of alginate and gelatin, designed to combine the improvement of suture resistance with an effective growth factor immobilization. We defined the procedures to incorporate a poly(dioxanone) membrane within the alginate/gelatin sponges and to functionalize the biomaterial with insulin-like growth factor-1, using the avidin–biotin-binding strategy. Morphological analysis of the reinforced scaffolds showed a porous structure and a good adhesion of the synthetic microporous membrane to the natural sponge. Infrared chemical imaging analysis demonstrated the efficacy of the chemical treatments performed for scaffold reinforcement and functionalization. A good hydrophilicity and an adequate permeability were shown by swelling and permeability tests. The inclusion of the synthetic membrane improved the viscoelastic properties, as measured by dynamic mechanical analysis, and the suture retention force under both dry and wet conditions. The in vitro and in vivo biological characterization showed that insulin-like growth factor-1 functionalization successfully enhanced cell adhesion and long-term retention after implantation on the damaged myocardium, together with improved suturability by poly(dioxanone) reinforcement.

Aluminum silicate materials were widely used for temporary hemostasis of external wounds. Although they are commonly deemed to be nontoxic, side effects were proved to have some potential risks. In addition to obvious thermal effect and distal thrombosis, other chemical analysis should be performed to validate whether there is active components in the blood circulation system even when there is no obvious distal thrombosis. On the other hand, blood electrolytes disturbance is a safety concern, and this issue has been ignored in previous studies. In this study, a systematic and stringent safety evaluation of aluminium silicate hemostatic agents was performed to provide useful information for their future clinical applications. In this study, a low-heat producing Zeolite Granular Dressing (Z-Granular, Zeo-Innov Medical Technology Co., Ltd, Hangzhou, China) was used as hemostatic agents for safety evaluation in a rabbit femoral artery hemorrhage model. In addition to the time to achieve definite hemostasis and heat producing properties, blood electrolytes concentrations of the rabbits pre- and post-application were measured. Although the in vitro electrolyte concentration tests indicated the significant change of Ca²⁺ and K⁺ after the zeolite-accelerated hemostasis, in vivo rabbit model suggested that no obvious blood electrolyte disordered occurred. X-ray photography confirmed that there is no zeolite residual granule remained in the wound sites after the debridement. Element analysis proved that the possibility of these inorganic materials entering the blood circulation is very low. The histological results revealed that no pathological changes resulting from Z-Granular were found. Thus, Zeolite Granular Dressing would be an effective and safe hemostatic agent for emergency arterial bleeding. Furthermore, packing zeolite granules within nonwoven-fabric bags would solve the problem of debridement without compromising their hemostatic efficiency. This is a systematic and stringent safety evaluation of aluminium silicate hemostatic agents and provides useful information for their future clinic applications.

Interpenetrating polymer network are a combination of two or more polymers that allow creating a new material with a unique set of properties. An ideal scaffold for an extracellular matrix could be achieved by the combination of polymers to improve the scaffold’s physical and chemical characteristics. The aim of this work was to synthesize and characterize an interpenetrating polymer network of polyvinylpyrrolidone and poly(acrylic acid) in contact with cells of the oral mucosa. A sequential synthesis method was performed, adding polyvinylpyrrolidone xerogel to the acrylic acid monomer. Infrared spectroscopy and differential scanning calorimetry were used to characterize these networks. Differences in swelling kinetics, porosity, and density were also studied. A similar swelling degree and percentage of porosity between interpenetrating polymer network and poly(acrylic acid) were found. Also, maximum swelling was achieved in both networks at the same time point. The hemocompatibility and cell viability of the networks in contact with oral mucosa cells was also evaluated. Cytotoxicity analysis indicates that the interpenetrating polymer network is not toxic for oral mucosa cells. Additionally, the percentage of hemolysis was reduced when both poly(acrylic acid) and polyvinylpyrrolidone were combined as an interpenetrating polymer network. The results indicate that the combination of both polymers as an interpenetrating polymer network generated a suitable matrix for oral mucosa cells.

Osteoporosis-induced impaired bone regeneration would result in compromised osseointegration of hydroxyapatite-coated titanium and high rate of implant failure. Local administration of aspirin promotes osteoblast proliferation and inhibits osteoclast proliferation, and positively affects bone regeneration in osteoporotic condition. We hypothesized that reduced osteogenesis may account for poor osseointegration of hydroxyapatite-coated titanium which could be ameliorated by using local aspirin. The aim of this study was to confirm the effect of the local incorporation of aspirin into hydroxyapatite-coated titanium implants in the osteoporotic and normal condition. Twelve-week-old female Sprague–Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into three groups: group Sham, group OVX and group OVX + ASP, and the rats from OVX and Sham received hydroxyapatite-coated implants and animals belong to group OVX + ASP received aspirin-hydroxyapatite-coated implants until death at 12 weeks, respectively. After 12-week healing period, local treatment with aspirin revealed improved osseointegration compared to OVX, with significant improvement of the bone area ratio and bone-to-implant contact in histomorphometry, the bone mass and trabecular architecture in micro-CT evaluation, and the maximal push-out force in push out test. Moreover, group OVX + ASP presented the strongest effect on Jagged1, Notch1, and Hes-1(P < 0.05). These results demonstrated that local administration of aspirin could enhance hydroxyapatite-coated titanium implant osseointegration in OVX rats by activation Wnt signaling pathway to improve implant fixation in osteoporotic bone.

This study investigates the optimization of the ply angle for cartilage regeneration using a composite scaffold for treating knee joint osteoarthritis. We propose a new paradigm for composite scaffold tissue engineering that focuses on the reconstitution of the anatomic fiber architecture and uses constitutive modeling to evaluate the function of the construct. The mechano-regulation algorithm for tissue differentiation was used to determine the influence of the composite scaffold with an optimized ply angle on chondrogenesis in a computational model of knee-joint severe osteoarthritis. The simulation results revealed that the optimized ply-angle composite scaffold, which had similar mechanical properties to the native cartilage, provided the most appropriate biomechanical environment for cartilage regeneration.

The iron chelator deferoxamine is a hypoxia biomimicry and has received interest as a potential therapeutic in tissue engineering and regenerative medicine. Recently, local injection of this iron chelator deferoxamine has proven to increase bone healing through the activation of the hypoxia-inducible factor-1 signaling pathway that augments angiogenesis and osteogenesis. Repeated injections of deferoxamine are required to achieve local therapeutic levels at fracture site. To achieve local therapeutic levels at fracture site without the use of multiples injections and associated pain and infection issues, we designed and prepared polymeric microspheres made of polycaprolactone and poly(ethylene oxide), in which deferoxamine was encapsulated, via a melting process. The application of this process has enabled to obtain spheres of different poly(ethylene oxide) concentrations for optimizing the drug release rate. The effective local release carrier offers a predetermined rate that can mimic the effect of repeated deferoxamine injections over a 14-day period to selectively stimulate bone repair and thus improve the biological performance to the point where ideally synthetics begin to challenge autograft dominance as the bone replacement of choice.