Effect of gelatin sponge with colloid silver on bone healing in infected cranial defects

Enhanced osteogenic and antibacterial properties of titanium implant surface modified with Zn-incorporated nanowires: Preclinical in vitro and in vivo investigations

OBJECTIVE

This study aimed to synthesize zinc-incorporated nanowires structure modified titanium implant surface (Zn-NW-Ti) and explore its superior osteogenic and antibacterial properties in vitro and in vivo.

MATERIALS AND METHODS

Zn-NW-Ti was synthesized via displacement reactions between zinc sulfate solutions and the titanium (Ti) surface, which was pretreated by hydrofluoric acid etching and hyperthermal alkalinization. The physicochemical properties of the Zn-NW-Ti surface were examined. Moreover, the biological effects of Zn-NW-Ti on MC3T3-E1 cells and its antibacterial property against oral pathogenic bacteria (Staphylococcus aureus, Porphyromonas gingivalis, and Actinobacillus actinomycetemcomitans) compared with sandblasted and acid-etched Ti (SLA-Ti) and nanowires modified Ti (NW-Ti) surface were assessed. Zn-NW-Ti and SLA-Ti modified implants were inserted into the anterior extraction socket of the rabbit mandible with or without exposure to the mixed bacterial solution (S. aureus, P. gingivalis, and A. actinomycetemcomitans) to investigate the osteointegration and antibacterial performance via radiographic and histomorphometric analysis.

RESULTS

The Zn-NW-Ti surface was successfully prepared. The resultant titanium surface appeared as a nanowires structure with hydrophilicity, from which zinc ions were released in an effective concentration range. The Zn-NW-Ti surface performed better in facilitating the adhesion, proliferation, and differentiation of MC3T3-E1 cells while inhibiting the colonization of bacteria compared with SLA-Ti and NW-Ti surface. The Zn-NW-Ti implant exhibited enhanced osseointegration in vivo, which was attributed to increased osteogenic activity and reduced bacterial-induced inflammation compared with the SLA-Ti implant.

CONCLUSIONS

The Zn-incorporated nanowires structure modified titanium implant surface exhibited improvements in osteogenic and antibacterial properties, which optimized osteointegration in comparison with SLA titanium implant surface.

Enhanced wound healing and hemostasis with exosome-loaded gelatin sponges from human umbilical cord mesenchymal stem cells

BACKGROUND

Rapid wound healing remains a pressing clinical challenge, necessitating studies to hasten this process. A promising approach involves the utilization of human umbilical cord mesenchymal stem cells (hUC-MSCs) derived exosomes. The hypothesis of this study was that these exosomes, when loaded onto a gelatin sponge, a common hemostatic material, would enhance hemostasis and accelerate wound healing.

AIM

To investigate the hemostatic and wound healing efficacy of gelatin sponges loaded with hUC-MSCs-derived exosomes.

METHODS

Ultracentrifugation was used to extract exosomes from hUC-MSCs. Nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and western blot techniques were used to validate the exosomes. In vitro experiments were performed using L929 cells to evaluate the cytotoxicity of the exosomes and their impact on cell growth and survival. New Zealand rabbits were used for skin irritation experiments to assess whether they caused adverse skin reactions. Hemolysis test was conducted using a 2% rabbit red blood cell suspension to detect whether they caused hemolysis. Moreover, in vivo experiments were carried out by implanting a gelatin sponge loaded with exosomes subcutaneously in Sprague-Dawley (SD) rats to perform biocompatibility tests. In addition, coagulation index test was conducted to evaluate their impact on blood coagulation. Meanwhile, SD rat liver defect hemostasis model and full-thickness skin defect model were used to study whether the gelatin sponge loaded with exosomes effectively stopped bleeding and promoted wound healing.

RESULTS

The NTA, TEM, and western blot experimental results confirmed that exosomes were successfully isolated from hUC-MSCs. The gelatin sponge loaded with exosomes did not exhibit significant cell toxicity, skin irritation, or hemolysis, and they demonstrated good compatibility in SD rats. Additionally, the effectiveness of the gelatin sponge loaded with exosomes in hemostasis and wound healing was validated. The results of the coagulation index experiment indicated that the gelatin sponge loaded with exosomes had significantly better coagulation effect compared to the regular gelatin sponge, and they showed excellent hemostatic performance in a liver defect hemostasis model. Finally, the full-thickness skin defect healing experiment results showed significant improvement in the healing process of wounds treated with the gelatin sponge loaded with exosomes compared to other groups.

CONCLUSION

Collectively, the gelatin sponge loaded with hUC-MSCs-derived exosomes is safe and efficacious for promoting hemostasis and accelerating wound healing, warranting further clinical application.

Bone tissue engineering for treating osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a devastating and complicated disease with an unclear etiology. Femoral head-preserving surgeries have been devoted to delaying and hindering the collapse of the femoral head since their introduction in the last century. However, the isolated femoral head-preserving surgeries cannot prevent the natural progression of ONFH, and the combination of autogenous or allogeneic bone grafting often leads to many undesired complications. To tackle this dilemma, bone tissue engineering has been widely developed to compensate for the deficiencies of these surgeries. During the last decades, great progress has been made in ingenious bone tissue engineering for ONFH treatment. Herein, we comprehensively summarize the state-of-the-art progress made in bone tissue engineering for ONFH treatment. The definition, classification, etiology, diagnosis, and current treatments of ONFH are first described. Then, the recent progress in the development of various bone-repairing biomaterials, including bioceramics, natural polymers, synthetic polymers, and metals, for treating ONFH is presented. Thereafter, regenerative therapies for ONFH treatment are also discussed. Finally, we give some personal insights on the current challenges of these therapeutic strategies in the clinic and the future development of bone tissue engineering for ONFH treatment.

Could Local Application of Hypoxia Inducible Factor 1-α Enhancer Deferoxamine Be Promising for Preventing of Medication-Related Osteonecrosis of the Jaw?

This experimental study investigates the prophylactic effect of deferoxamine (DFO) on medication-related osteonecrosis of the jaw (MRONJ). Thirty-six female Sprague Dawley rats received zoledronic acid (ZA) for eight weeks to create an osteonecrosis model. DFO was locally applied into the extraction sockets with gelatin sponge (GS) carriers to prevent MRONJ. The specimens were histopathologically and histomorphometrically evaluated. Hypoxia-inducible factor 1-alpha (HIF-1α) protein levels in the extraction sockets were quantified. New bone formation rate differed significantly between groups (p = 0.005). Newly formed bone ratios in the extraction sockets did not differ significantly between the control group and the GS (p = 1), GS/DFO (p = 0.749), ZA (p = 0.105), ZA-GS (p = 0.474), and ZA-GS/DFO (p = 1) groups. While newly formed bone rates were higher in the ZA-GS and ZA-GS/DFO groups than in the ZA group, the differences were not significant. HIF-1α levels differed significantly between groups (p < 0.001) and were significantly higher in the DFO and ZA-GS/DFO groups than in the control group (p = 0.001 and p = 0.004, respectively). While HIF-1α levels were higher in the ZA-GS/DFO group than in the ZA group, the difference was not significant. While HIF-1α protein levels and new bone formation rate were elevated in the DFO-treated group, the effect was not significant. Further large-scale studies are needed to understand DFO’s preventative effects on MRONJ and the role of HIF-1α in MRONJ pathogenesis.

Efficacy of gelatamp in controlling the postoperative sequelae following mandibular posterior teeth extraction - A split-mouth study

Purpose

This study aimed to evaluate the effectiveness of gelatamp on soft tissue healing, bleeding, and pain following mandibular posterior teeth extraction.

Methods

This study was designed as a split-mouth, prospective randomized double-blind controlled trial conducted in a single tertiary care center. Thirty-five subjects indicated for routine mandibular posterior teeth extraction were divided into two groups using the lottery technique: the experimental group (n = 30), which received gelatamp after extraction, and the control group (n = 30), which received no intervention. The primary outcomes included soft tissue healing(Landry, Turnbull, Howley index) and Pain(VAS score). The secondary outcomes assessed were bleeding(Maani et al. index) and swelling(Sauza and Consone assessment).

Result

The results showed a statistically significant difference in soft tissue healing on the third and seventh days in the experimental group (p ≤ 0.05) than in the control group. A significant difference in bleeding scores at 5 min, 30 min, and 2 h postoperatively in the study group (p ≤ 0.05) was noted. There was no significant difference between the groups for pain on the first, third or seventh day postoperatively (p ≤ 0.05). The swelling assessment also showed no significant changes (p = 0.831) for the study and the control group.

Conclusion

Based on the findings of this study, gelatamp can be effectively used to reduce postoperative sequelae such as bleeding with better soft tissue healing following extractions and surgical removal of tooth.

Photosensitive and Conductive Hydrogel Induced Innerved Bone Regeneration for Infected Bone Defect Repair

Repairing infected bone defects is a challenge in the field of orthopedics because of the limited self-healing capacity of bone tissue and the susceptibility of refractory materials to bacterial activity. Innervation is the initiating factor for bone regeneration and plays a key regulatory role in subsequent vascularization, ossification, and mineralization processes. Infection leads to necrosis of local nerve fibers, impeding the repair of infected bone defects. Herein, a biomaterial that can induce skeletal-associated neural network reconstruction and bone regeneration with high antibacterial activity is proposed for the treatment of infected bone defects. A photosensitive conductive hydrogel is prepared by incorporating magnesium-modified black phosphorus (BP@Mg) into gelatin methacrylate (GelMA). The near-infrared irradiation-based photothermal and photodynamic treatment of black phosphorus endows it with strong antibacterial activity, improving the inflammatory microenvironment and reducing bacteria-induced bone tissue damage. The conductive nanosheets and bioactive ions released from BP@Mg synergistically improve the migration and secretion of Schwann cells, promote neurite outgrowth, and facilitate innerved bone regeneration. In an infected skull defect model, the GelMA-BP@Mg hydrogel shows efficient antibacterial activity and promotes bone and CGRP⁺ nerve fiber regeneration. The phototherapy conductive hydrogel provides a novel strategy based on skeletal-associated innervation for infected bone defect repair.

The Antibacterial Effect, Biocompatibility, and Osteogenesis of Vancomycin-Nanodiamond Composite Scaffold for Infected Bone Defects

Purpose

The repair and treatment of infected bone defects (IBD) is a common challenge faced by orthopedic clinics, medical materials science, and tissue engineering.

Methods

Based on the treatment requirements of IBD, we utilized multidisciplinary knowledge from clinical medicine, medical materials science, and tissue engineering to construct a high-efficiency vancomycin sustained-release system with nanodiamond (ND) and prepare a composite scaffold. Its effect on IBD treatment was assessed from materials, cytology, bacteriology, and zoology perspectives.

Results

The results demonstrated that the Van-ND-45S5 scaffold exhibited an excellent antibacterial effect, biocompatibility, and osteogenesis in vitro. Moreover, an efficient animal model of IBD was established, and a Van-ND-45S5 scaffold was implanted into the IBD. Radiographic and histological analyses and bone repair-related protein expression, confirmed that the Van-ND-45S5 scaffold had good biocompatibility and osteogenic and anti-infective activities in vivo.

Conclusion

Collectively, our findings support that the Van-ND-45S5 scaffold is a promising new material and approach for treating IBD with good antibacterial effects, biocompatibility, and osteogenesis.

Small extracellular vesicles derived from hypoxic mesenchymal stem cells promote vascularized bone regeneration through the miR-210-3p/EFNA3/PI3K pathway

Angiogenesis is closely coupled with osteogenesis and has equal importance. Thus, promoting angiogenesis during the bone repair process is vital for ideal bone regeneration. As important mediators of cell-cell communication and biological homeostasis, mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) have been proved to be highly involved in bone and vascular regeneration. Because hypoxia microenvironment promotes the proangiogenic activity of MSCs, in the present study, we investigate the effect and underlying molecular mechanisms of sEVs from hypoxia-preconditioned MSCs (hypo-sEVs) on angiogenesis and develop an effective strategy to promote vascularized bone regeneration. Compared to sEVs from normoxia MSCs (nor-sEVs), hypo-sEVs promoted the proliferation, migration, and angiogenesis of HUVECs and ultimately enhanced bone regeneration and new blood vessel reconstruction in a critical-size calvarial bone defect model. miRNA sequence and the verified results showed that miR-210-3p in hypo-sEVs was increased via HIF-1α under hypoxia. The upregulated miR-210-3p in hypo-sEVs promoted angiogenesis by downregulating EFNA3 expression and enhancing the phosphorylation of the PI3K/AKT pathway. Thus, this study suggests a successful strategy to enhance vascularized bone regeneration by utilizing hypo-sEVs via the miR-210-3p/EFNA3/PI3K/AKT pathway. STATEMENT OF SIGNIFICANCE: Considering the significance of vascularization in ideal bone regeneration, strategies to promote angiogenesis during bone repair are required. Hypoxia microenvironment can promote the proangiogenic potential of mesenchymal stem cells (MSCs). Nonetheless, the therapeutic effect of small extracellular vesicles (sEVs) from hypoxia-preconditioned MSCs on cranio-maxillofacial bone defect remains unknown, and the underlying mechanism is poorly understood. This study shows that hypo-sEVs significantly enhance the proliferation, migration, and angiogenesis of HUVECs as well as promote vascularized bone formation. Moreover, this work indicates that HIF-1α can induce overexpression of miR-210-3p under hypoxia, and miR-210-3p can hinder EFNA3 expression and subsequently activate the PI3K/AKT pathway. The application of hypo-sEVs provides a facile and promising strategy to promote vascularized bone regeneration in a critical-size bone defect model.

High-Strength and Injectable Supramolecular Hydrogel Self-Assembled by Monomeric Nucleoside for Tooth-Extraction Wound Healing

Hydrogels with high mechanical strength and injectability have attracted extensive attention in biomedical and tissue engineering. However, endowing a hydrogel with both properties is challenging because they are generally inversely related. In this work, by constructing a multi-hydrogen-bonding system, a high-strength and injectable supramolecular hydrogel is successfully fabricated. It is constructed by the self-assembly of a monomeric nucleoside molecular gelator (2-amino-2'-fluoro-2'-deoxyadenosine (2-FA)) with distilled water/phosphate buffered saline as solvent. Its storage modulus reaches 1 MPa at a concentration of 5.0 wt%, which is the strongest supramolecular hydrogel comprising an ultralow-molecular-weight (MW < 300) gelator. Furthermore, it exhibits excellent shear-thinning injectability, and completes the sol-gel transition in seconds after injection at 37 °C. The multi-hydrogen-bonding system is essentially based on the synergistic interactions between the double NH₂ groups, water molecules, and 2'-F atoms. Furthermore, the 2-FA hydrogel exhibits excellent biocompatibility and antibacterial activity. When applied to rat molar extraction sockets, compared to natural healing and the commercial hemorrhage agent gelatin sponge, the 2-FA hydrogel exhibits faster degradation and induces less osteoclastic activity and inflammatory infiltration, resulting in more complete bone healing. In summary, this study provides ideas for proposing a multifunctional, high-strength, and injectable supramolecular hydrogel for various biomedical engineering applications.

Therapeutic Applications of Antimicrobial Silver-Based Biomaterials in Dentistry

Microbial infection accounts for many dental diseases and treatment failure. Therefore, the antibacterial properties of dental biomaterials are of great importance to the long-term results of treatment. Silver-based biomaterials (AgBMs) have been widely researched as antimicrobial materials with high efficiency and relatively low toxicity. AgBMs have a broad spectrum of antimicrobial properties, including penetration of microbial cell membranes, damage to genetic material, contact killing, and dysfunction of bacterial proteins and enzymes. In particular, advances in nanotechnology have improved the application value of AgBMs. Hence, in many subspecialties of dentistry, AgBMs have been researched and employed, such as caries arresting or prevention, root canal sterilization, periodontal plaque inhibition, additives in dentures, coating of implants and anti-inflammatory material in oral and maxillofacial surgery. This paper aims to provide an overview of the application approaches of AgBMs in dentistry and present better guidance for oral antimicrobial therapy via the development of AgBMs.

An injectable gellan gum-based hydrogel that inhibits Staphylococcus aureus for infected bone defect repair

The treatment of infected bone defects in complex anatomical structures, such as oral and maxillofacial structures, remains an intractable clinical challenge. Therefore, advanced biomaterials that have excellent anti-infection activity and allow convenient delivery are needed. We fabricated an innovative injectable gellan gum (GG)-based hydrogel loaded with nanohydroxyapatite particles and chlorhexidine (nHA/CHX). The hydrogel has a porous morphology, suitable swelling ratio, and good biocompatibility. It exerts strong antibacterial activity against Staphylococcus aureus growth and biofilm formation in vitro. We successfully established an infected calvarial defect rat model. Bacterial colony numbers were significantly lower in tissues surrounding the bone in rats of the GG/nHA/CHX group after debride surgery and hydrogel implantation in the defect regions than in rats of the blank group. Rats in the GG/nHA/CHX group exhibited significantly increased new bone formation compared to those in the blank group at 4 and 8 weeks. These findings indicate that gellan gum-based hydrogel with nHA/CHX can accelerate the repair of infected bone defects.

HPLC/MSn Profiling and Healing Activity of a Muco-Adhesive Formula of Salvadora persica against Acetic Acid-Induced Oral Ulcer in Rats

Salvadora persica L. (S. persica, Siwak) is an ethnic plant that is widely used for improving oral hygiene. This study aimed to provide a phytochemical profiling of S. persica ethyl acetate fraction (SPEAF) and to evaluate the healing activity of a muco-adhesive formula of the fraction against acetic acid-induced oral ulcers in rats. HPLC-ESI-QTOF-MS-MS analysis of SPEAF resulted in the tentative identification of 56 metabolites containing fatty acids (23%), urea derivatives (10.5%) and sulphur compounds (10%), in addition to several amides, polyphenols and organic acids (6.5%, 5% and 2%, respectively). For the first time, 19 compounds were identified from S. persica. In vitro and in vivo experiments indicated that the extract is non-toxic. SPEAF exhibited superior healing activities compared to both the negative and positive control groups on days 7 and 14 of tongue ulcer induction. This was confirmed by histopathological examinations of haematoxylin and eosin-stained (H&E) and Masson's trichrome-stained tongue sections. Moreover, SPEAF showed potent anti-inflammatory activities, as evidenced by the inhibited expression of interleukin-6 (IL-6) and tumour necrosis alpha (TNF-α). Moreover, SPEAF exhibited potent antioxidant activity, as it prevented malondialdehyde (MDA) accumulation, reduced glutathione (GSH) depletion and superoxide dismutase (SOD) exhaustion. SPEAF significantly enhanced hydroxyproline tongue content and upregulated collagen type I alpha 1 (Col1A1) mRNA expression. SPEAF also improved angiogenesis, as shown by the increased mRNA expression of the angiopoietin-1 (Ang-1). In conclusion, S. persica has a wide range of secondary metabolites and ameliorates acetic acid-induced tongue ulcers in rats. This can be attributed, at least partly, to its anti-inflammatory, antioxidant, procollagen and angiogenic activities. These findings provide support and validity for the use of S. persica as a traditional and conventional treatment for oral disorders.

Management of recurrent aphthous ulcers exploiting polymer-based Muco-adhesive sponges: in-vitro and in-vivo evaluation

Recurrent aphthous ulcer (RAU) is a well-known painful, inflammatory disease with uncertain etiology for which local symptomatic therapy is only available. The aim of this study was to formulate and characterize muco-adhesive sponges containing a mixture of tenoxicam and miconazole nitrate to manage pain, inflammation and avoid candida infection that may accompany RAU due to poor oral hygiene. Two polymers at different concentrations were used to prepare sponges applying simple freeze-drying. Medicated chitosan (2%) sponges (mC2) showed acceptable physical appearance, surface pH (6.3 ± 0.042), porosity (25.7% ± 1.8), swelling index (5.7 ± 0.11), in-vivo and ex-vivo muco-adhesion time (115 min.±0.813 and 155 min.±1.537, respectively), ex-vivo muco-adhesion force (0.09 N ± 0.002) and scanning electron microscope (SEM) images. For concurrent clear-cut determination of tenoxicam and miconazole nitrate from mC2, a new UPLC method was developed and validated. mC2 sponges exhibited superior in-vitro drug release profiles where ∼100% of tenoxicam released within 5 min for fast pain relief with a more prolonged miconazole nitrate release. Furthermore, in-vivo animal study revealed that mC2 caused a significant decrease in the acetic acid-induced ulcer size in rats after 6 days of treatment (p < .0001) compared to negative and positive controls. Additionally, histopathological examination showed faster healing with complete restoration of the normal oral histology in rats. The present study concludes that chitosan sponge loaded with a combination of tenoxicam and miconazole nitrate could improve healing of RAU cases.

A Review on the Application of Silver Nanoparticles in Oral and Maxillofacial Surgery

Silver nanoparticles (AgNPs) have been taken advantage of in dentistry because of their good antibacterial resistance and self-sustaining potential. However, in oral and maxillofacial surgery and implantology, there is a lesser amount of evidence. The few pieces of evidence need to be accentuated for possible amplification of its use in the dental setting. AgNPs in oral and maxillofacial surgery can be used in wound healing, bone healing, extractions, guided tissue regeneration, apical surgeries, oral cancer, and dental implants. This review aims to feature the utilization and application of AgNPs in oral and maxillofacial surgery and implant dentistry, emphasizing its need for potential future development in clinical settings.

Polymer-Based Carriers in Dental Local Healing-Review and Future Challenges

Polymers in drug formulation technology and the engineering of biomaterials for the treatment of oral diseases constitute a group of excipients that often possess additional properties in addition to their primary function, i.e., biological activity, sensitivity to stimuli, mucoadhesive properties, improved penetration of the active pharmaceutical ingredient (API) across biological barriers, and effects on wound healing or gingival and bone tissue regeneration. Through the use of multifunctional polymers, it has become possible to design carriers and materials tailored to the specific conditions and site of application, to deliver the active substance directly to the affected tissue, including intra-periodontal pocket delivery, and to release the active substance in a timed manner, allowing for the improvement of the form of application and further development of therapeutic strategies. The scope of this review is polymeric drug carriers and materials developed from selected multifunctional groups of natural, semi-synthetic, and synthetic polymers for topical therapeutic applications. Moreover, the characteristics of the topical application and the needs for the properties of carriers for topical administration of an active substance in the treatment of oral diseases are presented to more understand the difficulties associated with the design of optimal active substance carriers and materials for the treatment of lesions located in the oral cavity.

Copper Peroxide-Loaded Gelatin Sponges for Wound Dressings with Antimicrobial and Accelerating Healing Properties

Catalytic conversion of hydrogen peroxide (H₂O₂) to more toxic hydroxyl radicals (^•OH) is a good choice for sterilization and anti-infection, but endogenous H₂O₂ is insufficient to achieve satisfactory sterilization efficacy. Despite great efforts, designing and developing antimicrobial materials that specifically and effectively self-supply H₂O₂ at the wound site remain as tremendous challenges. Here, we report a pH-responsive copper peroxide-loaded wound dressing made from copper hydroxide and gelatin sponge and then reacted with H₂O₂. In vitro experiments show that the prepared wound dressing has good bactericidal properties against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa). Moreover, the as-prepared wound dressing can release ^•OH specifically in the bacterial-infected skin wound, rather than in normal tissues, and in vivo skin wound-healing experiments proved that the synthesized copper peroxide-loaded gelatin sponge could combat E. coli effectively; in addition, Cu²⁺ released from the gelatin sponge could stimulate angiogenesis and collagen deposition simultaneously. The study provides a strategy to improve antibacterial efficacy and reduce the toxic side effects through the release of ^•OH by bacterial self-activation.

Influence of silver speciation on the inflammatory regulation of AgNPs anchoring onto titania nanotubes

AgNPs were immobilized on titania nanotubes (TNT) by chelation of polydopamine (PD) to generate a TNT/PD/AgNPs (TPAS) via a simple dipping method. The inflammatory regulation of the TPAS coating were investigated. To gain a deep insight into the transformation of AgNPs in macrophages, a cation exchange reaction was introduced for speciation analysis of AgNPs and Ag⁺ by inductively coupled plasma-mass spectrometry. Owing to the magic signal amplification strategy, the trace AgNPs and Ag⁺ in release media and even in macrophages were easily detected. In simulated inflammatory microenvironment, M1 macrophages promoted the cell-responsive release of Ag⁺ from TPAS at 3 d, which dampened inflammation. Then, macrophages reduced Ag⁺ by intracellular metabolites, leading to the formation of new AgNPs in cells. This study give a new sight for discovering the inflammatory regulation mechanism of silver containing biomaterials.

Silver-loaded nanoparticles affect ex-vivo mechanical behavior and mineralization of dentin

Background

The aim was to evaluate the effect of silver loaded nanoparticles (NPs) application on the triboscopic, crystallographic and viscoelastic properties of demineralized dentin. Polymethylmetacrylate-based NPs and Ag loaded NPs were applied on demineralized dentin.

Material and Methods

Treated and untreated surfaces were probed by a nanoindenter to test viscoelasticity, and by atomic force microscopy to test nanoroughness and collagen fibril diameter. X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging were also used.

Results

Dentin treated with Ag-NPs attained the lowest complex modulus, and the highest tan delta values after 7 days of storage. Dentin treated with undoped-NPs achieved the lowest nanoroughness and the greatest collagen bandwidths among groups. Crystals were identified as hydroxyapatite with the highest crystallographic maturity and crystallite size in dentin treated with undoped-NPs. Texture increased in all samples from 24 h to 7 d, except in dentin surfaces treated with Ag-NPs at 310 plane. Polyhedral, block-like, hexagonal or plate-like shaped apatite crystals constituted the bulk of minerals in dentin treated with Ag-NPs, after 7 d. Polyhedral or rounded/drop-like, and polymorphic in strata crystal apatite characterized the minerals when undoped-NPs were used, with more crystalline characteristics after 7 d than that found when Ag-NPs were applied. Ag-NPs application did not improve the mechanical performance of dentin and did not produce dentin remineralization. However, energy was dissipated through the dentin without showing stress concentration; contrary was occurring at dentin treated with undoped-NPs, that provoked bridge-like mineral deposits at the dentin surface.

Conclusions

Ag-NPs application did not enhance the mechanical properties of cervical dentin, though the energy dissipation did not damage the dentin structure. Remineralization at dentin was not produced after Ag-NPs application, though improved crystallinity may lead to increase stability of the apatite that was generated at the dentin surface.

Key words:Dentin, mechanical, mineralization, roughness, silver, viscoelastic.

Inflammatory responses to micro/nano-structured titanium surfaces with silver nanoparticles in vitro

The fabricated AgPD-MNT exhibited potent antibacterial activity and mediated the inflammatory response.

Enhancement of hemostatic property of plant derived oxidized nanocellulose-silk fibroin based scaffolds by thrombin loading

To combat post-surgical and traumatic bleeding conditions effective hemostasis is of great importance. The study was designed to investigate the effect of thrombin (Th) loading on hemostatic performance of TEMPO-oxidized cellulose nanofiber (TOCN)-silk fibroin (SF) scaffolds. Addition of SF with TOCN significantly (***P < 0.001) increased blood absorption capacity and improved biocompatibility of TOCN. Thrombin loading potentiated platelet activation and hemostatic property of scaffolds (TOCN-SF-Th) compared to samples without thrombin (TOCN-SF). The hemostatic time of TOCN-SF5-Th in rabbit ear artery bleeding model was reduced (*** P < 0.001) to 114 s from 220 s of TOCN-SF5. Reduction in bleeding time and blood loss of TOCN-SF5-Th in rat tail amputation and liver avulsion model was comparable to commercial hemostat (Floseal). Surface morphology (SEM) of samples applied on bleeding site showed that RBCs and fibrin fiber could strongly interact with TOCN-SF and TOCN-SF-Th scaffolds. The result suggests that TOCN-SF-Th can be a promising candidate for designing hemostatic agents.

Hydrogel Effects Rapid Biofilm Debridement with ex situ Contact-Kill to Eliminate Multidrug Resistant Bacteria in vivo

Multidrug resistance and the refractory character of bacterial biofilms are among the most difficult challenges in infection treatment. Current antimicrobial strategies typically are much more effective for prevention of biofilm formation than for eradication of established biofilms; these strategies also leave dead bacteria and endotoxin in the infection site, which impairs healing. We report a novel hydrogel that eradicates biofilm bacteria by non-leaching-based debridement followed by ex situ contact-killing (DESCK) away from the infection site. The debridement effect is likely due to the high water swellability and microporosity of the cross-linked network which is made from polyethylene glycol dimethacrylate tethered with a dangling polyethylenimine (PEI) star copolymer. The large pore size of the hydrogel makes the cationic pore walls highly accessible to bacteria. The hydrogel also degrades in the presence of infection cells, releasing star cationic PEI into the infection site to contact-kill bacteria remaining there. DESCK hydrogel effectively kills (>99.9% reduction) biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Pseudomonas aeruginosa (CR-PA) and Acinetobacter baumannii in a murine excisional wound infection model. Silver-based wound dressings (controls) showed almost no killing of CR-PA and MRSA biofilms. This DESCK hydrogel greatly reduces the bioburden and inflammation and promotes wound healing. It has great potential for diverse infection treatment applications.

Preparation of micro/nanopatterned gelatins crosslinked with genipin for biocompatible dental implants

Background: Collagen is a basic component of the periodontium and plays an important role in the function of the periodontal unit. Therefore, coating with collagen/gelatin has been applied to enable dental implants to positively interact with peri-implant tissues. Although the micro/nanoscale topography is an important property of the surface of dental implants, smaller collagen/gelatin surface patterns have not been sufficiently developed. Furthermore, only few reports on the behavior of cells on gelatin surfaces with different patterns and sizes exist. In this study, we developed micro/nanometer-scaled gelatin surfaces using genipin crosslinking, with the aim of understanding the use of patterning in surface modification of dental implants. Results: Grooves, holes, and pillars, with widths or diameters of 2 µm, 1 µm, or 500 nm were fabricated using a combination of molding and genipin crosslinking of gelatin. The stability of the different gelatin patterns could be controlled by the degree of genipin crosslinking. The gelatin patterns at 20 mM concentration of genipin and 41% crosslinking maintained a stable, patterned shape for at least 14 days in a cell culture medium. A cell morphology study showed that the cells on groves were aligned along the direction of the grooves. In contrast, the cells on pillars and holes exhibited randomly elongated filopodia. The vinculin spots of the cells were observed on the top of ridges and pillars or the upper surface of holes. The results of a cell attachment assay showed that the number of surface-attached cells increased with increasing patterning of the gelatin surface. Unlike the cell attachment assay, the results of a cell proliferation assay showed that Saos-2 cells prefer grooves with diameters of approximately 2 µm and 1 µm and pillars with diameters of 1 µm and heights of 500 nm. The number of cells on pillars with heights of 2 µm was larger than those of the other gelatin surface patterns tested. Conclusion: These data support that a detailed design of the gelatin surface pattern can control both cell attachment and proliferation of Saos-2 cells. Thus, gelatin surfaces patterned using genipin crosslinking are now an available option for biocompatible material patterning.

Icariin Enhances Bone Repair in Rabbits with Bone Infection during Post-infection Treatment and Prevents Inhibition of Osteoblasts by Vancomycin

Vancomycin is an effective antibiotic for treatment of bone infection caused by Staphylococcus aureus, however, a high local concentration of vancomycin might induce a delay in bone union. Icariin has been reported to suppress osteoclastogenes and promote osteogenesis. Our study aimed to investigate the effect of icariin on bone repair after anti-infection treatment in vivo and to explore the resisting effect of icariin on rat calvarial osteoblasts (ROBs) inhibited with high doses of vancomycin. Rabbits with bone infection of S. aureus were treated with implanted vancomycin-calcium sulfate (VCS) and icariin at 10.86 mg/kg/day for consecutive 8 weeks. Micro-CT, morphology, blood biochemistry were evaluated. In addition, ROBs were treated with vancomycin and icariin at different doses. Cell proliferation and differentiation capabilities, BMP2, Runx2, OPG, RANKL mRNA levels and protein expression were assessed. The results indicated that high dose of vancomycin significantly decreased bone mass and inhibited osteocalcin secretion; icariin increased these indicators compared with the single vancomycin treatment. Over 0.1 mg/mL of vancomycin inhibited the proliferation and differentiation of ROBs, while icariin resisted the inhibition of vancomycin by regulating cell cycle and promoting the Alkaline phosphatase (ALP) activity. Moreover, icariin promote bone formation by up-regulating BMP2/Runx2 and OPG/RANKL pathways. Icariin exhibited osteoplastic properties on osteoblasts that had been inhibited with high doses of vancomycin. Therefore, icariin is helpful for post-infection treatment of bone infection.

Inhibition of glutathione metabolism attenuates esophageal cancer progression

Esophageal squamous cell carcinoma (ESCC) is a deadly malignancy with regard to mortality and prognosis, and the 5-year survival rate for all patients diagnosed with ESCC remains poor. A better understanding of the biological mechanisms of ESCC tumorigenesis and progression is of great importance to improve treatment of this disease. In this study, we demonstrated that the glutathione metabolism pathway is highly enriched in ESCC cells compared with normal esophageal epithelial cells in an in vivo mouse model. In addition, treatment with L-buthionine-sulfoximine (BSO) to deplete glutathione decreased the ESCC tumor burden in mice, thus demonstrating the critical role of glutathione metabolism in ESCC progression. BSO treatment also led to decreased cell proliferation and activation of cell apoptosis in ESCC. Finally, BSO treatment blocked NF-kB pathway activation in ESCC. Our study reveals a new pathway that regulates ESCC progression and suggests that inhibition of glutathione metabolism may be a potential strategy for ESCC treatment.