LBL assembly of Ag@Ti3C2TXand chitosan on PLLA substrate to enhance antibacterial and biocompatibility.

Poly L-lactic acid (PLLA) is a non-toxic, biocompatible degradable polymer material with excellent mechanical properties after moulding. However, it faces challenges in the use of biomedical materials because of its intolerance to bacteria. Here, we use an easy-to-operate method to prepare a composite multilayer membrane: PLLA membrane was used as substrates to assemble positively charged chitosan and negatively charged Ag@MXene on the surface using the layer-by-layer (LBL) method. The assembly process was detected by fluorescein isothiocyanate-labelled chitosan and the thickness of the coating multilayer was also detected as 210.0 ± 12.1 nm for P-M membrane and 460.5 ± 26.5 nm for P-Ag@M membrane. The surface self-assembled multilayers exhibited 91.27% and 96.11% growth inhibition ratio againstEscherichia coliandStaphylococcus aureusstrains under 808 nm near-infrared laser radiation with a synergistic photothermal antibacterial effect. Furthermore, best biocompatibility of P-M and P-Ag@M membranes compare to PLLA membrane motivated us to further explore its application in biomedical materials.

Clinical efficacy of mineralized collagen (MC) versus anorganic bovine bone (Bio-Oss) for immediate implant placement in esthetic area: a single-center retrospective study.

BACKGROUND: The purpose of this retrospective study was to evaluate the clinical efficacy of mineralized collagen (MC) versus anorganic bovine bone (Bio-Oss) for immediate implant placement in esthetic area. METHODS: Medical records of Department of Oral and Maxillofacial Surgery of Shandong Provincial Hospital were screened for patients who had been treated with immediate implant implantation in the esthetic area using either MC (Allgens®, Beijing Allgens Medical Science and Technology Co., Ltd., China) or Bio-Oss (Bio-Oss®, Geistlich Biomaterials, Wolhusen, Switzerland), between January 2018 and December 2019. All patients fulfilling the in-/exclusion criteria and following followed for a minimum period of 1 year after surgery were enrolled into the presented study. Implant survival rate, radiographic, esthetic and patient satisfactory evaluations were performed. RESULTS: Altogether, 70 patients were included in the study; a total of 80 implants were inserted. All implants had good initial stability. The survival rate of implants was 100% at 1-year follow-up. The differences in horizontal and vertical bone loss between the MC group (0.72 ± 0.26 mm, 1.62 ± 0.84 mm) and the Bio-Oss group (0.70 ± 0.52 mm, 1.57 ± 0.88 mm) were no significant difference statistically no significant 6 months after permanent restoration. Similar results occurred at 12 months after permanent restoration functional loaded. Clinical acceptability defined by pink esthetic score (PES) ≥ 6 (6.07 ± 1.62 vs. 6.13 ± 1.41) was not significantly different between groups. Patient satisfaction estimated by visual analog scale (VAS) was similar (8.56 ± 1.12 vs. 8.27 ± 1.44), and the difference was no significant difference between the two groups. CONCLUSIONS: The biomimetic MC showed a similar behaviour as Bio-Oss not only in its dimensional tissues changes but also in clinical acceptability and patient satisfaction. Within the limitations of this study, these cases show that MC could be considered as an alternative bone graft in IIP.

Modified poly(methyl methacrylate) bone cement in the treatment of Kümmell disease.

Kümmell disease (KD) causes serious vertebral body collapse in patients. However, only a few case reports have been conducted and the number of patients with KD investigated was limited. Additionally, the frequently used poly(methyl methacrylate) (PMMA) bone cement for KD is limited by excessive modulus and poor biocompatibility. Herein, we aimed to modify PMMA bone cement with mineralized collagen (MC), and compare the clinical effects, image performance and finite element analysis between the modified bone cement and PMMA bone cement for the treatment of phase I and II KD. Thirty-nine KD patients treated with PMMA bone cement and 40 KD patients treated with MC-modified PMMA bone cement from June 2015 to March 2017 were retrospectively analyzed. The surgical procedure, intraoperative blood loss, hospital stay and complications were compared between different groups. Visual analog scale, Oswestry disability index, anterior vertebral height, posterior vertebral height, computed tomography value, adjacent vertebral re-fracture, Cobb angle and wedge-shaped correction angle were evaluated. Additionally, the representative sample was selected for finite element analysis. We found that the MC-modified PMMA bone cement could achieve the same effect as that of PMMA bone cement and was associated with better vertebral height restoration in the long term.

Corrigendum to: Enhancement of BMP-2 and VEGF Carried by Mineralized Collagen for Mandibular Bone Regeneration.

[This corrects the article DOI: 10.1093/rb/rbaa022.].

The clinical results of treating Kummell's disease with mineralized collagen modified polymethyl methacrylate.

To investigate the clinical results of treating Kummell's Disease by using mineralized collagen modified polymethyl methacrylate bone cement, 23 cases (23 vertebras) who sustained Kummell's Disease treated with mineralized collagen modified polymethyl methacrylate bone cement from July 2017 to February 2019 were reviewed retrospectively. The visual analogue scale, vertebral body height, Cobb angle, CT values pre-operation and post-operation as well as incidence of complications were observed. All the patients were successfully followed up with an average period of 11.3 months (ranging from 6 to 12 months). The patients could ambulate on the second day after the operation. The visual analogue scale scores significantly decreased from two days after the operation to the last follow-up compared with that before the operation (p < 0.05); the average vertebral height and local Cobb angle had significant recovery (p < 0.05); the CT value of the treated vertebra significantly increased compared with that before the operation (p < 0.05). Bone cement leakage occurred in one case, anterior edge leakage occurred in one case, and no clinical symptoms caused by bone cement leakage occurred. No re-fracture of the treated vertebral body or adjacent vertebral bodies were observed in the follow-ups. With good osteogenic activity and degradable absorption characteristics, mineralized collagen was compounded with the existing polymethyl methacrylate bone cement to reduce its strength in the vertebral body and enhance biocompatibility, the incidence of adjacent vertebral fractures and re-fractures within the injured vertebrae is significantly reduced, and good clinical results are obtained, which is worthy of popularization.

Inflammation and immunity gene expression profiling of macrophages on mineralized collagen.

Mineralized collagen (MC) is a biomaterial that is commonly used in the treatment of bone defects. However, the inflammatory response after biomaterial implantation is a recurrent problem that requires urgent attention. Our previous studies on MC-macrophage interactions were descriptive but we did not perform an in-depth analysis on a genetic level to investigate the underlying mechanisms. In this study, we cultured RAW264.7 cells on MC or collagen and examined the proliferation of the macrophages by Cell Counting Kit-8 assay. We sequenced the RNA of the cultured cells to discover differential gene expression patterns and found that a total of 1183 genes were differentially expressed between the MC- and collagen-cultured groups, of which 396 genes were upregulated and 787 were downregulated. Gene ontology analysis revealed that biological processes in MC-cultured cells, such as inflammation and innate immunity, were downregulated; whereas nucleosome assembly, megakaryocyte differentiation, and chromatin assembly were upregulated. We identified several pathways associated with immunity that were significantly enriched using the Kyoto Encyclopedia of Genes and Genomes. Furthermore, we validated the differentially expressed genes from RNA sequencing by quantitative real-time polymerase chain reaction. This study provides insight into the macrophage phenotype based on the microenvironment, which is the foundation for the clinical application of MC-based interventions.

Preparation recombination human-like collagen/fibroin scaffold and promoting the cell compatibility with osteoblasts.

On this basis, a novel recombinant human-like collagen (RHLC)/silk fibroin scaffold material with high porosity and controllable aperture was prepared. The compatibility of osteoblasts (OB) with the blends was tested in vitro. The morphology, adhesion and growth of scaffold cells were observed by scanning electron microscope and laser confocal microscope. Extensive measurements, including 3-[4, 5-dimethylthiazole-2-acyl]-2, 5-diphenyl tetrabrominate assays, intracellular total protein content, and alkaline phosphatase activity assays were performed after 7 days of culture. Survival and protein content increased in RHLC/fibroin stents. LSCM and SEM results confirmed that the cells grew better in the mixed scaffolds than in the pure silk scaffolds, and showed that the cells were easy to adhere and diffuse in the RHLC/silk scaffolds. RHLC/silk fibroin scaffolds are promising biomaterials for bone tissue engineering.

Comparison of dynamic mechanical properties of dentin between deciduous and permanent teeth.

Purpose: Even though differences between deciduous and permanent dentin have been widely studied, their dynamic mechanical behavior has never been compared. The objective of the present study was to quantify the differences between deciduous and permanent dentin under cyclic mechanical loading, which is similar to masticatory stress.Materials and Methods: Deciduous and permanent teeth, respectively from children (9 ~ 12 years old) and young people (18 ~ 25 years old), were wet-sectioned perpendicular to the longitudinal axis and the central specimens of coronal dentin were evaluated by nanoscopic dynamic mechanical analysis (nanoDMA).Results: The average storage, loss, and complex moduli, as well as the hardness of deciduous dentin were significantly (p < 0.05) lower than those of permanent dentin. Moreover, the tan δ value of permanent dentin was significantly (p < 0.05) lower than that of deciduous dentin across the loading frequency range, indicating that viscoelastic behavior and loss of elastic energy were significantly reduced in the stiffer permanent dentin. All the nanoDMA responses showed a significant influence of the dynamic loading frequency (p < 0.05): Both deciduous and permanent dentin showed reduced viscoelasticty with increased loading frequencies.Conclusions: Compared with deciduous dentin, permanent dentin exhibits higher stiffness with reduced energy loss during deformation, and therefore superior mechanical characteristics for the mastication process.

Enhancement of BMP-2 and VEGF carried by mineralized collagen for mandibular bone regeneration.

Repairing damage in the craniofacial skeleton is challenging. Craniofacial bones require intramembranous ossification to generate tissue-engineered bone grafts via angiogenesis and osteogenesis. Here, we designed a mineralized collagen delivery system for BMP-2 and vascular endothelial growth factor (VEGF) for implantation into animal models of mandibular defects. BMP-2/VEGF were mixed with mineralized collagen which was implanted into the rabbit mandibular. Animals were divided into (i) controls with no growth factors; (ii) BMP-2 alone; or (iii) BMP-2 and VEGF combined. CT and hisomputed tomography and histological staining were performed to assess bone repair. New bone formation was higher in BMP-2 and BMP-2-VEGF groups in which angiogenesis and osteogenesis were enhanced. This highlights the use of mineralized collagen with BMP-2/VEGF as an effective alternative for bone regeneration.

Minimally invasive injectable lumbar interbody fusion with mineralized collagen-modified PMMA bone cement: A new animal model.

This study was to develop a feasible and safe animal model for minimally invasive injectable lumbar interbody fusion using a novel biomaterial, mineralized collagen-polymethylmethacrylate bone cement (MC-PMMA), with unilateral pedicle screw fixation in an in vivo goat model. Eight goats (Capra aegagrus hircus) were divided into three groups: MC-PMMA, unmodified commercial-polymethylmethacrylate bone cement (UC-PMMA), and a control group (titanium cage filled with autogenous bone, TC-AB). Each group of goats was treated with minimally invasive lumbar interbody fusion at the L3/L4 and L5/L6 disc spaces (injected for MC-PMMA and UC-PMMA, implanted for TC-AB). The pedicle screws were inserted at the L3, L4, L5, and L6 vertebrae, respectively, and fixed on the left side. The characteristics of osteogenesis and bone growth were assessed at the third and the sixth month, respectively. The methods of evaluation included the survival of each animal, X-ray imaging, and 256-layer spiral computed tomography (256-CT) scanning, imaged with three-dimensional microfocus computed tomography (micro-CT), and histological analysis. The results showed that PMMA bone cement can be extruded smoothly after doping MC, the MC-PMMA integrates better with bone than the UC-PMMA, and all goats recovered after surgery without nerve damage. After 3 and 6 months, the implants were stable. New trabecular bone was observed in the TC-AB group. In the UC-PMMA group a thick fibrous capsule had formed around the implants. The MC-PMMA was observed to have perfect osteogenesis and bone ingrowth to adjacent bone surface. Minimally invasive injectable lumbar interbody fusion using MC-PMMA bone cement was shown to have profound clinical value, and the MC-PMMA showed potential application prospects.

Poly(methyl methacrylate) bone cement composited with mineralized collagen for osteoporotic vertebral compression fractures in extremely old patients.

To examine the clinical effects of a new bone cement composed of poly(methyl methacrylate) (PMMA) and mineralized collagen (MC) compared with pure PMMA bone cement in treating osteoporotic vertebral compression fractures (OVCFs) in patients aged over 80. In all, 32 cases using pure PMMA bone cement and 31 cases using MC-modified PMMA (MC-PMMA) bone cement for OVCFs between June 2014 and March 2016 were screened as PMMA group and MC-PMMA group, respectively, with an average age of over 80. The operation duration, intraoperative blood loss, hospital stay, oswestry disability index (ODI), visual analogue scale (VAS), anterior vertebral height (AVH), intermediate vertebral height (IVH) and posterior vertebral height (PVH) of injured vertebrae, vertebral computed tomography value, re-fracture rate of adjacent vertebrae, correction rate of spinal kyphotic angle and wedge-shaped vertebra angle and surgical complications were compared between the two groups. In the early post-operative period, the VAS, ODI, AVH and IVH in MC-PMMA group were comparable to those in the traditional PMMA group. Moreover, the MC-PMMA group showed better effects compared with the PMMA group 12 months after surgery. Thus, this new bone cement has superior clinic effects in the long term.

Tuning pore features of mineralized collagen/PCL scaffolds for cranial bone regeneration in a rat model.

Porosity is indispensable for a bone tissue-engineered scaffold for facilitating endogenous cell migration and nascent bone ingrowth. In large-sized cranial bone defect repair, porous scaffolds meet great challenges to match cranial bone regeneration and provide sufficient protection with structural integrity. Therefore, the pore features of the scaffolds for cranial bone regeneration should differ from those typical porous scaffolds used in tubular bone repair and be finely tuned. In this study, a series of porous mineralized collagen/PCL scaffolds with different pore features were fabricated via freeze-drying and applied in a Sprague Dawley rat cranial bone calvarial defect model. The pore size for four groups increased from 10-45 µm to 40-130 µm. As scaffold porosity increased, the compressive strength decreased from 2.09 ±â€¯0.12 MPa to 0.51 ±â€¯0.04 MPa. The micro-computed tomography three-dimensional reconstruction images showed that as pore size and porosity increased, the amount of new bone formation had a maximum in group 3 (pore size: 20-100 µm, compressive strength: 1.06 ±â€¯0.03 MPa). In addition, the histological and histomorphometric analyses showed a consistent tendency which confirmed the Micro-CT results. Meanwhile, histological findings including bony bridging, tissue response at the bone-implant interface and fibrous capsule thickness indicated that the dura mater pathway played the most important role in the regenerative process of this calvarial defect model.

Enhanced angiogenesis by the hyaluronic acid hydrogels immobilized with a VEGF mimetic peptide in a traumatic brain injury model in rats.

Angiogenesis plays an important role in brain injury repair, which contributes to the reconstruction of regenerative neurovascular niche for promoting axonal regeneration in the lesion area. As a major component of developing brain extracellular matrix, hyaluronic acid (HA) has attracted more attention as a supporting matrix for brain repair. In the present study, HA-KLT hydrogel was developed via modifying HA with a VEGF mimetic peptide of KLT (KLTWQELYQLKYKGI). The characterization of the hydrogel shows that it could provide a porous, three-dimensional scaffold structure, which has a large specific surface area available for cell adhesion and interaction. Compared with the unmodified HA hydrogel, the HA-KLT hydrogel could effectively promote the attachment, spreading and proliferation of endothelial cells in vitro. Furthermore, the pro-angiogenic ability of hydrogels in vivo was evaluated by implanting them into the lesion cavities in the injured rat brain. Our results showed that the hydrogels could form a permissive interface with the host tissues at 4 weeks after implantation. Moreover, they could efficiently inhibit the formation of glial scars at the injured sites. The HA-KLT hydrogel could significantly increase the expression of endoglin/CD105 and promote the formation of blood vessels, suggesting that HA-KLT hydrogel promoted angiogenesis in vivo. Collectively, the HA-KLT hydrogel has the potential to repair brain defects by promoting angiogenesis and inhibiting the formation of glial-derived scar tissue.

A novel 3D printed cage with microporous structure and in vivo fusion function.

In this study, a novel 3D printed porous titanium cage (3D printed cage) with interconnected pores inside was designed and manufactured. Observations by scanning electron microscopy showed that the inside of the 3D printed cage had an octahedral porous structure, with the pores uniform in size and connected to each other. The mechanical properties analysis found that the Young's modulus and compressive strength of the porous structure were close to those of the bone structure, and the overall stiffness was slightly higher than that of the polyether ether ketone (PEEK) material, but was significantly lower than that of the titanium alloy solid module. Animal experiments indicated that the new 3D printed cage was equivalent to PEEK cage in fusion time. At 3 months, the new bone grew into the cage through the pores of the new 3D printed cage surface, which had a high bone contact rate. These results demonstrate that the 3D printed porous titanium cage has good biocompatibility and osseointegration, and has a potential clinical value as bone implants. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Mineralized Collagen Modified Polymethyl Methacrylate Bone Cement for Osteoporotic Compression Vertebral Fracture at 1-Year Follow-up.

STUDY DESIGN: Retrospective comparative study. OBJECTIVE: This study aimed to compare the clinical effects and imaging features of polymethyl methacrylate (PMMA) bone cement with and without mineralized collagen (MC) in percutaneous kyphoplasty (PKP) for osteoporotic vertebral compression fractures (OVCFs). SUMMARY OF BACKGROUND DATA: PKP with PMMA is widely performed for OVCF. However, numerous complications have also been reported about the PMMA bone cement. Moreover, PMMA bone cement with and without MC have not been compared with respect to their postoperative efficacy and long-term follow-up. METHODS: From July 2016 to July 2017, 105 OVCF patients were randomly divided into two groups based on their PKP treatment: MC-PMMA group and PMMA group. Clinical operation, cement leakage, Oswestry Disability Index, visual analog scale, height of the fractured vertebrae, Cobb angle, refracture of the adjacent vertebra, recompression, and computed tomography values of the injured vertebra were compared between the two groups postoperatively and after 1-year follow-up. RESULTS: Clinical operation showed no differences between the two groups. Visual analog scale scores, Oswestry Disability Index scores, and Cobb angles showed statistically significant differences between the two groups after 1-year follow-up. The height of the vertebral body showed significant difference at 3 days postoperatively and preoperatively in each group and significant difference after 1 year between the two groups. The rate of refracture and leakage of the MC-PMMA group was lower than that of the PMMA group. The computed tomography value of the MC-PMMA group was obviously higher than that of the PMMA group after 1-year follow-up. CONCLUSION: MC-modified PMMA did not change the beneficial properties of PMMA. This new bone cement has better biocompatibility, can form a stable structure in the vertebral body, and improve the prognosis of patients by reducing pain and reoperation. LEVEL OF EVIDENCE: 3.

A high-strength mineralized collagen bone scaffold for large-sized cranial bone defect repair in sheep.

Large-sized cranial bone defect repair presents a great challenge in the clinic. The ideal cranioplasty materials to realize the functional and cosmetic recovery of the defect must have sufficient mechanical support, excellent biocompatibility, good osseointegration and biodegradability as well. In this study, a high-strength mineralized collagen (MC) bone scaffold was developed with biomimetic composition, microstructure and mechanical properties for the repair of sheep large-sized cranial bone defects in comparison with two traditional cranioplasty materials, polymethyl methacrylate and titanium mesh. The compact MC scaffold showed no distinct pore structure and therefore possessed good mechanical properties. The strength and elastic modulus of the scaffold were much higher than those of natural cancellous bone and slightly lower than those of natural compact bone. In vitro cytocompatibility evaluation revealed that the human bone marrow mesenchymal stem cells (hBMSC) had good viability, attachment and proliferation on the compact MC scaffold indicating its excellent biocompatibility. An adult sheep cranial bone defect model was constructed to evaluate the performances of these cranioplasty materials in repairing the cranial bone defects. The results were investigated by gross observation, computed tomography scanning as well as histological assessments. The in vivo evaluations indicated that compact MC scaffold showed notable osteoconductivity and osseointegration with surrounding cranial bone tissues by promoting bone regeneration. Our results suggested that the compact MC scaffold has a promising potential for large-sized cranial bone defect repair.

Callicarpa nudiflora loaded on chitosan-collagen/organomontmorillonite composite membrane for antibacterial activity of wound dressing.

A biopolymer membrane chitosan-collagen/organomontmorillonite loaded with Callicarpa nudiflora (CS-COL/CN-OMMT) was prepared as a wound dressing. Three composite membranes including chitosan-collagen (CS-COL), chitosan-collagen/montmorillonite (CS-COL/MMT) and chitosan-collagen/organomontmorillonite (CS-COL/OMMT) were studied from physicochemical, swelling ratio, degradation ratio in vitro and moisture permeability properties. The CS-COL/OMMT composite membrane with porous layered structure exhibited a significantly higher swelling ratio, lower degradation ratio and rather excellent moisture permeability properties than other membranes. Callicarpa nudiflora were loaded on CS-COL/OMMT composite membrane to improve antibacterial activity from 20.20 ±â€¯0.50% to 68.60 ±â€¯0.10%.

An Antimicrobial Peptide-Loaded Gelatin/Chitosan Nanofibrous Membrane Fabricated by Sequential Layer-by-Layer Electrospinning and Electrospraying Techniques.

Guided bone regeneration (GBR) technique is widely used in the treatment of bone defects caused by peri-implantitis, periodontal disease, etc. However, the GBR membranes commonly used in clinical treatments currently have no antibacterial activity. Therefore, in this study, sequential layer-by-layer electrospinning and electrospraying techniques were utilized to prepare a gelatin (Gln) and chitosan (CS) composite GBR membrane containing hydroxyapatite nanoparticles (nHAp) and antimicrobial peptide (Pac-525)-loaded PLGA microspheres (AMP@PLGA-MS), which was supposed to have osteogenic and antibacterial activities. The scanning electron microscope (SEM) observation showed that the morphology of the nanofibers and microspheres could be successfully produced. The diameters of the electrospun fibers with and without nHAp were 359 ± 174 nm and 409 ± 197 nm, respectively, and the mechanical properties of the membrane were measured according to the tensile stress-strain curve. Both the involvement of nHAp and the chemical crosslinking were able to enhance their tensile strength. In vitro cell culture of rat bone marrow mesenchymal stem cells (rBMSCs) indicated that the Gln/CS composite membrane had an ideal biocompatibility with good cell adhesion, spreading, and proliferation. In addition, the Gln/CS membrane containing nHAp could promote osteogenic differentiation of rBMSCs. Furthermore, according to the in vitro drug release assay and antibacterial experiments, the composite GBR membrane containing AMP@PLGA-MS exhibited a long-term sustained release of Pac-525, which had bactericidal activity within one week and antibacterial activity for up to one month against two kinds of bacteria, S. aureus and E. coli. Our results suggest that the antimicrobial peptide-loaded Gln/CS composite membrane (AMP@PLGA-MS@Gln/CS/nHAp) has a great promise in bone generation-related applications for the unique functions of guiding bone regeneration and inhibiting bacterial infection as well.

The observed difference of RAW264.7 macrophage phenotype on mineralized collagen and hydroxyapatite.

Understanding the interaction between biomaterials and the immune system has become increasingly important. Mineralized collagen (MC) has the same chemical components and microstructures to natural bone tissue, and is considered as a better biomaterial for bone prostheses compared to hydroxyapatite (HA). However, there is little information about how MC affects inflammatory responses. In this study, we investigate the inflammatory responses to MC and HA by culturing RAW264.7 cells on their surfaces. We observed that MC increases CD206+ staining and IL-10 (M2 macrophages), whereas HA shows cells expressing more CD86 and secreting more TNF-α. This result indicates that MC may attenuate inflammatory responses to implanted bone prostheses.

A review on the exploitation of biodegradable magnesium-based composites for medical applications.

In recent years, materials science research based on magnesium (Mg) alloys has increased significantly due to their notable advantages over traditional metals. However, magnesium alloys are susceptible to excessive degradation and subsequent disruption of mechanical integrity; this phenomenon limits the utility of these materials. Mg alloys can thus be combined with other materials to form composites for medical applications. The present article describes key advances in and considerations for the development of biodegradable Mg-based composites (BMCs). The primary characteristics of these materials include their controllable degradation rates, tunable mechanical properties, adjustable structures to promote tissue repair, improved biocompatibility, and added functionality according to the purpose of the applications. Here we provide an overview of the current research on and development status of BMCs for biomedical materials, including the present limitations and challenges of their use. Finally, this paper comprehensively discusses the most promising directions of future development for these materials.