Dual-functional 3D-printed composite scaffold for inhibiting bacterial infection and promoting bone regeneration in infected bone defect models

Imaging Manifestations and Evaluation of Postoperative Complications of Bone and Joint Infections under Deep Learning

To explore and evaluate the imaging manifestations of postoperative complications of bone and joint infections based on deep learning, a retrospective study was performed on 40 patients with bone and joint infections in the Department of Orthopedics of Orthopedics Hospital of Henan Province of Luoyang City. Sensitivity and Dice similarity coefficient (DSC) were used to evaluate the image results by convolutional neural network (CNN) algorithm. Imaging features of postoperative complications in 40 patients were analyzed. Then, three imaging methods were used to diagnose the features. Sensitivity and specificity were used to evaluate the diagnostic performance of three imaging methods for imaging features. Compared with professional doctors and biomarker algorithms, the sensitivity of CNN algorithm proposed was 90.6%, and DSC was 84.1%. Compared with traditional methods, the CNN algorithm has higher image resolution and wider and more accurate lesion area recognition and division. The three manifestations of soft tissue abscess, periosteum swelling, and bone damage were postoperative imaging features of bone and joint infections. In addition, compared with X-ray, CT examination and MRI examination were better for the examination of imaging characteristics. CT and MRI had higher sensitivity and specificity than X-ray. The experimental results show that CNN algorithm can effectively identify and divide pathological images and assist doctors to diagnose the images more efficiently in clinic.

Bone Scaffolds: An Incorporation of Biomaterials, Cells, and Biofactors

Large injuries to bones are still one of the most challenging musculoskeletal problems. Tissue engineering can combine stem cells, scaffold biomaterials, and biofactors to aid in resolving this complication. Therefore, this review aims to provide information on the recent advances made to utilize the potential of biomaterials for making bone scaffolds and the assisted stem cell therapy and use of biofactors for bone tissue engineering. The requirements and different types of biomaterials used for making scaffolds are reviewed. Furthermore, the importance of stem cells and biofactors (growth factors and extracellular vesicles) in bone regeneration and their use in bone scaffolds and the key findings are discussed. Lastly, some of the main obstacles in bone tissue engineering and future trends are highlighted.

A biopolymer hydrogel electrostatically reinforced by amino-functionalized bioactive glass for accelerated bone regeneration

Composite hydrogels incorporating natural polymers and bioactive glass (BG) are promising materials for bone regeneration. However, their applications are compromised by the poor interfacial compatibility between organic and inorganic phases. In this study, we developed an electrostatically reinforced hydrogel (CAG) with improved interfacial compatibility by introducing amino-functionalized 45S5 BG to the alginate/gellan gum (AG) matrix. BAG composed of AG and unmodified BG (10 to 100 μm in size) was prepared as a control. Compared with BAG, CAG had a more uniform porous structure with a pore size of 200 μm and optimal compressive strength of 66 kPa. Furthermore, CAG promoted the M2 phenotype transition of macrophages and up-regulated the osteogenic gene expression of stem cells. The new bone formation in vivo was also accelerated due to the enhanced biomineralization of CAG. Overall, this work suggests CAG with improved interfacial compatibility is an ideal material for bone regeneration application.

Osteogenic Capability of Vaterite-Coated Nonwoven Polycaprolactone Scaffolds for In Vivo Bone Tissue Regeneration

In current orthopedic practice, bone implants used to-date often exhibit poor osteointegration, impaired osteogenesis, and, eventually, implant failure. Actively pursued strategies for tissue engineering could overcome these shortcomings by developing new hybrid materials with bioinspired structure and enhanced regenerative potential. In this study, the osteogenic and therapeutic potential of bioactive vaterite is investigated as a functional component of a fibrous polymeric scaffold for bone regeneration. Hybrid two-layered polycaprolactone scaffolds coated with vaterite (PCL/CaCO₃ ) are studied during their 28-days implantation period in a rat femur defect. After this period, the study of tissue formation in the defected area is performed by the histological study of femur cross-sections. Immobilization of alkaline phosphatase (ALP) into PCL/CaCO₃ scaffolds accelerates new bone tissue formation and defect repair. PCL/CaCO₃ and PCL/CaCO₃ /ALP scaffolds reveal 37.3% and 62.9% areas, respectively, filled with newly formed bone tissue in cross-sections compared to unmineralized PCL scaffold (17.5%). Bone turnover markers are monitored on the 7th and 28th days after implantation and reveal an increase of osteocalcin level for both PCL/CaCO₃ and PCL/CaCO₃ /ALP compared with PCL indicating the activation of osteogenesis. These findings indicate that vaterite, as an osteoconductive component of polymeric scaffolds, promotes osteogenesis, supports angiogenesis, and facilitates bone defect repair.

Complementary Effect of Non-Persistent Silver Nano-Architectures and Chlorhexidine on Infected Wound Healing

Surgical site infection (SSI) substantially contributes each year to patients' morbidity and mortality, accounting for about 15% of all nosocomial infections. SSI drastically increases the rehab stint and expenses while jeopardizing health outcomes. Besides prevention, the treatment regime relies on an adequate antibiotic therapy. On the other hand, resistant bacterial strains have currently reached up to 34.3% of the total infections, and this percentage grows annually, reducing the efficacy of the common treatment schemes. Thus, new antibacterial strategies are urgently demanded. Here, we demonstrated in rats the effectiveness of non-persistent silver nano-architectures (AgNAs) in infected wound healing together with their synergistic action in combination with chlorhexidine. Besides the in vivo efficacy evaluation, we performed analysis of the bacteriological profile of purulent wound, histological evaluations, and macrophages polarization quantifications to further validate our findings and elucidate the possible mechanisms of AgNAs action on wound healing. These findings open the way for the composition of robust multifunctional nanoplatforms for the translation of safe and efficient topical treatments of SSI.

A 3D printed Ga containing scaffold with both anti-infection and bone homeostasis-regulating properties for the treatment of infected bone defects

Large bone defects face a high risk of infection, which can also lead to bone homeostasis disorders. This seriously hinders the bone healing process; therefore, the help of a dual-functional scaffold that has both anti-infection and bone-homeostasis-regulating capacities is needed in the treatment of infected bone defects. In this study, a 3D printed dual-functional scaffold composed of poly-ε-caprolactone (PCL), mesoporous bioactive glasses (MBG), and gallium (Ga) was produced. In vitro experiments demonstrated the excellent antibacterial ability of the PCL/MBG/Ga scaffold against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). The scaffold also significantly inhibited osteoclastic activity and promoted osteogenic differentiation. Furthermore, a rabbit model with an infected bone defect in the radius was used to evaluate the in vivo bone healing capability of PCL/MBG/Ga. The results demonstrate that the PCL/MBG/Ga scaffold can significantly accelerate bone healing and prevent bone resorption, suggesting its potential for application in repairing infected bone defects.

Dual-functional hybrid quaternized chitosan/Mg/alginate dressing with antibacterial and angiogenic potential for diabetic wound healing

BACKGROUND

Clinic treatment of diabetic foot ulcers (DFUs) is considerably challenging. Impaired wound healing may be caused by poor vascularization and dysfunction of the extracellular matrix, which leads to poor re-epithelialization and increased risk of infection. In this study, we evaluated the treatment potential of a functional dressing comprising quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan) and magnesium (Mg) on DFUs.

METHODS

Dressings were prepared by vacuum freeze-drying. The cellular proliferation, migration, and angiogenesis potential of the functional dressings were determined in vitro. Methicillin-resistant Staphylococcus aureus (MRSA, ATCC43300) and methicillin-resistant Staphylococcus epidermidis 287 (MRSE287) were used to evaluate the antibacterial efficiency of the dressings. Finally, a diabetic rat model with infected wounds was used to further evaluate the effects of functional dressings on the healing of DFUs.

RESULTS

Functional dressings facilitated the migration of human dermal fibroblasts and human umbilical vein endothelial cells (HUVECs), while also stimulating angiogenesis in HUVECs. Additionally, the functional dressing could effectively eradicate MRSA and MRSE, exhibiting excellent antibacterial ability against drug-resistant bacteria. The results of in vivo microbiological and histological tests demonstrated effective anti-infection ability and wound-healing potential of this functional dressing.

CONCLUSIONS

The dual-functional dressing exhibited wound-healing ability and anti-infection efficiency, demonstrating potential application prospects in DFU treatment.

TRANSLATIONAL POTENTIAL OF THIS ARTICLE

As one of the common and serious complications of diabetes, DFUs do not heal easily, causing great suffering to patients. Therefore, improvement in the prognosis of DFUs is a crucial clinical need. The dual-functional dressing prepared in this study was proven to improve the treatment of DFUs, both in vitro and in vivo. Considering its urgent clinical necessity and good biocompatibility of its raw materials, such as alginate, Mg, and chitosan derivatives, this dual-functional dressing presents good prospects for clinical translation.

Antibacterial efficacy of quaternized chitosan coating on 3D printed titanium cage in rat intervertebral disc space

BACKGROUND CONTEXT

Infection around intervertebral fusion cages can be intractable because of the avascular nature of the intervertebral disc space. Intervertebral cages with antibacterial effects may be a method by which this complication can be prevented.

PURPOSE

To investigate the bacterial load on the antibacterial coating cages for spinal interbody fusion STUDY DESIGN: An experimental in vitro and in vivo study.

METHODS

Based on the micro-computed tomography (CT) data of rat caudal discs, mesh-like titanium (Ti) cages that anatomically fit into the discs were fabricated by three-dimensional (3D) printing. Additionally, an antibacterial coating was applied with quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan, HACC). In vitro release kinetics of the HACC was performed, and the antibacterial performance of the HACC-coated (Ti-HACC) cages (via inhibition zone assay, bacterial adhesion assay, and biofilm formation assay) was evaluated. Then, Ti-HACC- or noncoated (Ti) cages were implanted in the caudal discs of rats with bioluminescent Staphylococcus aureus. Bacterial survival was investigated using an in vivo imaging system (IVIS) on postoperative days 1, 3, and 5. On day 5, the infection-related changes (bone destruction and migration of cages) were assessed using micro-CT, and the healing status of the surgical wounds was also assessed. After the removal of the cages, the quantification of bacteria attached to the cages was obtained by IVIS. Histological evaluation was performed by hematoxylin and eosin staining and TRAP (tartrate-resistant acid phosphatase) staining.

RESULTS

Release kinetic analysis showed the sustained release of HACC over 3 days from Ti-HACC cages. Antibacterial effects of Ti-HACC cages were demonstrated in all in vitro assays. IVIS evaluation indicated that the in vivo implantation of Ti-HACC cages with S. aureus exhibited better wound healing, less infection-related changes on micro-CT, and reduced bacterial quantity in the extracted cages compared to Ti cages. Histological evaluation demonstrated an increased number of TRAP-positive osteoclasts and severe bone destruction in the rats treated with Ti cages.

CONCLUSIONS

We developed a novel antibacterial HACC-coated intervertebral cage that exhibited prominent antibacterial efficacy and prevented the structural damage caused by the infection in rat caudal discs.

CLINICAL SIGNIFICANCE

HACC-coated titanium intervertebral cages may be a promising option for preventing intractable postoperative infection in spinal interbody fusion surgery.

Chitosan-based 3D-printed scaffolds for bone tissue engineering

Despite the spontaneous regenerative properties of autologous bone grafts, this technique remains dilatory and restricted to fractures and injuries. Conventional grafting strategies used to treat bone tissue damage have several limitations. This highlights the need for novel approaches to overcome the persisting challenges. Tissue-like constructs that can mimic natural bone structurally and functionally represent a promising strategy. Bone tissue engineering (BTE) is an approach used to develop bioengineered bone with subtle architecture. BTE utilizes biomaterials to accommodate cells and deliver signaling molecules required for bone rejuvenation. Among the various techniques available for scaffold creation, 3D-printing technology is considered to be a superior technique as it enables the design of functional scaffolds with well-defined customizable properties. Among the biomaterials obtained from natural, synthetic, or ceramic origins, naturally derived chitosan (CS) polymers are promising candidates for fabricating reliable tissue constructs. In this review, the physicochemical-biological properties and applications of CS-based 3D-printed scaffolds and their future perspectives in BTE are summarized.

Recent advances in PLGA-based biomaterials for bone tissue regeneration

Bone regeneration is an interdisciplinary complex lesson, including but not limited to materials science, biomechanics, immunology, and biology. Having witnessed impressive progress in the past decades in the development of bone substitutes; however, it must be said that the most suitable biomaterial for bone regeneration remains an area of intense debate. Since its discovery, poly (lactic-co-glycolic acid) (PLGA) has been widely used in bone tissue engineering due to its good biocompatibility and adjustable biodegradability. This review systematically covers the past and the most recent advances in developing PLGA-based bone regeneration materials. Taking the different application forms of PLGA-based materials as the starting point, we describe each form's specific application and its corresponding advantages and disadvantages with many examples. We focus on the progress of electrospun nanofibrous scaffolds, three-dimensional (3D) printed scaffolds, microspheres/nanoparticles, hydrogels, multiphasic scaffolds, and stents prepared by other traditional and emerging methods. Finally, we briefly discuss the current limitations and future directions of PLGA-based bone repair materials. STATEMENT OF SIGNIFICANCE: As a key synthetic biopolymer in bone tissue engineering application, the progress of PLGA-based bone substitute is impressive. In this review, we summarized the past and the most recent advances in the development of PLGA-based bone regeneration materials. According to the typical application forms and corresponding crafts of PLGA-based substitutes, we described the development of electrospinning nanofibrous scaffolds, 3D printed scaffolds, microspheres/nanoparticles, hydrogels, multiphasic scaffolds and scaffolds fabricated by other manufacturing process. Finally, we briefly discussed the current limitations and proposed the newly strategy for the design and fabrication of PLGA-based bone materials or devices.

Trends in Managing Cardiac and Orthopaedic Device-Associated Infections by Using Therapeutic Biomaterials

Over the years, there has been an increasing number of cardiac and orthopaedic implanted medical devices, which has caused an increased incidence of device-associated infections. The surfaces of these indwelling devices are preferred sites for the development of biofilms that are potentially lethal for patients. Device-related infections form a large proportion of hospital-acquired infections and have a bearing on both morbidity and mortality. Treatment of these infections is limited to the use of systemic antibiotics with invasive revision surgeries, which had implications on healthcare burdens. The purpose of this review is to describe the main causes that lead to the onset of infection, highlighting both the biological and clinical pathophysiology. Both passive and active surface treatments have been used in the field of biomaterials to reduce the impact of these infections. This includes the use of antimicrobial peptides and ionic liquids in the preventive treatment of antibiotic-resistant biofilms. Thus far, multiple in vivo studies have shown efficacious effects against the antibiotic-resistant biofilm. However, this has yet to materialize in clinical medicine.

An overview of polyester/hydroxyapatite composites for bone tissue repairing

Objectives

The polyester/hydroxyapatite (polyester/HA) composites play an important role in bone tissue repairing, mostly because they mimic the composition and structure of naturally mineralized bone tissue. This review aimed to discuss commonly used geometries of polyester/HA composites, including microspheres, membranes, scaffolds and bulks, and their applications in bone tissue repairing and to discuss existed restrictions and developing trends of polyester/HA.

Methods

The current review was conducted by searching Web of Science, and Google Scholar for relevant studies published related with polyester/HA composites. Selected studies were analyzed with a focus on the fabrication techniques, properties (mechanical properties, biodegradable properties and biological properties) and applications of polyester/HA composites in bone repairing.

Results

A total of 111 articles were introduced to discuss the review. Different geometries of polyester/HA composites were discussed. In addition, properties and applications of polyester/HA composites were evaluated. The addition of HA into polyester can adjust the mechanical and biodegradability of composites. Besides, the addition of HA into polyester can improve its osteogenic abilities. The results showed that polyester/HA composites can ideal candidate for bone tissue repairing.

Conclusion

Polyester/HA composites have many remarkable properties, such as appropriate mechanical strength, biodegradability, favorable biological properties. Diverse geometries of polyester/HA composites have been used in bone repairing, drug delivery and implant fixation. Further work needs to be done to investigate existed restrictions, including the controlled degradation rate, controlled drug release performance, well-matched mechanical properties, and novel fabrication techniques.

The translational potential of this article

The present review reveals the current state of the polyester/HA composites used in bone tissue repairing, contributing to future trends of polyester/HA composites in the forthcoming future.

Thermosensitive quaternized chitosan hydrogel scaffolds promote neural differentiation in bone marrow mesenchymal stem cells and functional recovery in a rat spinal cord injury model

A thermosensitive quaternary ammonium chloride chitosan/β-glycerophosphate (HACC/β-GP) hydrogel scaffold combined with bone marrow mesenchymal stem cells (BMSCs) transfected with an adenovirus containing the glial cell-derived neurotrophic factor (GDNF) gene (Ad-rGDNF) was applied to spinal cord injury (SCI) repair. The BMSCs from rats were transfected with Ad-rGDNF, resulting in the expression of GDNF mRNA in the BMSCs increasing and their spontaneous differentiation into neural-like cells expressing neural markers such as NF-200 and GFAP. After incubation with HACC/β-GP hydrogel scaffolds for 2 weeks, neuronal differentiation of the BMSCs was confirmed using immunofluorescence (IF), and the expression of GDNF by the BMSCs was detected by Western blot at different time points. MTT assay and scanning electron microscopy confirmed that the HACC scaffold provides a non-cytotoxic microenvironment that supports cell adhesion and growth. Rats with SCI were treated with BMSCs, BMSCs carried by the HACC/β-GP hydrogel (HACC/BMSCs), Ad-rGDNF-BMSCs, or Ad-rGDNF-BMSCs carried by the hydrogel (HACC/GDNF-BMSCs). Animals were sacrificed at 2, 4, and 6 weeks of treatment. IF staining and Western blot were performed to detect the expression of NeuN, NF-200, GFAP, CS56, and Bax in the lesion sites of the injured spinal cord. Upon treatment with HACC/BMSCs, NF200 and GFAP were upregulated but CS56 and Bax were downregulated in the SCI lesion site. Furthermore, transplantation of HACC/GDNF-BMSCs into an SCI rat model significantly improved BBB scores and regeneration of the spinal cord. Thus, HACC/β-GP hydrogel scaffolds show promise for functional recovery in spinal cord injury patients.

Constructing a biomimetic nanocomposite with the in situ deposition of spherical hydroxyapatite nanoparticles to induce bone regeneration

Inspired by the nanostructure of bone, biomimetic nanocomposites comprising natural polymers and inorganic nanoparticles have gained much attention for bone regenerative applications. However, the mechanical and biological performances of nanocomposites are largely limited by the inhomogeneous distribution, uncontrolled size and irregular morphology of inorganic nanoparticles at present. In this work, an innovative in situ precipitation method has been developed to construct a biomimetic nanocomposite which consists of spherical hydroxyapatite (HA) nanoparticles and gelatin (Gel). The homogeneous dispersion of HA nanoparticles in nHA-Gel endowed it with a low swelling ratio, enhanced mechanical properties and slow degradation. Moreover, strontium (Sr) was incorporated into HA nanoparticles to further enhance the bioactivity of nanocomposites. In vitro experiments suggested that nHA-Gel and Sr-nHA-Gel facilitated cell spreading and promoted osteogenic differentiation of bone-marrow-derived mesenchymal stem cells (BMSCs) as compared to pure Gel and mHA-Gel conventional composites developed by mechanical mixing. In vivo rat critical-sized calvarial defect repair further confirmed that nHA-Gel and Sr-nHA-Gel possessed relatively effective bone regenerative abilities among the four groups. Collectively, the biomimetic nanocomposites of nHA-Gel and Sr-nHA-Gel have good efficacy in inducing bone regeneration and would be a promising alternative to bone grafts for clinical applications.

Antibacterial biomaterials in bone tissue engineering

Bone infection is a devastating disease characterized by recurrence, drug-resistance, and high morbidity, that has prompted clinicians and scientists to develop novel approaches to combat it. Currently, although numerous biomaterials that possess excellent biocompatibility, biodegradability, porosity, and mechanical strength have been developed, their lack of effective antibacterial ability substantially limits bone-defect treatment efficacy. There is, accordingly, a pressing need to design antibacterial biomaterials for effective bone-infection prevention and treatment. This review focuses on antibacterial biomaterials and strategies; it presents recently reported biomaterials, including antibacterial implants, antibacterial scaffolds, antibacterial hydrogels, and antibacterial bone cement types, and aims to provide an overview of these antibacterial materials for application in biomedicine. The antibacterial mechanisms of these materials are discussed as well.

A novel biocomposite scaffold with antibacterial potential and the ability to promote bone repair

Clinical treatment of bone defects caused by trauma, tumor resection and other bone diseases, especially bone defects that can lead to infection, remains a major challenge. Currently, autologous bone implantation is the gold standard for treatment of bone defects, but it is limited by secondary trauma and insufficient autologous material. Moreover, postoperative infection is an important factor affecting bone healing.AcN-RADARADARADARADA-CONH2 (RADA) is a new type of self-assembling peptide(SAP) composed of Arg,Ala,Asp and other amino acids was designed and prepared. The "RADA" self-assembling peptide hydrogels has excellent biological activity and it's completely biodegradable and non-toxic.It is also have been confirmed to promote cell proliferation, wound healing, tissue repair, and drug delivery. To promote bone regeneration and simultaneously prevent bacterial infection, we designed biocomposite scaffolds comprising RADA and calcium phosphate cement (CPC), termed RADA-CPC. The morphological features of the scaffold were characterized by scanning electron microscopy (SEM). In vitro studies demonstrated that RADA-CPC enhances osteoblast proliferation, differentiation and mineralization. In addition, the scaffold was used as a drug delivery system to treat postoperative infections by sustained release of ciprofloxacin (CIP). The RADA-CPC scaffold may have potential application prospects in orthopedics field because of its role in promoting bone repair and as a sustained-release drug carrier to prevent infections.

Imminent antimicrobial bioink deploying cellulose, alginate, EPS and synthetic polymers for 3D bioprinting of tissue constructs

3D printing, one of its kinds has been a recent technological trend to fabricate complex and patterned biomaterial with controlled precision. With the conventional kick-start of printing metals and plastics, advancements in printing viable cells, polysaccharides or microbes themselves have been achieved. The additive antimicrobial properties in bioinks sourced from organic and inorganic materials have profound implications in tissue engineering. Cellulose, alginate, exopolysaccharides, ceramics and synthetic polymers are integrated as a viable component in inks and used for bio-printing. To date, bacterial infection and immunogenicity pose a potential health risk during a tissue implant or bone substitution. In order to mitigate microbial infection, antimicrobial bioinks with significant antimicrobial potential have been the much sought after strategies. This approach could be an effective frontline defense against microbial interference in tissue engineering and biomedical applications. An overview on the antimicrobial potential of polysaccharides as bioinks for 3D bioprinting has been critically reviewed.

Additive manufacturing pertaining to bone: Hopes, reality and future challenges for clinical applications

For the past 20 years, the democratization of additive manufacturing (AM) technologies has made many of us dream of: low cost, waste-free, and on-demand production of functional parts; fully customized tools; designs limited by imagination only, etc. As every patient is unique, the potential of AM for the medical field is thought to be considerable: AM would allow the division of dedicated patient-specific healthcare solutions entirely adapted to the patients' clinical needs. Pertinently, this review offers an extensive overview of bone-related clinical applications of AM and ongoing research trends, from 3D anatomical models for patient and student education to ephemeral structures supporting and promoting bone regeneration. Today, AM has undoubtably improved patient care and should facilitate many more improvements in the near future. However, despite extensive research, AM-based strategies for bone regeneration remain the only bone-related field without compelling clinical proof of concept to date. This may be due to a lack of understanding of the biological mechanisms guiding and promoting bone formation and due to the traditional top-down strategies devised to solve clinical issues. Indeed, the integrated holistic approach recommended for the design of regenerative systems (i.e., fixation systems and scaffolds) has remained at the conceptual state. Challenged by these issues, a slower but incremental research dynamic has occurred for the last few years, and recent progress suggests notable improvement in the years to come, with in view the development of safe, robust and standardized patient-specific clinical solutions for the regeneration of large bone defects.

Biomimetic mineralized hybrid scaffolds with antimicrobial peptides

Infection in hard tissue regeneration is a clinically-relevant challenge. Development of scaffolds with dual function for promoting bone/dental tissue growth and preventing bacterial infections is a critical need in the field. Here we fabricated hybrid scaffolds by intrafibrillar-mineralization of collagen using a biomimetic process and subsequently coating the scaffold with an antimicrobial designer peptide with cationic and amphipathic properties. The highly hydrophilic mineralized collagen scaffolds provided an ideal substrate to form a dense and stable coating of the antimicrobial peptides. The amount of hydroxyapatite in the mineralized fibers modulated the rheological behavior of the scaffolds with no influence on the amount of recruited peptides and the resulting increase in hydrophobicity. The developed scaffolds were potent by contact killing of Gram-negative Escherichia coli and Gram-positive Streptococcus gordonii as well as cytocompatible to human bone marrow-derived mesenchymal stromal cells. The process of scaffold fabrication is versatile and can be used to control mineral load and/or intrafibrillar-mineralized scaffolds made of other biopolymers.

•

A biomimetic intrafibrillar-mineralized scaffold was prepared using a non-classical pathway for mineralization.

•

The mineralized scaffold was stably coated with designer antimicrobial peptide GL13K.

•

The hybrid scaffold was cytocompatible and potent against biofilms of model Gram-positive and Gram-negative bacteria.

•

The mineral content affected the rheological properties of the scaffolds, but not the loading of antimicrobial peptides.

Challenges in Bone Tissue Regeneration: Stem Cell Therapy, Biofunctionality and Antimicrobial Properties of Novel Materials and Its Evolution

An aging population leads to increasing demand for sustained quality of life with the aid of novel implants. Patients expect fast healing and few complications after surgery. Increased biofunctionality and antimicrobial behavior of implants, in combination with supportive stem cell therapy, can meet these expectations. Recent research in the field of bone implants and the implementation of autologous mesenchymal stem cells in the treatment of bone defects is outlined and evaluated in this review. The article highlights several advantages, limitations and advances for metal-, ceramic- and polymer-based implants and discusses the future need for high-throughput screening systems used in the evaluation of novel developed materials and stem cell therapies. Automated cell culture systems, microarray assays or microfluidic devices are required to efficiently analyze the increasing number of new materials and stem cell-assisted therapies. Approaches described in the literature to improve biocompatibility, biofunctionality and stem cell differentiation efficiencies of implants range from the design of drug-laden nanoparticles to chemical modification and the selection of materials that mimic the natural tissue. Combining suitable implants with mesenchymal stem cell treatment promises to shorten healing time and increase treatment success. Most research studies focus on creating antibacterial materials or modifying implants with antibacterial coatings in order to address the increasing number of complications after surgeries that are mostly caused by bacterial infections. Moreover, treatment of multiresistant pathogens will pose even bigger challenges in hospitals in the future, according to the World Health Organization (WHO). These antibacterial materials will help to reduce infections after surgery and the number of antibiotic treatments that contribute to the emergence of new multiresistant pathogens, whilst the antibacterial implants will help reduce the amount of antibiotics used in clinical treatment.

Shapable bulk agarose-gelatine-hydroxyapatite-minocycline nanocomposite fabricated using a mineralising system aided with electrophoresis for bone tissue regeneration

To develop a shapable bulk antibacterial nanocomposite biomaterial for bone regeneration. A bulk agarose-gelatine hydrogel was through mineralised using a hydrogel mineralising system aided with electrophoresis, and the mineralised hydrogel was loaded with minocycline to obtain the agarose-gelatine-hydroxyapatite-minocycline nanocomposite. The nanocomposite had a large BET surface area of 44.4518m2/g and a high porosity of 76.9%. Hydroxyapatite crystals were well developed in the hydrogel matrix and exhibited a hybrid structure of microscale and nanoscale motifs. The addition of minocycline resulted in a continuous antibiotic release, inhibiting the growth of Staphylococcus aureus over two weeks in vitro. Exposed to rabbit bone marrow mesenchymal stem cells, the nanocomposite revealed good cytocompatibility in vitro. Furthermore, the biomaterial could effectively enhance the bone regeneration in a critical-size rabbit cranial defect model in vivo. These findings depicted that the nanocomposite, with good biocompatibility and good antibacterial property, is a promising candidate for future clinical application in bone tissue engineering or as a prospective bone replacement biomaterial.

Inside-outside Ag nanoparticles-loaded polylactic acid electrospun fiber for long-term antibacterial and bone regeneration

Bone infections caused by bacteria during bone graft implantations can impair the ability of bone tissue repair, which is currently a clinical problem. In this study, the electrospinning technique was used to prepare a polylactic acid (PLLA)/silver (Ag) composite fiber, in which the silver nanoparticles (Ag-NPs) were uniformly distributed on the inner surface of PLLA fibers; dopamine (DA) was self-polymerized on the composite fiber surface to construct the adhesive polydopamine (PDA) film and chitosan (CS) was used to regulate Ag⁺ in situ through pulse electrochemical deposition for the construction of a stable Ag-NPs coating (CS/Ag), achieving the steady and slow release of Ag-NPs, therefore accomplishing the construction of a "inside-outside" Ag-NPs-loaded PLLA/Ag@PDA@CS/Ag composite fiber with dual functions of long-lasting antibacterial effect as well as bone regeneration promotion ability. The study results showed that the composite fiber has an excellent antibacterial effect against E. coli and S. aureus, and good osteoinductive and angiogenic properties. In summary, under the dual regulations of the strong adhesion of PDA and CS chelation, the "inside-outside" Ag-NPs-loaded composite fiber was endowed with good physiological stability, long-term antibacterial effect and bone infection inhibition ability, making it a promising bone implant material.

A 3D-bioprinted scaffold with doxycycline-controlled BMP2-expressing cells for inducing bone regeneration and inhibiting bacterial infection

Large bone defects face a high risk of pathogen exposure due to open wounds, which leads to high infection rates and delayed bone union. To promote successful repair of infectious bone defects, fabrication of a scaffold with dual functions of osteo-induction and bacterial inhibition is required. This study describes creation of an engineered progenitor cell line (C3H10T1/2) capable of doxycycline (DOX)-mediated release of bone morphogenetic protein-2 (BMP2). Three-dimensional bioprinting technology enabled creation of scaffolds, comprising polycaprolactone/mesoporous bioactive glass/DOX and bioink, containing these engineered cells. In vivo and in vitro experiments confirmed that the scaffold could actively secrete BMP2 to significantly promote osteoblast differentiation and induce ectopic bone formation. Additionally, the scaffold exhibited broad-spectrum antibacterial capacity, thereby ensuring the survival of embedded engineered cells when facing high risk of infection. These findings demonstrated the efficacy of this bioprinted scaffold to release BMP2 in a controlled manner and prevent the occurrence of infection; thus, showing its potential for repairing infectious bone defects.

•

Genetic engineering and 3D bioprinting.

•

Dual-functional.

•

Suitable for infectious bone defect repair.

Characterization of an Acute Rodent Osteomyelitis Infectious Model Using a Tibial Intramedullary Implant Inoculation

Chronic osteomyelitis in presence of orthopedic implants is a condition observed in the field of biomaterials as it impairs early bone-implant contact, fixation and integration. In this study, a surgical intramedullary tibial insertion was performed using a titanium wire previously inoculated with Staphylococcus aureus in order to develop an osteomyelitis model in a clinically relevant long bone and in absence of any prophylactic treatment. As such, twenty-two male Sprague-Dawley rats received a sterile or inoculated intramedullary biomaterial with either 2 × 10⁶ or 1 × 10⁷S. aureus colony forming units. Bacterial burden, inflammation, morphological changes, as well as newly formed bone tissues were evaluated for histopathology following a period of either eight or fifteen days of implantation. The implant inoculated in presence of the highest bacterial load was effective to produce significant periprosthetic infection observations in addition to hard and soft tissue inflammation consistent with the development of osteomyelitis. In contrast, neither the sterile nor the low-dose implant inoculation showed inflammation and clinical infection signs, but rather produced an expected bone remodeling and appropriate healing associated with biomaterial implantation. Complete health assessment is presented with histopathological periprosthetic results.

Combined Effect of Naturally-Derived Biofilm Inhibitors and Differentiated HL-60 Cells in the Prevention of Staphylococcus aureus Biofilm Formation

Nosocomial diseases represent a huge health and economic burden. A significant portion is associated with the use of medical devices, with 80% of these infections being caused by a bacterial biofilm. The insertion of a foreign material usually elicits inflammation, which can result in hampered antimicrobial capacity of the host immunity due to the effort of immune cells being directed to degrade the material. The ineffective clearance by immune cells is a perfect opportunity for bacteria to attach and form a biofilm. In this study, we analyzed the antibiofilm capacity of three naturally derived biofilm inhibitors when combined with immune cells in order to assess their applicability in implantable titanium devices and low-density polyethylene (LDPE) endotracheal tubes. To this end, we used a system based on the coculture of HL-60 cells differentiated into polymorphonuclear leukocytes (PMNs) and Staphylococcus aureus (laboratory and clinical strains) on titanium, as well as LDPE surfaces. Out of the three inhibitors, the one coded DHA1 showed the highest potential to be incorporated into implantable devices, as it displayed a combined activity with the immune cells, preventing bacterial attachment on the titanium and LDPE. The other two inhibitors seemed to also be good candidates for incorporation into LDPE endotracheal tubes.

Inspired by nature: facile design of nanoclay-organic hydrogel bone sealant with multifunctional properties for robust bone regeneration

Bone repair is a complex process involving the sophisticated interplay of osteogenic stem cells, extracellular matrix, and osteoinductive factors, and it is affected by bacterial toxins and oxidative stress. Inspired by the nature of plant-derived phytochemicals and inorganic-organic analogues of the bone extracellular matrix, we report herein the facile design of a nanoclay-organic hydrogel bone sealant (NoBS) that integrates multiple physico-chemical cues for bone regeneration into a single system. Assembly of phytochemical-modified organic chitosan and silica-rich inorganic nanoclay serves as highly biocompatible and osteoconductive extracellular matrix mimics. The decorated phytochemical exerts inherent bactericidal and antioxidant activities, and acts as an intermolecular networking precursor for gelation with injectable and self-healing capabilities. Moreover, the NoBS exerts osteoinductive effects mediated by the nanoclay, which regulates the Wnt/β-catenin pathway, along with the addition of osteoinductive signals, resulting in bone regeneration in a non-healing cranial defect. Engineering of this integrated bone graft substitute with multifunctional properties inspired by natural materials may suggest a promising and effective approach for creating a favorable microenvironment for optimal bone healing.

Chitosan-based drug delivery systems: From synthesis strategy to osteomyelitis treatment - A review

Osteomyelitis is a complex disease in orthopedics mainly caused by bacterial pathogens invading bone or bone marrow. The treatment of osteomyelitis is highly difficult and it is a major challenge in orthopedic surgery. The long-term systemic use of antibiotics may lead to antibiotic resistance and has limited effects on eradicating local biofilms. Localized antibiotic delivery after surgical debridement can overcome the problem of antibiotic resistance and reduce systemic toxicity. Chitosan, a special cationic polysaccharide, is a product extracted from the deacetylation of chitin. It has numerous advantages, such as nontoxicity, biocompatibility, and biodegradability. Recently, chitosan has attracted significant attention in bacterial inhibition and drug delivery. Because chitosan contains many functional bioactive groups conducive to chemical reaction and modification, some chitosan-based biomaterials have been applied as the local antibiotic delivery systems in the treatment of osteomyelitis. This review aims to introduce recent advances in the biomedical applications of chitosan-based drug delivery systems in osteomyelitis treatment and to highlight the perspectives for further studies.

Strontium-substituted hydroxyapatite grown on graphene oxide nanosheet-reinforced chitosan scaffold to promote bone regeneration

The strontium-substituted hydroxyapatite (SrHA) is a commonly used material in bone regeneration for its good osteoconductivity and high alkaline phosphatase (ALP) activity. Scaffolds used in bone defects require a high compressive modulus. However, the SrHA nanoparticle-doped scaffold cannot properly fit the required mechanical properties. Therefore, a lot of effort has been used to fabricate synthetic bone scaffolds with biocompatibility, suitable mechanical properties, antibacterial ability and osteoconductivity. Here, we used a facile hydrothermal method to synthesize graphene oxide (GO)-reinforced SrHA nanoparticles. The incorporation of GO can be used as nucleation and growth active sites of hydroxyapatite. In addition, GO is easy to self-assemble into a layered structure in the dispersion, which can effectively regulate the deposition of hydroxyapatite on the surface of GO. The scaffold was fabricated using a freeze-drying method by incorporating SrHA/GO nanoparticles into chitosan (CS) and quaternized chitosan (QCS) mixed solutions. The compressive modulus of the CS/QCS/SrHA/GO scaffold reached 438.5 kPa, which was 4-fold higher than that of the CS/QCS scaffold. The CS/QCS/SrHA/GO scaffold exhibited significantly higher in vitro mineralization levels and ALP activity. In vivo rat skull repair indicated that the CS/QCS/SrHA/GO scaffold had a significant role in promoting bone regeneration. This study provides a new strategy for modifying hydroxyapatite to satisfy the biomedical demand of bone tissue engineering scaffolds.

Biomaterials against Bone Infection

Chronic bone infection is considered as one of the most problematic biofilm-related infections. Its recurrent and resistant nature, high morbidity, prolonged hospitalization, and costly medical care expenses have driven the efforts of the scientific community to develop new therapies to improve the standards used today. There is great debate on the management of this kind of infection in order to establish consistent and agreed guidelines in national health systems. The scientific research is oriented toward the design of anti-infective biomaterials both for prevention and cure. The properties of these materials must be adapted to achieve better anti-infective performance and good compatibility, which allow a good integration of the implant with the surrounding tissue. The objective of this review is to study in-depth the antibacterial biomaterials and the strategies underlying them. In this sense, this manuscript focuses on antimicrobial coatings, including the new technological advances on surface modification; scaffolding design including multifunctional scaffolds with both antimicrobial and bone regeneration properties; and nanocarriers based on mesoporous silica nanoparticles with advanced properties (targeting and stimuli-response capabilities).

Advanced Black Phosphorus Nanomaterials for Bone Regeneration

Bone regeneration remains a great clinical challenge. Two-dimensional materials, especially graphene and its derivative graphene oxide, have been widely used for bone regeneration. Since its discovery in 2014, black phosphorus (BP) nanomaterials including BP nanosheets and BP quantum dots have attracted considerable scientific attention and are considered as prospective graphene substitutes. BP nanomaterials exhibit numerous advantages such as excellent optical and mechanical properties, electrical conductivity, excellent biocompatibility, and good biodegradation, all of which make them particularly attractive in biomedicine. In this review, we comprehensively summarize recent advances of BP-based nanomaterials in bone regeneration. The advantages are reviewed, the different synthesis methods of BP are summarized, and the applications to promote bone regeneration are highlighted. Finally, the existing challenges and perspectives of BP in bone regeneration are briefly discussed.

Preparation of antibacterial and osteoconductive 3D-printed PLGA/Cu(I)@ZIF-8 nanocomposite scaffolds for infected bone repair

BACKGROUND

The repair of large bone defects is a great challenge in clinical practice. In this study, copper-loaded-ZIF-8 nanoparticles and poly (lactide-co-glycolide) (PLGA) were combined to fabricate porous PLGA/Cu(I)@ZIF-8 scaffolds using three-dimensional printing technology for infected bone repair.

METHODS

The surface morphology of PLGA/Cu(I)@ZIF-8 scaffolds was investigated by transmission electron microscopy and scanning electron microscopy. The PLGA/Cu(I)@ZIF-8 scaffolds were co-cultured with bacteria to determine their antibacterial properties, and with murine mesenchymal stem cells (MSCs) to explore their biocompatibility and osteoconductive properties. The bioactivity of the PLGA/Cu(I)@ZIF-8 scaffolds was evaluated by incubating in simulated body fluid.

RESULTS

The results revealed that the PLGA/Cu(I)@ZIF-8 scaffolds had porosities of 80.04 ± 5.6% and exhibited good mechanical properties. When incubated with H₂O₂, Cu(I)@ZIF-8 nanoparticles resulted generated reactive oxygen species, which contributed to their antibacterial properties. The mMSCs cultured on the surface of PLGA/Cu(I)@ZIF-8 scaffolds were well-spread and adherent with a high proliferation rate, and staining with alkaline phosphatase and alizarin red was increased compared with the pure PLGA scaffolds. The mineralization assay showed an apatite-rich layer was formed on the surface of PLGA/Cu(I)@ZIF-8 scaffolds, while there was hardly any apatite on the surface of the PLGA scaffolds. Additionally, in vitro, Staphylococcus aureus cultured on the PLGA/Cu(I)@ZIF-8 scaffolds were almost all dead, while in vivo inflammatory cell infiltration and bacteria numbers were dramatically reduced in infected rats implanted with PLGA/Cu@ZIF-8 scaffolds.

CONCLUSION

All these findings demonstrate that PLGA/Cu(I)@ZIF-8 scaffolds possess excellent antibacterial and osteoconductive properties, as well as good biocompatibility and high bioactivity. This study suggests that the PLGA/Cu(I)@ZIF-8 scaffolds could be used as a promising biomaterial for bone tissue engineering, especially for infected bone repair.

In vitro antibacterial activity and cytocompatibility of magnesium-incorporated poly(lactide-co-glycolic acid) scaffolds

BACKGROUND

Bone defects are often combined with the risk of infection in the clinic, and artificial bone substitutes are often implanted to repair the defective bone. However, the implant materials are carriers for bacterial growth, and biofilm can form on the implant surface, which is difficult to eliminate using antibiotics and the host immune system. Magnesium (Mg) was previously reported to possess antibacterial potential.

METHODS

In this study, Mg was incorporated into poly(lactide-co-glycolic acid) (PLGA) to fabricate a PLGA/Mg scaffold using a low-temperature rapid-prototyping technique. All scaffolds were divided into three groups: PLGA (P), PLGA/10 wt% Mg with low Mg content (PM-L) and PLGA/20 wt% Mg with high Mg content (PM-H). The degradation test of the scaffolds was conducted by immersing them into the trihydroxymethyl aminomethane-hydrochloric acid (Tris-HCl) buffer solution and measuring the change of pH values and concentrations of Mg ions. The antibacterial activity of the scaffolds was investigated by the spread plate method, tissue culture plate method, scanning electron microscopy and confocal laser scanning microscopy. Additionally, the cell attachment and proliferation of the scaffolds were evaluated by the cell counting kit-8 (CCK-8) assay using MC3T3-E1 cells.

RESULTS

The Mg-incorporated scaffolds degraded and released Mg ions and caused an increase in the pH value. Both PM-L and PM-H inhibited bacterial growth and biofilm formation, and PM-H exhibited higher antibacterial activity than PM-L after incubation for 24 and 48 h. Cell tests revealed that PM-H exerted a suppressive effect on cell attachment and proliferation.

CONCLUSIONS

These findings demonstrated that the PLGA/Mg scaffolds possessed favorable antibacterial activity, and a higher content of Mg (20%) exhibited higher antibacterial activity and inhibitory effects on cell attachment and proliferation than low Mg content (10%).

The combination of multi-functional ingredients-loaded hydrogels and three-dimensional printed porous titanium alloys for infective bone defect treatment

Biomaterial with the dual-functions of bone regeneration and antibacterial is a novel therapy for infective bone defects. Three-dimensional (3D)-printed porous titanium (pTi) benefits bone ingrowth, but its microporous structure conducive to bacteria reproduction. Herein, a multifunctional hydrogel was prepared from dynamic supramolecular assembly of sodium tetraborate (Na2B4O7), polyvinyl alcohol (PVA), silver nanoparticles (AgNPs) and tetraethyl orthosilicate (TEOS), and composited with pTi as an implant system. The pTi scaffolds have ideal pore size and porosity matching with bone, while the supramolecular hydrogel endows pTi scaffolds with antibacterial and biological activity. In vitro assessments indicated the 3D composite implant was biocompatible, promoted bone marrow mesenchymal stem cells (BMSCs) proliferation and osteogenic differentiation, and inhibited bacteria, simultaneously. In vivo experiments further demonstrated that the implant showed effective antibacterial ability while promoting bone regeneration. Besides distal femur defect, the innovative scaffolds may also serve as an ideal biomaterial (e.g. dental implants) for other contaminated defects.

Poly(Dopamine) Coating on 3D-Printed Poly-Lactic-Co-Glycolic Acid/β-Tricalcium Phosphate Scaffolds for Bone Tissue Engineering

Bone defects caused by osteoporosis, bone malignant tumors, and trauma are very common, but there are many limiting factors in the clinical treatment of them. Bone tissue engineering is the most promising treatment and is considered to be the main strategy for bone defect repair. We prepared polydopamine-coated poly-(lactic-co-glycolic acid)/β-tricalcium phosphate composite scaffolds via 3D printing, and a series of characterization and biocompatibility tests were carried out. The results show that the mechanical properties and pore-related parameters of the composite scaffolds are not affected by the coatings, and the hydrophilicities of the surface are obviously improved. Scanning electron microscopy and micro-computed tomography display the nanoscale microporous structure of the bio-materials. Biological tests demonstrate that this modified surface can promote cell adhesion and proliferation and improve osteogenesis through the increase of polydopamine (PDA) concentrations. Mouse cranial defect experiments are conducted to further verify the conclusion that scaffolds with a higher content of PDA coatings have a better effect on the formation of new bones. In the study, the objective of repairing critical-sized defects is achieved by simply adding PDA as coatings to obtain positive results, which can suggest that this modification method with PDA has great potential.

Three-Dimensional Printing in Minimally Invasive Spine Surgery

PURPOSE OF REVIEW

To summarize the recent advances in 3D printing technology as it relates to spine surgery and how it can be applied to minimally invasive spine surgery.

RECENT FINDINGS

Most early literature about 3D printing in spine surgery was focused on reconstructing biomodels based on patient imaging. These biomodels were used to simulate complex pathology preoperatively. The focus has shifted to guides, templates, and implants that can be used during surgery and are specific to patient anatomy. However, there continues to be a lack of long-term outcomes or cost-effectiveness analyses. 3D printing also has the potential to revolutionize tissue engineering applications in the search for the optimal scaffold material and structure to improve bone regeneration without the use of other grafting materials. 3D printing has many potential applications to minimally invasive spine surgery requiring more data for widespread adoption.

Preparation and bioactivity of acetylated konjac glucomannan fibrous membrane and its application for wound dressing

Biomaterial-host interactions significantly affect tissue repair, which is modulated by macrophages. In this study, a polysaccharide, konjac glucomannan (KGM), was acetylated with different degrees of substitution (DS), and the acetylated KGM (AceKGM)-based fibrous membrane was designed to modulate the activity of macrophages for accelerating wound healing. AceKGM was biocompatible and easily dissolved in organic solvents. The adhesion force between Raw264.7 cells and the AceKGM substrate was quantitatively detected by atomic force microscopy (AFM). The enzyme-linked immunosorbent assay (ELISA) results showed that the AceKGM fibrous membrane enhanced macrophage expression of anti-inflammatory and pro-regenerative cytokines, and the DS of AceKGM significantly affected membrane bioactivity. The full-thickness mouse skin wound repair experiments indicated that the AceKGM-containing fibrous membranes significantly accelerated wound healing by promoting re-epithelialization, tissue remodeling, and collagen deposition. In summary, AceKGM-based fibrous membranes have potential as bioactive scaffolds for wound regeneration.

3D printed porous PLA/nHA composite scaffolds with enhanced osteogenesis and osteoconductivity in vivo for bone regeneration

Repair and regeneration of large bone defects is still a challenge, especially for defects which are the irregular and complex. Three-dimension (3D) printing, as an advanced fabrication technology, has been received considerable attentions due to its high precision, customized geometry and personalization. In this study, 3D porous polylactic acid/nano hydroxyapatite (PLA/nHA) composite scaffolds with enhanced osteogenesis and osteoconductivity were successfully fabricated by desktop fused deposition modeling technology. Morphological, composition and structural analysis revealed that nHA was successfully introduced into the PLA system and homogeneously dispersed in the printed PLA/nHA scaffolds. In vitro antibacterial experiment confirmed that the printed porous PLA/nHA scaffolds have good ability for loading and releasing vancomycin and levofloxacin. Meanwhile, MG-63 cells were used to evaluate the cytocompatibility of printed porous PLA/nHA scaffolds by proliferation and cellular morphological analysis. In addition, rabbit model was established to evaluate the osteogenesis and osteoconductivity of printed PLA/nHA scaffolds. All these results suggested that the 3D printed PLA/nHA scaffolds have great potential for repairing and regeneration of large bone defects.

Vancomycin- and Strontium-Loaded Microspheres with Multifunctional Activities against Bacteria, in Angiogenesis, and in Osteogenesis for Enhancing Infected Bone Regeneration

Biomaterials that have capacities to simultaneously induce bone regeneration and kill bacteria are in demand because bone defects face risks of severe infection in clinical therapy. To meet the demand, multifunctional biodegradable microspheres are fabricated, which contain vancomycin to provide antibacterial activity and strontium-doped apatite to provide osteocompatibility. Moreover, the strontium component shows activity in promoting angiogenesis, which further favors osteogenesis. For producing the microspheres, vancomycin is loaded into mesoporous silica and embedded in polylactide-based microspheres via the double emulsion technique and the strontium-doped apatite is deposited onto the microspheres via biomineralization in strontium-containing simulated body fluid. Sustained release behaviors of both vancomycin and Sr²⁺ ions are achieved. The microspheres exhibit strong antibacterial effect against Staphylococcus aureus, while demonstrating excellent cell/tissue compatibility. Studies of differentiation confirm that the introduction of strontium element strengthens the angiogenic and osteogenic expressions of mesenchymal stromal cells. Subcutaneous injection of the microspheres into rabbit's back confirms their effectiveness in inducing neovascularization and ectopic osteogenesis. Finally, an infected rabbit femoral condyle defect model is created with S. aureus infection and the multifunctional microspheres are injected, which display significant antibacterial activity in vivo and achieve efficient new bone formation in comparison with biomineralized microspheres without vancomycin loading. The vancomycin- and strontium-loaded microspheres, being biomineralized, injectable, and biodegradable, are attractive because of their flexibility in integrating multiple functions into one design, whose potentials in treating infected bone defects are highly expected.

A dual functional bone-defect-filling material with sequential antibacterial and osteoinductive properties for infected bone defect repair

Infected bone defect healing is hindered by infection and compromised bone regenerative capacity. In this study, we designed a dual functional bone-defect-filling material with a sequential release system, that is, a burst release of a potent antibacterial agent, hydroxypropyltrimethyl ammonium chloride chitosan (HACC), followed by a controlled release of osteoinductive bone morphogenic protein (BMP2) to repair the infected bone defect. Minimum bactericidal concentration (MBC) of HACC against methicillin-resistant Staphylococcus aureus was 40 μg/mL. HACC at 40 μg/mL did not affect preosteoblast proliferation and did not influence the BMP2-induced alkaline phosphatase activity, osteocalcin expression, and matrix mineralization. in vitro release profile revealed burst release of HACC followed by a slow release of BMP2. in vivo bone formation was observed only in the BMP2-containing groups. HACC did not influence of biomimetic calcium phosphate (BioCaP) resorption and BMP2-induced bone formation. In conclusion, the optimized HACC/BMP2-incorporated BioCaP complex showed strong antibacterial effect and robustly enhanced osteoinduction both in vitro and in vivo.

Effects of Programmed Local Delivery from a Micro/Nano-Hierarchical Surface on Titanium Implant on Infection Clearance and Osteogenic Induction in an Infected Bone Defect

The two major causes for implant failure are postoperative infection and poor osteogenesis. Initial period of osteointegration is regulated by immunocytes and osteogenic-related cells resulting in inflammatory response and tissue healing. The healing phase can be influenced by various environmental factors and biological cascade effect. To synthetically orchestrate bone-promoting factors on biomaterial surface, built is a dual delivery system coated on a titanium surface (abbreviated as AH-Sr-AgNPs). The results show that this programmed delivery system can release Ag⁺ and Sr²⁺ in a temporal-spatial manner to clear pathogens and activate preosteoblast differentiation partially through manipulating the polarization of macrophages. Both in vitro and in vivo assays show that AH-Sr-AgNPs-modified surface renders a microenvironment adverse for bacterial survival and favorable for macrophage polarization (M2), which further promotes the differentiation of preosteoblasts. Infected New Zealand rabbit femoral metaphysis defect model is used to confirm the osteogenic property of AH-Sr-AgNPs implants through micro-CT, histological, and histomorphometric analyses. These findings demonstrate that the programmed surface with dual delivery of Sr²⁺ and Ag⁺ has the potential of achieving an enhanced osteogenic outcome through favorable immunoregulation.

Highly Effective Bone Fusion Induced by the Interbody Cage Made of Calcium Silicate/Polyetheretherketone in a Goat Model

Interbody fusion surgery is often used to settle matters such as degenerative disc disease or disc herniation in clinical orthopedics. Considering the deficiencies of the current treatment methods, we developed an interbody fusion cage made of calcium silicate (CS)/polyetheretherketone (PEEK) and hoped that the bioactive cage could exhibit great fusion ability and maintain stable mechanical function. In the goat model of cervical interbody fusion, the CS/PEEK cage showed stronger interbody fusion at 12 and 26 weeks compared with pure PEEK cage based on the X-ray analysis. The micro-CT scanning and analysis indicated that the CS/PEEK cage induced more new bone ingrowth than the PEEK cage and led to nearly complete interbody fusion at 26 weeks. Moreover, the CS/PEEK group showed excellent mechanical stability and stiffness as evaluated by the spine kinematic assay at the time points. The histological assessment showed the rapid osseointegration and mineralized bone formation around the CS/PEEK cage. This study confirmed that the bioactive CS/PEEK cage is capable of inducing highly effective bone fusion and has high potential to be used in the clinics of spine surgery.

Review of craniofacial regeneration in China

AIM

Tissue engineering has been recognised as one of the most effective means to form a new viable tissue for medical purpose. Tissue engineering involves a combination of scaffolds, cells, suitable biochemical and physicochemical factors, and engineering and materials methods. This review covered some biomedicine, such as biomaterials, bioactive factors, and stem cells, and manufacturing technologies used in tissue engineering in the oral maxillofacial region, especially in China.

MATERIALS AND METHODS

Data for this review were identified by searches of Web of Science and PubMed, and references from relevant articles using the search terms "biomaterials", "oral tissue regeneration", "bioactive factors" and "stem cells". Only articles published in English between 2013 and 2018 were included.

CONCLUSION

The combination of stem cells, bioactive factors and 3D scaffolds could be of far-reaching significance for the future therapies in tissue repair or tissue regeneration. Furthermore, the review also mentions issues that need to be solved in the application of these biomedicines.

Quaternized chitosan promotes the antiproliferative effect of vemurafenib in melanoma cells by increasing cell permeability

Background

As one of the most invasive cutaneous carcinomas among all types of skin cancer, malignant melanoma remains a severe challenge in oncology and plastic surgery. Selective small-molecule inhibitors of V600E-mutant B-Raf (vemurafenib, for instance) have demonstrated satisfactory therapeutic efficacy in melanoma patients. However, acquired resistance during the period of drug administration has limited their clinical application.

Materials and methods

In the present study, human melanoma cells with the B-Raf^V600E mutation were treated with the indicated concentrations of vemurafenib, quaternized chitosan, or a combination of vemurafenib and quaternized chitosan. Cell proliferation and viability were evaluated using cell counting kit-8 assay and DAPI staining, and the IC₅₀ values for vemurafenib in melanoma cells were also determined. Cell apoptosis was evaluated by Live/Dead cell staining using confocal laser scanning microscopy and Annexin V-FITC Apoptosis detection using flow cytometry, respectively. The leakage of ATP and K⁺ into the cell supernatants was measured to evaluate cell permeability. Furthermore, the surface charge variation of melanoma cells after drug treatment was determined by measuring the zeta potential of the cell membrane to clarify the electrostatic interaction between quaternized chitosan and the cells.

Results

Our results indicated that the addition of quaternized chitosan could promote the antiproliferative effect of vemurafenib in melanoma cells and could also promote the cell apoptosis of melanoma cells treated with vemurafenib. In addition, quaternized chitosan could increase cell permeability at early stages of co-culture, thus contributing to the improvement in intracellular drug uptake. Meanwhile, the majority of the negative surface charge of the cells was counteracted by the quaternized chitosan, indicating that the surface charge of melanoma cells was disturbed after the addition of quaternized chitosan.

Conclusion

This study indicated that disturbance of the surface charge of the cell membrane by quaternized chitosan is an important mechanism involved in changes in cell permeability, which promote the antiproliferative effect of vemurafenib in melanoma cells. Our preliminarily investigation provides new insights into the improvement of clinical melanoma therapy in the future.