Surface-transformed osteoinductive polyethylene terephthalate scaffold as a dual system for bone tissue regeneration with localized antibiotic delivery

Additively manufactured polyethylene terephthalate scaffolds for scapholunate interosseous ligament reconstruction

The regeneration of the ruptured scapholunate interosseous ligament (SLIL) represents a clinical challenge. Here, we propose the use of a Bone-Ligament-Bone (BLB) 3D-printed polyethylene terephthalate (PET) scaffold for achieving mechanical stabilisation of the scaphoid and lunate following SLIL rupture. The BLB scaffold featured two bone compartments bridged by aligned fibres (ligament compartment) mimicking the architecture of the native tissue. The scaffold presented tensile stiffness in the range of 260 ± 38 N/mm and ultimate load of 113 ± 13 N, which would support physiological loading. A finite element analysis (FEA), using inverse finite element analysis (iFEA) for material property identification, showed an adequate fit between simulation and experimental data. The scaffold was then biofunctionalized using two different methods: injected with a Gelatin Methacryloyl solution containing human mesenchymal stem cell spheroids (hMSC) or seeded with tendon-derived stem cells (TDSC) and placed in a bioreactor to undergo cyclic deformation. The first approach demonstrated high cell viability, as cells migrated out of the spheroid and colonised the interstitial space of the scaffold. These cells adopted an elongated morphology suggesting the internal architecture of the scaffold exerted topographical guidance. The second method demonstrated the high resilience of the scaffold to cyclic deformation and the secretion of a fibroblastic related protein was enhanced by the mechanical stimulation. This process promoted the expression of relevant proteins, such as Tenomodulin (TNMD), indicating mechanical stimulation may enhance cell differentiation and be useful prior to surgical implantation. In conclusion, the PET scaffold presented several promising characteristics for the immediate mechanical stabilisation of disassociated scaphoid and lunate and, in the longer-term, the regeneration of the ruptured SLIL.

The Role of Microsphere Structures in Bottom-Up Bone Tissue Engineering

Bone defects have caused immense healthcare concerns and economic burdens throughout the world. Traditional autologous allogeneic bone grafts have many drawbacks, so the emergence of bone tissue engineering brings new hope. Bone tissue engineering is an interdisciplinary biomedical engineering method that involves scaffold materials, seed cells, and "growth factors". However, the traditional construction approach is not flexible and is unable to adapt to the specific shape of the defect, causing the cells inside the bone to be unable to receive adequate nourishment. Therefore, a simple but effective solution using the "bottom-up" method is proposed. Microspheres are structures with diameters ranging from 1 to 1000 µm that can be used as supports for cell growth, either in the form of a scaffold or in the form of a drug delivery system. Herein, we address a variety of strategies for the production of microspheres, the classification of raw materials, and drug loading, as well as analyze new strategies for the use of microspheres in bone tissue engineering. We also consider new perspectives and possible directions for future development.

Mesoporous Silica Promotes Osteogenesis of Human Adipose-Derived Stem Cells Identified by a High-Throughput Microfluidic Chip Assay

Silicon-derived biomaterials are conducive to regulating the fate of osteo-related stem cells, while their effects on the osteogenic differentiation of human adipose-derived stem cells (hADSCs) remain inconclusive. Mesoporous silica (mSiO₂) is synthesized in a facile route that exhibited the capability of promoting osteogenic differentiation of hADSCs. The metabolism of SiO₂ in cells is proposed according to the colocalization fluorescence analysis between lysosomes and nanoparticles. The released silicon elements promote osteogenic differentiation. The detection of secretory proteins through numerous parallel experiments performed via a microfluidic chip confirms the positive effect of SiO₂ on the osteogenic differentiation of hADSCs. Moreover, constructed with superparamagnetic iron oxide (Fe₃O₄), the magnetic nanoparticles (MNPs) of Fe₃O₄@mSiO₂ endow the cells with magnetic resonance imaging (MRI) properties. The MNP-regulated osteogenic differentiation of autologous adipose-derived stem cells provides considerable clinical application prospects for stem cell therapy of bone tissue repair with an effective reduction in immune rejection.

Poly(DL-lactic acid) scaffolds as a bone targeting platform for the co-delivery of antimicrobial agents against S. aureus-C. albicans mixed biofilms

New strategies for the treatment of polymicrobial bone infections are required. In this study, the co-delivery of two antimicrobials by poly(D,L-lactic acid) (PDLLA) scaffolds was investigated in a polymicrobial biofilm model. PDLLA scaffolds were prepared by solvent casting/particulate leaching methodology, incorporating minocycline and voriconazole as clinically relevant antimicrobial agents. The scaffolds presented a sponge-like appearance, suitable to support cell proliferation and drug release. Single- and dual-species biofilm models of Staphylococcus aureus and Candida albicans were developed and characterized. S. aureus presented a higher ability to form single-species biofilms, compared to C. albicans. Minocycline and voriconazole-loaded PDLLA scaffolds showed activity against S. aureus and C. albicans single- and dual-biofilms. Ultimately, the cytocompatibility/functional activity of PDLLA scaffolds observed in human MG-63 osteosarcoma cells unveil their potential as a next-generation co-delivery system for antimicrobial therapy in bone infections.

Silver-decorated black phosphorus: a synergistic antibacterial strategy

Black phosphorus (BP) exhibits great potential as antibacterial materials due to its unique photocatalytic activity. However, the unsatisfactory optical absorption and quick recombination of photoinduced electron-hole pairs restrain its photocatalytic antibacterial performance. In this work, silver nanoparticles (AgNPs) were decorated on BP to construct BP@AgNPs nanohybrids and then introduced into poly-l-lactic acid scaffold. Combining the tunable bandgap of BP and the LSPR effect of AgNPs, BP@AgNPs nanohybrids displayed the broaden visible light absorption. Furthermore, AgNPs acted as electron acceptors could accelerate charge transfer and suppress electron-hole recombination. Therefore, BP@AgNPs nanohybrids achieved synergistically enhanced photocatalytic antibacterial activity under visible light irradiation. Fluorescence probe experiment verified that BP@AgNPs promoted the generation of reactive oxygen species, which could disrupt bacteria membrane, damage DNA and oxide proteins, and finally lead to bacteria apoptosis. As a result, the scaffold possessed strong antibacterial efficiency with a bactericidal rate of 97% under light irradiation. Moreover, the scaffold also exhibited good cytocompatibility. This work highlighted a new strategy to develop photocatalytic antibacterial scaffold for bone implant application.

Non-Leaching, Rapid Bactericidal and Biocompatible Polyester Fabrics Finished with Benzophenone Terminated N-halamine

Pathogenic bacteria can proliferate rapidly on porous fabrics to form bacterial plaques/biofilms, resulting in potential sources of cross-transmissions of diseases and increasing cross-infection in public environments. Many works on antibacterial modification of cotton fabrics have been reported, while very few works were reported to endow poly(ethylene terephthalate) (PET) fabrics with non-leaching antibacterial function without compromising their innate physicochemical properties though PET is the most widely used fabric. Therefore, it is urgent to impart the PET fabrics with non-leaching antibacterial activity. Herein, a novel N-halamine compound, 1-chloro-3-benzophenone-5,5-dimethylhydantoin (Cl-BPDMH), was developed to be covalently bonded onto PET fabrics, rendering non-leaching antibacterial activity while negligible cytotoxicity based on contact-killing principle. Bacterial was easily adhered to Cl-BPDMH finished PET fabrics, and then it was inactivated quickly within 10 s. Furthermore, the breaking strength, breaking elongation, tearing strength, water vapor permeability, air permeability and whiteness of Cl-BPDMH finished PET fabrics were improved obviously compared to raw PET fabrics. Hence, this work developed a facile approach to fabricate multifunctional synthetic textiles to render outstanding and rapid bactericidal activity without compromising their physicochemical properties and biocompatibility.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42765-021-00100-z.

Recent advances in the local antibiotics delivery systems for management of osteomyelitis

Chronic osteomyelitis is a challenging disease due to its serious rates of mortality and morbidity while the currently available treatment strategies are suboptimal. In contrast to the adopted systemic treatment approaches after surgical debridement in chronic osteomyelitis, local drug delivery systems are receiving great attention in the recent decades. Local drug delivery systems using special carriers have the pros of enhancing the feasibility of penetration of antimicrobial agents to bone tissues, providing sustained release and localized concentrations of the antimicrobial agents in the infected area while avoiding the systemic side effects and toxicity. Most important, the incorporation of osteoinductive and osteoconductive materials in these systems assists bones proliferation and differentiation, hence the generation of new bone materials is enhanced. Some of these systems can also provide mechanical support for the long bones during the healing process. Most important, if the local systems are designed to be injectable to the affected site and biodegradable, they will reduce the level of invasion required for implantation and can win the patients’ compliance and reduce the healing period. They will also allow multiple injections during the course of therapy to guard against the side effect of the long-term systemic therapy. The current review presents different available approaches for delivering antimicrobial agents for the treatment of osteomyelitis focusing on the recent advances in researches for local delivery of antibiotics.

HIGHLIGHTS

Chronic osteomyelitis is a challenging disease due to its serious mortality and morbidity rates and limited effective treatment options.

Local drug delivery systems are receiving great attention in the recent decades.

Osteoinductive and osteoconductive materials in the local systems assists bones proliferation and differentiation

Local systems can be designed to provide mechanical support for the long bones during the healing process.

Designing the local system to be injectable to the affected site and biodegradable will reduces the level of invasion and win the patients’ compliance.

Injectable polyelectrolyte complex-nascent HAP biodegradable antibiotic delivery system for the treatment of osteomyelitis

An injectable osteoconductive polyelectrolyte complex -hydroxyapatite formulation capable of controlled delivery of ciprofloxacin has been developed from a novel biodegradable polyelectrolyte complex and antibiotic loaded nascent hydroxyapatite (n-HAP) for the treatment of osteomyelitis. A single source (chitosan) derived polyelectrolytes were complexed in situ in the presence of n-HAP, pre-loaded with ciprofloxacin. The PEC- (n-HAP) nanoformulation (HPEC) was characterized by FT-IR, XRD, TGA and TEM analyses. HPEC combines functionalities of n-HAP (crystallinity and osteoconductivity) as well as PEC (biodegradable hydrophilic electrostatically bound macromolecular network) imparting better control over swelling and degradation kinetics favourable for drug release and transport of micronutrients. MTT assay and cytoskeleton staining (MG 63 cells) established cytocompatibility of HPEC. Early biomimetic mineralization of apatite was manifested under simulated physiological condition with a Ca/P of 1.23 (day 3) and 1.55 (day 6) complimented by in vitro biomineralization of MG-63 and Human Osteosarcoma (HOS) cells in a week (Alizarin Red S staining), which was further validated by calcium quantification. Antibacterial efficacy of HPEC has been evaluated by delivery kinetics of ciprofloxacin and by disc diffusion method against S. aureus and E. coli. The injectable system therefore possesses unique combination of functionalities: osteoconduction enriched with early biomineralization, antibacterial activity and is biodegradable; hence highly suitable for osteomyelitis treatment.

Effects of bioactive strontium-substituted hydroxyapatite on osseointegration of polyethylene terephthalate artificial ligaments

The insufficient bioactivity of polyethylene terephthalate (PET) artificial ligaments severely weakens the ligament-bone healing in anterior cruciate ligament (ACL) reconstruction, while osteogenic modification is a prevailing method to enhance osseointegration of PET artificial ligaments. In the present study, strontium-substituted hydroxyapatite (SrHA) nanoparticles with different strontium (Sr) contents were synthesized via microwave-hydrothermal method and subsequently were coated on the surface of PET artificial ligaments. The results of XRD, FT-IR, TEM and ICP-OES revealed that the doping of Sr ions had no great influences on the phase composition, morphology and particle size of HA, but affected its chemical compositions and crystallinity. The SEM images showed that nanoparticles were successfully deposited on the surface of PET grafts, the surface hydrophilicity of which was significantly improved by the prepared coatings. The in vitro study revealed that the osteogenic activity of rat bone marrow mesenchymal stem cells (rBMSCs) was affected by varying concentrations of Sr ions in coatings and the optimal osteogenic differentiation was observed in the 2SrHA-PET group, which significantly up-regulated the expression of BMP-2, OCN, Col-I and VEGF. The enhanced osteogenic ability of the 2SrHA-PET group was further demonstrated through an in vivo study, which obviously promoted ligament-bone integration compared with that of PET and HA-PET groups, thus improving the biomechanical strength of the graft-bone complex. This study confirms that SrHA coatings can facilitate osseointegration in the repair of ligament injury in rabbits and thus offers a prospective method for ACL reconstruction by using Sr-containing biomaterial-modified PET artificial ligaments.

An enhanced periosteum structure/function dual mimicking membrane forin-siturestorations of periosteum and bone

Periosteum plays a pivotal role in bone formation and reconstruction. The ideal repair process for critical-size bone defects with periosteum damage is to induce regeneration of periosteum tissue and the subsequent bone regeneration derived by the periosteum. Inspired by the bilayer structure of the natural periosteum, we develop a periosteum structure/function dual mimicking membrane for thein-siturestoration of periosteum and bone tissue. Among them, the macroporous fluffy guiding layer (TPF) simulates the fibrous layer of the natural periosteum, which is conducive to infiltration and oriented growth of fibroblasts. And the extracellular matrix-like bioactive layer (TN) simulates the cambium layer of the natural periosteum, which significantly enhances the proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells. A middle dense layer (PC) connects the above two layers and has the function of preventing the invasion of soft tissues while enhancing the biomimetic periosteum.In vivorestoration results show that the tri-layer biomimetic periosteum (TPF/PC/TN) has an outstanding effect in promoting the regeneration of both vascularized periosteum and bone at the same time. Therefore, the enhanced biomimetic periosteum developed in this research has a great clinical value in the efficient and high-quality reconstruction of critical-size bone defects with periosteum damage.

Degradation Behavior of Polymers Used as Coating Materials for Drug Delivery-A Basic Review

The purpose of the work was to emphasize the main differences and similarities in the degradation mechanisms in the case of polymeric coatings compared with the bulk ones. Combined with the current background, this work reviews the properties of commonly utilized degradable polymers in drug delivery, the factors affecting degradation mechanism, testing methods while offering a retrospective on the evolution of the controlled release of biodegradable polymeric coatings. A literature survey on stability and degradation of different polymeric coatings, which were thoroughly evaluated by different techniques, e.g., polymer mass loss measurements, surface, structural and chemical analysis, was completed. Moreover, we analyzed some shortcomings of the degradation behavior of biopolymers in form of coatings and briefly proposed some solving directions to the main existing problems (e.g., improving measuring techniques resolution, elucidation of complete mathematical analysis of the different degradation mechanisms). Deep studies are still necessary on the dynamic changes which occur to biodegradable polymeric coatings which can help to envisage the future performance of synthesized films designed to be used as medical devices with application in drug delivery.

Hierarchically Porous Osteoinductive Poly(hydroxyethyl methacrylate-co-methyl methacrylate) Scaffold with Sustained Doxorubicin Delivery for Consolidated Osteosarcoma Treatment and Bone Defect Repair

A bifronted cure system for osteosarcoma, a common aggressive bone tumor, is highly in demand to prevail the postsurgical adversities in connection with systemic chemotherapy and repair of critical-size bone defects. The hierarchically porous therapeutic scaffolds presented here are synthesized by free radical-initiated copolymerization of hydroxyethyl methacrylate and methyl methacrylate [HEMA/MMA 80:20 and 90:10 mM, H₂O/NaCl porogen], which are further surface-phosphorylated [P-PHM] and transformed to bifunctional by impregnating doxorubicin (DOX) [DOXP-PHM]. The P-PHM scaffolds exhibited porous microarchitecture analogous to native cancellous bone (scanning electron microscopy analysis), while X-ray photoelectron spectroscopy analysis authenticated surface phosphorylation. Based on pore characteristics, swelling attributes and slow-pace degradation, P-PHM9163 and P-PHM8263 (HEMA/MMA 90:10 and 80:20 with H₂O/NaCl: 60/3.0 weight %, respectively) were chosen from the series and evaluated for osteoinductive efficacy in vitro. Both P-PHM9163 and P-PHM8263 invoked calcium phosphate mineralization in simulated physiological conditions (day 14) with Ca/P ratios of 1.58 and 1.66 respectively, comparable to human bone (1.67). Early biomineralization (Alizarin Red S and von Kossa staining) was evidenced at day 7, while osteoblast differentiation was verified by time-dependent expression of the typical late marker, osteocalcin, at day 14 and 21 in rat bone marrow mesenchymal cells. DOX-loaded P-PHM9163 (DOXP-PHM9163) exhibited pH-responsive (tumor analogous pH; 6.5) sustained release of DOX for prolonged time (up to 45 days) and invoked cellular alterations by cortical stress fiber formation and DNA fragmentation in human osteosarcoma cells leading to early apoptosis (24 h), validated by annexin V/PI staining (FACS) and immunostaining (F-actin/DAPI). Subsequent to DOX release tenure, the scaffold induced the formation of well-organized, porous post-release Ca-P apatite coating (Ca/P is 1.3) in simulated body fluid (day 14) which further endorses the dual functionality of the system. Altogether, the results accentuate that DOXP-PHM9163 is a potential bifunctional therapeutic scaffold capable of extended localized chemotherapeutic delivery in-line with inherent osteogenesis for efficient bone cancer treatment.

Effect of inorganic phosphate on migration and osteogenic differentiation of bone marrow mesenchymal stem cells

Background

Phosphate is the major ingredient of bone tissue, and is also an important component of commercial bone substitute materials, bone scaffolds, and implant surface coatings. With the dissolution of the bone substitute materials and the degradation by cells, local ion concentrations will change and affect bone tissue reconstruction. Bone marrow -derived mesenchymal stem cells (BM-MSCs) are main autologous cells to repair injured bone. When bone injure occurs, BM-MSCs migrate to the damaged area, differentiate into osteoblasts, and secrete bioactive factors to promote bone tissue repaired. This study aimed to investigate the effect of inorganic phosphate (Pi) at a series of concentration on migration and osteogenic differentiation of human bone marrow -derived mesenchymal stem cells(hBM-MSCs).

Methods

The culture of hBM-MSCs in mediums with different concentration of Pi from 2 mM to 10 mM were performed. HBM-MSCs migration were examined with transwell assays. HBM-MSCs proliferation were evaluated by cell counting kit-8 colorimetric method. Osteogenic genes expression were analyzed by real-time reverse transcriptase polymerase chain reaction. Mineralized nodules formation were demonstrated by Alizarin red staining.

Result

4–10 mM Pi could effectively promote the migration of hBM-MSCs at 12 h and 18 h. There was no significant difference in the migration number of hBM-MSCs in Pi culture mediums at a concentration of 6, 8, and10mM. 2–10 mM Pi could promote the proliferation of hBM-MSCs to varying degrees in the observation period, while 4–10 mM Pi could promote the osteogenic differentiation and mineralization of hBM-MSCs.

Conclusion

The findings in our study showed 4-10 mM Pi could promote the migration, osteogenic differentiation, and mineralization of hBM-MSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12861-020-00229-x.

Mineralization of Biomaterials for Bone Tissue Engineering

Mineralized biomaterials have been demonstrated to enhance bone regeneration compared to their non-mineralized analogs. As non-mineralized scaffolds do not perform as well as mineralized scaffolds in terms of their mechanical and surface properties, osteoconductivity and osteoinductivity, mineralization strategies are promising methods in the development of functional biomimetic bone scaffolds. In particular, the mineralization of three-dimensional (3D) scaffolds has become a promising approach for guided bone regeneration. In this paper, we review the major approaches used for mineralizing tissue engineering constructs. The resulting scaffolds provide minerals chemically similar to the inorganic component of natural bone, carbonated apatite, Ca5(PO4,CO3)3(OH). In addition, we discuss the characterization techniques that are used to characterize the mineralized scaffolds, such as the degree of mineralization, surface characteristics, mechanical properties of the scaffolds, and the chemical composition of the deposited minerals. In vitro cell culture studies show that the mineralized scaffolds are highly osteoinductive. We also summarize, based on literature examples, the applications of 3D mineralized constructs, as well as the rationale behind their use. The mineralized scaffolds have improved bone regeneration in animal models due to the enhanced mechanical properties and cell recruitment capability making them a preferable option for bone tissue engineering over non-mineralized scaffolds.

Deposition of Copper on Polyester Knitwear Fibers by a Magnetron Sputtering System. Physical Properties and Evaluation of Antimicrobial Response of New Multi-Functional Composite Materials

In this study, copper films were deposited by magnetron sputtering on poly(ethylene terephthalate) knitted textile to fabricate multi-functional, antimicrobial composite material. The modified knitted textile composites were subjected to microbial activity tests against colonies of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and antifungal tests against Chaetomium globosum fungal molds species. The prepared samples were characterized by UV/VIS transmittance, scanning electron microscopy (SEM), tensile and filtration parameters and the ability to block UV radiation. The performed works proved the possibility of manufacturing a new generation of antimicrobial textile composites with barrier properties against UV radiation, produced by a simple, zero-waste method. The specific advantages of using new poly(ethylene terephthalate)-copper composites are in biomedical applications areas.

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).