Activated Carbon Fiber Cloth/Biomimetic Apatite: A Dual Drug Delivery System

Biphasic Calcium Phosphate and Activated Carbon Microparticles in a Plasma Clot for Bone Reconstruction and In Situ Drug Delivery: A Feasibility Study

The development of bone-filling biomaterials capable of delivering in situ bone growth promoters or therapeutic agents is a key area of research. We previously developed a biomaterial constituting biphasic calcium phosphate (BCP) microparticles embedded in an autologous blood or plasma clot, which induced bone-like tissue formation in ectopic sites and mature bone formation in orthotopic sites, in small and large animals. More recently, we showed that activated carbon (AC) fiber cloth is a biocompatible material that can be used, due to its multiscale porosity, as therapeutic drug delivery system. The present work aimed first to assess the feasibility of preparing calibrated AC microparticles, and second to investigate the properties of a BCP/AC microparticle combination embedded in a plasma clot. We show here, for the first time, after subcutaneous (SC) implantation in mice, that the addition of AC microparticles to a BCP/plasma clot does not impair bone-like tissue formation and has a beneficial effect on the vascularization of the newly formed tissue. Our results also confirm, in this SC model, the ability of AC in particle form to adsorb and deliver large molecules at an implantation site. Altogether, these results demonstrate the feasibility of using this BCP/AC/plasma clot composite for bone reconstruction and drug delivery.

Current application and future perspectives of antimicrobial degradable bone substitutes for chronic osteomyelitis

Chronic osteomyelitis remains a persistent challenge for the surgeons due to its refractory nature. Generally, treatment involves extensive debridement of necrotic bone, filling of dead space, adequate antimicrobial therapy, bone reconstruction, and rehabilitation. However, the optimal choice of bone substitute to manage the bone defect remains debatable. This paper reviewed the clinical evidence for antimicrobial biodegradable bone substitutes in the treatment of osteomyelitis in recent years. Indeed, this combination was proved to eradicate infection and facilitate bone reconstruction, which might reduce the cost and hospital stay. Handling was associated with increased risk of unwanted side effect to affect bone healing. The study provides some valuable insights into the clinical evaluation of treatment outcomes in the aspects of infection eradication, bone reconstruction, and complications caused by materials. However, achieving complete infection eradication and subsequently perfect bone reconstruction remains challenging in compromised conditions, hence advanced innovative bone substitutes are imperative. In this review, we mainly focus on the desired functional effects of advanced bone substitutes on infection eradication and bone reconstruction from the future perspective. Handling property was optimized to simplify surgery process. It is expected that this review will provide an important opportunity to enhance the understanding of the design and application of innovative biomaterials to synergistically eradicate infection and restore integrity and function of bone.

Long-Term Fate and Efficacy of a Biomimetic (Sr)-Apatite-Coated Carbon Patch Used for Bone Reconstruction

Critical bone defect repair remains a major medical challenge. Developing biocompatible materials with bone-healing ability is a key field of research, and calcium-deficient apatites (CDA) are appealing bioactive candidates. We previously described a method to cover activated carbon cloths (ACC) with CDA or strontium-doped CDA coatings to generate bone patches. Our previous study in rats revealed that apposition of ACC or ACC/CDA patches on cortical bone defects accelerated bone repair in the short term. This study aimed to analyze in the medium term the reconstruction of cortical bone in the presence of ACC/CDA or ACC/10Sr-CDA patches corresponding to 6 at.% of strontium substitution. It also aimed to examine the behavior of these cloths in the medium and long term, in situ and at distance. Our results at day 26 confirm the particular efficacy of strontium-doped patches on bone reconstruction, leading to new thick bone with high bone quality as quantified by Raman microspectroscopy. At 6 months the biocompatibility and complete osteointegration of these carbon cloths and the absence of micrometric carbon debris, either out of the implantation site or within peripheral organs, was confirmed. These results demonstrate that these composite carbon patches are promising biomaterials to accelerate bone reconstruction.

Fabrication, characterization and biological properties evaluation of bioactive scaffold based on mineralized carbon nanofibers

Tissue engineering as an innovative approach aims to combine engineering, biomaterials and biomedicine to eliminate the drawbacks of conventional bone defect treatment. In the current study, we fabricated bioengineered electroactive and bioactive mineralized carbon nanofibers as the scaffold for bone tissue engineering applications. The scaffold was fabricated using the sol-gel method and thoroughly characterized by SEM imaging, EDX analysis and a 4-point probe. The results showed that the CNFs have a diameter of 200 ± 19 nm and electrical conductivity of 1.02 ± 0.12 S cm-1. The in vitro studies revealed that the synthesized CNFs were osteoactive and supported the mineral crystal deposition. The hemolysis study confirmed the hemocompatibility of the CNFs and cell viability/proliferation sassy using an MTT assay kit showed the proliferative activities of mineralized CNFs. In conclusion, this study revealed that the mineralized CNFs synthesized by the combination of sol-gel and electrospinning techniques were electroactive, osteoactive and biocompatible, which can be considered an effective bone tissue engineering scaffold.Communicated by Ramaswamy H. Sarma.

Osteogenic Effect of Fisetin Doping in Bioactive Glass/Poly(caprolactone) Hybrid Scaffolds

Treating large bone defects or fragile patients may require enhancing the bone regeneration rate to overcome a weak contribution from the body. This work investigates the osteogenic potential of nutrient fisetin, a flavonoid found in fruits and vegetables, as a doping agent inside the structure of a SiO₂-CaO bioactive glass-poly(caprolactone) (BG-PCL) hybrid scaffold. Embedded in the full mass of the BG-PCL hybrid during one-pot synthesis, we demonstrate fisetin to be delivered sustainably; the release follows a first-order kinetics with active fisetin concentration being delivered for more than 1 month (36 days). The biological effect of BG-PCL-fisetin-doped scaffolds (BG-PCL-Fis) has been highlighted by in vitro and in vivo studies. A positive impact is demonstrated on the adhesion and the differentiation of rat primary osteoblasts, without an adverse cytotoxic effect. Implantation in critical-size mouse calvaria defects shows bone remodeling characteristics and remarkable enhancement of bone regeneration for fisetin-doped scaffolds, with the regenerated bone volume being twofold that of nondoped scaffolds and fourfold that of a commercial trabecular bovine bone substitute. Such highly bioactive materials could stand as competitive alternative strategies involving biomaterials loaded with growth factors, the use of the latter being the subject of growing concerns.

Activated Carbon for Drug Delivery from Composite Biomaterials: The Effect of Grinding on Sirolimus Binding and Release

Activated carbon (AC) could be potentially useful as a drug carrier in fiber polymer scaffolds destined for prolonged drug delivery. To be introduced, AC must be ground into smaller-sized particles to be introduced in scaffolds, as most biocompatible scaffolds consist of fibers with a diameter of less than 1 µm. In this study, the adsorption of sirolimus (SRL) from phosphate-buffered saline (PBS) solution and blood plasma (BP) onto AC of AX-21 type, as well as the release of SRL from AC depending on its fragmentation, were studied. Two-stage grinding of the AC, first with a ball mill, and then with a bead mill, was performed. Grinding with a bead mill was performed either in water or in polyvinylpyrrolidone to prevent aggregation of AC particles. Dynamic light scattering and scanning electron microscopy (SEM) demonstrated that the size of the particles obtained after grinding with a ball mill was 100–10,000 nm, and after grinding with a bead mill, 100–300 nm. Adsorption in PBS was significantly higher than in BP for all fractions, and depended on SRL concentration. The fraction obtained after grinding with a ball mill showed maximal SRL adsorption, both in PBS and BP, and slow SRL release, in comparison with other fractions. The 100–300 nm AC fractions were able to adsorb and completely release SRL into BP, in contrast to other fractions, which strongly bound a significant amount of SRL. The data obtained are to be used for controlled SRL delivery, and thus in the modification of drug delivery in biological media.

Nature-Inspired Effects of Naturally Occurring Trace Element-Doped Hydroxyapatite Combined with Surface Interactions of Mineral-Apatite Single Crystals on Human Fibroblast Behavior

Innovative engineering design for biologically active hydroxyapatites requires enhancing both mechanical and physical properties, along with biocompatibility, by doping with appropriate chemical elements. Herein, the purpose of this investigation was to evaluate and elucidate the model of naturally occurring hydroxyapatite and the effects of doped trace elements on the function of normal human fibroblasts, representing the main cells of connective tissues. The substrates applied (geological apatites with hexagonal prismatic crystal habit originated from Slyudyanka, Lake Baikal, Russia (GAp) and from Imilchil, The Atlas Mountains, Morocco (YAp)) were prepared from mineral natural apatite with a chemical composition consistent with the building blocks of enamel and enriched with a significant F⁻ content. Materials in the form of powders, extracts and single-crystal plates have been investigated. Moreover, the effects on the function of fibroblasts cultured on the analyzed surfaces in the form of changes in metabolic activity, proliferation and cell morphology were evaluated. Apatite plates were also evaluated for cytotoxicity and immune cell activation capacity. The results suggest that a moderate amount of F⁻ has a positive effect on cell proliferation, whereas an inhibitory effect was attributed to the Cl⁻ concentration. It was found that for (100) GAp plate, fibroblast proliferation was significantly increased, whereas for (001) YAp plate, it was significantly reduced, with no cytotoxic effect and no immune response from macrophages exposed to these materials. The study of the interaction of fibroblasts with apatite crystal surfaces provides a characterization relevant to medical applications and may contribute to the design of biomaterials suitable for medical applications and the evaluation of their bioavailability.