Bone defect reconstruction with a novel biomaterial containing calcium phosphate and aluminum oxide reinforcement

A composite of polymethylmethacrylate, hydroxyapatite, and β-tricalcium phosphate for bone regeneration in an osteoporotic rat model

The purpose of this study was to test several modifications of the polymethylmethacrylate (PMMA) bone cement by incorporating osteoconductive and biodegradable materials for enhancing bone regeneration capacity in an osteoporotic rat model. Three bio-composites (PHT-1 [80% PMMA, 16% HA, 4% β-TCP], PHT-2 [70% PMMA, 24% HA, 6% β-TCP], and PHT-3 [30% PMMA, 56% HA, 14% β-TCP]) were prepared using different concentrations of PMMA, hydroxyapatite (HA), and β-tricalcium phosphate (β-TCP). Their morphological structure was then examined using a scanning electron microscope (SEM) and mechanical properties were determined using a MTS 858 Bionics test machine (MTS, Minneapolis, MN, USA). For in vivo studies, 35 female Wister rats (250 g, 12 weeks of age) were prepared and divided into five groups including a sham group (control), an ovariectomy-induced osteoporosis group (OVX), an OVX with pure PMMA group (PMMA), an OVX with PHT-2 group (PHT-2), and an OVX with PHT-3 group (PHT-3). In vivo bone regeneration efficacy was assessed using micro-CT and histological analysis after injecting the prepared bone cement into the tibial defects of osteoporotic rats. SEM investigation showed that the PHT-3 sample had the highest porosity and roughness among all samples. In comparison to other samples, the PHT-3 exhibited favorable mechanical properties for use in vertebroplasty procedures. Micro-CT and histological analysis of OVX-induced osteoporotic rats revealed that PHT-3 was more effective in regenerating bone and restoring bone density than other samples. This study suggests that the PHT-3 bio-composite can be a promising candidate for treating osteoporosis-related vertebral fractures.

Speed and quality of interbody fusion in porous bioceramic Al2O3 and polyetheretherketone cages for anterior cervical discectomy and fusion: a comparative study

BACKGROUND

The objective of this prospective randomized monocentric study is to compare the speed and quality of interbody fusion of implanted porous Al₂O₃ (aluminium oxide) cages with PEEK (polyetheretherketone) cages in ACDF (anterior cervical discectomy and fusion).

MATERIALS AND METHODS

A total of 111 patients were enrolled in the study, which was carried out between 2015 and 2021. The 18-month follow-up (FU) was completed in 68 patients with an Al₂O₃ cage and 35 patients with a PEEK cage in one-level ACDF. Initially, the first evidence (initialization) of fusion was evaluated on computed tomography. Subsequently, interbody fusion was evaluated according to the fusion quality scale, fusion rate and incidence of subsidence.

RESULTS

Signs of incipient fusion at 3 months were detected in 22% of cases with the Al₂O₃ cage and 37.1% with the PEEK cage. At 12-month FU, the fusion rate was 88.2% for Al₂O₃ and 97.1% for PEEK cages, and at the final FU at 18 months, 92.6% and 100%, respectively. The incidence of subsidence was observed to be 11.8% and 22.9% of cases with Al₂O₃ and PEEK cages, respectively.

CONCLUSIONS

Porous Al₂O₃ cages demonstrated a lower speed and quality of fusion in comparison with PEEK cages. However, the fusion rate of Al₂O₃ cages was within the range of published results for various cages. The incidence of subsidence of Al₂O₃ cages was lower compared to published results. We consider the porous Al₂O₃ cage as safe for a stand-alone disc replacement in ACDF.

Existing and Novel Biomaterials for Bone Tissue Engineering

The treatment of bone defects remains one of the major challenges in modern clinical practice. Nowadays, with the increased incidence of bone disease in an aging population, the demand for materials to repair bone defects continues to grow. Recent advances in the development of biomaterials offer new possibilities for exploring modern bone tissue engineering strategies. Both natural and synthetic biomaterials have been used for tissue repair. A variety of porous structures that promote cell adhesion, differentiation, and proliferation enable better implant integration with increasingly better physical properties. The selection of a suitable biomaterial on which the patient's new tissue will grow is one of the key issues when designing a modern tissue scaffold and planning the entire treatment process. The purpose of this article is to present a comprehensive literature review of existing and novel biomaterials used in the surgical treatment of bone tissue defects. The materials described are divided into three groups-organic, inorganic, and synthetic polymers-taking into account current trends. This review highlights different types of existing and novel natural and synthetic materials used in bone tissue engineering and their advantages and disadvantages for bone defects regeneration.

A PMMA bone cement with improved antibacterial function and flexural strength

A novel non-leaching antibacterial bone cement has been developed and evaluated. An antibacterial furanone derivative was synthesized and covalently coated onto the surface of alumina filler particles, followed by mixing into a conventional poly(methyl methacrylate) bone cement. Flexural strength and bacterial viability were used to evaluate the modified cements. Effects of coated antibacterial moiety content, coated alumina filler particle size and loading were investigated. Results showed that almost all the modified cements showed higher flexural strength (up to 10%), flexural modulus (up to 18%), and antibacterial activity (up to 67% to S. aureus and up to 84% to E. coli), as compared to original poly(methyl methacrylate) cement. Increasing antibacterial moiety and filler loading significantly enhanced antibacterial activity. On the other hand, increasing coated filler particle size decreased antibacterial activity. Increasing antibacterial moiety content and particle size did not significantly affect flexural strength and modulus. Increasing filler loading did not significantly affect flexural modulus but reduced flexural strength. Antibacterial agent leaching tests showed that it seems no leachable antibacterial component from the modified experimental cement to the surrounding environment. Within the limitations of this study, the modified poly(methyl methacrylate) bone cement may potentially be developed into a clinically useful bone cement for reducing in-surgical and post-surgical infection.

Immobilized anticancer agents and metal nanoparticles in a matrix of gellan: achievements and prospects

A review is devoted to recent achievements in development of anticancer drugs based on natural polysaccharide – gellan that possesses coil-helix conformational transition, sol-gel phase transition, thermo- and salt sensitivity. The characteristics of high- and low-acyl gellan are briefly given and the influence of mono- and multivalent metal ions on the gelation efficiency is described. The mucoadhesive properties of gellan and its modified derivatives are briefly considered in the context of application in pharmacy as oral, buccal, nasal, ophthalmologic, vaginal forms. The main attention is paid to anticancer drugs, gold and silver nanoparticles immobilized within gellan matrix by chemical bonds, physical adsorption and chemosorption. The state-of-the art and perspectives of development of plasmonic photothermal therapy of cancer cells that is one of the promising direction of nanomedicine in diagnosis and treatment of oncological diseases are highlighted. It is outlined that the further strategy of development and application of plasmonic photothermal therapy into clinical practice is due to selection of metal nanoparticles with optimal sizes, high concentration, low cytotoxicity and suitable optical characteristics.

A novel vertical aligned mesoporous silica coated nanohydroxyapatite particle as efficient dexamethasone carrier for potential application in osteogenesis

Bone defect is a common problem and inducing osteoblasts differentiation is the key process for the regenerative repair. Recently, the mesoporous silica (MS) coated nanohydroxyapatite particles nHA (nHA-MS) has shown enhanced intrinsic potency for bone regeneration, whereas whether the osteogenesis potency can be further enhanced after drug delivery has not been investigated. In this study, the nHA-MS was fabricated by a novel biphase stratification growth way. The cytotoxicity in MC3T3-E1 was validated by MTT assay, apoptosis analysis and cell cycle examination. The cell uptake was observed by confocal laser scanning microscope and transmission electron microscope respectively. After adsorption with dexamethasone (DEX), the osteogenic differentiation was determined both in vitro and in vivo. The synthesized nHA-MS showed a core-shell structure that the nanorod-like nHA was coated by a porous MS shell (~5 nm pores diameter, ~50 nm thickness). A dose-dependent cytotoxicity was observed and below 10 µg/ml was a safe concentration. The nHA-MS also showed efficient cell uptake efficiency and more efficient in DEX loading and release. After DEX adsorption, the nanoparticles exhibited enhanced osteogenic induction in MC3T3-E1 and rat calvarial bone defect regeneration. In conclusion, the nHA-MS is a favorable platform for drug delivery to obtain more enhanced osteogenesis capabilities.