Simvastatin-loaded β-TCP drug delivery system induces bone formation and prevents rhabdomyolysis in OVX mice

An Innovative Drug Delivery System Loaded with a Modified Combination of Triple Antibiotics for Use in Endodontic Applications

The objective of the current study was to introduce "Polylactic co-Glycolic Acid- (PLGA-) Coated Ceramic Microparticles" as an innovative drug delivery system, loaded with a new combination of triple antibiotics (penicillin G, metronidazole, and ciprofloxacin (PMC)) for use in endodontic treatments. Ceramic microparticles were made from β-tricalcium phosphate and hydroxyapatite and examined by "Scanning Electronic Microscope (SEM)." Then, fixed amounts of the selected antibiotics were added to a prepared PLGA solution and stirred thoroughly. Next, the prepared ceramic microparticles were dispersed completely in the drugs solution. The deposited "PMC-loaded PLGA-coated ceramic microspheres (PPCMs)" were dried and incubated in phosphate buffer saline (PBS) for 21 days. The drug release from PPCMs was quantified by a UV spectrophotometer. The antimicrobial activity of PPCMs was investigated using the "Agar Plate Diffusion Test (ADT)," "Minimum Inhibitory Concentration (MIC)," and "Minimum Bactericidal Concentration (MBC)" against Enterococcus faecalis (E. faecalis) and Aggregatibacter actinomycetemcomitans (A.a). The cell viability test (MTT) was conducted for cytotoxicity against human gingival fibroblasts. SEM micrographs of PPCMs showed spherical-like ceramic microparticles with smooth surfaces. Crystal-like antibiotic particles (chunks) were also found on PPCMs. Initial burst of antibiotics (31 µg/mL, 160 µg/mL, and 18 µg/mL for ciprofloxacin, metronidazole, and penicillin G, respectively, in the first 4 days) followed by gradual and sustained release was observed within a period of 21 days. PPCMs demonstrated pH close to normal physiological environment and antibacterial activity against E. faecalis and A.a in the first 2 days. MTT showed cell viability of more than 70% for PPCMs after 24 h and 72 h of exposure. In conclusion, PPCMs demonstrated satisfactory release of antibiotics, antibacterial activity against the selected microorganisms, and biocompatibility. Thus, PPCMs may be used to deliver modified triple antibiotics to the root canal system for use in endodontic applications.

Calcareous Foraminiferal Shells as a Template for the Formation of Hierarchal Structures of Inorganic Nanomaterials

A microorganism template approach has been explored for the fabrication of various well-defined three-dimensional (3D) structures. However, most of these templates suffer from small size (few μm), difficulty to remove the template, or low surface area, which affect their potential use in different applications or makes industrial scale-up difficult. Conversely, foraminifer's microorganisms are large (up to 200 mm), consist of CaCO₃ (easy to dissolve in mild acid), and have a relatively high surface area (≈5 m² g^-1). Herein, we demonstrate the formation of hierarchical structures of inorganic materials using calcareous foraminiferal shells such as Sorites, Globigerinella siphonifera, Lox-ostomina amygdaleformis, Calcarina baculatus or hispida, and Peneroplis planatus. Several techniques, such as thermal decomposition of single-source precursors of metal oxides or sulfides, reduction of metal salts directly on the surfaces, and redox reactions, were used for coating of different shell materials and several hybrid compositions, which possess nanofeatures. Finally, we examined the role of the prepared 3D structures on the reduction of 4-nitrophenol (4-NP), ethanol electrooxidation, and water purification. A remarkable performance was achieved in each application. The hierarchical structure leads to the reduction of 4-NP within several minutes, a 27 mA cm^-2 current density peak was obtained for ethanol electrooxidation, and more than 95% of the organic dye contaminants were successfully removed. These results show that using foraminiferal shells offers a new way for designing complex hierarchical structures with unique properties.

Bioinspired Hierarchical Porous Structures for Engineering Advanced Functional Inorganic Materials

Tremendous efforts have been directed at designing functional and well-defined 3D structures in recent decades. Many approaches have been devised and are currently used to create 3D structures, including lithography, 3D printing, assembly, and template-mediated (natural or synthetic) methods. Natural scaffolds offer some unique traits, as compared to their artificial counterparts, presenting highly ordered, porous, identical, abundant, and diverse structures. Various organisms, such as viruses, bacteria, diatoms, foraminifera, and others, are used as templates to form 3D structures. Herein, advancements made in using the shell of marine microorganisms, diatoms, and foraminifera, as scaffolds for designing functional 3D structures are reported. Furthermore, a succinct overview of various synthetic methods used to coat these scaffolds with inorganic materials (i.e., metals, metal oxides, and metal sulfides) is provided. Finally, the use of such fabricated functional 3D structures in a wide range of applications, such as catalysis, sensing, drug delivery, photo-electrochemical uses, batteries, and others, is considered.

Rebamipide delivered by brushite cement enhances osteoblast and macrophage proliferation

Many of the bioactive agents capable of stimulating osseous regeneration, such as bone morphogenetic protein-2 (BMP-2) or prostaglandin E2 (PGE2), are limited by rapid degradation, a short bioactive half-life at the target site in vivo, or are prohibitively expensive to obtain in large quantities. Rebamipide, an amino acid modified hydroxylquinoline, can alter the expression of key mediators of bone anabolism, cyclo-oxygenase 2 (COX-2), BMP-2 and vascular endothelial growth factor (VEGF), in diverse cell types such as mucosal and endothelial cells or chondrocytes. The present study investigates whether Rebamipide enhances proliferation and differentiation of osteoblasts when delivered from brushite cement. The reactive oxygen species (ROS) quenching ability of Rebampide was tested in macrophages as a measure of bioactivity following drug release incubation times, up to 14 days. Rebamipide release from brushite occurs via non-fickian diffusion, with a rapid linear release of 9.70% ± 0.37% of drug per day for the first 5 days, and an average of 0.5%-1% per day thereafter for 30 days. Rebamipide slows the initial and final cement setting time by up to 3 and 1 minute, respectively, but does not significantly reduce the mechanical strength below 4% (weight percentage). Pre-osteoblast proliferation increases by 24% upon exposure to 0.4 uM Rebamipide, and by up to 73% when Rebamipide is delivered via brushite cement. Low doses of Rebamipide do not adversely affect peak alkaline phosphatase activity in differentiating pre-osteoblasts. Rebamipide weakly stimulates proliferation in macrophages at low concentrations (118 ± 7.4% at 1 uM), and quenches ROS by 40-60%. This is the first investigation of Rebamipide in osteoblasts.

Inflammation-induced drug release by using a pH-responsive gas-generating hollow-microsphere system for the treatment of osteomyelitis

In the conventional treatment of osteomyelitis, the penetration of antibiotics into the infected bone is commonly poor. To ensure that the local antibiotic concentration is adequate, this work develops an injectable calcium phosphate (CP) cement in which is embedded pH-responsive hollow microspheres (HMs) that can control the release of a drug according to the local pH. The HMs are fabricated using a microfluidic device, with a shell of poly(D,L-lactic-co-glycolic acid) (PLGA) and an aqueous core that contains vancomycin (Van) and NaHCO3. At neutral pH, the CP/HM cement elutes a negligible concentration of the drug. In an acidic environment, the NaHCO3 that is encapsulated in the HMs reacts with the acid rapidly to generate CO2 bubbles, disrupting the PLGA shells and thereby releasing Van locally in excess of a therapeutic threshold. The feasibility of using this CP/HM cement to treat osteomyelitis is studied using a rabbit model. Analytical results reveal that the CP/HM cement provides highly effective local antibacterial activity. Histological examination further verifies the efficacy of the treatment by the CP/HM cement. The above findings suggest that the CP/HM cement is a highly efficient system for the local delivery of antibiotics in the treatment of osteomyelitis.

Bone regeneration of rat tibial defect by zinc-tricalcium phosphate (Zn-TCP) synthesized from porous Foraminifera carbonate macrospheres

Foraminifera carbonate exoskeleton was hydrothermally converted to biocompatible and biodegradable zinc-tricalcium phosphate (Zn-TCP) as an alternative biomimetic material for bone fracture repair. Zn-TCP samples implanted in a rat tibial defect model for eight weeks were compared with unfilled defect and beta-tricalcium phosphate showing accelerated bone regeneration compared with the control groups, with statistically significant bone mineral density and bone mineral content growth. CT images of the defect showed restoration of cancellous bone in Zn-TCP and only minimal growth in control group. Histological slices reveal bone in-growth within the pores and porous chamber of the material detailing good bone-material integration with the presence of blood vessels. These results exhibit the future potential of biomimetic Zn-TCP as bone grafts for bone fracture repair.