In situ forming biomaterials

A bone replacement-type calcium phosphate cement that becomes more porous in vivo by incorporating a degradable polymer

This study investigated whether mixing low viscosity alginic acid with calcium phosphate cement (CPC) causes interconnected porosity in the CPC and enhances bone replacement by improving the biological interactions. Furthermore, we hypothesized that low viscosity alginic acid would shorten the setting time of CPC and improve its strength. CPC samples were prepared with 0, 5, 10, and 20% low viscosity alginic acid. After immersion in acetate buffer, possible porosification in CPC was monitored in vitro using scanning electron microscopy (SEM), and the setting times and compressive strengths were measured. In vivo study was conducted by placing CPC in a hole created on the femur of New Zealand white rabbit. Microcomputed tomography and histological examination were performed 6 weeks after implantation. SEM images confirmed that alginic acid enhanced the porosity of CPC compared to the control, and the setting time and compressive strength also improved. When incorporating a maximum amount of alginic acid, the new bone mass was significantly higher than the control group (P = 0.0153). These biological responses are promising for the translation of these biomaterials and their commercialization for clinic applications.

Saturated Fatty Acid-Based In Situ Forming Matrices for Localized Antimicrobial Delivery

In recent years, the world has faced the issue of antibiotic resistance. Methicillin-resistant Staphylococcus aureus (MRSA) is a significant problem in various treatments and control of infections. Biocompatible materials with saturated fatty acids of different chain lengths (C₈-C₁₈) were studied as matrix formers of localized injectable vancomycin HCl (VCM)-loaded antisolvent-induced in situ forming matrices. The series of fatty acid-based in situ forming matrices showed a low viscosity (5.47-13.97 cPs) and pH value in the range of 5.16-6.78, with high injectability through a 27-G needle (1.55-3.12 N). The preparations exhibited low tolerance to high concentrations of KH₂PO₄ solution (1.88-5.42% v/v) and depicted an electrical potential change during phase transformation. Their phase transition and matrix formation at the microscopic and macroscopic levels depended on the chain length of fatty acids and solvent characteristics. The VCM release pattern depended on the nucleation/crystallization and solvent exchange behaviors of the delivery system. The 35% w/v of C₁₂-C₁₆ fatty acid-based in situ forming matrix prolonged the VCM release over seven days in which C₁₂, C₁₄, C₁₆ -based formulation reached 56, 84, and 85% cumulative drug release at 7^th day. The release data fitted well with Higuchi's model. The developed formulations presented efficient antimicrobial activities against standard S. aureus, MRSA, Escherichia coli, and Candida albicans. Hence, VCM-loaded antisolvent-induced fatty acid-based in situ forming matrix is a potential local delivery system for the treatment of local Gram-positive infection sites, such as joints, eyes, dermis of surgery sites, etc., in the future.

Liposomal delivery of horseradish peroxidase for thermally triggered injectable hyaluronic acid–tyramine hydrogel scaffolds

A thermally triggered injectable scaffold was developed by utilizing thermoresponsive liposomes to segregate the crosslinking agent from a polymer.

Soft tissue engineering in craniomaxillofacial surgery

Craniofacial soft tissue reconstruction may be required following trauma, tumor resection, and to repair congenital deformities. Recent advances in the field of tissue engineering have significantly widened the reconstructive armamentarium of the surgeon. The successful identification and combination of tissue engineering, scaffold, progenitor cells, and physiologic signaling molecules has enabled the surgeon to design, recreate the missing tissue in its near natural form. This has resolved the issues like graft rejection, wound dehiscence, or poor vascularity. Successfully reconstructed tissue through soft tissue engineering protocols would help surgeon to restore the form and function of the lost tissue in its originality. This manuscript intends to provide a glimpse of the basic principle of tissue engineering, contemporary, and future direction of this field as applied to craniofacial surgery.

Hp-β-CD-voriconazole in situ gelling system for ocular drug delivery: in vitro, stability, and antifungal activities assessment

The objective of the present study was to design ophthalmic delivery systems based on polymeric carriers that undergo sol-to-gel transition upon change in temperature or in the presence of cations so as to prolong the effect of HP- β -CD Voriconazole (VCZ) in situ gelling formulations. The in situ gelling formulations of Voriconazole were prepared by using pluronic F-127 (PF-127) or with combination of pluronic F-68 (PF-68) and sodium alginate by cold method technique. The prepared formulations were evaluated for their physical appearance, drug content, gelation temperature (T gel), in vitro permeation studies, rheological properties, mucoadhesion studies, antifungal studies, and stability studies. All batches of in situ formulations had satisfactory pH ranging from 6.8 to 7.4, drug content between 95% and 100%, showing uniform distribution of drug. As the concentration of each polymeric component was increased, that is, PF-68 and sodium alginate, there was a decrease in T gel with increase in viscosity and mucoadhesive strength. The in vitro drug release decreased with increase in polymeric concentrations. The stability data concluded that all formulations showed the low degradation and maximum shelf life of 2 years. The antifungal efficiency of the selected formulation against Candida albicans and Asperigillus fumigatus confirmed that designed formulation has prolonged effect and retained its properties against fungal infection.

Alginate combined calcium phosphate cements: mechanical properties and in vitro rat bone marrow stromal cell responses

Here, we prepared self-setting calcium phosphate cements (CPCs) based on α-tricalcium phosphate with the incorporation of sodium alginate, and their mechanical properties and in vitro cellular responses were investigated. The addition of alginate enhanced the hardening reaction of CPCs showing shorter setting times within a range of powder-to-liquid ratios. When immersed in a body simulating fluid the alginate-CPCs fully induced a formation of an apatite crystalline phase similar to that of bare CPCs. The compressive and tensile strengths of the CPCs were found to greatly improve during immersion in the fluid, and this improvement was more pronounced in the alginate-CPCs. As a result, the alginate-CPCs retained significantly higher strength values than the bare CPCs after 3-7 days of immersion. The rat bone marrow derived stromal cells (rBMSCs) cultured on the alginate-CPCs initially adhered to and then spread well on the cements surface, showed an on-going increase in the population with culture time, and differentiated into osteoblasts expressing bone-associated genes (collagen type I, osteopontin and bone sialoprotein) and synthesizing alkaline phosphatase. However, the stimulated level of osteogenic differentiation was not confirmative with the incorporation of alginate into the CPC composition based on the results. One merit of the use of alginate was its usefulness in forming CPCs into a variety of scaffold shapes including microspheres and fibers, which is associated with the cross-link of alginate under the calcium-containing solution.

Application of oral implants to the general dental practice

BACKGROUND

The use of dental implants has become a management strategy for replacing missing teeth. As new implant surface technologies develop and prosthetic options increase, the field of dental implantology continues to change. General dentists con sidering the use of this treatment modality in their practices should understand the vital role treatment planning plays in achieving predictable outcomes.

OVERVIEW

This article reviews specific issues the general dentist typically faces when considering patients for single-tooth, partially-edentulous-arch and full-arch tooth replacement using dental implants. The author analyzes patient-based assessments, as well as diagnostic criteria and steps, to help practitioners predict patient-specific issues that may signal complications. He also discusses approaches for resolving complications. The article emphasizes the importance of careful evaluation in predicting patient-specific issues that can lead to gingival recession and suggests approaches to manage these situations.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Dental implants have become an increasingly common treatment option for missing dentition. Because innovations in implant surfaces continue to promote faster bone growth with better predictability, general dentists should be aware of the importance of treatment planning, assessment and teamwork in achieving successful outcomes.

In situ crosslinking of a biomimetic peptide-PEG hydrogel via thermally triggered activation of factor XIII

There is a medical need for robust, biocompatible hydrogels that can be rapidly crosslinked in situ through the use of gentle and non-toxic triggers, which could be used as a surgical adhesive, a bone-inductive material, or for drug and gene delivery. The complete gelation system described here includes calcium-loaded liposomes, hrFactor XIII. thrombin, and an enzymatic substrate based on a four-armed PEG in which each arm terminates with a 20mer peptide sequence derived from the gamma-chain of fibrin. Controlled release of calcium ions for efficient hrFXIII activation was accomplished by thermal triggering of a tailored liposome phase transition at 37 degrees C, which allowed the entire gelation system to be stored in aqueous solution at room temperature without premature gelation. When the system temperature was raised to 37 degrees C (body temperature), the released calcium activates the hrFactor XIII, and gelation was observed to occur within 9 min. Rheological studies performed to quantitatively determine the storage modulus (G') of the gel during oscillatory shear show that it behaves as a robust, elastic solid. Scanning electron microscopy studies revealed the hydrogel to have a very dense morphology overall, however spherical voids are observed in regions where calcium-loaded liposomes were entrapped during gelation.

Formation of fibrinogen-based hydrogels using phototriggerable diplasmalogen liposomes

We report the triggered release of Ca2+ from liposomal compartments to induce rapid gelation of protein-based hydrogels. Phototriggerable liposomes were designed by entrapping CaCl(2) within liposomes composed of 38:57:5 diplasmenylcholine (DPPlsC):disteroylphosphatidylcholine (DSPC):bacteriochlorophyll (Bchl). These liposomes release >80% of their entrapped Ca2+ within 15 min when irradiated at 800 nm (800 mW/cm2). A precursor solution, containing liposomes suspended in aqueous human fibrinogen and transglutaminase (TGase), remained fluid for several hours in the dark, but gelled rapidly when exposed to 800 nm excitation, as a result of photosensitized Ca2+ release and TG-induced fibrinogen cross-linking. TGase and hrFXIII activities, determined using a fluorimetric dansylcadaverine assay, were found to depend strongly on irradiation time and reaction temperature. SDS-PAGE of the photolyzed reaction mixture revealed that gelation arises from enzyme-catalyzed cross-linking of predominately the alpha and gamma chains of fibrinogen. This approach to the phototriggered formation of protein hydrogels creates new opportunities for biomaterials applications in drug delivery, tissue engineering, and wound healing.