Marine Skeletons: Towards Hard Tissue Repair and Regeneration.

Musculoskeletal disorders in the elderly have significantly increased due to the increase in an ageing population. The treatment of these diseases necessitates surgical procedures, including total joint replacements such as hip and knee joints. Over the years a number of treatment options have been specifically established which are either permanent or use temporary natural materials such as marine skeletons that possess unique architectural structure and chemical composition for the repair and regeneration of bone tissue. This review paper will give an overview of presently used materials and marine structures for hard tissue repair and regeneration, drugs of marine origin and other marine products which show potential for musculoskeletal treatment.

Bioresorbable zinc hydroxyapatite guided bone regeneration membrane for bone regeneration.

OBJECTIVES: The aim of this study was to investigate the bone regenerative properties of a heat treated cross-linked GBR membrane with zinc hydroxyapatite powders in the rat calvarial defect model over a 6-week period. MATERIAL AND METHODS: In vitro physio-chemical characterization involved X-ray diffraction analysis, surface topology by scanning electron microscopy, and zinc release studies in physiological buffers. Bilateral rat calvarial defects were used to compare the Zn-HAp membranes against the commercially available collagen membranes and the unfilled defect group through radiological and histological evaluation. RESULTS: The synthesized Zn-MEM (100 µm thick) showed no zinc ions released in the phosphate buffer solution (PBS) buffer, but zinc was observed under acidic conditions. At 6 weeks, both the micro-CT and histological analyses revealed that the Zn-MEM group yielded significantly greater bone formation with 80 ± 2% of bone filled, as compared with 60 ± 5% in the collagen membrane and 40 ± 2% in the unfilled control group. CONCLUSION: This study demonstrated the use of heat treatment as an alternative method to cross-linking the Zn-MEM to be applied as a GBR membrane. Its synthesis and production are relatively simple to fabricate, and the membrane had rough surface features on one side, which might be beneficial for cellular activities. In a rat calvarial defect model, it was shown that new bone formation was accelerated in comparison with the collagen membrane and the unfilled defect groups. These results would suggest that Zn-MEM has the potential for further development in dental applications.

Marine structure derived calcium phosphate-polymer biocomposites for local antibiotic delivery.

Hydrothermally converted coralline hydroxyapatite (HAp) particles loaded with medically active substances were used to develop polylactic acid (PLA) thin film composites for slow drug delivery systems. The effects of HAp particles within PLA matrix on the gentamicin (GM) release and release kinetics were studied. The gentamicin release kinetics seemed to follow Power law Korsmeyer Peppas model with mainly diffusional process with a number of different drug transport mechanisms. Statistical analysis shows very significant difference on the release of gentamicin between GM containing PLA (PLAGM) and GM containing HAp microspheres within PLA matrix (PLAHApGM) devices, which PLAHApGM displays lower release rates. The use of HAp particles improved drug stabilization and higher drug encapsulation efficiency of the carrier. HAp is also the source of Ca2+ for the regeneration and repair of diseased bone tissue. The release profiles, exhibited a steady state release rate with significant antimicrobial activity against Staphylococcus aureus (S. aureus) (SH1000) even at high concentration of bacteria. The devices also indicated significant ability to control the growth of bacterial even after four weeks of drug release. Clinical release profiles can be easily tuned from drug-HAp physicochemical interactions and degradation kinetics of polymer matrix. The developed systems could be applied to prevent microbial adhesion to medical implant surfaces and to treat infections mainly caused by S. aureus in surgery.

Coral exoskeletons as a precursor material for the development of a calcium phosphate drug delivery system for bone tissue engineering.

With the global rise in aging of populations, the occurrence of osteoporosis will continue to increase. Biomaterial and pharmaceutical scientists continue to develop innovative strategies and materials to address this disease. In this article, we describe a new perspective and approach into the use of coral exoskeletons as a precursor material to synthesize a calcium phosphate-based drug delivery system. Studies detailing the methodology of the conversion methods and the strategies and approach for the development of these novel drug delivery systems are described. Furthermore, in vivo studies in osteoporotic mice using a drug loaded and chemically modified version of the biomimetic delivery system showed significant cortical and cancellous bone increases. These studies support the notion and the rationale for future research and development of the use of coral exoskeletons as materials for drug delivery applications.

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.

Effects of micromovement on the changes in stress distribution of partially stabilized zirconia (PS-ZrO2) dental implants and bridge during clenching: a three-dimensional finite element analysis.

OBJECTIVE: This investigation aims to evaluate the changes in stress magnitudes and distributions on Partially Stabilized Zirconia (PS-ZrO(2)) dental implants and bridges and on the mandible caused by fibrous encapsulations during clenching. MATERIALS AND METHODS: Four 3.26 mm diameter PS-ZrO(2) dental implants with lengths of 12 mm were modelled and placed in the second premolar and first molar region on both sides of the mandible model. A rigid zirconia bridge with a thickness of 0.5 mm connects the PS-ZrO(2) dental implants placed in the second premolar and first molar. Four periodontal ligament (PDL) case studies were examined: PDL in the second premolars; PDL in the first molars; PDL in both the second premolars and first molars; and no PDL present. RESULTS: The results reveal the magnitudes and distributions of stresses on the dental implants and connecting bridges were governed by the PDLs. A significant drop in stress levels were recorded when the PDL encapsulates the roots of the dental implants. Of the four PDL case studies, it was found that when the PDLs are present in both the second premolars and first molars the lowest stress magnitudes are generated. The analysis also revealed that, during the healing process after implant insertion and the result of fibrous encapsulation, the dental implant system will experience a varying amount of stress levels. CONCLUSION: This study was intended to produce more insight into the influence of the PDL on the changes in stress distribution on the dental implant system during clenching.

Finite element stress analysis of Ti-6Al-4V and partially stabilized zirconia dental implant during clenching.

OBJECTIVE: The purpose of this paper is to compare the differences in stress between Ti-6Al-4V and PS-ZrO(2) dental implant during clenching and whether these changes are clinically significant to limit the use of zirconia in oral implantology. MATERIALS AND METHODS: The model geometry was derived from position measurements taken from 28 diamond blade cut cross-sections of an average size human adult edentulous mandible and generated using a special sequencing method. Data on anatomical, structural, functional aspects and material properties were obtained from measurements and published data. Ti-6Al-4V and PS-ZrO(2) dental implants were modelled as cylindrical structure with a diameter of 3.26 mm and length of 12.00 mm was placed in the first molar region on the right hemimandible. RESULTS: The analysis revealed an increase of 2-3% in the averaged tensile and compressive stress and an increase of 8% in the averaged Von Mises stress were recorded in the bone-implant interface when PS-ZrO(2) dental implant was used instead of Ti-6Al-4V dental implant. The results also revealed only relatively low levels of stresses were transferred from the implant to the surrounding cortical and cancellous bone, with the majority of the stresses transferred to the cortical bone. CONCLUSION: Even though high magnitudes of tensile, compressive and Von Mises stresses were recorded on the Ti-6Al-4V and PS-ZrO(2) dental implants and in the surrounding osseous structures, the stresses may not be clinically critical since the mechanical properties of the implant material and the cortical and cancellous bone could withstand stress magnitudes far greater than those recorded in this analysis.

In vitro testing and efficacy of poly-lactic acid coating incorporating antibiotic loaded coralline bioceramic on Ti6Al4V implant against Staphylococcus aureus.

Biofilm formation on an implant surface is most commonly caused by the human pathogenic bacteria Staphylococcus aureus, which can lead to implant related infections and failure. It is a major problem for both implantable orthopedic and maxillofacial devices. The current antibiotic treatments are typically delivered orally or in an injectable form. They are not highly effective in preventing or removing biofilms, and they increase the risk of antibiotic resistance of bacteria and have a dose-dependent negative biological effect on human cells. Our aim was to improve current treatments via a localized and controlled antibiotic delivery-based implant coating system to deliver the antibiotic, gentamicin (Gm). The coating contains coral skeleton derived hydroxyapatite powders (HAp) that act as antibiotic carrier particles and have a biodegradable poly-lactic acid (PLA) thin film matrix. The system is designed to prevent implant related infections while avoiding the deleterious effects of high concentration antibiotics in implants on local cells including primary human adipose derived stem cells (ADSCs). Testing undertaken in this study measured the rate of S. aureus biofilm formation and determined the growth rate and proliferation of ADSCs. After 24 h, S. aureus biofilm formation and the percentage of live cells found on the surfaces of all 5%-30% (w/w) PLA-Gm-(HAp-Gm) coated Ti6Al4V implants was lower than the control samples. Furthermore, Ti6Al4V implants coated with up to 10% (w/w) PLA-Gm-(HAp-Gm) did not have noticeable Gm related adverse effect on ADSCs, as assessed by morphological and surface attachment analyses. These results support the use and application of the antibacterial PLA-Gm-(HAp-Gm) thin film coating design for implants, as an antibiotic release control mechanism to prevent implant-related infections.

Synthetic tissue engineering with smart, cytomimetic protocells.

Synthetic protocells are rudimentary origin-of-life versions of natural cell counterparts. Protocells are widely engineered to advance efforts and useful accepted outcomes in synthetic biology, soft matter chemistry and bioinspired materials chemistry. Protocells in collective symbiosis generate synthetic proto-tissues that display unprecedented autonomy and yield advanced materials with desirable life-like features for smart multi-drug delivery, micro bioreactors, renewable fuel production, environmental clean-up, and medicine. Current levels of protocell and proto-tissue functionality and adaptivity are just sufficient to apply them in tissue engineering and regenerative medicine, where they animate biomaterials and increase therapeutic cell productivity. As of now, structural biomaterials for tissue engineering lack the properties of living biomaterials such as self-repair, stochasticity, cell synergy and the sequencing of molecular and cellular events. Future protocell-based biomaterials provide these core properties of living organisms, but excluding evolution. Most importantly, protocells are programmable for a broad array of cell functions and behaviors and collectively in consortia are tunable for multivariate functions. Inspired by upcoming designs of smart protocells, we review their developmental background and cover the most recently reported developments in this promising field of synthetic proto-biology. Our emphasis is on manufacturing proto-tissues for tissue engineering of organoids, stem cell niches and reprogramming and tissue formation through stages of embryonic development. We also highlight the exciting reported developments arising from fusing living cells and tissues, in a valuable hybrid symbiosis, with synthetic counterparts to bring about novel functions, and living tissue products for a new synthetic tissue engineering discipline.

Comparative Analysis of NF-κB in the MyD88-Mediated Pathway After Implantation of Titanium Alloy and Stainless Steel and the Role of Regulatory T Cells.

OBJECTIVE: Development of immunologically smart implants, integrated to biological systems, is a key aim to minimize the inflammatory response of the host to biomaterial implants. METHODS: The aim of this study is to investigate the influence of titanium alloy and stainless steel implants on immunological responses in rats by comparative analysis of nuclear factor kappa B (NF-κB) profiles in the activation of inflammatory signaling pathways and the role of CD4+CD25+Foxp3+. RESULTS: Both Ti alloy and stainless steel alloy group implantation affect Toll-like receptors-4 pathways and CD4+CD25+ regulatory T cells in different ways. CONCLUSIONS: Results show that NF-κB/p65 and NF-κB1/p50 possess potential as a therapeutic target in the prevention of adverse reactions to metal, especially for controlling inflammation after the implantation.

Mechanical testing of antimicrobial biocomposite coating on metallic medical implants as drug delivery system.

Post-operative infection often occurs following orthopedic and dental implant placement requiring systemically administered antibiotics. However, this does not provide long-term protection. Over the last few decades, alternative methods involving slow drug delivery systems based on biodegradable poly-lactic acid and antibiotic loaded hydroxyapatite microspheres were developed to prevent post-operative infection. In this study, thermally anodised and untreated Ti6Al4V discs were coated with Poly-Lactic Acid (PLA) containing Gentamicin (Gm) antibiotic-loaded coralline Hydroxyapatite (HAp) are investigated. Following chemical characterization, mechanical properties of the coated samples were measured using nanoindentation and scratch tests to determine the elastic modulus, hardness and bonding adhesion between film and substrate. It was found that PLA biocomposite multilayered films were around 400nm thick and the influence and effect of the substrate were clearly observed during the nanoindentation studies with heavier loads. Scratch tests of PLA coated samples conducted at ~160nm depth showed the minimal difference in the measured friction between Gm and non Gm containing films. It is also observed that the hardness values of PLA film coated anodised samples ranged from 0.45 to 1.9GPa (dependent on the applied loads) against untreated coated samples which ranged from 0.28 to 0.8GPa.

Porous orbital implants in enucleation: a systematic review.

Orbital implants have been used for cosmesis following surgical removal of the eyeball, or enucleation, for over a century. Implant design has progressed significantly in recent years with the use of porous devices, with the theoretical advantages of reduced complications and improved cosmesis. However, in some cases the theoretical benefits have not fully translated into clinical results. In this article the use of orbital implants in enucleation, with a particular focus on the newer porous biomaterials that have gained prominence over the last 15 years, is reviewed. Specific factors identified as affecting the performance of porous orbital implants include the material used, pore size, and morphology. Mechanical factors have received little consideration in the past and may form a basis for the use of higher compliance porous materials in the future. Of the porous materials in use, current clinical evidence is not sufficient to suggest either that porous implants are superior to non-porous implants, or that one material is more suited to the application than another. Future developments in this field require randomized controlled clinical trials with extensive follow-up as complications may not become evident until over 5 years post-implantation.

Development and dissolution studies of bisphosphonate (clodronate)-containing hydroxyapatite-polylactic acid biocomposites for slow drug delivery.

An increase in clinical demand on the controlled release of bisphosphonates (BPs) due to complications associated with systemic administration, has been the current driving force on the development of BP drug-release systems. Bisphosphonates have the ability to bind to divalent metal ions, such as Ca2+ , in bone mineral and prevent bone resorption by influencing the apoptosis of osteoclasts. Localized delivery using biodegradable materials, such as polylactic acid (PLA) and hydroxyapatite (HAp), which are ideal in this approach, have been used in this study to investigate the dissolution of clodronate (non-nitrogen-containing bisphosphonate) in a new release system. The effects of coral structure-derived HAp and the release kinetics of the composites were evaluated. The release kinetics of clodronate from PLA-BP and PLA-HAp-BP systems seemed to follow the power law model described by Korsmeyer-Peppas. Drug release was quantified by 31 P-NMR with detection and quantification limits of 9.2 and 30.7 mM, respectively. The results suggest that these biocomposite systems could be tuned to release clodronate for both relatively short and prolonged period of time. In addition to drug delivery, the degradation of HAp supplies both Ca2+ and phosphate ions that can help in bone mineralization. Copyright © 2015 John Wiley & Sons, Ltd.

Three-Dimensional Implant Positioning with a Piezosurgery Implant Site Preparation Technique and an Intraoral Surgical Navigation System: Case Report.

This case report describes new implant site preparation techniques joining the benefits of using an intraoral navigation system to optimize three-dimensional implant site positioning in combination with an ultrasonic osteotomy. A report of five patients is presented, and the implant positions as planned in the navigation software with the postoperative scan image were compared. The preliminary results are useful, although further clinical studies with larger populations are needed to confirm these findings.

Functionalisation of Ti6Al4V and hydroxyapatite surfaces with combined peptides based on KKLPDA and EEEEEEEE peptides.

Surface modifications are usually performed on titanium alloys to improve osteo-integration and surface bioactivity. Modifications such as alkaline and acid etching, or coating with bioactive materials such as hydroxyapatite, have previously been demonstrated. The aim of this work is to develop a peptide with combined titanium oxide and hydroxyapatite binders in order to achieve a biomimetic hydroxyapatite coating on titanium surfaces. The technology would also be applicable for the functionalisation of titanium and hydroxyapatite surfaces for selective protein adsorption, conjugation of antimicrobial peptides, and adsorption of specialised drugs for drug delivery. In this work, functionalisation of Ti6Al4V and hydroxyapatite surfaces was achieved using combined titanium-hydroxyapatite (Ti-Hap) peptides based on titanium peptide binder (KKLPDA) and hydroxyapatite peptide binder (EEEEEEEE). Homogeneous peptide coatings on Ti6Al4V surfaces were obtained after surface chemical treatments with a 30wt% aqueous solution of H2O2 for 24 and 48h. The treated titanium surfaces presented an average roughness of Sa=197nm (24h) and Sa=128nm (48h); an untreated mirror polished sample exhibited an Sa of 13nm. The advancing water contact angle of the titanium oxide layer after 1h of exposure to 30wt% aqueous solution of H2O2 was around 65°, decreasing gradually with time until it reached 35° after a 48h exposure, suggesting that the surface hydrophilicity increased over etching time. The presence of a lysine (L) amino acid in the sequence of the titanium binder resulted in fluorescence intensity roughly 16% higher compared with the arginine (R) amino acid analogue and therefore the lysine containing titanium peptide binder was used in this work. The Ti-Hap peptide KKLPDAEEEEEEEE (Ti-Hap1) was not adsorbed by the treated Ti6Al4V surfaces and therefore was modified. The modifications involved the inclusion of a glycine spacer between the binding terminals (Ti-Hap2) and the addition of a second titanium binder (KKLPDA) (Ti-Hap3 and Ti-Hap4). The combined Ti-Hap peptide which exhibited the strongest intensity after the titanium surface dip coating was KKLPDAKKLPDAEEEEEEEE (Ti-HAp4). On the other hand, hydroxyapatite surfaces, exhibiting an average roughness of Sa=1.42µm, showed a higher fluorescence for peptides with a higher negative net charge.

Natural and Synthetic Coral Biomineralization for Human Bone Revitalization.

Coral skeletons can regenerate replacement human bone in nonload-bearing excavated skeletal locations. A combination of multiscale, interconnected pores and channels and highly bioactive surface chemistry has established corals as an important alternative to using healthy host bone replacements. Here, we highlight how coral skeletal systems are being remolded into new calcified structures or synthetic corals by biomimetic processes, as places for the organized permeation of bone tissue cells and blood vessels. Progressive technologies in coral aquaculture and self-organization inorganic chemistry are helping to modify natural corals and create synthetic coral architectures able to accelerate bone regeneration with proper host integration at more skeletal locations, adapted to recent surgical techniques and used to treat intrinsic skeletal deformities and metabolic conditions.

Calcium phosphate nanocoatings and nanocomposites, part 2: thin films for slow drug delivery and osteomyelitis.

During the last two decades although many calcium phosphate based nanomaterials have been proposed for both drug delivery, and bone regeneration, their coating applications have been somehow slow due to the problems related to their complicated synthesis methods. In order to control the efficiency of local drug delivery of a biomaterial the critical pore sizes as well as good control of the chemical composition is pertinent. A variety of calcium phosphate based nanocoated composite drug delivery systems are currently being investigated. This review aims to give an update into the advancements of calcium phosphate nanocoatings and thin film nanolaminates. In particular recent research on PLA/hydroxyapatite composite thin films and coatings into the slow drug delivery for the possible treatment of osteomyelitis is covered.

Calcium phosphate nanocoatings and nanocomposites, part I: recent developments and advancements in tissue engineering and bioimaging.

A number of materials have been applied as implant coatings and as tissue regeneration materials. Calcium phosphate holds a special consideration, due to its chemical similarity to human bone and, most importantly, its dissolution characteristics, which allow for bone growth and regeneration. The applications of molecular and nanoscale-based biological materials have been and will continue to play an ever increasing role in enhancing and improving the osseointegration of dental and orthopedic implants. More recently, extensive research efforts have been focused on the development and applications of fluorescent nanoparticles and nanocoatings for in vivo imaging and diagnostics as well as devising methods of adding luminescent or fluorescent capabilities to enhance the in vivo functionality of calcium phosphate-based biomedical materials.

Nanobiomaterial Coatings in Dentistry.

During the last decade, there has been a major increase in the interest of nanostructured materials in advanced technologies for biomedical and dental clinical applications. Nanostructured materials are associated with a variety of applications within the dental and biomedical field, for example nanoparticles in drug delivery systems and nanostructured scaffolds in tissue engineering. More importantly, nanotechnology has also been linked with the modification of surface properties of synthetic implants in an attempt to improve their bioactivity, reliability and protection from the release of harmful or unnecessary metal ions. This is achieved through the use of nanocoatings and nanocomposite coatings. These new-generation coatings based on inorganic materials and biological materials such as proteins and peptides are currently investigated and applied. This chapter aims to give an overview of the recent advances in nanocoatings and their composites being investigated or used in dentistry.

Biomechanics and functional distortion of the human mandible.

The reaction to the use of finite element analysis (FEA) in the study of the human body has been particularly enthusiastic. Of equal and challenging complexity is the investigation of load/stress distribution and morphological distortion of the human mandible under functional loads. Furthermore, the mandible also impacts directly on body function and esthetics, playing a vital role, such as mastication and speech. The application of FEA to the biomechanical investigation of the oral systems, such as human teeth and mandibular bone remodeling, began in the early 1970s. The clinical significance of jaw deformation is unknown. The primary concern is that deformation might result in an ill-fitting superstructure or the creation of harmful strains in the patient-implant complex. Although mandibular implant treatment has a high success rate, the possibility of failure caused by these dimensional changes and the related micromotion cannot be ignored.