Osteoblast function on nanophase alumina materials: Influence of chemistry, phase, and topography

Biological evaluation and osteogenic potential of polyhydroxybutyrate-keratin/Al2O3 electrospun nanocomposite scaffold: A novel bone regeneration construct

In this study, the effect of alumina nanowire on the physical and biological properties of polyhydroxybutyrate-keratin (PHB-K) electrospun scaffold was investigated. First, PHB-K/alumina nanowire nanocomposite scaffolds were made with an optimal concentration of 3 wt% alumina nanowire by using the electrospinning method. The samples were examined in terms of morphology, porosity, tensile strength, contact angle, biodegradability, bioactivity, cell viability, ALP activity, mineralization ability, and gene expression. The nanocomposite scaffold provided a porosity of >80 % and a tensile strength of about 6.72 Mpa, which were noticeable for an electrospun scaffold. AFM images showed an increase in the surface roughness with the presence of alumina nanowires. This led to an improvement in the degradation rate and bioactivity of PHB-K/alumina nanowire scaffolds. The viability of mesenchymal cells, alkaline phosphatase secretion, and mineralization significantly increased with the presence of alumina nanowire compared to PHB and PHB-K scaffolds. In addition, the expression level of collagen I, osteocalcin, and RUNX2 genes in nanocomposite scaffolds increased significantly compared to other groups. In general, this nanocomposite scaffold could be a novel and interesting construct for osteogenic induction in bone tissue engineering.

Surface Characteristics and Bone Biocompatibility of Cold-Sprayed Porous Titanium on Polydimethylsiloxane Substrates

A variant of the cold spray (CS) technique was applied for the functionalization of polymer-based materials such as polydimethylsiloxane (PDMS) to improve the extent of mammalian cell interactions with these substrates. This was demonstrated by the embedment of porous titanium (pTi) into PDMS substrates using a single-step CS technique. CS processing parameters such as gas pressure and temperature were optimized to achieve the mechanical interlocking of pTi in the compressed PDMS to fabricate a unique hierarchical morphology possessing micro-roughness. As evidenced by the preserved porous structure, the pTi particles did not undergo any significant plastic deformation upon impact with the polymer substrate. The thickness of the particle embedment layer was determined, by cross-sectional analysis, ranging from 120 μm to over 200 μm. The behavior of osteoblast-like cells MG63 coming into contact with the pTi-embedded PDMS was examined. The results showed that the pTi-embedded PDMS samples promoted 80-96% of cell adhesion and proliferation during the early stages of incubation. The low cytotoxicity of the pTi-embedded PDMS was confirmed, with cell viability of the MG63 cells being above 90%. Furthermore, the pTi-embedded PDMS facilitated the production of alkaline phosphatase and calcium deposition in the MG63 cells, as demonstrated by the higher amount of alkaline phosphatase (2.6 times) and calcium (10.6 times) on the pTi-embedded PDMS sample fabricated at 250 °C, 3 MPa. Overall, the work demonstrated that the CS process provided flexibility in the parameters used for the production of the modified PDMS substrates and is highly efficient for the fabrication of coated polymer products. The results obtained in this study suggest that a tailorable porous and rough architecture could be achieved that promoted osteoblast function, indicating that the method has promise in the design of titanium-polymer composite materials applied to biomaterials used in musculoskeletal applications.

The Safety of Micro-Implants for the Brain

Technological advancements in electronics and micromachining now allow the development of discrete wireless brain implantable micro-devices. Applications of such devices include stimulation or sensing and could enable direct placement near regions of interest within the brain without the need for electrode leads or separate battery compartments that are at increased risk of breakage and infection. Clinical use of leadless brain implants is accompanied by novel risks, such as migration of the implant. Additionally, the encapsulation material of the implants plays an important role in mitigating unwanted tissue reactions. These risks have the potential to cause harm or reduce the service of life of the implant. In the present study, we have assessed post-implantation tissue reaction and migration of borosilicate glass-encapsulated micro-implants within the cortex of the brain. Twenty borosilicate glass-encapsulated devices (2 × 3.5 × 20 mm) were implanted into the parenchyma of 10 sheep for 6 months. Radiographs were taken directly post-surgery and at 3 and 6 months. Subsequently, sheep were euthanized, and GFAP and IBA-1 histological analysis was performed. The migration of the implants was tracked by reference to two stainless steel screws placed in the skull. We found no significant difference in fluoroscopy intensity of GFAP and a small difference in IBA-1 between implanted tissue and control. There was no glial scar formation found at the site of the implant’s track wall. Furthermore, we observed movement of up to 4.6 mm in a subset of implants in the first 3 months of implantation and no movement in any implant during the 3–6-month period of implantation. Subsequent histological analysis revealed no evidence of a migration track or tissue damage. We conclude that the implantation of this discrete micro-implant within the brain does not present additional risk due to migration.

Improved osseointegration properties of hierarchical microtopographic/nanotopographic coatings fabricated on titanium implants

Background

Titanium (Ti) implants are extensively used in reconstructive surgery and orthopedics. However, the intrinsic inertness of untreated Ti implants usually results in insufficient osseointegration. In order to improve the osteoconductivity properties of the implants, they are coated with hierarchical microtopographic/nanotopographic coatings employing the method of molecular layering of atomic layer deposition (ML-ALD).

Results

The analysis of the fabricated nanostructured relief employing scanning electron microscopy, atomic force microscopy, and electron spectroscopy for chemical analysis clearly demonstrated the formation of the nanotopographic (<100 nm) and microtopographic (0.1–0.5 μm) titano-organic structures on the surface of the nanograined Ti implants. Subsequent coincubation of the MC3T3-E1 mouse osteoblasts on the microtopographic/nanotopographic surface of the implants resulted in enhanced osteogenic cell differentiation (the production of alkaline phosphatase, osteopontin, and osteocalcin). In vivo assessment of the osseointegrative properties of the microtopographically/nanotopographically coated implants in a model of below-knee amputation in New Zealand rabbits demonstrated enhanced new bone formation in the zone of the bone–implant contact (as measured by X-ray study) and increased osseointegration strength (removal torque measurements).

Conclusion

The fabrication of the hierarchical microtopographic/nanotopographic coatings on the nanograined Ti implants significantly improves the osseointegrative properties of the intraosseous Ti implants. This effect could be employed in both translational and clinical studies in orthopedic and reconstructive surgery.

Hydrogels 2.0: improved properties with nanomaterial composites for biomedical applications

The incorporation of nanomaterials in hydrogels (hydrated networks of crosslinked polymers) has emerged as a useful method for generating biomaterials with tailored functionality. With the available engineering approaches it is becoming much easier to fabricate nanocomposite hydrogels that display improved performance across an array of electrical, mechanical, and biological properties. In this review, we discuss the fundamental aspects of these materials as well as recent developments that have enabled their application. Specifically, we highlight synthesis and fabrication, and the choice of nanomaterials for multifunctionality as ways to overcome current material property limitations. In addition, we review the use of nanocomposite hydrogels within the framework of biomedical and pharmaceutical disciplines.

Composites of Polymer Hydrogels and Nanoparticulate Systems for Biomedical and Pharmaceutical Applications

Due to their unique structures and properties, three-dimensional hydrogels and nanostructured particles have been widely studied and shown a very high potential for medical, therapeutic and diagnostic applications. However, hydrogels and nanoparticulate systems have respective disadvantages that limit their widespread applications. Recently, the incorporation of nanostructured fillers into hydrogels has been developed as an innovative means for the creation of novel materials with diverse functionality in order to meet new challenges. In this review, the fundamentals of hydrogels and nanoparticles (NPs) were briefly discussed, and then we comprehensively summarized recent advances in the design, synthesis, functionalization and application of nanocomposite hydrogels with enhanced mechanical, biological and physicochemical properties. Moreover, the current challenges and future opportunities for the use of these promising materials in the biomedical sector, especially the nanocomposite hydrogels produced from hydrogels and polymeric NPs, are discussed.

Lightweight breast implants: a novel solution for breast augmentation and reconstruction mammaplasty

Breast augmentation and reconstruction mammaplasty have been in practice for decades and are highly prevalent surgeries performed worldwide. While overall patient satisfaction is high, common long-term effects include breast tissue atrophy, accelerated ptosis and inframammary fold breakdown. Increasing evidence attributes these events to the durative loading and compressive forces introduced by the breast implants. Mechanical challenges exceeding the elastic capacity of the breast tissue components, eventually lead to irreversible tissue stretching, directly proportional to the introduced mass. Thus, it is suggested that, contrary to long-standing dogmas, implant weight, rather than its volume, stands at the basis of future tissue compromise and deformation. A novel lightweight implant has been developed to address the drawbacks of traditional breast implants, which demonstrate equivalence between their size and weight. The B-Lite^® breast implant (G&G Biotechnology Ltd., Haifa, Israel) design allows for a reduction in implant weight of up to 30%, while maintaining the size, form, and function of traditional breast implants. The CE-marked device can be effectively implanted using standard of care procedures and has been established safe for human use. Implantation of the B-Lite^® breast implant is projected to significantly reduce the inherent strains imposed by standard implants, thereby conserving tissue stability and integrity over time. In summary, this novel, lightweight breast implant promises to reduce breast tissue compromise and deformation and subsequent reoperation, further improving patient safety and satisfaction.

Shape and surface effects on the cytotoxicity of nanoparticles: Gold nanospheres versus gold nanostars

Gold nanoparticles are materials with unique optical properties that have made them very attractive for numerous biomedical applications. With the increasing discovery of techniques to synthesize novel nanoparticles such as star-shaped gold nanoparticles for biomedical applications, the safety and performance of these new nanomaterials must be systematically assessed before use. In this study, gold nanostars (AuNSTs) with multibranched surface structures were synthesized, and their influence on the cytotoxicity of human skin fibroblasts and rat fat pad endothelial cells (RFPECs) were assessed and compared with that of gold nanospheres (AuNSPs) with unbranched surfaces. Results showed that the AuNSPs with diameters of approximately 61.46 nm showed greater toxicity with fibroblast cells and RFPECs compared with the synthesized AuNSTs with diameters of approximately 33.69 nm. The AuNSPs were lethal at concentrations of 40 μg/mL for both cell lines, whereas the AuNSTs were less toxic at higher concentrations (400 μg/mL). The calculated IC50 (50% inhibitory concentration) values of the AuNSPs exposed to fibroblast cells were greater at 1 and 4 days of culture (26.4 and 27.7 μg/mL, respectively) compared with the RFPECs (13.6 and 13.8 μg/mL, respectively), indicating that the AuNSPs have a greater toxicity to endothelial cells. It was proposed that possible factors that could be promoting the reduced toxicity effects of the AuNSTs to fibroblast cells and RFPECs, compared with the AuNSPs may be size, surface chemistry, and shape of the gold nanoparticles. The reduced cell toxicity observed with the AuNSTs suggests that AuNSTs may be a promising material for use in biomedical applications.

Nanosurface - the future of implants

Nanotechnology is a relatively newer field of science that is finding enormous scope in the dental & medical science. Use of endosseous dental implant surfaces having nano-scale topography is fast becoming part of modern implantology. The purpose of this review is to discuss and understand the role of nanoscale surface modification of titanium materials for the purpose of improving various phases of implantology including osseointegration. Nanotechnology equips bioengineers with newer ways of interacting with relevant biological processes. On the other hand, the field of nanotechnology provides means of understanding and achieving cell specific functions. An understanding of the role of nano-topography leads to the significant osseointegration modulations by nanoscale modification of the implants surface. Use of nanotechnology to modify the topography of titanium endosseous implant can drastically improve cellular and tissue responses that may benefit osseointegration and dental implant procedures.

Nanotechnology in dentistry today

A review was done of nanotechnology as it applies to dentistry today. Information was gathered from literature search, research data and material inserts in products.Nanotechnology deals with the physical, chemical and biological properties of structures and their components at nanoscale dimensions. One of the biggest contributionS to restorative and aesthetic dentistry has been nanocomposites. These composites are characterized by filler-particle sizes ≤ 100 nm and offer aesthetic and strength advantages over the current microfilled and hybrid resin-based composites. Nanoparticles for coating implant surfaces and the nanopatterning of dental implants is leading to better osseointegration and improved physiologic functions of implants, while nanophase hydroxyapatite has improved its adaptation into bone graft sites. Nano-biochips are now making oral cancer screening and diagnosis of diseases by saliva easier and more affordable.

Technological advances in nanoscale biomaterials: the future of synthetic vascular graft design

Currently, autologous veins are the first choice for patients in need of bypass grafting materials. However, due to either pre-existing conditions or previous bypass surgery, some patients lack the necessary amount of host tissue for such procedures. Unfortunately, current synthetic vascular grafts of less than 6 mm in diameter have been plagued by a variety of problems. For this reason, there has been significant research aimed at finding more suitable small-diameter vascular graft materials. In order to improve vascular cell functions on such synthetic materials, several techniques are currently under development that attempt to mimic the natural nanometer architecture of the vascular basement membrane. This review presents several processes including colloidal lithography, chemical etching, electrospinning and solid free-form fabrication that could play a role in the future of vascular nanostructured biomaterial development.

Tailor-made charge-conversional nanocomposite for pH-responsive drug delivery and cell imaging

Imaging labels, therapeutic drugs, as well as many other agents can all be integrated into one nanoplatform to allow for molecular imaging and therapy. With this in mind, herein we report the first example of a tailor-made charge-conversional nanocomposite composed of mesoporous γ-AlO(OH) and upconversion nanoparticles (UCNPs) via a simple and versatile method, and the obtained nanocomposite could be performed as a drug delivery carrier and applied for cell imaging. The nanocomposite (UCNPs-Al) was found to be able to efficiently transport DOX, a typical chemotherapeutic anticancer drug, into the cancer cell and release DOX from UCNPs-Al triggering by the mildly acidic environment. In vitro cell cytotoxicity assay verified that DOX-loaded nanocomposites (UCNPs-Al-DOX) exhibited greater cytotoxicity with respect to free DOX at the same concentrations, because of the increase in cell uptake of anti-cancer drug delivery vehicles mediated by the charge-conversional property. Moreover, the UCL emission from UCNPs and the red fluorescence of DOX allow the nanocomposite to track and monitor the drug delivery system simultaneously. These findings have opened up new insights into designing and producing the highly versatile multifunctional nanoparticles for simultaneous imaging and therapeutic applications.

Nanocomposite hydrogels for biomedical applications

Hydrogels mimic native tissue microenvironment due to their porous and hydrated molecular structure. An emerging approach to reinforce polymeric hydrogels and to include multiple functionalities focuses on incorporating nanoparticles within the hydrogel network. A wide range of nanoparticles, such as carbon-based, polymeric, ceramic, and metallic nanomaterials can be integrated within the hydrogel networks to obtain nanocomposites with superior properties and tailored functionality. Nanocomposite hydrogels can be engineered to possess superior physical, chemical, electrical, and biological properties. This review focuses on the most recent developments in the field of nanocomposite hydrogels with emphasis on biomedical and pharmaceutical applications. In particular, we discuss synthesis and fabrication of nanocomposite hydrogels, examine their current limitations and conclude with future directions in designing more advanced nanocomposite hydrogels for biomedical and biotechnological applications.

Titanium implant with nanostructured zirconia surface promotes maturation of peri-implant bone in osseointegration

The goal of the experiment outlined in this article is to improve upon noncemented methods of arthroplasty for clinical application in elderly patients. This was done by determining whether titanium implants with a novel nanostructured zirconia surface, which was created by ion beam-assisted deposition, would prevent impaired osseointegration of intramedullary implants in 1-year-old rats receiving a protein-deficient diet. Specifically, we asked whether the implant with the nanostructured zirconia surface would increase expression of markers of bone maturation within the remodeling of peri-implant woven bone. The control implants, which were made of commercially pure titanium, had a polished surface ex vivo but are known to acquire a microstructured titania surface in vivo. Ten 1-year-old rats received experimental implant (group A) and 10 had control (group B) implants. Ten 3-month-old rats received normal protein diet and the control implant (group C). Animals were euthanized 8 weeks after implantation, and transverse sections of femur-implant samples were used for histology, micro-computed tomography and immunohistochemical evaluations. In group B, the expression of α2β1 and α5β1 integrins, which are known to mediate osteoblast adhesion, glycosaminoglycans, heparan sulfate and chondroitin sulfate, was less than half of that in group C. Important to this study, the zirconia surface used in group A prevented these deficiencies. Therefore, these results indicate that nanostructured zirconia surface created on clinical implants by ion beam-assisted deposition may prevent impaired osseointegration in elderly patients by promoting quicker maturation of peri-implant woven bone.

Implants in bone: part I. A current overview about tissue response, surface modifications and future perspectives

PURPOSE

The aim of study paper is to present an overview of osseointegration of dental implants, focusing on tissue response, surface modifications and future perspective.

DISCUSSION

Great progress has been made over the decades in the understanding of osseous peri-implant healing of dental implants, leading to the development of new implant materials and surfaces. However, failures and losses of implants are an indicator that there is room for improvement. Of particular importance is the understanding of the biological interaction between the implant and its surrounding bone.

CONCLUSION

The survival rates of dental implants in bone of over 90 % after 10 years show that they are an effective and well-established therapy option. However, new implant materials and surface modifications may be able to improve osseointegration of medical implants especially when the wound healing is compromised. Advanced techniques of evaluation are necessary to understand and validate osseointegration in these cases. An overview regarding the current state of the art in experimental evaluation of osseointegration of implants and implant material modifications will be given in Part II.

Nanosurface design of dental implants for improved cell growth and function

A strategy was proposed for the topological design of dental implants based on an in vitro survey of optimized nanodot structures. An in vitro survey was performed using nanodot arrays with dot diameters ranging from 10 to 200 nm. MG63 osteoblasts were seeded on nanodot arrays and cultured for 3 days. Cell number, percentage undergoing apoptotic-like cell death, cell adhesion and cytoskeletal organization were evaluated. Nanodots with a diameter of approximately 50 nm enhanced cell number by 44%, minimized apoptotic-like cell death to 2.7%, promoted a 30% increase in microfilament bundles and maximized cell adhesion with a 73% increase in focal adhesions. An enhancement of about 50% in mineralization was observed, determined by von Kossa staining and by Alizarin Red S staining. Therefore, we provide a complete range of nanosurfaces for growing osteoblasts to discriminate their nanoscale environment. Nanodot arrays present an opportunity to positively and negatively modulate cell behavior and maturation. Our results suggest a topological approach which is beneficial for the design of dental implants.

Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature

Thin (380-510 nm) films of a low silica content bioglass with MgO, B(2)O(3), and CaF(2) as additives were deposited at low-temperature (150°C) by radio-frequency magnetron sputtering onto titanium substrates. The influence of sputtering conditions on morphology, structure, composition, bonding strength and in vitro bioactivity of sputtered bioglass films was investigated. Excellent pull-out adherence (~73 MPa) was obtained when using a 0.3 Pa argon sputtering pressure (BG-a). The adherence declined (~46 MPa) upon increasing the working pressure to 0.4 Pa (BG-b) or when using a reactive gas mixture (~50 MPa). The SBF tests clearly demonstrated strong biomineralization features for all bioglass sputtered films. The biomineralization rate increased from BG-a to BG-b, and yet more for BG-c. A well-crystallized calcium hydrogen phosphate-like phase was observed after 3 and 15 days of immersion in SBF in all bioglass layers, which transformed monotonously into hydroxyapatite under prolonged SBF immersion. Alkali and alkali-earth salts (NaCl, KCl and CaCO(3)) were also found at the surface of samples soaked in SBF for 30 days. The study indicated that features such as composition, structure, adherence and bioactivity of bioglass films can be tailored simply by altering the magnetron sputtering working conditions, proving that this less explored technique is a promising alternative for preparing implant-type coatings.

Advances in bone repair with nanobiomaterials: mini-review

Nanotechnology has emerged to be one of the most powerful engineering approaches in the past half a century. Nanotechnology brought nanomaterials for biomedical use with diverse applications. In the present manuscript we summarize the recent progress in adopting nanobiomaterials for bone healing and repair approaches. We first discuss the use of nanophase surface modification in manipulating metals and ceramics for bone implantation, and then the use of polymers as nanofiber scaffolds in bone repair. Finally we briefly present the potential use of the nanoparticle delivery system as adjunct system in promoting bone regeneration following fracture.

Comparative cell behavior on carbon-coated TiO2 nanotube surfaces for osteoblasts vs. osteo-progenitor cells

Surface engineering approaches that alter the topological chemistry of a substrate could be used as an effective tool for directing cell interactions and their subsequent function. It is well known that the physical environment of nanotopography has positive effects on cell behavior, yet direct comparisons of nanotopographic surface chemistry have not been fully explored. Here we compare TiO(2) nanotubes with carbon-coated TiO(2) nanotubes, probing osteogenic cell behavior, including osteoblast (bone cells) and mesenchymal stem cell (MSC) (osteo-progenitor cells) interactions with the different surface chemistries (TiO(2) vs. carbon). The roles played by the material surface chemistry of the nanotubes did not have an effect on the adhesion, growth or morphology, but had a major influence on the alkaline phosphatase (ALP) activity of osteoblast cells, with the original TiO(2) chemistry having higher ALP levels. In addition, the different chemistries caused different levels of osteogenic differentiation in MSCs; however, it was the carbon-coated TiO(2) nanotubes that had the greater advantage, with higher levels of osteo-differentiation. It was observed in this study that: (a) chemistry plays a role in cell functionality, such as ALP activity and osteogenic protein gene expression (PCR); (b) different cell types may have different chemical preferences for optimal function. The ability to optimize cell behavior using surface chemistry factors has a profound effect on both orthopedic and tissue engineering in general. This study aims to highlight the importance of the chemistry of the carrier material in osteogenic tissue engineering schemes.

Bone grafting, orthopaedic biomaterials, and the clinical need for bone engineering

As the population ages, the number of operations performed on bone is expected to increase. Diseases such as arthritis, tumours, and trauma can lead to defects in the skeleton requiring an operation to replace or restore the lost bone. Surgeons can use autografts, allografts, and/or bone graft substitutes to restore areas of bone loss. Surgical implants are also used in addition or in isolation to replace the diseased bone. This review considers the application of available bone grafts in different clinical settings. It also discusses recently introduced bioactive biomaterials and highlights the clinical difficulties and technological deficiencies that exist in our current surgical practice.

Dual-Scale Polymeric Constructs as Scaffolds for Tissue Engineering

This research activity was aimed at the development of dual-scale scaffolds consisting of three-dimensional constructs of aligned poly(ε-caprolactone) (PCL) microfilaments and electrospun poly(lactic-co-glycolic acid) (PLGA) fibers. PCL constructs composed by layers of parallel microsized filaments (0/90° lay-down pattern), with a diameter of around 365 μm and interfilament distance of around 191 μm, were produced using a melt extrusion-based additive manufacturing technique. PLGA electrospun fibers with a diameter of around 1 μm were collected on top of the PCL constructs with different thicknesses, showing a certain degree of alignment. Cell culture experiments employing the MC3T3 murine preosteoblast cell line showed good cell viability and adhesion on the dual-scale scaffolds. In particular, the influence of electrospun fibers on cell morphology and behavior was evident, as well as in creating a structural bridging for cell colonization in the interfilament gap.

Laser engineered multilayer coating of biphasic calcium phosphate/titanium nanocomposite on metal substrates

In this work, laser coating of biphasic calcium phosphate/titanium (BCP/Ti) nanocomposite on Ti-6Al-4 V substrates was developed. A continuous wave neodymium-doped yttrium aluminium garnet (Nd:YAG) laser was used to form a robust multilayer of BCP/Ti nanocomposite starting from hydroxyapatite and titanium nanoparticles. In this process, low power coating is realized because of the strong laser-nanoparticle interaction and good sinterability of nanosized titanium. To guide the optimization of laser processing conditions for the coating process, a multiphysics model coupling electromagnetic module with heat transfer module was developed. This model was validated by laser coating experiments. Important features of the coated samples, including microstructures, chemical compositions, and interfacial bonding strength, were characterized. We found that a multilayer of BCP, consisting of 72% hydroxyapatite (HA) and 28% beta-tricalcium phosphate (β-TCP), and titanium nanocomposite was formed on Ti-6Al-4 V substrates. Significantly, the coating/substrate interfacial bonding strength was found to be two times higher than that of the commercial plasma sprayed coatings. Preliminary cell culture studies showed that the resultant BCP/Ti nanocomposite coating supported the adhesion and proliferation of osteoblast-like UMR-106 cells.

Characterization of bionanocomposite scaffolds comprised of amine-functionalized single-walled carbon nanotubes crosslinked to an acellular porcine tendon

Carbon nanotubes (CNT) possess many unique electrical and mechanical properties that make them useful for a variety of industrial and biomedical applications. They are especially attractive materials for biomedical applications since their dimensions are similar to components of the extracellular matrix. In this study, amine-functionalized single-walled carbon nanotubes were crosslinked to an acellular porcine diaphragm tendon. The resulting bionanocomposite scaffolds were subjected to a number of materials characterization techniques including a collagenase assay, uniaxial tensile testing, modulated differential scanning calorimetry, and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to determine whether the properties of the original extracellular matrix were altered by the treatment processes. A variety of SWCNT concentrations were investigated. While none of the conditions investigated resulted in bionanocomposites with significantly improved physicochemical properties, no detrimental effects were observed due to any of the processing steps. Future studies should be performed to determine if carbon nanotubes can influence cellular adhesion and function in order to promote rapid integration and remodeling.

The effect of anatase TiO2 nanotube layers on MC3T3-E1 preosteoblast adhesion, proliferation, and differentiation

Titanium oxide nanotube layers by anodization have received considerable attention in biomedical application. Previous studies have demonstrated increased osteoblast (bone-forming cell) adhesion and function on nanotube layers compared with unanodized counterparts. More recently, one study showed amorphous TiO(2) nanotube diameter determined cell fate. The anatase phase is known to be much more beneficial for bone growth than amorphous phase, so there is increasing demand to explore the response of osteoblast on anatase phase TiO(2) nanotube layers. For this reason, we evaluated MC3T3-E1 preosteoblast behavior on different diameter nanotube layers with anatase phase. The results showed that the diameter of 20-70 nm provided an effective length scale for cell adhesion, alkaline phosphatase activity, and mineralization. However, cell adhesion, alkaline phosphatase activity, and mineralization were severely impaired on nanotube layers with 100-120 nm. Interestingly, the filopodia seemed not spread into the nanotubular and like extending anatase nanotube walls, where there may be higher numbers of atoms at the surface compared to the nanotubular architecture. To our surprise, the proliferation rates of cells cultured on anatase nanotube layers increased with increasing tube diameter from 20 to 120 nm, which may be attributed to different length and nanometer-scale roughness of the nanotube layers.

The combination of micron and nanotopography by H(2)SO(4)/H(2)O(2) treatment and its effects on osteoblast-specific gene expression of hMSCs

H(2)SO(4)/H(2)O(2) treatment of titanium implants imparts nanofeatures to the surface and alters the osteoblast response. The aim of this study was to evaluate the effect of H(2)SO(4)/H(2)O(2) treatment of commercially pure Titanium (cpTi) surfaces on gene expression of human mesenchymal stem cells (hMSCs) differentiated into osteoblasts. Commercially pure grade IV titanium disks (20.0 mm x 1.0 mm) were polished or polished and subsequently treated by grit blasting or grit-blasting/acid etching with an H(2)SO(4)/H(2)O(2) solution. The surfaces were divided into three groups: smooth (S), grit-blasted (Gb), and nanostructured: grit-blasted/acid etched (Nano). Surfaces were examined by scanning electron microscopy and atomic force microscopy. HMSCs were grown on the disks. The data points analyzed were at 3, 7, 14, and 28 days. Real-time PCR was used to measure the mRNA levels of ALP, BSP, Runx2, OCN, OPN, and OSX. The housekeeping gene GAPDH was used as a control. Descriptive statistics were calculated using Microsoft Excel. T-test was performed for comparison of mRNA levels when compared with S surfaces (p < 0.05). All osteoblast-specific genes were regulated in surface-dependent patterns and most of them were upregulated on the Nano surfaces. Runx2 and OSX mRNAs were more than threefold upregulated at days 14 and 28 on Nano. Higher levels for ALP (38-fold), BSP (76-fold), and OCN (3-fold) were also observed on the Nano surfaces. A grit-blasted surface imparted with nanofeatures by H(2)SO(4)/H(2)O(2) treatment affected adherent cell bone-specific gene expression. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Nanotextured titanium surfaces for enhancing skin growth on transcutaneous osseointegrated devices

A major problem with transcutaneous osseointegrated implants is infection, mainly due to improper closure of the implant-skin interface. Therefore, the design of transcutaneous osseointegrated devices that better promote skin growth around these exit sites needs to be examined and, if successful, would clearly limit infection. Due to the success already demonstrated for orthopedic implants, developing surfaces with biologically inspired nanometer features is a design criterion that needs to be investigated for transcutaneous devices. This study therefore examined the influence of nanotextured titanium (Ti) created through electron beam evaporation and anodization on keratinocyte (skin-forming cell) function. Electron beam evaporation created Ti surfaces with nanometer features while anodization created Ti surfaces with nanotubes. Conventional Ti surfaces were largely micron rough, with few nanometer surface features. Results revealed increased keratinocyte adhesion in addition to increased keratinocyte spreading and differences in keratinocyte filopodia extension on the nanotextured Ti surfaces prepared by either electron beam evaporation or anodization compared to their conventional, unmodified counterparts after 4h. Results further revealed increased keratinocyte proliferation and cell spreading over 3 and 5days only on the nanorough Ti surfaces prepared by electron beam evaporation compared to both the anodized nanotubular and unmodified Ti surfaces. Therefore, the results from this in vitro study provided the first evidence that nano-modification techniques should be further researched as a means to possibly improve skin growth, thereby improving transcutaneous osseointegrated orthopedic implant longevity.

Synthesis of nano-sized biphasic calcium phosphate ceramics with spherical shape by flame spray pyrolysis

Nanometer size biphasic calcium phosphate (BCP) powders with various Ca/P molar ratios satisfied with appropriate phase ratios of HA/beta-TCP were prepared by high temperature flame spray pyrolysis process. The BCP powders had spherical shapes and narrow size distributions irrespective of the ratios of Ca/P. The mean size of the BCP powders measured from the TEM image was 38 nm. The composition ratio of Ca/P was controlled from 1.500 to 1.723 in the spray solution, and required phase ratios of HA/TCP are controlled systematically. The calcium dissolution of the pellets obtained from the BCP powders directly prepared by flame spray pyrolysis in buffer solution increased with the decrease of Ca/P ratios except with the Ca/P ratio of 1.713. The pellet surface with Ca/P ratio of 1.500, which consisted of beta-TCP, was eroded dramatically for 7 days. On the other hand, the pellet surface with Ca/P ratio of 1.667 was stable and did not disintegrate after immersion in Tris-HCl buffer solution based on the SEM observation.

Human mesenchymal stem cell adhesion and proliferation in response to ceramic chemistry and nanoscale topography

Modification of the chemistry and surface topography of nanophase ceramics was used to provide biomaterial formulations designed to direct the adhesion and proliferation of human mesenchymal stem cells (HMSCs). HMSC adhesion was dependent upon both the substrate chemistry and grain size, but not on surface roughness or crystal phase. Specifically, cell adhesion on alumina and hydroxyapatite was significantly reduced on the 50 and 24 nm surfaces, as compared with the 1500 and 200 nm surfaces, but adhesion on titania substrates was independent of grain size. HMSC proliferation was minimal on the 50 and 24 nm substrates of any chemistry tested, and thus significantly lower than the densities observed on either the 1500 or 200 nm surfaces after 3 or more consecutive days of culture. Furthermore, HMSC proliferation was enhanced on the 200 nm substrates, compared with results obtained on the 1500 nm substrates after 7 or more days of culture. HMSC proliferation was independent of both substrate surface roughness and crystal phase. Rat osteoblast and fibroblast adhesion and proliferation exhibited similar trends to that of HMSCs on all substrates tested. These results demonstrated the potential of nanophase ceramic surfaces to modulate functions of HMSCs, which are pertinent to biomedical applications such as implant materials and devices.

The role of nanomedicine in growing tissues

Nanomedicine (a division of nanotechnology) is an interdisciplinary research field incorporating biology, chemistry, engineering and medicine with the intention to improve disease prevention, diagnosis, and treatment. Specifically, there have been great strides made in using nanomedicine to enhance the functions of cells necessary to regenerate a diverse number of tissues (such as bone, blood vessels, the bladder, teeth, the nervous system, and the heart to name a few). Traditional (micron-structured or nano-smooth) implants suffer from: (i) infection, (ii) inflammation, and (iii) insufficient prolonged bonding between the implanted material and surrounding tissue. To date, such conventional implants have been improved by implementing nanotopographical features on their surfaces. In this review paper, the application of nanomaterials to regenerate numerous organs (including, as specific examples, bone, neural, and bladder tissues) will be presented with necessary future directions highlighted for the field of nanomedicine to progress.

Reduced responses of macrophages on nanometer surface features of altered alumina crystalline phases

Extensive prolonged interactions of inflammatory cells (such as macrophages) at the host-implant interface may lead to implant failure. While previous studies have shown increased in vitro and in vivo bone cell adhesion, proliferation and mineralization on nanophase compared to currently implanted ceramics, few studies have been conducted to elucidate inflammatory cell responses on such nanophase ceramics. Controlling surface feature size and corresponding surface roughness on implants may clearly alter immune cell responses, which would be an extremely important consideration for the use of nanostructured materials as improved biomaterials. In this study, reduced macrophage density was observed on alumina (Al(2)O(3)) compacts with greater nanometer surface roughness accompanied by changes in crystallinity for up to 24 h in culture. Since alumina is a commonly used ceramic in orthopedic applications, this in vitro study continues to support the use of nanophase ceramics as improved orthopedic implants by demonstrating reduced macrophage responses.

The effects of implant surface nanoscale features on osteoblast-specific gene expression

This study investigated the influence of nanoscale implant surface features on osteoblast differentiation. Titanium disks (20.0 x 1.0 mm) with different nanoscale materials were prepared using sol-gel-derived coatings and characterized by scanning electron microscopy, atomic force microscopy and analyzed by X-ray Photoelectron Spectrometer. Human Mesenchymal Stem Cells (hMSCs) were cultured on the disks for 3-28 days. The levels of ALP, BSP, Runx2, OCN, OPG, and OSX mRNA and a panel of 76 genes related to osteogenesis were evaluated. Topographical and chemical evaluation confirmed nanoscale features present on the coated surfaces only. Bone-specific mRNAs were increased on surfaces with superimposed nanoscale features compared to Machined (M) and Acid etched (Ac). At day 14, OSX mRNA levels were increased by 2-, 3.5-, 4- and 3-fold for Anatase (An), Rutile (Ru), Alumina (Al), and Zirconia (Zr), respectively. OSX expression levels for M and Ac approximated baseline levels. At days 14 and 28 the BSP relative mRNA expression was significantly up-regulated for all surfaces with nanoscale coated features (up to 45-fold increase for Al). The PCR array showed an up-regulation on Al coated implants when compared to M. An improved response of cells adhered to nanostructured-coated implant surfaces was represented by increased OSX and BSP expressions. Furthermore, nanostructured surfaces produced using aluminum oxide significantly enhanced the hMSC gene expression representative of osteoblast differentiation. Nanoscale features on Ti implant substrates may improve the osseointegration response by altering adherent cell response.

In vivo evaluation of anodic TiO2 nanotubes: an experimental study in the pig

Because of their ability to mimic the dimensions of constituent components of natural bone and the possibility to serve as a gene and drug-delivery carrier, nanotubes seem to be a promising coating for medical implants. Aim of this study was to investigate the effects of a TiO(2) nanotube structured surface on periimplant bone formation in vivo when compared with an untreated standard titanium surface. Twenty-five titanium implants covered with an ordered TiO(2) nanotube layer with an individual tube diameter of 30 nm and 25 commercially pure titanium (cp-Ti) implants were placed in the frontal skull of 25 domestic pigs. To evaluate the effects of the nanotube structured implants on the periimplant bone formation, bone-implant contact (BIC), and immunohistochemistry analysis were performed at day 3, 7, 14, 30, and 90. Evaluating immunohistochemistry, a significantly higher collagen type- I expression occurred at day 7 (p = 0.003), day 14 (p = 0.016), and day 30 (p = 0.044), for the nanostructured implants in comparison with the control group. It could be found that a nanotube structured implant surface with a diameter of 30 nm does influence bone formation and bone development by enhancing osteoblast function. SEM evaluation of the specimen surfaces revealed that the nanotube coatings do resist shearing forces that evoked by implant insertion. Because of their simple, low cost, flexible manufacturing and the possibility for the usage as drug or growth factor delivery system, nanotubes seem to be a promising method for future medical implant coatings.

Nano rough micron patterned titanium for directing osteoblast morphology and adhesion

Previous studies have demonstrated greater functions of osteoblasts (bone-forming cells) on nanophase compared with conventional metals. Nanophase metals possess a biologically inspired nanostructured surface that mimics the dimensions of constituent components in bone, including collagen and hydroxyapatite. Not only do these components possess dimensions on the nanoscale, they are aligned in a parallel manner creating a defined orientation in bone. To date, research has yet to evaluate the effect that organized nanosurface features can have on the interaction of osteoblasts with material surfaces. Therefore, to determine if surface orientation of features can mediate osteoblast adhesion and morphology, this study investigated osteoblast function on patterned titanium substrates containing alternating regions of micron rough and nano rough surfaces prepared by novel electron beam evaporation techniques. This study was also interested in determining whether or not the size of the patterned regions had an effect on osteoblast behavior and alignment. Results indicated early controlled osteoblast alignment on these patterned materials as well as greater osteoblast adhesion on the nano rough regions of these patterned substrates. Interestingly, decreasing the width of the nano rough regions (from 80 μm to 22 μm) on these patterned substrates resulted in a decreased number of osteoblasts adhering to these areas. Changes in the width of the nano rough regions also resulted in changes in osteoblast morphology, thus, suggesting there is an optimal pattern dimension that osteoblasts prefer. In summary, results of this study provided evidence that aligned nanophase metal features on the surface of titanium improved early osteoblast functions (morphology and adhesion) promising for their long term functions, criteria necessary to improve orthopedic implant efficacy.