Altered responses of chondrocytes to nanophase PLGA/nanophase titania composites

Physical characterization, biocompatibility, and antimicrobial activity of polyvinyl alcohol/sodium alginate blend doped with TiO2 nanoparticles for wound dressing applications

The ability of wound dressing materials to tackle skin pathogens colonization that is associated with open wound infections is limited. Recently, green-synthesized metal oxide nanoparticles has received a lot of attention to overcome this limitation. However, titanium dioxide nanoparticles (TiO2-NPs) exhibit exceptional antibacterial properties. In this work, several concentrations (0, 1, 3, and 5 wt.%) of TiO2 NPs prepared using Aloe vera leaf extract were added to a blend of polyvinyl alcohol and sodium alginate (PVA:SA). This nanocomposite was designed to enhance the healing process of wounds. The interaction between the PVA:SA composite and the TiO2 NPs was confirmed by FTIR. The thermal behavior of the nanocomposite films was investigated using DSC and TGA. The experimental results indicate that the glass transition temperatures of the nanocomposites increased by increasing the added amount of TiO2 NPs to be 53.7 °C (1 wt.%), 55.8 °C (3 wt.%), and 60.6 °C (5 wt.%), which were consistently lower than the glass transition temperature of the matrix material (69.6 °C). The Dynamic Mechanical Analysis was examined. The nanocomposite doped with 5 wt.% of TiO2 NPs detected a high storage modulus (21.6 × 108). Based on swelling and degradation studies, the prepared PVA:SA:TiO2 nanocomposite films have an excellent swelling rate, and the inclusion of TiO2 NPs increases the stability of the polymeric matrix. The PVA:SA:TiO2 nanocomposite films exhibited a superior antibacterial efficacy against Gram-positive bacteria such as Bacillus cereus and Staphylococcus aureus, compared to their effectiveness against Gram-negative bacteria like Escherichia coli. Moreover, the nanocomposite films were biocompatible with Human Skin Fibroblast. Therefore, the developed PVA:SA:TiO2 nanocomposite films suit wound dressing applications.

Response of mesenchymal stem cells to surface topography of scaffolds and the underlying mechanisms

Mesenchymal stem/stromal cells (MSCs) serve as essential components of regenerative medicine. Their destiny is influenced by the interaction of the cells with the external environment. In addition to the biochemical cues in a microenvironment, physical cues of the topography of the surrounding materials such as the extracellular matrix emerge as a crucial regulator of stem cell destiny and function. With recent advances in technologies of materials production and surface modification, surfaces with micro/nanotopographical characteristics can be fabricated to mimic the micro/nanoscale mechanical stimuli of the extracellular matrix environment and regulate the biological behavior of cells. Understanding the interaction of cells with the topography of a surface is conducive to the control of stem cell fate for application in regenerative medicine. However, the mechanisms by which topography affects the biological behavior of stem cells have not been fully elucidated. This review will present the effects of surface topography at the nano/micrometer scale on stem cell adhesion, morphology, proliferation, migration, and differentiation. It also focuses on discussing current theories about the sensing and recognition of surface topology cues, the transduction of the extracellular cues into plasma, and the final activation of related signaling pathways and downstream gene expression in MSCs. These insights will provide a theoretical basis for the future design of biomaterial scaffolds for application in regenerative medicine and tissue engineering.

The effect of chitosan/TiO2/hyaluronic acid subphase on the behaviour of 1,2-dioleoyl-sn-glycero-3-phosphocholine membrane

The main aim of the study was to determine the effect of two polysaccharides: chitosan (Ch) and hyaluronic acid (HA), and/or titanium dioxide (TiO₂) on the structure and behaviour of the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membrane. To achieve this goal the surface pressure as a function of the area per molecule (π-A) isotherm for the phospholipid monolayer was recorded. The shape of the π-A isotherms and compression-decompression cycles, as well as the compression modulus values, were analysed in terms of biocompatibility. Besides, morphology and thickness of the phospholipid layers obtained by means of Brewster angle microscope at different π, were determined. The obtained results show that both polysaccharides Ch, HA, as well inorganic TiO₂ affect slightly the structure of the DOPC monolayer but do not disrupt it. Their presence brings no typical arrangements of both the polar heads and tails of DOPC molecules at the interface.

Biocompatibility improvement and controlled in vitro degradation of poly (lactic acid)-b-poly(lactide-co-caprolactone) by formation of highly oriented structure for orthopedic application

Poly (lactic acid) (PLA) has been proposed as a promising orthopedic implant material, whereas insufficient mechanical strength, unsatisfied biocompatibility and inappropriate degradation rate restrict its further application. In this work, self-reinforced poly (lactic acid)-b-poly(lactide-co-caprolactone) (PLA-b-PLCL) block copolymer with long-chain branches was fabricated through two-stage orientation. Compared with smooth and hydrophobic PLA surface, the surface of PLA-b-PLCL presented micro-phase separated structure with improved hydrophilicity, and cells seeded on it showed improved adhesion/proliferation and high alkaline phosphatase (ALP) activity. After the 1st stage orientation at temperature higher than T_g1 (glass transition temperature of PLA phase), the amount of CH₃ and CO groups on surface of PLA-b-PLCL increased, while "groove-ridge" structure formed, resulting in enhancement of surface hydrophobicity. After the 2nd stage orientation at T_g1  ~ T_g2 (glass transition temperature of PLCL phase), surface hydrophobicity/amount of CO groups further increased and "groove-ridge" structure became more significant. Due to suitable wettability and enhanced material-cell mechanical interlocking, cell proliferation/ALP activity were improved and a continuous cell layer formed on sample surface. During in vitro degradation in phosphate buffered saline solution, by introduction of PLCL segments, the crystallinity decreased and solution absorption increased, resulting in a rapid deterioration of mechanical properties. After the 1st stage orientation, a dense microfibrillar structure with high crystallinity formed, which hindered diffusion of solution and delay hydrolytic degradation. After the 2nd stage orientation, PLCL segments were arranged more closely, resulting in a further inhibition of degradation, which was helpful for controlling the strength decay rate of PLA as bone fixation materials.

PLGA-Based Composites for Various Biomedical Applications

Polymeric materials have been extensively explored in the field of nanomedicine; within them, poly lactic-co-glycolic acid (PLGA) holds a prominent position in micro- and nanotechnology due to its biocompatibility and controllable biodegradability. In this review we focus on the combination of PLGA with different inorganic nanomaterials in the form of nanocomposites to overcome the polymer’s limitations and extend its field of applications. We discuss their physicochemical properties and a variety of well-established synthesis methods for the preparation of different PLGA-based materials. Recent progress in the design and biomedical applications of PLGA-based materials are thoroughly discussed to provide a framework for future research.

A novel pathway to produce biodegradable and bioactive PLGA/TiO2 nanocomposite scaffolds for tissue engineering: Air-liquid foaming

Poly (lactate-co-glycolate) (PLGA) is a typical biocompatible and biodegradable synthetic polymer. The addition of TiO₂ nanoparticles has shown to improve compressive modulus of PLGA scaffolds and reduced fast degradation. A novel method has been applied to fabricate PLGA/TiO₂ scaffolds without using any inorganic solvent, with aim of improving the biocompatibility, macroscale morphology, and well inter-connected pores efficacy: Air-Liquid Foaming. Field Emission Scanning Electron Microscopy (FESEM) revealed an increase in interconnected porosity of up to 98%. As well the compressive testing showed enhancement in modulus. Bioactivity and in vitro degradation were studied with immersion of scaffolds in Simulated Body Fluid (SBF) and incubation in Phosphate Buffered Saline (PBS), respectively. Formation of apatite layer corroborated the bioactivity after soaking in SBF. Degradation rate of scaffolds was increased with excessive addition of TiO₂ contents withal. The in vitro cultured human-like MG63 ostoblast cells showed attachment, proliferation, and nontoxcitiy in contact, using MTT assay [3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide]. According to the results, the novel method utilized in this study generated porous viable tissue without using any inorganic solvent or porogen can be a promising candidate in further treatment of orthopedic patients effectively.

Preparation and Characterization of Poly(δ-Valerolactone)/TiO2 Nanohybrid Material with Pores Interconnected for Potential Use in Tissue Engineering

Titanium dioxide/poly(δ-valerolactone) (TiO₂/Pδ-VL) nanohybrid material containing interconnected pores with sizes in the range 80–150 μm were prepared by the solvent casting and polymer melting routes, and the dispersion of the TiO₂ nanofiller in the Pδ-VL matrix and its adhesion were characterized by X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy. A significant depression in the glass transition temperature (T_g) and melting temperature (T_m) values were revealed for the polymer nanocomposites prepared by the solvent casting technique. For the potential application of the prepared materials in the biomedical domain, complementary analyses were performed to examine the dynamic mechanical properties, and cell adhesion (using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay), and the results obtained for the samples prepared by the two methods were compared. Interconnected pores were successively produced in the new material by employing naphthalene microparticles as a porogen for the first time, and the results obtained were very promising.

The relationship between substrate topography and stem cell differentiation in the musculoskeletal system

It is well known that biomaterial topography can exert a profound influence on various cellular functions such as migration, polarization, and adhesion. With the development and refinement of manufacturing technology, much research has recently been focused on substrate topography-induced cell differentiation, particularly in the field of tissue engineering. Even without biological and chemical stimuli, the differentiation of stem cells can also be initiated by various biomaterials with different topographic features. However, the underlying mechanisms of this biological phenomenon remain elusive. During the past few decades, many researchers have demonstrated that cells can sense the topography of materials through the assembly and polymerization of membrane proteins. Following the activation of RHO, TGF-b or FAK signaling pathways, cells can be induced into various differentiation states. But these signaling pathways often coincide with canonical mechanical transduction pathways, and no firm conclusion has been reached among researchers in this field on topography-specific signaling pathways. On the other hand, some substrate topographies are reported to have the ability to inhibit differentiation and maintain the 'stemness' of stem cells. In this review, we will summarize the role of topography in musculoskeletal system regeneration and explore possible topography-related signaling pathways involved in cell differentiation.

Nano-TiO2 Doped Chitosan Scaffold for the Bone Tissue Engineering Applications

The present focus is on the synthesis of highly effective, porous, biocompatible, and inert scaffold by using ceramic nanoparticles and natural polymer for the application in tissue engineering. Freeze-drying method was used to fabricate nano-TiO₂ doped chitosan sample scaffold. Nano-TiO₂/chitosan scaffold can considered as an effective solution for damaged tissue regeneration. The interaction between chitosan (polysaccharide) and nano-TiO₂ makes it highly porous and brittle that could be an effective substitute for bone tissue engineering. The TiO₂ nanoparticles have a great surface area and inert properties while chitosan is highly biocompatible and antibacterial. The physiochemical properties of TiO₂ nanoparticles and scaffold are evaluated by XRD and FTIR. The nanoparticles doped scaffold has given improved density (1.2870g/cm³) that is comparatively relevant to the dry bone (0.8 - 1.2 gm/cm³). The open and closed porosity of sample scaffold were measured by using Brunauer–Emmett–Teller analyzer (BET) and scanning electron microscopy (SEM). The mechanical properties are examined by stable microsystem (Texture Analyzer). The in vitro degradation of scaffold is calculated in PBS containing lysozyme at pH 7.4. Electron and fluorescence microscopy are used to study morphological characteristics of the scaffolds and TiO₂ nanoparticles. The growth factor and drug-loaded composites can improve osteogenesis and vascularization.

Nanomedicine and epigenome. Possible health risks

Nanomedicine is an emerging field that combines knowledge of nanotechnology and material science with pharmaceutical and biomedical sciences, aiming to develop nanodrugs with increased efficacy and safety. Compared to conventional therapeutics, nanodrugs manifest higher stability and circulation time, reduced toxicity and improved targeted delivery. Despite the obvious benefit, the accumulation of imaging agents and nanocarriers in the body following their therapeutic or diagnostic application generates concerns about their safety for human health. Numerous toxicology studies have demonstrated that exposure to nanomaterials (NMs) might pose serious risks to humans. Epigenetic modifications, representing a non-genotoxic mechanism of toxicant-induced health effects, are becoming recognized as playing a potential causative role in the aetiology of many diseases including cancer. This review i) provides an overview of recent advances in medical applications of NMs and ii) summarizes current evidence on their possible epigenetic toxicity. To discern potential health risks of NMs, since current data are mostly based upon in vitro and animal models, a better understanding of functional relationships between NM exposure, epigenetic deregulation and phenotype is required.

The effect of carbon nanoparticles on biological properties of polyester nanocomposites

The aim of present study was to determine the hemocompatibility, cellular response of endothelial cells and bacterial adhesion to a new polyester nanocomposite. The carbon nanoparticle nanocomposite was prepared via in situ polymerization of monomers to obtain material of hardness 55 Sh D similar to polyurethanes used in medical applications, for example, in heart-assisting devices. The carbon nanoparticle-containing polyester exhibits markedly reduced bacterial colonization, as compared to commercially available polyurethanes. Further the nanocomposite possesses markedly improved hemocompatibility, as determined by flow cytometry, and robust endothelialization. Possible explanations for these beneficial properties include surface nanoroughness of carbon nanoparticle-containing nanocomposites and presence of fatty acid sequences within polymer structure.

An overview of chitin or chitosan/nano ceramic composite scaffolds for bone tissue engineering

Chitin and chitosan based nanocomposite scaffolds have been widely used for bone tissue engineering. These chitin and chitosan based scaffolds were reinforced with nanocomponents viz Hydroxyapatite (HAp), Bioglass ceramic (BGC), Silicon dioxide (SiO₂), Titanium dioxide (TiO₂) and Zirconium oxide (ZrO₂) to develop nanocomposite scaffolds. Plenty of works have been reported on the applications and characteristics of the nanoceramic composites however, compiling the work done in this field and presenting it in a single article is a thrust area. This review is written with an aim to fill this gap and focus on the preparations and applications of chitin or chitosan/nHAp, chitin or chitosan/nBGC, chitin or chitosan/nSiO₂, chitin or chitosan/nTiO₂ and chitin or chitosan/nZrO₂ in the field of bone tissue engineering in detail. Many reports so far exemplify the importance of ceramics in bone regeneration. The effect of nanoceramics over native ceramics in developing composites, its role in osteogenesis etc. are the gist of this review.

Influence of ceria nanoparticles on chemical structure and properties of segmented polyesters

In this work, we present new nanocomposite materials derived from segmented copolyesters, comprising ethylene terephthalate (PET) segments and dimerized linoleic acid (DLA), and nanometric cerium oxide particles (CeO2). Nanoparticles were incorporated in situ during polycondensation in various concentrations, from 0.1 up to 0.6 wt.%. It was found that preparation of nanocomposites in situ, during polycondensation, had no significant influence on changes in segmental composition as determined from (1)H and (13)C, as well as 2D NMR. Thermal analysis and calculated degree of crystallinity showed that increasing concentration of ceria nanoparticles lead to an increase in mass content of PET crystallites in hard segments. The XRD investigations also showed an increased intensity of characteristic signals with increasing ceria concentration. Simultaneously, the incorporation of CeO2 led to an increase in tensile strength and elongation at break, indicating a reinforcing and plasticizing effect of ceria nanoparticles. However, the modulus at 10% strain decreased with increasing amount of nanoparticles. The in vitro culture of human cardiac progenitor cells (hCPCs) on the new materials indicated a homogenous cell displacement across the samples after 5 days with no signs of cytotoxicity, indicating good biocompatibility in vitro of CeO2-based nanocomposites and a potential for biomedical applications.

Titania nanostructures: a biomedical perspective

A systematic and comprehensive summary of various TNS-based biomedical research with a special emphasis on drug-delivery, tissue engineering, biosensor, and anti-bacterial applications.

Combined effects of connective tissue growth factor-modified bone marrow-derived mesenchymal stem cells and NaOH-treated PLGA scaffolds on the repair of articular cartilage defect in rabbits

In cartilage tissue engineering using stem cells, it is important to stimulate proliferation and control the differentiation of stem cells to specific lineages. Here we reported a combined technique for articular cartilage repair, consisting of bone marrow mesenchymal stem cells (BMMSCs) transfected with connective tissue growth factor (CTGF) gene and NaOH-treated poly(lactic-co-glycolic) acid (PLGA) scaffolds. In the present study, BMMSCs or CTGF-modified BMMSCs seeded on PLGA or NaOH-treated PLGA scaffolds were incubated in vitro and NaOH-treated PLGA significantly stimulated proliferation of BMMSCs, while CTGF gene transfer promoted chondrogenic differentiation. The effects of the composite on the repair of cartilage defects were evaluated in rabbit knee joints in vivo. Full-thickness cartilage defects (diameter: 5 mm; depth: 3 mm) were created unilaterally in the patellar groove. Defects were either left empty (n = 18) or implanted with BMMSCs/PLGA (n = 18), BMMSCs/NaOH-treated PLGA (n = 18), or CTGF-modified BMMSCs/NaOH-treated PLGA (n = 18). The defect area was examined grossly, histologically, and mechanically at 6, 12, and 24 weeks postoperatively. Implanted cells were tracked using adeno-LacZ labeling at 6 weeks after implantation. Overall, the CTGF-modified BMMSCs/NaOH-treated PLGA group showed successful hyaline-like cartilage regeneration similar to normal cartilage, which was superior to the other groups using gross examination, qualitative and quantitative histology, and mechanical assessment. The in vivo viability of the implanted cells was demonstrated by their retention for 6 weeks after implantation. These findings suggested that a combination of CTGF-modified BMMSCs and NaOH-treated PLGA may be an alternative treatment for large osteochondral defects in high-loading sites.

Novel nano-rough polymers for cartilage tissue engineering

This study presents an innovative method for creating a highly porous surface with nanoscale roughness on biologically relevant polymers, specifically polyurethane (PU) and polycaprolactone (PCL). Nanoembossed polyurethane (NPU) and nanoembossed polycaprolactone (NPCL) were produced by the casting of PU and PCL over a plasma-deposited, spiky nanofeatured crystalline titanium (Ti) surface. The variables used in the process of making the spiky Ti surface can be altered to change the physical properties of the spiky particles, and thus, the cast polymer substrate surface can be altered. The spiky Ti surface is reusable to produce additional nanopolymer castings. In this study, control plain PU and PCL polymers were produced by casting the polymers over a plain Ti surface (without spikes). All polymer surface morphologies were characterized using both scanning electron microscopy and atomic force microscopy, and their surface energies were measured using liquid contact angle measurements. The results revealed that both NPU and NPCL possessed a higher degree of nanometer surface roughness and higher surface energy compared with their respective unaltered polymers. Further, an in vitro study was carried out to determine chondrocyte (cartilage-producing cells) functions on NPU and NPCL compared with on control plain polymers. Results of this study provided evidence of increased chondrocyte numbers on NPU and NPCL compared with their respective plain polymers after periods of up to 7 days. Moreover, the results provide evidence of greater intracellular protein production and collagen secretion by chondrocytes cultured on NPU and NPCL compared with control plain polymers. In summary, the present in vitro results of increased chondrocyte functions on NPU and NPCL suggest these materials may be suitable for numerous polymer-based cartilage tissue-engineering applications and, thus, deserve further investigation.

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.

Carbon nanotubes reinforced chitosan films: mechanical properties and cell response of a novel biomaterial for cardiovascular tissue engineering

Carbon nanotubes have been proposed as fillers to reinforce polymeric biomaterials for the strengthening of their structural integrity to achieve better biomechanical properties. In this study, a new polymeric composite material was introduced by incorporating various low concentrations of multiwalled carbon nanotubes (MWCNTs) into chitosan (CS), aiming at achieving a novel composite biomaterial with superior mechanical and biological properties compared to neat CS, in order to be used in cardiovascular tissue engineering applications. Both mechanical and biological characteristics in contact with the two relevant cell types (endothelial cells and vascular myofibroblasts) were studied. Regarding the mechanical behavior of MWCNT reinforced CS (MWCNT/CS), 5 and 10 % concentrations of MWCNTs enhanced the mechanical behavior of CS, with that of 5 % exhibiting a superior mechanical strength compared to 10 % concentration and neat CS. Regarding biological properties, MWCNT/CS best supported proliferation of endothelial and myofibroblast cells, MWCNTs and MWCNT/CS caused no apoptosis and were not toxic of the examined cell types. Conclusively, the new material could be suitable for tissue engineering (TE) and particularly for cardiovascular TE applications.

Nano-regenerative medicine towards clinical outcome of stem cell and tissue engineering in humans

Nanotechnology is a fast growing area of research that aims to create nanomaterials or nanostructures development in stem cell and tissue-based therapies. Concepts and discoveries from the fields of bio nano research provide exciting opportunities of using stem cells for regeneration of tissues and organs. The application of nanotechnology to stem-cell biology would be able to address the challenges of disease therapeutics. This review covers the potential of nanotechnology approaches towards regenerative medicine. Furthermore, it focuses on current aspects of stem- and tissue-cell engineering. The magnetic nanoparticles-based applications in stem-cell research open new frontiers in cell and tissue engineering.

Titania-polymeric powder coatings with nano-topography support enhanced human mesenchymal cell responses

Titanium implant osseointegration is dependent on the cellular response to surface modifications and coatings. Titania-enriched nanocomposite polymeric resin coatings were prepared through the application of advanced ultrafine powder coating technology. Their surfaces were readily modified to create nano-rough (<100 nm) surface nano-topographies that supported human embryonic palatal mesenchymal cell responses. Energy dispersive x-ray spectroscopy confirmed continuous and homogenous coatings with a similar composition and even distribution of titanium. Scanning electron microscopy (SEM) showed complex micro-topographies, and atomic force microscopy revealed intricate nanofeatures and surface roughness. Cell counts, mitochondrial enzyme activity reduction of yellow 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to dark purple, SEM, and inverted fluorescence microscopy showed a marked increase in cell attachment, spreading, proliferation, and metabolic activity on the nanostructured surfaces. Reverse Transcription- Polymerase Chain Reaction (RT-PCR) analysis showed that type I collagen and Runx2 expression were induced, and Alizarin red staining showed that mineral deposits were abundant in the cell cultures grown on nanosurfaces. This enhancement in human mesenchymal cell attachment, growth, and osteogenesis were attributed to the nanosized surface topographies, roughness, and moderate wetting characteristics of the coatings. Their dimensional similarity to naturally occurring matrix proteins and crystals, coupled with their increased surface area for protein adsorption, may have facilitated the response. Therefore, this application of ultrafine powder coating technology affords highly biocompatible surfaces that can be readily modified to accentuate the cellular response.

In vitro and in vivo response to nanotopographically-modified surfaces of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and polycaprolactone

Colloidal lithography and embossing master are new techniques of producing nanotopography, which have been recently applied to improve tissue response to biomaterials by modifying the surface topography on a nano-scale dimension. A natural polyester (Biopol), 8% 3-hydroxyvalerate-component (D400G) and a conventional biodegradable polycaprolactone (PCL) were studied, both nanostructured and native forms, in vitro and in vivo. Nanopits (100-nm deep, 120-nm diameter) on the D400G surface were produced by the embossing master technique (Nano-D400G), while nanocylinders (160-nm height, 100-nm diameter) on the PCL surface were made by the colloidal lithography technique (Nano-PCL). L929 fibroblasts were seeded on polyesters, and cell proliferation, cytotoxic effect, synthetic and cytokine production were assessed after 72 h and 7 days. Then, under general anesthesia, 3 Sprague-Dawley rats received dorsal subcutaneous implants of nanostructured and native polyesters. At 1, 4 and 12 weeks the animals were pharmacologically euthanized and implants with surrounding tissue studied histologically and histomorphometrically. In vitro results showed significant differences between D400G and PCL in Interleukin-6 production at 72 h. At 7 days, significant (P < 0.05) differences were found in Interleukin-1beta and tumor necrosis factor-alpha release for Nano-PCL when compared to Nano-D400G, and for PCL in comparison with D400G. In vivo results indicated that Nano-D400G implants produced a greater extent of inflammatory tissue than Nano-PCL at 4 weeks. The highest vascular densities were observed for Nano-PCL at 4 and 12 weeks. Chemical and topographical factors seem to be responsible for the different behaviour, and from the obtained results a prevalence of chemistry on in vitro data and nanotopography on soft tissue response in vivo are hypothesized, although more detailed investigations are necessary in this field.

Functionalized nanostructures with application in regenerative medicine

In the last decade, both regenerative medicine and nanotechnology have been broadly developed leading important advances in biomedical research as well as in clinical practice. The manipulation on the molecular level and the use of several functionalized nanoscaled materials has application in various fields of regenerative medicine including tissue engineering, cell therapy, diagnosis and drug and gene delivery. The themes covered in this review include nanoparticle systems for tracking transplanted stem cells, self-assembling peptides, nanoparticles for gene delivery into stem cells and biomimetic scaffolds useful for 2D and 3D tissue cell cultures, transplantation and clinical application.

Strategies for articular cartilage lesion repair and functional restoration

Injury of articular cartilage due to trauma or pathological conditions is the major cause of disability worldwide, especially in North America. The increasing number of patients suffering from joint-related conditions leads to a concomitant increase in the economic burden. In this review article, we focus on strategies to repair and replace knee joint cartilage, since knee-associated disabilities are more prevalent than any other joint. Because of inadequacies associated with widely used approaches, the orthopedic community has an increasing tendency to develop biological strategies, which include transplantation of autologous (i.e., mosaicplasty) or allogeneic osteochondral grafts, autologous chondrocytes (autologous chondrocyte transplantation), or tissue-engineered cartilage substitutes. Tissue-engineered cartilage constructs represent a highly promising treatment option for knee injury as they mimic the biomechanical environment of the native cartilage and have superior integration capabilities. Currently, a wide range of tissue-engineering-based strategies are established and investigated clinically as an alternative to the routinely used techniques (i.e., knee replacement and autologous chondrocyte transplantation). Tissue-engineering-based strategies include implantation of autologous chondrocytes in combination with collagen I, collagen I/III (matrix-induced autologous chondrocyte implantation), HYAFF 11 (Hyalograft C), and fibrin glue (Tissucol) or implantation of minced cartilage in combination with copolymers of polyglycolic acid along with polycaprolactone (cartilage autograft implantation system), and fibrin glue (DeNovo NT graft). Tissue-engineered cartilage replacements show better clinical outcomes in the short term, and with advances that have been made in orthopedics they can be introduced arthroscopically in a minimally invasive fashion. Thus, the future is bright for this innovative approach to restore function.

Ex vivo expansion of human circulating myogenic progenitors on cluster-assembled nanostructured TiO2

Ex vivo expansion of hematopoietic stem cells has been explored in the fields of stem cell biology, gene therapy and clinical transplantation. Recently, we demonstrated the existence of a circulating myogenic progenitor expressing the CD133 antigen. The relative inability of circulating CD133+ stem cells to reproduce themselves ex vivo imposes substantial limitations on their use for clinical applications in muscular dystrophies. Here we report that the use of cluster-assembled nanostructured titanium dioxide (ns-TiO(2)) substrates, in combination with cytokine enriched medium, enables high-level expansion of circulating CD133+ stem cells in vitro. Furthermore, we demonstrate that expanded circulating CD133+ stem cells retain their in vitro capacity to differentiate into myogenic cells. The exploitation of cluster-assembled ns-TiO(2) substrates for the expansion of CD133+ stem cells in vitro could therefore make the clinical application of these stem cells for the treatment of muscle diseases practical.

Calcification capacity of porous pHEMA-TiO₂ composite hydrogels

Many investigations have been attempted to promote calcification of synthetic polymers for applications as orthopaedic and dental implants. In this study, novel titanium dioxide (TiO(2)) reinforced porous poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels were synthesized. Calcification capacity of the composite polymers was examined using light microscopy, scanning electron microscopy and Fourier transform infrared spectroscopy after incubation of the materials in a simulated body fluid up to 53 days. Mechanical strength, porosity and in vitro cytotoxicity were also investigated. Calcification capacity of porous pHEMA was significantly enhanced by the addition of TiO(2) particulates. Infiltration of calcium phosphate, up to 1000 mum, was observed. The diffusion capacity of calcium ions was affected by the porosity and the interconnectivity of pores in the hydrogel polymers which were influenced by the presence of TiO(2) and the monomer concentration. Cell viability tests indicated that porous hydrogels containing 7.5% TiO(2) were not toxic to 3T3 fibroblast cells. These results demonstrate that incorporating TiO(2) nanoparticulates can promote enhanced formation of calcium phosphate whilst maintaining the porosity and interconnectivity of the hydrogel polymers and would be very useful for the development of orthopaedic tissue engineering scaffolds.

In vitro evaluation of macroporous hydrogels to facilitate stem cell infiltration, growth, and mineralization

Hydrogels have gained acceptance as biomaterials in a wide range of applications, including pharmaceutical formulations, drug delivery, and tissue sealants. However, exploiting the potential of hydrogels as scaffolds for cell transplantation, tissue engineering, and regenerative medicine still remains a challenge due to, in part, scaffold design limitations. Here, we describe a highly interconnected, macroporous poly(ethylene glycol) diacrylate hydrogel scaffold, with pores ranging from 100 to 600 microm. The scaffold exhibits rapid cell uptake and cell seeding without the need of any external force or device with high incorporation efficiency. When human mesenchymal stem cells are seeded within the porous scaffolds, the scaffolds were found to promote long-term stem cell viability, and on exposure to osteogenic medium, elicit an mineralization response as evaluated by an increased alkaline phosphatase activity (per cell) and calcium and phosphate content within the constructs. The atomic composition of the mineralized matrix was further determined by energy dispersive spectroscopy and found to be similar to calcium-deficient hydroxyapatite, the amorphous biological precursor of bone. The macroporous design of the hydrogel appears advantageous over similar porous hydrogel scaffolds with respect to ease of synthesis, ease of stem cell seeding, and its ability to support long-term stem cell survival and possible differentiation.

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.

Improving biocompatibility of implantable metals by nanoscale modification of surfaces: an overview of strategies, fabrication methods, and challenges

The human body is an intricate biochemical-mechanical system, with an exceedingly precise hierarchical organization in which all components work together in harmony across a wide range of dimensions. Many fundamental biological processes take place at surfaces and interfaces (e.g., cell-matrix interactions), and these occur on the nanoscale. For this reason, current health-related research is actively following a biomimetic approach in learning how to create new biocompatible materials with nanostructured features. The ultimate aim is to reproduce and enhance the natural nanoscale elements present in the human body and to thereby develop new materials with improved biological activities. Progress in this area requires a multidisciplinary effort at the interface of biology, physics, and chemistry. In this Review, the major techniques that have been adopted to yield novel nanostructured versions of familiar biomaterials, focusing particularly on metals, are presented and the way in which nanometric surface cues can beneficially guide biological processes, exerting influence on cellular behavior, is illustrated.

Increased chondrocyte adhesion on nanotubular anodized titanium

Previous studies have demonstrated increased osteoblast (bone-forming cells) functions (including adhesion, synthesis of intracellular collagen, alkaline phosphatase activity, and deposition of calcium-containing minerals) on titanium anodized to possess nanometer features compared with their unanodized counterparts. Such titanium materials were anodized to possess novel nanotubes also capable of drug delivery. Since titanium has not only experienced wide spread commercial use in orthopedic but also in cartilage applications, the objective of the present in vitro study was for the first time to investigate chondrocyte (cartilage synthesizing cells) functions on titanium anodized to possess nanotubes. For this purpose, titanium was anodized in dilute hydrofluoric acid at 20 V for 20 min. Results showed increased chondrocyte adhesion on anodized titanium with nanotube structures compared with unanodized titanium. Importantly, the present study also provided evidence why. Since material characterization studies revealed significantly greater nanometer roughness and similar chemistry as well as crystallinity between nanotubular anodized and unanodized titanium, the results of the present study highlight the importance of the nanometer roughness provided by anodized nanotubes on titanium for enhancing chondrocyte adhesion. In this manner, the results of the present in vitro study indicated that anodization might be a promising quick and inexpensive method to modify the surface of titanium-based implants to induce better chondrocyte adhesion for cartilage applications.

Nanostructured bioceramics for maxillofacial applications

Biomaterials science and technology have been expanding tremendously the recent years. The results of this evolution are obvious in maxillofacial applications especially with the contemporary development of Nanotechnology. Among biomaterials, bioceramics possess a specific field due to various interactions with the biological tissues. The combination of bioceramics and nanotechnology has resulted in enhanced skeletal interactions in maxillofacial applications. Nanotechnology secures better mechanical properties and more effective biological interactions with jaws. The main production methods for the synthesis of nanostructured materials include plasma arcing, chemical vapour deposition, sol-gel and precipitation. The bioceramics in Dentistry comprise inert, bioactive, resorbable and composite systems. The purpose of the present article is to describe the available nanotechnology methods and how these could be addressed to synthesise maxillofacial bioceramics with advanced properties for better biological applications. Additionally, it describes specific clinical applications in maxillofacial surgery of these biomaterials--either by themselves or in combination with others--that can be promising candidates for bone tissue engineering. Such applications include replacement of lost teeth, filling of jaws defects or reconstruction of mandible and temporomandibular joint.

Titanium dioxide (TiO(2)) nanoparticles filled poly(D,L lactid acid) (PDLLA) matrix composites for bone tissue engineering

Titanium dioxide (TiO(2)) nanoparticles were investigated for bone tissue engineering applications with regard to bioactivity and particle cytotoxicity. Composite films on the basis of poly(D,L lactid acid) (PDLLA) filled with 0, 5 and 30 wt% TiO(2) nanoparticles were processed by solvent casting. Bioactivity, characterised by formation of hydroxyapatite (HA) on the materials surface, was investigated for both the free TiO(2) nanoparticles and PDLLA/TiO(2) composite films upon immersion in supersaturated simulated body fluid (1.5 SBF) for up to 3 weeks. Non-stoichiometric HA nanocrystals (ns-HA) with an average diameter of 40 nm were formed on the high content (30 wt% TiO(2)) composite films after 2 weeks of immersion in 1.5 SBF. For the pure PDLLA film and the low content composite films (5 wt% TiO(2)) trace amounts of ns-HA nanocrystals were apparent after 3 weeks. The TiO(2) nanopowder alone showed no bioactivity. The effect of TiO(2) nanoparticles (0.5-10,000 microg/mL) on MG-63 osteoblast-like cell metabolic activity was assessed by the MTT assay. TiO(2) particle concentrations of up to 100 microg/mL had no significant effect on MG-63 cell viability.

Nanotechnology: Better Materials for All Implants

Nanotechnology is being used to mimic structural components of our tissues in synthetic materials intended for various implant applications. Recent studies have highlighted that when compared to flat or micron rough surfaces, surfaces with nanofeatures promote optimal initial protein interactions necessary to mediate cell adhesion and subsequent tissue regrowth. This has been demonstrated for a wide range of implant chemistries (from ceramics to metals to polymers) and for a wide range of tissues (including bone, vascular, cartilage, bladder, and the central and peripheral nervous system). Importantly, these results have been seen at the in vitro and in vivo level. This short review paper will cover some of the more significant advancements in creating better implants through nanotechnology efforts.