Science of nanofibrous scaffold fabrication: strategies for next generation tissue-engineering scaffolds

Incorporating the Antioxidant Fullerenol into Calcium Phosphate Bone Cements Increases Cellular Osteogenesis without Compromising Physical Cement Characteristics

Herein, fullerenol (Ful), a highly water-soluble derivative of C60 fullerene with demonstrated antioxidant activity, is incorporated into calcium phosphate cements (CPCs) to enhance their osteogenic ability. CPCs with added carboxymethyl cellulose/gelatin (CMC/Gel) are doped with biocompatible Ful particles at concentrations of 0.02, 0.04, and 0.1 wt v%-1 and evaluated for Ful-mediated mechanical performance, antioxidant activity, and in vitro cellular osteogenesis. CMC/gel cements with the highest Ful concentration decrease setting times due to increased hydrogen bonding from Ful's hydroxyl groups. In vitro studies of reactive oxygen species (ROS) scavenging with CMC/gel cements demonstrate potent antioxidant activity with Ful incorporation and cement scavenging capacity is highest for 0.02 and 0.04 wt v%-1 Ful. In vitro cytotoxicity studies reveal that 0.02 and 0.04 wt v%-1 Ful cements also protect cellular viability. Finally, increase of alkaline phosphatase (ALP) activity and expression of runt-related transcription factor 2 (Runx2) in MC3T3-E1 pre-osteoblast cells treated with low-dose Ful cements demonstrate Ful-mediated osteogenic differentiation. These results strongly indicate that the osteogenic abilities of Ful-loaded cements are correlated with their antioxidant activity levels. Overall, this study demonstrates exciting potential of Fullerenol as an antioxidant and proosteogenic additive for improving the performance of calcium phosphate cements in bone reconstruction procedures.

Strategies to Induce Blood Vessel Ingrowth into Skin Grafts and Tissue-Engineered Substitutes

Skin is a multilayer organ consisting of several tissues and appendages residing in a complex niche. Adequate and physiologically regulated vascularization is an absolute requirement for skin homeostasis, regeneration, and wound healing. The lack of vascular networks and ischemia results in delayed wound closure. In addition, vascularization is critical for the prolonged function and survival of skin grafts and tissue-engineered skin substitutes. This study highlights the clinical challenges associated with the limited vascularization in the cutaneous wounds. Then, we highlight the novel approaches for the development of vascular networks in the skin autografts, allografts, and artificial substitutes. Also, the future directions to overcome the existing vascularization complications in skin grafting and synthetic skin substitutes are presented. Statement of Significance Delayed closure of large dermal wounds, such as burn injuries, results from the lack of vascular networks and ischemia. The amount of blood supply in the skin graft is the primary factor determining the quality of the transplanted grafts. The current skin grafts and their fabrication methods lack the appropriate features that contribute to the vascularization and integration of the wound bed and graft and adherence to the skin layers. Therefore, the new generation of skin grafts should consider advanced technologies to induce vascularization and overcome current challenges.

Boosting Antitumor Sonodynamic Therapy Efficacy of Black Phosphorus via Covalent Functionalization

Sonodynamic therapy (SDT) triggered by ultrasound represents an emerging tumor therapy approach with minimally invasive treatment featuring nontoxicity and deep tissue-penetration, and its efficacy sensitively depends on the sonosensitizer which determines the generation of reactive oxygen species (ROS). Herein, for the first time covalently functionalized few-layer black phosphorus nanosheets (BPNSs) are applied as novel sonosensitizers in SDT, achieving not only boosted SDT efficacy but also inhibited cytotoxicity relative to the pristine BPNSs. Three different covalently functionalized-BPNSs are synthesized, including the first fullerene-functionalized BPNSs with C60 covalently bonded onto the surface of BPNSs (abbreviated as C60 -s-BP), surface-functionalized BPNSs by benzoic acid (abbreviated as BA-s-BP), and edge-functionalized BPNSs by C60 (abbreviated as C60 -e-BP), and the role of covalent functionalization pattern of BPNSs on its SDT efficacy is systematically investigated. Except C60 -e-BP, both surface-functionalized BPNSs (C60 -s-BP, BA-s-BP) exhibit higher SDT efficacies than the pristine BPNSs, while the highest SDT efficacy is achieved for BA-s-BP due to its strongest capability of generating the hydroxyl (·OH) radicals, which act as the dominant ROS to kill the tumor cells.

Polyester Polymeric Nanoparticles as Platforms in the Development of Novel Nanomedicines for Cancer Treatment

Many therapeutic agents have failed in their clinical development, due to the toxic effects associated with non-transformed tissues. In this context, nanotechnology has been exploited to overcome such limitations, and also improve navigation across biological barriers. Amongst the many materials used in nanomedicine, with promising properties as therapeutic carriers, the following one stands out: biodegradable and biocompatible polymers. Polymeric nanoparticles are ideal candidates for drug delivery, given the versatility of raw materials and their feasibility in large-scale production. Furthermore, polymeric nanoparticles show great potential for easy surface modifications to optimize pharmacokinetics, including the half-life in circulation and targeted tissue delivery. Herein, we provide an overview of the current applications of polymeric nanoparticles as platforms in the development of novel nanomedicines for cancer treatment. In particular, we will focus on the raw materials that are widely used for polymeric nanoparticle generation, current methods for formulation, mechanism of action, and clinical investigations.

The Impact of Melt Electrowritten Scaffold Design on Porosity Determined by X-Ray Microtomography

IMPACT STATEMENT

Melt electrowriting is an AM technology that bridges the gap between solution electrospinning and melt microextrusion technologies. It can be applied to biomaterials and tissue engineering by making a spectrum of scaffolds with various laydown patterns at dimensions not previously studied. Using submicrometer X-ray tomography, a "fingerprint" of porosity for such scaffolds can be obtained and used as an important measure for quality control, to ensure that the scaffold fabricated is the one designed and allows the selection of specific scaffolds based on desired porosities.

Polymer scaffold architecture is a key determinant in mast cell inflammatory and angiogenic responses

Implanted polymer scaffolds can induce inflammation leading to the foreign body response (FBR), fibrosis, and implant failure. Thus, it is important to understand how immune cells interact with scaffolds to mitigate inflammation and promote a regenerative response. We previously demonstrated that macrophage phenotype is modulated by fiber and pore diameters of an electrospun scaffold. However, it is unclear if this effect is consistent among other innate immune cells. Mast cells are inflammatory sentinels that play a vital role in the FBR of implanted biomaterials, as well as angiogenesis. We determined if altering electrospun scaffold architecture modulates mast cell responses, with the goal of promoting regenerative cell-scaffold interactions. Polydioxanone (PDO) scaffolds were made from 60 mg/mL or 140 mg/mL PDO solutions, yielding structures with divergent fiber and pore diameters. Mouse mast cells plated on these scaffolds were activated with IL-33 or lipopolysaccharide (LPS). Relative to the 60 mg/mL scaffold, 140 mg/mL scaffolds yielded less IL-6 and TNF, and greater VEGF secretion. Pores >4-6 μm elicited less IL-6 and TNF secretion. IL-33-induced VEGF regulation was more complex, showing effects of both pore size and fiber diameter. These data indicate parameters that can predict mast cell responses to scaffolds, informing biomaterial design to increase wound healing and diminish implant rejection. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 884-892, 2019.

Mesenchymal Stem Cells Derived from Healthy and Diseased Human Gingiva Support Osteogenesis on Electrospun Polycaprolactone Scaffolds

Periodontitis is a chronic inflammatory disease affecting almost half of the adult US population. Gingiva is an integral part of the periodontium and has recently been identified as a source of adult gingiva-derived mesenchymal stem cells (GMSCs). Given the prevalence of periodontitis, the purpose of this study is to evaluate differences between GMSCs derived from healthy and diseased gingival tissues and explore their potential in bone engineering. Primary clonal cell lines were established from harvested healthy and diseased gingival and characterized for expression of known stem-cell markers and multi-lineage differentiation potential. Finally, they were cultured on electrospun polycaprolactone (PCL) scaffolds and evaluated for attachment, proliferation, and differentiation. Flow cytometry demonstrated cells isolated from healthy and diseased gingiva met the criteria defining mesenchymal stem cells (MSCs). However, GMSCs from diseased tissue showed decreased colony-forming unit efficiency, decreased alkaline phosphatase activity, weaker osteoblast mineralization, and greater propensity to differentiate into adipocytes than their healthy counterparts. When cultured on electrospun PCL scaffolds, GMSCs from both sources showed robust attachment and proliferation over a 7-day period; they exhibited high mineralization as well as strong expression of alkaline phosphatase. Our results show preservation of ‘stemness’ and osteogenic potential of GMSC even in the presence of disease, opening up the possibility of using routinely discarded, diseased gingival tissue as an alternate source of adult MSCs.

Fibrous scaffolds for building hearts and heart parts

Extracellular matrix (ECM) structure and biochemistry provide cell-instructive cues that promote and regulate tissue growth, function, and repair. From a structural perspective, the ECM is a scaffold that guides the self-assembly of cells into distinct functional tissues. The ECM promotes the interaction between individual cells and between different cell types, and increases the strength and resilience of the tissue in mechanically dynamic environments. From a biochemical perspective, factors regulating cell-ECM adhesion have been described and diverse aspects of cell-ECM interactions in health and disease continue to be clarified. Natural ECMs therefore provide excellent design rules for tissue engineering scaffolds. The design of regenerative three-dimensional (3D) engineered scaffolds is informed by the target ECM structure, chemistry, and mechanics, to encourage cell infiltration and tissue genesis. This can be achieved using nanofibrous scaffolds composed of polymers that simultaneously recapitulate 3D ECM architecture, high-fidelity nanoscale topography, and bio-activity. Their high porosity, structural anisotropy, and bio-activity present unique advantages for engineering 3D anisotropic tissues. Here, we use the heart as a case study and examine the potential of ECM-inspired nanofibrous scaffolds for cardiac tissue engineering. We asked: Do we know enough to build a heart? To answer this question, we tabulated structural and functional properties of myocardial and valvular tissues for use as design criteria, reviewed nanofiber manufacturing platforms and assessed their capabilities to produce scaffolds that meet our design criteria. Our knowledge of the anatomy and physiology of the heart, as well as our ability to create synthetic ECM scaffolds have advanced to the point that valve replacement with nanofibrous scaffolds may be achieved in the short term, while myocardial repair requires further study in vitro and in vivo.

Mesoporous silica-layered biopolymer hybrid nanofibrous scaffold: a novel nanobiomatrix platform for therapeutics delivery and bone regeneration

Nanoscale scaffolds that characterize high bioactivity and the ability to deliver biomolecules provide a 3D microenvironment that controls and stimulates desired cellular responses and subsequent tissue reaction. Herein novel nanofibrous hybrid scaffolds of polycaprolactone shelled with mesoporous silica (PCL@MS) were developed. In this hybrid system, the silica shell provides an active biointerface, while the 3D nanoscale fibrous structure provides cell-stimulating matrix cues suitable for bone regeneration. The electrospun PCL nanofibers were coated with MS at controlled thicknesses via a sol-gel approach. The MS shell improved surface wettability and ionic reactions, involving substantial formation of bone-like mineral apatite in body-simulated medium. The MS-layered hybrid nanofibers showed a significant improvement in mechanical properties, in terms of both tensile strength and elastic modulus, as well as in nanomechanical surface behavior, which is favorable for hard tissue repair. Attachment, growth, and proliferation of rat mesenchymal stem cells were significantly improved on the hybrid scaffolds, and their osteogenic differentiation and subsequent mineralization were highly up-regulated by the hybrid scaffolds. Furthermore, the mesoporous surface of the hybrid scaffolds enabled the loading of a series of bioactive molecules, including small drugs and proteins at high levels. The release of these molecules was sustainable over a long-term period, indicating the capability of the hybrid scaffolds to deliver therapeutic molecules. Taken together, the multifunctional hybrid nanofibrous scaffolds are considered to be promising therapeutic platforms for stimulating stem cells and for the repair and regeneration of bone.

Fabrication and characterization of air-impedance electrospun polydioxanone templates

Electrospinning, a fabrication technique used to create non-woven, porous templates from natural and synthetic polymers, is commonly used in tissue engineering because it is highly tailorable. However, traditional electrospinning creates restrictive pore sizes that limit the required cell migration. Therefore, tissue engineering groups have sought to enhance and regulate porosity of tissue engineering templates. Air-impedance electrospinning generates templates with tailorable, patterned areas of low and high density fiber deposition. Here we demonstrate an improved air-impedance electrospinning system, consisting of a newly designed funnel equipped to hold changeable porous deposition plates and administer air flow in a confined and focused manner, with parameters that maintain template integrity. In this preliminary study, we quantify the increase in porosity of polydioxanone templates with use of traditional fiber and pore analysis as well as with mercury porosimetry. Additionally, we validate the system’s significance in fabricating enhanced porosity templates that maintain their mechanical properties (i.e. elastic modulus, tensile strength, and suture retention strength) despite the deliberate increase in porosity. This is of exceptional value to the template’s integrity and efficacy as these parameters can be further optimized to induce the desired template porosity, strength, and texture for a given application.

Hybrid fullerene conjugates as vectors for DNA cell-delivery

C60-PEI and C60-PEG-PEI as efficient binders of dsDNA, with good transfection up to 25%, high cytocompatibility and cell proliferation up to 200%.

Establishment of a three-dimensional culture system of gastric stem cells supporting mucous cell differentiation using microfibrous polycaprolactone scaffolds

OBJECTIVES

To generate various polycaprolactone (PCL) scaffolds and test their suitability for growth and differentiation of immortalized mouse gastric stem (mGS) cells.

MATERIALS AND METHODS

Non-porous, microporous and three-dimensional electrospun microfibrous PCL scaffolds were prepared and characterized for culture of mGS cells. First, growth of mGS cells was compared on these different scaffolds after 3 days culture, using viability assay and microscopy. Secondly, growth pattern of the cells on microfibrous scaffolds was studied after 3, 6, 9 and 12 days culture using DNA PicoGreen assay and scanning electron microscopy. Thirdly, differentiation of the cells grown on microfibrous scaffolds for 3 and 9 days was analysed using lectin/immunohistochemistry.

RESULTS

The mGS cells grew preferentially on microfibrous scaffolds. From 3 to 6 days, there was increase in cell number, followed by reduction by days 9 and 12. To test whether the reduction in cell number was associated with cell differentiation, cryosections of cell-containing scaffolds cultured for 3 and 9 days were probed with gastric epithelial cell differentiation markers. On day 3, none of the markers examined bound to the cells. However by day 9, approximately, 50% of them bound to N-acetyl-d-glucosamine-specific lectin and anti-trefoil factor 2 antibodies, indicating their differentiation into glandular mucus-secreting cells.

CONCLUSIONS

Microfibrous PCL scaffolds supported growth and differentiation of mGS cells into mucus-secreting cells. These data will help lay groundwork for future experiments to explore use of gastric stem cells and PCL scaffolds in stomach tissue engineering.

Viscoelasticity of repaired sciatic nerve by poly(lactic-co-glycolic acid) tubes

Medical-grade synthetic poly(lactic-co-glycolic acid) polymer can be used as a biomaterial for nerve repair because of its good biocompatibility, biodegradability and adjustable degradation rate. The stress relaxation and creep properties of peripheral nerve can be greatly improved by repair with poly(lactic-co-glycolic acid) tubes. Ten sciatic nerve specimens were harvested from fresh corpses within 24 hours of death, and were prepared into sciatic nerve injury models by creating a 10 mm defect in each specimen. Defects were repaired by anastomosis with nerve autografts and poly(lactic-co-glycolic acid) tubes. Stress relaxation and creep testing showed that at 7 200 seconds, the sciatic nerve anastomosed by poly(lactic-co-glycolic acid) tubes exhibited a greater decrease in stress and increase in strain than those anastomosed by nerve autografts. These findings suggest that poly(lactic-co-glycolic acid) exhibits good viscoelasticity to meet the biomechanical require-ments for a biomaterial used to repair sciatic nerve injury.

Effect of fullerenol surface chemistry on nanoparticle binding-induced protein misfolding

Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation - a common strategy for solubilizing and functionalizing fullerene - on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding.

Electrospun fibers as a scaffolding platform for bone tissue repair

The purpose of the study is to investigate the effects of electrospun fiber diameter and orientation on differentiation and ECM organization of bone marrow stromal cells (BMSCs), in attempt to provide rationale for fabrication of a periosteum mimetic for bone defect repair. Cellular growth, differentiation, and ECM organization were analyzed on PLGA-based random and aligned fibers using fluorescent microscopy, gene analyses, electron scanning microscopy (SEM), and multiphoton laser scanning microscopy (MPLSM). BMSCs on aligned fibers had a reduced number of ALP+ colony at Day 10 as compared to the random fibers of the same size. However, the ALP+ area in the aligned fibers increased to a similar level as the random fibers at Day 21 following stimulation with osteogenic media. Compared with the random fibers, BMSCs on the aligned fibers showed a higher expression of OSX and RUNX2. Analyses of ECM on decellularized spun fibers showed highly organized ECM arranged according to the orientation of the spun fibers, with a broad size distribution of collagen fibers in a range of 40-2.4 μm. Taken together, our data support the use of submicron-sized electrospun fibers for engineering of oriented fibrous tissue mimetic, such as periosteum, for guided bone repair and reconstruction.

Fabrication of nano-fibrous poly(L-lactic acid) scaffold reinforced by surface modified chitosan micro-fiber

To mimic the fibrillar structure of natural extracellular matrix and optimize the chemical composition of the scaffold, a nano-fibrous poly(L-lactic acid) (PLLA) scaffold reinforced by surface modified chitosan micro-fiber (MCTSF) was fabricated using the thermally induced phase separation method. The composite scaffold has a novel structure comprised of a nano-matrix with reinforcing micro-fibers, in which the nano-fibrous PLLA matrix promotes cell adhesion and proliferation, while the MCTSF provides the mechanical support and adjusts the biocompatibility. The morphology of the composite scaffold showed a nano-fibrous PLLA matrix (100-500 nm fiber diameter), an interconnected microporous structure (1.0-8.0 μm pore size), and high porosity (>90%). MCTSF were homogeneously distributed in the composite scaffold and had intimate interactions with PLLA matrix. As a result, the compressive modulus of PLLA/MCTSF (100:40, w/w) increased 4.7-fold compared with that of a pristine PLLA scaffold. The prepared composite scaffold also showed good properties including buffering the acidic degradation of PLLA during in vitro degradation, enhanced protein adsorption capacity, and good cytocompatibility, suggesting that the PLLA/MCTSF composite scaffolds are potential candidate materials in tissue engineering.

Hyaluronic acid based scaffolds for tissue engineering--a review

This review focuses on hyaluronic acid (HA) tissue scaffolding materials. Scaffolds are defined in terms of formation mechanisms and mode of action. Solution properties are discussed as an understanding of the hydrodynamics of HA is fundamental in optimising the subsequent modification and the chemistries behind important tissue engineering applications that are emerging from recent research on this increasingly valuable carbohydrate polymer are described. Key scaffold characteristics such as mechanical, biological function and degradation are discussed. The latest technologies behind scaffold processing are assessed and the applications of HA based scaffolds are discussed.

In vitro and in vivo investigations of upconversion and NIR emitting Gd₂O₃:Er³⁺,Yb³⁺ nanostructures for biomedical applications

The use of an "over 1000-nm near-infrared (NIR) in vivo fluorescence bioimaging" system based on lanthanide containing inorganic nanostructures emitting in the visible and NIR range under 980-nm excitation is proposed. It may overcome problems of currently used biomarkers including color fading, phototoxicity and scattering. Gd(2)O(3):Er(3+),Yb(3+) nanoparticles and nanorods showing upconversion and NIR emission are synthesized and their cytotoxic behavior is investigated by incubation with B-cell hybridomas and macrophages. Surface modification with PEG-b-PAAc provides the necessary chemical durability reducing the release of toxic Gd(3+) ions. NIR fluorescence microscopy is used to investigate the suitability of the nanostructures as NIR-NIR biomarkers. The in vitro uptake of bare and modified nanostructures by macrophages is investigated by confocal laser scanning microscopy. In vivo investigations revealed nanostructures in liver, lung, kidneys and spleen a few hours after injection into mice, while most of the nanostructures have been removed from the body after 24 h.

Dendrimer-Fullerenol Soft-Condensed Nanoassembly

Nanoscale assembly is an area of research that has vast implications for molecular design, sensing, nanofabrication, supramolecular chemistry, catalysis, and environmental remediation. Here we show that poly(amidoamine) (PAMAM) dendrimers of both generations 1 (G1) and 4 (G4) can host 1 fullerenol per 2 dendrimer primary amines as evidenced by isothermal titration calorimetry, dynamic light scattering and spectrofluorometry. Thermodynamically, the interactions were similarly spontaneous between both generations of dendrimers and fullerenols, however, G4 formed stronger complexes with fullerenols resulting from their higher surface charge density and more internal voids, as demonstrated by spectrofluorometry. In addition to hydrogen bonding that existed between the dendrimer primary amines and the fullerenol oxygens, hydrophobic and electrostatic interactions also contributed to complex formation and dynamics. Such hybrid of soft and condensed nanoassembly may have implications for environmental remediation of discharged nanomaterials and entail new applications in drug delivery.

Carbon nanotubes promote growth and spontaneous electrical activity in cultured cardiac myocytes

Nanoscale manipulations of the extracellular microenvironment are increasingly attracting attention in tissue engineering. Here, combining microscopy, biological, and single-cell electrophysiological methodologies, we demonstrate that neonatal rat ventricular myocytes cultured on substrates of multiwall carbon nanotubes interact with carbon nanotubes by forming tight contacts and show increased viability and proliferation. Furthermore, we observed changes in the electrophysiological properties of cardiomyocytes, suggesting that carbon nanotubes are able to promote cardiomyocyte maturation.

Electrospun nanofibers for regenerative medicine

This Progress Report reviews recent progress in applying electrospun nanofibers to the emerging field of regenerative medicine. It begins with a brief introduction to electrospinning and nanofibers, with a focus on issues related to the selection of materials, incorporation of bioactive molecules, degradation characteristics, control of mechanical properties, and facilitation of cell infiltration. Next, a number of approaches to fabricate scaffolds from electrospun nanofibers are discussed, including techniques for controlling the alignment of nanofibers and for producing scaffolds with complex architectures. The article also highlights applications of the nanofiber-based scaffolds in four areas of regenerative medicine that involve nerves, dural tissues, tendons, and the tendon-to-bone insertion site. The Progress Report concludes with perspectives on challenges and future directions for design, fabrication, and utilization of scaffolds based on electrospun nanofibers.

Engineered tissue grafts: opportunities and challenges in regenerative medicine

The human body has limited regenerative capacity in most of the major tissues and organs. This fact has spurred the field of regenerative medicine, promising to repair damage following traumatic injury or disease. Multiple therapeutic strategies are being explored including small molecules, gene delivery, and stem cells; however, tissue engineering remains a primary approach to achieving regeneration. Organ transplantation demonstrates that damaged tissues can be replaced, but technology to regenerate complex organs de novo is not yet available. Instead, tissue engineering can augment the body's own regenerative ability by replacing tissue sections and enhancing the regenerative cascade. As a consequence of these opportunities, it is timely to review the criteria and current status of engineered tissue grafts designed as patches to replace or regenerate damaged or diseased tissue and restore organ function. This topic will be explored starting from the biomaterials and cells incorporated into the engineered graft, the environment into which the graft is implanted and the integration of the engineered graft with the host. Common issues will be addressed that are relevant to regeneration in multiple tissue and organ systems. Specific examples will focus on engineered grafts for myocardial and corneal repair to illustrate the tissue-specific challenges and opportunities and highlight the innovation needed as the field moves forward.

Cytoprotective properties of a fullerene derivative against copper

To delineate the complexity of the response of cells to nanoparticles we have performed a study on HT-29 human colon carcinoma cells exposed first to a fullerene derivative C(60)(OH)(20) and then to physiological copper ions. Our cell viability, proliferation, and intracellular reactive oxygen species (ROS) production assays clearly indicated that C(60)(OH)(20) suppressed cell damage as well as ROS production induced by copper, probably through neutralization of the metal ions by C(60)(OH)(20) in the extracellular space, as well as by adsorption and uptake of the nanoparticles surface-modified by the biomolecular species in the cell medium. This double-exposure study provides new data on the effects of nanoparticles on cell metabolism and may aid the treatment of oxidant-mediated diseases using nanomedicine.

DNA exposure to buckminsterfullerene (C60): toward DNA stability, reactivity, and replication

Buckminsterfullerene (C(60)) has received great research interest due to its extraordinary properties and increasing applications in manufacturing industry and biomedical technology. We recently reported C(60) could enter bacterial cells and bind to DNA molecules. This study was to further determine how the DNA-C(60) binding affected the thermal stability and enzymatic digestion of DNA molecules, and DNA mutations. Nano-C(60) aggregates and water-soluble fullerenols were synthesized and their impact on DNA biochemical and microbial activity was investigated. Our results revealed that water-soluble fullerenols could bind to lambda DNA and improve DNA stability remarkably against thermal degradation at 70-85 °C in a dose-dependent manner. DNase I and HindIII restriction endonuclease activities were inhibited after interacting with fullerenols at a high dose. Experimental results also showed the different influence of fullerenol and nano-C(60) on their antibacterial mechanisms, where fullerenols contributed considerable impact on cell damage and mutation rate. This preliminary study indicated that the application of fullerenols results in significant changes in the physical structures and biochemical functions of DNA molecules.

Design of three-dimensional biomimetic scaffolds

A detailed understanding of the biophysical features that affect cell growth and development is important in guiding the design of biomimetic scaffolds. The cellular microenvironment is a network of structural and functional components that provide mechanical and chemical stimuli, which influence cell function and fate. Important developmental signals are conveyed to cells through interactions with neighboring cells, the extracellular matrix (ECM), and growth factors. Currently, there are number of approaches to create 3D tissue models in vitro that allow for control over cell adhesion, the physical properties of the surrogate matrix, and the spatial distribution of growth factors. This review describes some of the most significant biological features of the ECM, and several engineering methods currently being implemented to design and tune synthetic scaffolds to mimic these features.

Efficient synthesis of fullerenol in anion form for the preparation of electrodeposited films

The first electrochemical characterization of the much-studied "fullerenols" has been carried out. The fullerenol was prepared by the reaction of C(60) in deoxygenated tetrahydrofuran with an aqueous NaOH solution using sodium zincate as an electrophilic reagent. The obtained fullerenol is not simply polyhydroxylated C(60) but is a structurally and electronically complex C(60) anion with a molecular formula of Na(+) (2)[C(60) (OH)(12)(O)(2)](2-). This negatively charged fullerenol is in the form of a spherical cluster of 50 nm in diameter, and it can migrate in the same solution to an anode surface and be oxidized into the less soluble fullerenol C(60)O(OH)(12), when 10 V is applied to the electroplating bath. A uniform film, with a particle of 50-250 nm in diameter and a thickness of a few 10-100s of nanometers, is obtained by drying the fullerenol covered anode. This is the first time that studies of water-soluble fullerenols acting as anions for electrodeposited film preparation have been reported. The deposition mechanism has been further demonstrated by electrochemical measurements and dissolved oxygen concentration testing to be an oxidation process consisting of two anodic oxygen evolution processes.

Nanotechnology in drug delivery and tissue engineering: from discovery to applications

The application of nanotechnology in medicine, referred to as nanomedicine, is offering numerous exciting possibilities in healthcare. Herein, we discuss two important aspects of nanomedicine, drug delivery and tissue engineering, highlighting the advances we have recently experienced, the challenges we are currently facing, and what we are likely to witness in the near future.