Nanotechnology in regenerative medicine: the materials side

The big picture on nanomedicine: the state of investigational and approved nanomedicine products

Developments in nanomedicine are expected to provide solutions to many of modern medicine's unsolved problems, so it is no surprise that the literature contains many articles discussing the subject. However, existing reviews tend to focus on specific sectors of nanomedicine or to take a very forward-looking stance and fail to provide a complete perspective on the current landscape. This article provides a more comprehensive and contemporary inventory of nanomedicine products. A keyword search of literature, clinical trial registries, and the Web yielded 247 nanomedicine products that are approved or in various stages of clinical study. Specific information on each was gathered, so the overall field could be described based on various dimensions, including FDA classification, approval status, nanoscale size, treated condition, nanostructure, and others. In addition to documenting the many nanomedicine products already in use in humans, this study identifies several interesting trends forecasting the future of nanomedicine.

FROM THE CLINICAL EDITOR

In this one of a kind review, the state of nanomedicine commercialization is discussed, concentrating only on nanomedicine-based developments and products that are either in clinical trials or have already been approved for use.

Nanotechnology and stem cell therapy for cardiovascular diseases: potential applications

The use of stem cell therapy for the treatment of cardiovascular diseases has generated significant interest in recent years. Limitations to the clinical application of this therapy center on issues of stem cell delivery, engraftment, and fate. Nanotechnology-based cell labeling and imaging techniques facilitate stem cell tracking and engraftment studies. Nanotechnology also brings exciting new opportunities to translational stem cell research as it enables the controlled engineering of nanoparticles and nanomaterials that can properly relate to the physical scale of cell-cell and cell-niche interactions. This review summarizes the most relevant potential applications of nanoscale technologies to the field of stem cell therapy for the treatment of cardiovascular diseases.

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.

Shining light on nanotechnology to help repair and regeneration

Phototherapy can be used in two completely different but complementary therapeutic applications. While low level laser (or light) therapy (LLLT) uses red or near-infrared light alone to reduce inflammation, pain and stimulate tissue repair and regeneration, photodynamic therapy (PDT) uses the combination of light plus non-toxic dyes (called photosensitizers) to produce reactive oxygen species that can kill infectious microorganisms and cancer cells or destroy unwanted tissue (neo-vascularization in the choroid, atherosclerotic plaques in the arteries). The recent development of nanotechnology applied to medicine (nanomedicine) has opened a new front of advancement in the field of phototherapy and has provided hope for the development of nanoscale drug delivery platforms for effective killing of pathological cells and to promote repair and regeneration. Despite the well-known beneficial effects of phototherapy and nanomaterials in producing the killing of unwanted cells and promoting repair and regeneration, there are few reports that combine all three elements i.e. phototherapy, nanotechnology and, tissue repair and regeneration. However, these areas in all possible binary combinations have been addressed by many workers. The present review aims at highlighting the combined multi-model applications of phototherapy, nanotechnology and, reparative and regeneration medicine and outlines current strategies, future applications and limitations of nanoscale-assisted phototherapy for the management of cancers, microbial infections and other diseases, and to promote tissue repair and regeneration.

Orchestrating cell/material interactions for tissue engineering of surgical implants

Research groups are currently recognising a critical clinical need for innovative approaches to organ failure and agenesis. Allografting, autologous reconstruction and prosthetics are hampered with severe limitations. Pertinently, readily available 'laboratory-grown' organs and implants are becoming a reality. Tissue engineering constructs vary in their design complexity depending on the specific structural and functional demands. Expeditious methods on integrating autologous stem cells onto nanoarchitectured 3D nanocomposites, are being transferred from lab to patients with a number of successful first-in-man experiences. Despite the need for a complete understanding of cell/material interactions tissue engineering is offering a plethora of exciting possibilities in regenerative medicine.

Designing nanostructured block copolymer surfaces to control protein adhesion

The profile and conformation of proteins that are adsorbed onto a polymeric biomaterial surface have a profound effect on its in vivo performance. Cells and tissue recognize the protein layer rather than directly interact with the surface. The chemistry and morphology of a polymer surface will govern the protein behaviour. So, by controlling the polymer surface, the biocompatibility can be regulated. Nanoscale surface features are known to affect the protein behaviour, and in this overview the nanostructure of self-assembled block copolymers will be harnessed to control protein behaviour. The nanostructure of a block copolymer can be controlled by manipulating the chemistry and arrangement of the blocks. Random, A-B and A-B-A block copolymers composed of methyl methacrylate copolymerized with either acrylic acid or 2-hydroxyethyl methacrylate will be explored. Using atomic force microscopy (AFM), the surface morphology of these block copolymers will be characterized. Further, AFM tips functionalized with proteins will measure the adhesion of that particular protein to polymer surfaces. In this manner, the influence of block copolymer morphology on protein adhesion can be measured. AFM tips functionalized with antibodies to fibronectin will determine how the surfaces will affect the conformation of fibronectin, an important parameter in evaluating surface biocompatibility.

Osteointegration of titanium implant is sensitive to specific nanostructure morphology

An important aspect of orthopedic implant integration is the enhancement of functional activity of osteoblasts at the tissue-implant interface without any fibrous tissue intervention. Nanostructured implant surfaces are known to enhance osteoblast activity. Previously, we have reported a simple hydrothermal method for the fabrication of non-periodic nanostructures (nanoscaffold, nanoleaves and nanoneedles) on titanium implants showing good biocompatibility and a distinct osteoblast response in vitro in terms of osteoblast adhesion to the surface. In the present work, these nanostructures have been evaluated for their detailed in vitro cellular response as well as in vivo osteointegration. Our studies showed that a specific surface nanomorphology, viz. nanoleaves, which is a network of vertically aligned, non-periodic, leaf-like structures with thickness in the nanoscale, provided a distinct increase in osteoblast cell proliferation, alkaline phosphatase (ALP) activity and collagen synthesis compared to several other types of nanomorphology, such as nanotubes, nanoscaffold and nanoneedles (rods). Gene expression analysis of ALP, osteocalcin, collagen, decorin and Runx2 showed ~20- to 40-fold up-regulation on the leaf-like topography. Cytoskeletal arrangement studies on this substrate again revealed a unique response with favorable intracellular protein expressions of vinculin, FAK and src. In vivo osteointegration study over 12 weeks on rat model (Sprague-Dawley) showed early-stage bone formation (60% bone contact by week 2 and ~85% by week 8, p<0.01) in the leaf-like nanopattern, without any inflammatory cytokine production.

Physically crosslinked nanocomposites from silicate-crosslinked PEO: mechanical properties and osteogenic differentiation of human mesenchymal stem cells

The mechanical and biological properties of silicate-crosslinked PEO nanocomposites are studied. A strong correlation is observed between silicate concentration and mechanical properties. In vitro cell culture studies reveal that an increase in silicate concentration enhances the attachment and proliferation of human mesenchymal stem cells significantly. An upregulation in the expression of osteocalcin on nanocomposites compared to the tissue culture polystyrene control is observed. Together, these results suggest that silicate-based nanocomposites are bioactive and have the potential to be used in a range of biotechnological and biomedical applications such as injectable matrices, biomedical coatings, drug delivery, and regenerative medicine.

Conductive hybrid nanofibers self-assembled with three different amphiphilic salts

Upon supramolecular self-assembly, novel conductive hybrid nanofibers were successfully fabricated using three amphiphilic salts, azopyridinium, aniline hydrochloride, and alkylbenzenesulfate-based anionic surfactants. The interactions like π-π stacking and ionic bonding among the different compounds played important roles in preparation of these multicomponent hybrid nanofibers. These were demonstrated by measurements of XRD, UV-vis absorption, and FTIR spectra. Interesting conductivity in an order of magnitude of 1 × 10(-7) to 1 × 10(-5) S/cm was observed in films of the fabricated hybrid nanofibers, which was attributed to the existence of freely movable ions, showing their possible applications as bionanomaterials and nanoelectronic devices. The fabrication processes of the conductive nanofibers might provide references for simulation of nerve fibers in nature.

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.

Functionalization of surfaces with synthetic oligonucleotides

There is a large interest in the use of nucleic acids covalently bound to surfaces for a variety of biomedical uses: biosensors, microarrays, drug delivery, lab-on-chip devices, and gene therapy, etc. Most of these applications require the covalent attachment of oligonucleotides via specific reactive groups on both modified oligonucleotide and/or surface. The purpose of this chapter is to provide experimental protocols for the synthesis of oligonucleotides and for the immobilization of these synthetic oligonucleotides onto surfaces such as gold and silicon oxide.

Preparation of polyelectrolyte nanocomplexes containing recombinant human hepatocyte growth factor as potential oral carriers for liver regeneration

The large number of cytokines and growth factors implicated in the regulation of liver regeneration has led to the possibility of using these molecules in therapy, namely, in the case of recombinant human hepatocyte growth factor (rhHGF). The importance and potential clinical usefulness of rhHGF has been extensively studied and documented, with results suggesting that this molecule could be a powerful tool toward increased success in hepatic regenerative therapy. However, the peptidic nature of this drug presents several challenges toward its effective administration and targeting. The possibility of encapsulating rhHGF in dextran sulfate/chitosan nanoparticles to allow its oral administration and direct liver-targeting is discussed in this manuscript. Details of a rapid and simple method for the preparation of such rhHGF-loaded nanocomplexes are presented. Beyond the practical aspects of the method, characterization techniques and main experimental features of obtained nanocarriers are also briefly analyzed and discussed.

Phage-chips for novel optically readable tissue engineering assays

We report novel phage-based array chips that are optically readable for cell proliferation and morphology assays. Using M13 phages that were engineered to display RGD on its major coat proteins and/or immobilize FGFb on its minor coat proteins, we prepared arrays of phage spot matrices composed of self-assembled nanofibrous network structures. We cultured fibroblasts on the arrays and, using surface plasmon resonance (SPR) spectroscopy, monitored the effects of the biochemical cues displayed by the phage on cell proliferation and morphology. This study demonstrates the utility of engineered phages as promising coating materials for lab-on-a-chip (LOC) platforms, allowing sensitive monitoring of the effects of functional peptides on cell growth. Phage-chips have great potential for use as high-throughput screening systems for biochemical assays and biosensors and the discovery of novel drugs.

Block copolymer arrangement and composition effects on protein conformation using atomic force microscope-based antigen-antibody adhesion

The conformational changes of fibronectin (FN) deposited on various block copolymers where one block is composed of poly(methyl methacrylate) (PMMA) and the other block is either poly(acrylic acid) (PAA) or poly(2-hydroxyethyl methacrylate) (PHEMA) were investigated using a functionalized atomic force microscope (AFM) tip. The tip was modified with an antibody sensitive to the exposure of the arginine-glycine-aspartic acid (RGD) groups in FN. By studying the adhesive interactions between the antibody and the proteins adsorbed on the block copolymer surface and phase imaging, it was found that the triblock copolymers PAA-b-PMMA-b-PAA and PMMA-b-PHEMA-b-PMMA, which both have large domain sizes, are conducive to the exposure of the FN RGD groups on the surface. On the basis of these results, it is concluded that the surface chemistry as well as the nanomorphology dictated by the block copolymer arrangement could both tune protein conformation and orientation and optimize cell adhesion to the biomaterial surface.

Stimuli responsive polymers for nanoengineering of biointerfaces

There is an increasing demand on the development of "smart" switchable interfaces since controlling surface topography and chemical functionality on a nanometer scale is crucial for numerous biomedical applications. Those surfaces, which are based on stimuli responsive polymers (SRPs), are able to modify their interactions with cells, biomolecules responding to different physical (e.g., temperature) or chemical (e.g., pH) stimuli. Such behavior may partially mimic complex dynamic properties of natural systems that are regulated by many biological stimuli. This paper reviews major studies and applications of SRPs as biointerfaces in a form of thin polymeric films (gels) and surface tethered polymers (brushes).

Nanotechnological Strategies for Biofabrication of Human Organs

Nanotechnology is a rapidly emerging technology dealing with so-called nanomaterials which at least in one dimension have size smaller than 100 nm. One of the most potentially promising applications of nanotechnology is in the area of tissue engineering, including biofabrication of 3D human tissues and organs. This paper focused on demonstrating how nanomaterials with nanolevel size can contribute to development of 3D human tissues and organs which have macrolevel organization. Specific nanomaterials such as nanofibers and nanoparticles are discussed in the context of their application for biofabricating 3D human tissues and organs. Several examples of novel tissue and organ biofabrication technologies based on using novel nanomaterials are presented and their recent limitations are analyzed. A robotic device for fabrication of compliant composite electrospun vascular graft is described. The concept of self-assembling magnetic tissue spheroids as an intermediate structure between nano- and macrolevel organization and building blocks for biofabrication of complex 3D human tissues and organs is introduced. The design of in vivo robotic bioprinter based on this concept and magnetic levitation of tissue spheroids labeled with magnetic nanoparticles is presented. The challenges and future prospects of applying nanomaterials and nanotechnological strategies in organ biofabrication are outlined.

Bioceramics: from bone regeneration to cancer nanomedicine

Research on biomaterials has been growing in the last few years due to the clinical needs in organs and tissues replacement and regeneration. In addition, cancer nanomedicine has recently appeared as an effective means to combine nanotechnology developments towards a clinical application. Ceramic materials are suitable candidates to be used in the manufacturing of bone-like scaffolds. Bioceramic materials may also be designed to deliver biologically active substances aimed at repairing, maintaining, restoring or improving the function of organs and tissues in the organism. Several materials such as calcium phosphates, glasses and glass ceramics able to load and subsequently release in a controlled fashion drugs, hormones, growth factors, peptides or nucleic acids have been developed. In particular, to prevent post surgical infections bioceramics may be surface modified and loaded with certain antibiotics, thus preventing the formation of bacterial biofilms. Remarkably, mesoporous bioactive glasses have shown excellent characteristics as drug carrying bone regeneration materials. These bioceramics are not only osteoconductive and osteoproductive, but also osteoinductive, and have therefore been proposed as ideal components for the fabrication of scaffolds for bone tissue engineering. A recent promising development of bioceramic materials is related to the design of magnetic mediators against tumors. Magnetic composites are suitable thermoseeds for cancer treatment by hyperthermia. Moreover, magnetic nanomaterials offer a wide range of possibilities for diagnosis and therapy. These nanoparticles may be conjugated with therapeutic agents and heat the surrounding tissue under the action of alternating magnetic fields, enabling hyperthermia of cancer as an effective adjunct to chemotherapy regimens.

Cell adhesion and proliferation enhancement by gelatin nanofiber scaffolds

Gelatin nanofibers (GNs) prepared by electrospinning were cross-linked with glutaraldehyde vapor to improve their water-resistant ability. After cross-linking treatment, the form of the fibers expressed no substantial change, but the average diameter of the fibers increased with increasing cross-linking time. The swelling induced by the moisture during the cross-linking process was moderated when the cross-linking time reached 45 min. The contact angle measurements confirmed that the electrospun gelatin fibers were more hydrophilic than the gelatin film (GF). Increasing the cross-linking time did not alter the hydrophilic properties of the gelatin fibers. The cell compatibility was evaluated based on 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay, scanning electron microscope and confocal microscope observations, and Western blot analysis by culturing MG-63 cells on the GFs and GNs. The nanofibrous structure fabricated by an electrospinning technique was found to enhance cell adhesion and proliferation. This process is a cost-effective simulation of GN structures’ promising applications on scaffold preparation for tissue engineering.

Analysis of the cytotoxicity of differentially sized titanium dioxide nanoparticles in murine MC3T3-E1 preosteoblasts

There is an increased use of nanophase titanium dioxide (TiO(2)) in bone implants and scaffolds. However, nano-debris is generated at the bone-biomaterial interface. Therefore, TiO(2) nanoparticles (NPs) of many sizes were investigated for cytotoxic effects on murine MC3T3-E1 preosteoblasts. These TiO(2) NPs induced a time- and dose-dependent decrease in cell viability. There was a significant increase in lactate dehydrogenase (LDH) release, apoptosis and mitochondrial membrane permeability following short-term exposure of the cells to TiO(2) NPs. These NPs also increased granulocyte-macrophage colony stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) gene expression. Compared with the 32 nm TiO(2) NPs, 5 nm TiO(2) NPs were more toxic, induced more apoptosis, increased mitochondrial membrane permeability and stimulated more GM-CSF expression at a high concentration (≥100 μg/ml). The results implied that the differential toxicity was associated with variations in size, so more attention should be given to the toxicity of small NPs for the design of future materials for implantation.

Hydrogels in spinal cord injury repair strategies

Nowadays there are at present no efficient therapies for spinal cord injury (SCI), and new approaches have to be proposed. Recently, a new regenerative medicine strategy has been suggested using smart biomaterials able to carry and deliver cells and/or drugs in the damaged spinal cord. Among the wide field of emerging materials, research has been focused on hydrogels, three-dimensional polymeric networks able to swell and absorb a large amount of water. The present paper intends to give an overview of a wide range of natural, synthetic, and composite hydrogels with particular efforts for the ones studied in the last five years. Here, different hydrogel applications are underlined, together with their different nature, in order to have a clearer view of what is happening in one of the most sparkling fields of regenerative medicine.

Characterization and degradation behavior of agar-carbomer based hydrogels for drug delivery applications: solute effect

In this study hydrogels synthesized from agarose and carbomer 974P macromers were selected for their potential application in spinal cord injury (SCI) repair strategies following their ability to carry cells and drugs. Indeed, in drug delivery applications, one of the most important issues to be addressed concerns hydrogel ability to provide a finely controlled delivery of loaded drugs, together with a coherent degradation kinetic. Nevertheless, solute effects on drug delivery system are often neglected in the large body of literature, focusing only on the characterization of unloaded matrices. For this reason, in this work, hydrogels were loaded with a chromophoric salt able to mimic, in terms of steric hindrance, many steroids commonly used in SCI repair, and its effects were investigated both from a structural and a rheological point of view, considering the pH-sensitivity of the material. Additionally, degradation chemistry was assessed by means of infrared bond response (FT-IR) and mass loss.

Development of bioactive photocrosslinkable fibrous hydrogels

Three-dimensional (3D) fibrous hydrogels were fabricated by blending two photoactive polymers, poly(ethylene glycol) diacrylate (PEGDA) and poly(vinyl alcohol) (PVA), and the resulting solution was electrospun. PEGDA is a commonly used hydrogel material for tissue engineering applications since its interaction with cells can be tuned by crosslinking in a variety of bioactive molecules including peptides and proteins. The PVA in these materials aids in fiber formation and stabilizes the fibrous network when hydrated. The average dry fiber diameter in the hydrogels was 1.02 μm and upon swelling, the fiber diameter increased approximately six-fold. Fibers were stable under cell culture conditions for up to 5 days. The adhesive ligand, RGDS, was readily incorporated into the fibrous network via the conjugation of RGDS to PEG-monoacrylate which was then crosslinked with the fibers. The bioactivity of the fibrous hydrogels was compared with peptide-modified PEGDA-based hydrogels. The two hydrogel materials had similar cell adhesion and viability. Cell morphology on the fibrous hydrogels was dendritic showing a more in vivo like representation, as compared to spread cell morphology on the PEGDA gels. The ability to generate 3D fibrous architectures in hydrogel systems opens up new areas of investigation in cell-material interactions and tissue formation.

Recent applications of carbon-based nanomaterials in analytical chemistry: critical review

The objective of this review is to provide a broad overview of the advantages and limitations of carbon-based nanomaterials with respect to analytical chemistry. Aiming to illustrate the impact of nanomaterials on the development of novel analytical applications, developments reported in the 2005-2010 period have been included and divided into sample preparation, separation, and detection. Within each section, fullerenes, carbon nanotubes, graphene, and composite materials will be addressed specifically. Although only briefly discussed, included is a section highlighting nanomaterials with interesting catalytic properties that can be used in the design of future devices for analytical chemistry.

Nanomaterials for regenerative medicine

The application of nanotechnology has opened a new realm of advancement in the field of regenerative medicine and has provided hope for the culmination of long-felt needs by the development of an ideal means to control the biochemical and mechanical microenvironment for successful cell delivery and tissue regeneration. Both top-down and bottom-up approaches have been widely used in the advancement of this field, be it by improvement in scaffolds for cell growth, development of new and efficient delivery devices, cellular modification and tracking applications or by development of nanodevices such as biosensors. The current review elaborates the various nanomaterials used in regenerative medicine with a special focus on the development of this field during the last 5 years and the recent advances in their aforementioned applications. Furthermore, the key issues and challenges in using nanotechnology-based approaches are highlighted with an outlook on the likely future of nano-assisted regenerative medicine.

Nanomedicine: promises and challenges for the future of public health

As the scope of nanotechnology applications in medicine evolves, it is important to simultaneously recognize and advance contributions germane to public health. A wide range of innovations in nanomedicine stand to impact nearly every medical specialty and unveil novel ways to improve the quality and extend the duration of life – these gains can be measured at both individual and population levels. For example, heart disease and cancer combined make up approximately half of all deaths in the United States per year, and already, advances in nanomedicine demonstrate great potential to reduce rates of morbidity and mortality due to these diseases. Meanwhile, public health applications of nanomedicine such as rapid and portable diagnostics and more effective vaccinations have the potential to revolutionize global health. Research driven by innovators across disciplines such as engineering, biology, medicine, and public health should collaborate in order to achieve maximal potential impact in health for individuals and populations. In turn, knowledge gaps regarding the potential health and safety implications of exposure to engineered nanomaterials must be continuously addressed and actively researched. Dynamic, proactive, and socially responsible research will drive nanomedicine as it plays an increasingly integral and transformative role in medicine and public health in the 21st century.

Osteogenic differentiation of bone marrow stromal cells on poly(epsilon-caprolactone) nanofiber scaffolds

Nanofiber poly(epsilon-caprolactone) (PCL) scaffolds were fabricated by electrospinning, and their ability to enhance the osteoblastic behavior of marrow stromal cells (MSCs) in osteogenic media was investigated. MSCs were isolated from Wistar rats and cultured on nanofiber scaffolds to assess short-term cytocompatibility and long-term phenotypic behavior. Smooth PCL substrates were used as control surfaces. The short-term cytocompatibility results indicated that nanofiber scaffolds supported greater cell adhesion and viability compared with control surfaces. In osteogenic conditions, MSCs cultured on nanofiber scaffolds also displayed increased levels of alkaline phosphatase activity for 3 weeks of culture. Calcium phosphate mineralization was substantially accelerated on nanofiber scaffolds compared to control surfaces as indicated through von Kossa and calcium staining, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Increased levels of intra- and extracellular levels of osteocalcin and osteopontin were observed on nanofiber scaffolds using immunofluorescence techniques after 3 weeks of culture. These results demonstrate the enhanced tissue regeneration property of nanofiber scaffolds, which may be of potential use for engineering osteogenic scaffolds for orthopedic applications.

Prospects of nanotechnology in clinical immunodiagnostics

Nanostructured materials are promising compounds that offer new opportunities as sensing platforms for the detection of biomolecules. Having micrometer-scale length and nanometer-scale diameters, nanomaterials can be manipulated with current nanofabrication methods, as well as self-assembly techniques, to fabricate nanoscale bio-sensing devices. Nanostructured materials possess extraordinary physical, mechanical, electrical, thermal and multifunctional properties. Such unique properties advocate their use as biomimetic membranes to immobilize and modify biomolecules on the surface of nanoparticles. Alignment, uniform dispersion, selective growth and diameter control are general parameters which play critical roles in the successful integration of nanostructures for the fabrication of bioelectronic sensing devices. In this review, we focus on different types and aspects of nanomaterials, including their synthesis, properties, conjugation with biomolecules and their application in the construction of immunosensing devices. Some key results from each cited article are summarized by relating the concept and mechanism behind each sensor, experimental conditions and the behavior of the sensor under different conditions, etc. The variety of nanomaterial-based bioelectronic devices exhibiting novel functions proves the unique properties of nanomaterials in such sensing devices, which will surely continue to expand in the future. Such nanomaterial based devices are expected to have a major impact in clinical immunodiagnostics, environmental monitoring, security surveillance and for ensuring food safety.

Direct differentiation of human embryonic stem cells into selective neurons on nanoscale ridge/groove pattern arrays

Human embryonic stem cells (hESCs) are pluripotent cells that have the potential to be used for tissue engineering and regenerative medicine. Repairing nerve injury by differentiating hESCs into a neuronal lineage is one important application of hESCs. Biochemical and biological agents are widely used to induce hESC differentiation. However, it would be better if we could induce differentiation of hESCs without such agents because these factors are expensive and it is difficult to control the optimal concentrations for efficient differentiation with reduced side effects. Moreover, the mechanism of differentiation induced by these factors is still not fully understood. In this study, we present evidence that nanoscale ridge/groove pattern arrays alone can effectively and rapidly induce the differentiation of hESCs into a neuronal lineage without the use any differentiation-inducing agents. Using UV-assisted capillary force lithography, we constructed nanoscale ridge/groove pattern arrays with a dimension and alignment that were finely controlled over a large area. Human embryonic stem cells seeded onto the 350-nm ridge/groove pattern arrays differentiated into neuronal lineage after five days, in the absence differentiation-inducing agents. This nanoscale technique could be used for a new neuronal differentiation protocol of hESCs and may also be useful for nanostructured scaffolding for nerve injury repair.

Nanopatterning of collagen scaffolds improve the mechanical properties of tissue engineered vascular grafts

Tissue engineered constructs with cells growing in an organized manner have been shown to have improved mechanical properties. This can be especially important when constructing tissues that need to perform under load, such as cardiac and vascular tissue. Enhancement of mechanical properties of tissue engineered vascular grafts via orientation of smooth muscle cells by the help of topographical cues have not been reported yet. In the present study, collagen scaffolds with 650, 500, and 332.5 nm wide nanochannels and ridges were designed and seeded with smooth muscle cells isolated from the human saphenous vein. Cell alignment on the construct was shown by SEM and fluorescence microscopy. The ultimate tensile strength (UTS) and Young's modulus of the scaffolds were determined after 45 and 75 days. Alamar Blue assay was used to determine the number of viable cells on surfaces with different dimensioned patterns. Presence of nanopatterns increased the UTS from 0.55 +/- 0.11 to as much as 1.63 +/- 0.46 MPa, a value within the range of natural arteries and veins. Similarly, Young's modulus values were found to be around 4 MPa, again in the range of natural vessels. The study thus showed that nanopatterns as small as 332.5 nm could align the smooth muscle cells and that alignment significantly improved mechanical properties, indicating that nanopatterned collagen scaffolds have the potential for use in the tissue engineering of small diameter blood vessels.

Enabling individualized therapy through nanotechnology

Individualized medicine is the healthcare strategy that rebukes the idiomatic dogma of 'losing sight of the forest for the trees'. We are entering a new era of healthcare where it is no longer acceptable to develop and market a drug that is effective for only 80% of the patient population. The emergence of "-omic" technologies (e.g. genomics, transcriptomics, proteomics, metabolomics) and advances in systems biology are magnifying the deficiencies of standardized therapy, which often provide little treatment latitude for accommodating patient physiologic idiosyncrasies. A personalized approach to medicine is not a novel concept. Ever since the scientific community began unraveling the mysteries of the genome, the promise of discarding generic treatment regimens in favor of patient-specific therapies became more feasible and realistic. One of the major scientific impediments of this movement towards personalized medicine has been the need for technological enablement. Nanotechnology is projected to play a critical role in patient-specific therapy; however, this transition will depend heavily upon the evolutionary development of a systems biology approach to clinical medicine based upon "-omic" technology analysis and integration. This manuscript provides a forward looking assessment of the promise of nanomedicine as it pertains to individualized medicine and establishes a technology "snapshot" of the current state of nano-based products over a vast array of clinical indications and range of patient specificity. Other issues such as market driven hurdles and regulatory compliance reform are anticipated to "self-correct" in accordance to scientific advancement and healthcare demand. These peripheral, non-scientific concerns are not addressed at length in this manuscript; however they do exist, and their impact to the paradigm shifting healthcare transformation towards individualized medicine will be critical for its success.

Immobilization of poly (ethylene imine) on poly (L-lactide) promotes MG63 cell proliferation and function

Poly (ethylene imine) (PEI) is a polycation widely used for DNA transfection to cells but also applied as primary polycation for layer-by-layer (LBL) assembly of polyelectrolytes. The aim of the present study was to investigate the effect of modification with PEI on the biocompatibility of poly (L-lactide) (PLLA) films. PEI with different molecular weight was immobilized on PLLA by either adsorption or covalent binding. Cell morphologies, immuno-fluorescence staining, cell proliferation by lactate dehydrogenase assay and cell differentiation by alkaline phosphatase assay were utilized to assess the biocompatibility of the modified PLLA using osteoblast cell line MG63. Results revealed that PEI modification remarkably improved cell adhesion, viability, proliferation and function compared with plain PLLA. Hence, PEI-modified PLLA is acceptable as transfection vehicle for engineering of bone and other tissues, or as primary layer to allow LBL assembly to generate biomimetic surface coatings.

The role of surface energy of technical polymers in serum protein adsorption and MG-63 cells adhesion

Polymeric materials are widely used as supports for cell culturing in medical implants and as scaffolds for tissue regeneration. However, novel applications in the biosensor field require materials to be compatible with cell growth and at the same time be suitable for technological processing. Technological polymers are key materials in the fabrication of disposable parts and other sensing elements. As such, it is essential to characterize the surface properties of technological polymers, especially after processing and sterilization. It is also important to understand how technological polymers affect cell behavior when in contact with polymer materials. Therefore, the aim of this research was to study how surface energy and surface roughness affect the biocompatibility of three polymeric materials widely used in research and industry: poly(methyl methacrylate), polystyrene, and poly(dimethylsiloxane). Glass was used as the control material.

FROM THE CLINICAL EDITOR

Polymeric materials are widely used as supports for cell culturing in medical implants and as scaffolds for tissue regeneration. The aim of this research is to study how surface energy and surface roughness affect the biocompatibility of three polymeric materials widely used in research and industry: poly(methylmethacrylate) (PMMA), polystyrene (PS), and poly(dimethylsiloxane) (PDMS).