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A set of poly(δ-valerolactone-co-d,l-lactide)-b-poly(ethylene glycol)-b-poly(δ-valerolactone-co-d,l-lactide) (PVLA-PEG-PVLA) triblock copolymers was synthesized and the solution properties were characterized using rheology, cryo-TEM, cryo-SEM, SANS, and degradation studies. This polymer self-assembles into a low viscosity fluid with flowerlike spherical micelles in water at room temperature and transforms into a wormlike morphology upon heating, accompanied by gelation. At even higher temperatures syneresis is observed. At physiological temperature (37 °C) the hydrogel’s average pore size is around 600 nm. The PVLA-PEG-PVLA gel degrades in about 45 days in cell media, making this unique hydrogel a promising candidate for biomedical applications.

Gene therapy is aimed at selectively knocking up or knocking down the target genes involved in the development of diseases. In many human diseases, dysregulation of disease-associated genes is occurred concurrently: some genes are abnormally turned up and some are turned down. In the field of non-viral gene therapy, plasmid DNA (pDNA) and small interfering RNA (siRNA) are suggested as representative regulation tools for activating and silencing the expression of genes of interest, representatively. Herein, we simultaneously loaded both siRNA (Src homology region 2 domain-containing tyrosine phosphatase-1 siRNA, siSHP-1) for anti-apoptosis and pDNA (hypoxia-inducible vascular endothelial growth factor expression vector, pHI-VEGF) for angiogenesis in a single polymeric nanocarrier and used to synergistically attenuate ischemia-reperfusion (IR)-induced myocardial infarction, which is mainly caused by dysregulating of cardiac apoptosis and angiogenesis. For dual-modality cardiac gene delivery, siSHP-1 and pHI-VEGF were sequentially incorporated into a stable nanocomplex by using deoxycholic acid-modified polyethylenimine (DA-PEI). The resulting DA-PEI/siSHP-1/pHI-VEGF complexes exhibited the high structural stability against polyanion competition and the improved resistance to digestion by nucleases. The cardiac administration of DA-PEI/siSHP-1/pHI-VEGF reduced cardiomyocyte apoptosis and enhanced cardiac microvessel formation, thereby reducing infarct size in rat ischemia-reperfusion model. The simultaneous anti-apoptotic and angiogenic gene therapies synergized the cardioprotective effects of each strategy; thus our dual-modal single-carrier gene delivery system can be considered as a promising candidate for treating ischemic heart diseases.

Small interfering RNA (siRNA), a 21-23nt double-stranded RNA responsible for post-transcriptional gene silencing, has attracted great interests as promising genomic drugs, due to its strong ability to silence target genes in a sequence-specific manner. Despite high silencing efficiency and on-target specificity, the clinical translation of siRNA has been hindered by its inherent features: poor intracellular delivery, limited blood stability, unpredictable immune responses and unwanted off-targeting effects. To overcome these hindrances, researchers have made various advances to modify siRNA itself and to improve its delivery. In this review paper, first we briefly discuss the innate properties and delivery barriers of siRNA. Then, we describe recent progress in (1) chemically and structurally modified siRNAs to solve their intrinsic problems and (2) siRNA delivery formulations including siRNA conjugates, polymerized siRNA, and nucleic acid-based nanoparticles to improve in vivo delivery.

Cancer is a multifactorial disease which involves complex genetic mutation and dysregulation. Combinatorial RNAi technology and concurrent multiple gene silencing are expected to provide advanced strategies for effective cancer therapy, but a safe and effective carrier system is a prerequisite to successful siRNA delivery in vivo. We previously developed an effective tumor-targeting siRNA delivery system for in vivo application. In response to the success of this development, herein we present a dual-gene targeted siRNA and its delivery system, to achieve synergistic effects in cancer therapy. Two different sequences of siRNA were chemically modified to be randomly copolymerized in a single backbone of siRNA polymer (Dual-poly-siRNA), and the resulting Dual-poly-siRNA was incorporated into tumor-homing glycol chitosan nanoparticles. Based on the stability in serum and delivery in a tumor-targeted manner, intravenously administered Dual-poly-siRNA carrying glycol chitosan nanoparticles (Dual-NP) demonstrated successful dual-gene silencing in tumors. Notably, co-delivery of VEGF and Bcl-2 targeting siRNA led to more effective cancer therapy for convenient application.

Expression of receptor for advanced glycation end-products (RAGE) is suggested to play a crucial role in mediating cardiac ischemia/reperfusion (IR) injury, and the blockade of RAGE signaling has been considered as a potential therapeutic strategy for the treatment of IR-induced cardiac damage. In this study, we primarily investigated the effects of RAGE suppression particularly on IR-induced ventricular arrhythmia. To inhibit the IR-induced upregulation of RAGE, siRNA targeting RAGE (siRAGE) was delivered to myocardium by using deoxycholic acid-modified polyethylenimine (PEI-DA) as a non-viral gene carrier. The resultant PEI-DA/siRAGE nanocomplexes successfully silenced the expression of RAGE and attenuated the inflammation and apoptosis in the ischemic-reperfused myocardium. According to our results, the electrophysiological properties (e.g., action potential propagation, action potential duration, and conduction velocity), disrupted by IR injury, were restored to normal level and the induction of ventricular tachycardia was abolished by RAGE silencing. We further found that RAGE suppression led to the activation of Wnt signaling, followed by the expression of gap junction protein, connexin43. Thus it could be concluded that successful siRAGE delivery is protective against IR-induced ventricular arrhythmia.

This study aims to develop bioreducible polyethylenimine (rPEI)/siRNA polyplexes with high stability, high transfection efficiency, and low cytotoxicity for efficient cytoplasmic siRNA delivery. rPEI successfully incorporated siRNA into stable and compact nanocomplexes, and the disulfide linkages in rPEI/siRNA were cleaved under reductive environments, resulting in efficient intracellular translocation and siRNA release. In this study, receptor for advanced glycation end-products (RAGE) was selected as a therapeutic target gene because it is associated with inflammatory responses in ischemia/reperfusion injury. rPEI/siRAGE exhibited high target gene silencing and low cytotoxicity in cardiomyocytes, and the treatment of rPEI/siRAGE reduced the myocardial infarction size.

Technological advances opened up new ways of directing cell fate conversion from one cell lineage to another. The direct cell conversion technique has recently attracted much attention in regenerative medicine to treat devastated organs and tissues, particularly having limited regenerative capacity such as the heart and brain. Unfortunately, its clinical application is severely limited due to a safety concern and immunogenicity of viral vectors, as human gene therapy did in the beginning stages. In this study, we examined the possibility of adopting non-viral vectors to direct cell conversion from mouse embryonic fibroblasts to induced cardiomyocytes (iCM) by transient transfection of four types of chemically synthesized micro-RNA mimics (miRNA-1, 133, 208, and 499). Herein, we tested several commercial and synthetic non-viral gene delivery carriers, which could be divided into three different categories: polymers [branched PEI (bPEI), bioreducible PEI (PEI-SS), deoxycholic acid-conjugated PEI (DA-PEI), jetPEI™, SuperFect™], lipids (Lipofectamine 2000™), and peptides (PepMute™). According to the analyses of physicochemical properties, cellular uptake, and cytotoxicity of the carrier/miRNA complexes, DA-PEI exhibited excellent miRNA delivery efficiency to mouse embryonic fibroblasts. One week after a single treatment of DA-PEI/miRNA without other adjuvants, the cells started to express cardiomyocyte-specific markers, such as α-actinin and α-MHC, indicating the formation of cardiomyocyte-like cells. Although the overall frequency of non-viral vector induced cardiomyogenic transdifferentiation was quite low (ca. 0.2%), this study can provide compelling support to develop clinically applicable transdifferentiation techniques.

A natural based polymer, chitosan has received widespread attention in drug delivery systems due to its valuable physicochemical and biological characteristics. In particular, hydrophobic moiety-conjugated glycol chitosan can form amphiphilic self-assembled glycol chitosan nanoparticles (GCNPs) and simultaneously encapsulate hydrophobic drug molecules inside their hydrophobic core. This GCNP-based drug delivery systems exhibit excellent tumor-homing efficacy, attributed to the long blood circulation and the enhanced permeability and retention effect; this tumor-targeting drug delivery results in improved therapeutic efficiency. In this review, we describe the requisite properties of GCNPs for cancer therapy as well as imaging for diagnosis, such as their basic characteristics, in vitro delivery efficiency and in vivo tumor-targeting ability.

Theranostics was proposed as a combined process of therapeutics and diagnostics methodology for increasing treatment efficacy and safety with simultaneous monitoring of the response to treatment. In the past two decades, nanotechnology has been the focus of developing strategies for drug delivery and imaging functions, and it has expanded to the design of multifunctional nanoparticles and the creation of “nanotheranostics” (i.e., theranostic nanomedicines). Nanotheranostics also shows potential in gene therapy; however, nanoparticle-mediated delivery of genes still faces major obstacles related to (1) the uptake by the reticuloendothelial system, (2) the ability to get across the target cell membranes through endocytosis, and (3) the ability to accumulate in organs with permeable vasculature. Here, we review the development and application of nanotheranostics, highlighting their relevance to gene therapy as well as molecular imaging.

RNA, one of the major biological macromolecules, has been considered as an attractive building material for bottom-up fabrication of nanostructures in the past few decades due to advancements in RNA biology, RNA chemistry and RNA nanotechnology. Most recently, an isothermal enzymatic nucleic acid amplification method termed rolling circle transcription (RCT), which achieves a large-scale synthesis of RNA nanostructures, has emerged as one of fascinating techniques for RNAi-based therapies. Herein, we proposed a newly designed RCT method for synthesis of polymeric siRNA nanoflower, referred to 'RCT and annealing-generated polymeric siRNA (RAPSI)': (1) Amplification of the antisense strand of siRNA via RCT process and (2) annealing of chimeric sense strand containing 3'-terminal DNA nucleotides that provide enzyme cleavage sites. To verify its potentials in RNAi-based cancer therapy, the newly designed RAPSI nanoflower was further complexed with glycol chitosan (GC) derivatives, and systemically delivered to PC-3 xenograft tumors. The resultant RAPSI nanoparticles exhibited the improved particle stability against polyanion competition or nuclease attack. When the RAPSI nanoparticles reached to the cytoplasmic region, active mono siRNA was liberated and significantly down-regulated the expression of target VEGF gene in PC-3 cells. Excellent tumor-homing efficacy and anti-tumor effects of the RAPSI nanoparticles were further demonstrated. Overall, the proposed RCT-based polymeric siRNA nanoflower formulation can provide a new platform technology that allows further functional modifications via an advanced annealing method for systemic cancer RNAi therapy.

Poly(ethylene glycol)-coated cross-linked iron oxide nanoparticles (PCIONs) are developed for therapeutic engineering of mesenchymal stem cells (MSCs) and their monitoring via magnetic resonance (MR) imaging at a time. PCIONs successfully combine with plasmid DNA (pDNA) via ionic interaction. Accordingly, PCION/pDNA complexes mediate superior translocations of vascular endothelial growth factor (VEGF) pDNA into intracellular regions of MSCs under external magnetic field, which significantly elevate production of VEGF from MSCs. Genetically engineered MSCs are also clearly visualized via MR imaging after administration to rat cerebrovascular ischemia models, which enable tracking of MSCs migration from injected sites to injured ischemic area.

Carbon-based nanomaterials such as graphene sheets and carbon nanotubes possess unique mechanical, electrical, and optical properties that present new opportunities for tissue engineering, a key field for the development of biological alternatives that repair or replace whole or a portion of tissue. Carbon nanomaterials can also provide a similar microenvironment as like a biological extracellular matrix in terms of chemical composition and physical structure, making them a potential candidate for the development of artificial scaffolds. In this review, we summarize recent research advances in the effects of carbon nanomaterial-based substrates on cellular behaviors, including cell adhesion, proliferation, and differentiation into osteo- or neural- lineages. The development of 3D scaffolds based on carbon nanomaterials (or their composites with polymers and inorganic components) is introduced, and the potential of these constructs in tissue engineering, including toxicity issues, is discussed. Future perspectives and emerging challenges are also highlighted.

A self-assembled peptide hydrogel consisting of Fmoc-diphenylalanine has been employed as a biosensing platform through the encapsulation of enzyme bioreceptors (e.g., glucose oxidase or horseradish peroxidase) and fluorescent reporters (e.g., CdTe and CdSe quantum dots). Enzymes and quantum dots (QDs) were physically immobilized within the hydrogel matrix in situ in a single step by simply mixing aqueous solution containing QDs and enzymes with monomeric peptide (Fmoc-diphenylalanine) solution. By using atomic force microscopy and scanning transmission electron microscopy, we observed that the self-assembled peptide hydrogel had a three-dimensional network of nanofibers (with a diameter of approximately 70-90 nm) that physically hybridized with QDs and encapsulated enzyme bioreceptors with a minimal leakage. We successfully applied the peptide hydrogel to the detection of analytes such as glucose and toxic phenolic compounds by using a photoluminescence quenching of the hybridized QDs. The Michaelis-Menten constant (K(M)) of the photoluminescent peptide hydrogel was found to be 3.12 mM (GOx for glucose) and 0.82 mM (HRP for hydroquinone), respectively, which were much lower than those of conventional gel materials. These results suggest that the peptide hydrogel is an alternative optical biosensing platform with practical advantages such as simple fabrication via self-assembly, efficient diffusion of target analytes, and high encapsulation efficiencies for fluorescent reporters and bioreceptors.

The endothelialization of prosthetic scaffolds is considered to be an effective strategy to improve the effectiveness of small-diameter vascular grafts. We report the development of a nanofibrous scaffold that has a polymeric core and a shell mimicking mussel adhesive for enhanced attachment, proliferation, and phenotypic maintenance of human endothelial cells. Polycaprolactone (PCL) was chosen as a core material because of its good biodegradability and mechanical properties suitable for tissue engineering. PCL was electrospun into nanofibers with a diameter of approximately 700 nm and then coated with poly(dopamine) (PDA) to functionalize the surface of PCL nanofibers with numerous catechol moieties similar to mussel adhesives in nature. The formation of a PDA ad-layer was analyzed using multiple techniques, including scanning electron microscopy, Raman spectroscopy, and water contact angle measurements. When PDA-coated PCL nanofibers were compared to unmodified and gelatin-coated nanofibers, human umbilical vein endothelial cells (HUVECs) exhibited highly enhanced adhesion and viability, increased stress fiber formation, and positive expression of endothelial cell markers (e.g., PECAM-1 and vWF).

The spatial control and patterning of mammalian cells were achieved by using the universal adhesive property of mussel-inspired polydopamine (PDA). The self-polymerization of dopamine, a small molecule inspired by the DOPA motif of mussel foot proteins, resulted in the formation of a PDA adlayer when aqueous dopamine solution was continuously injected into poly(dimethylsiloxane) microchannels. We found that various cells (fibrosarcoma HT1080, mouse preosteoblast MC3T3-E1, and mouse fibroblast NIH-3T3) predominantly adhered to PDA-modified regions, maintaining their normal morphologies. The cells aligned in the direction of striped PDA patterns, and this tendency was not limited by the type of cell line. Because PDA modification does not require complex chemical reactions and is applicable to any type of material, it enables cell patterning in a simple and versatile manner as opposed to conventional methods based on the immobilization of adhesive proteins. The PDA-based method of cell patterning should be useful in many biomaterial research areas such as the fabrication of tissue engineering scaffolds, cell-based devices for drug screening, and the fundamental study of cell-material interactions.

Bone tissue is a complex biocomposite material with a variety of organic (e.g., proteins, cells) and inorganic (e.g., hydroxyapatite crystals) components hierarchically organized with nano/microscale precision. Based on the understanding of such hierarchical organization of bone tissue and its unique mechanical properties, efforts are being made to mimic these organic–inorganic hybrid biocomposites. A key factor for the successful designing of complex, hybrid biomaterials is the facilitation and control of adhesion at the interfaces, as many current synthetic biomaterials are inert, lacking interfacial bioactivity. In this regard, researchers have focused on controlling the interface by surface modifications, but the development of a simple, unified way to biofunctionalize diverse organic and inorganic materials remains a critical challenge. Here, a universal biomineralization route, called polydopamine-assisted hydroxyapatite formation (pHAF), that can be applied to virtually any type and morphology of scaffold materials is demonstrated. Inspired by the adhesion mechanism of mussels, the pHAF method can readily integrate hydroxyapatites on ceramics, noble metals, semiconductors, and synthetic polymers, irrespective of their size and morphology (e.g., porosity and shape). Surface-anchored catecholamine moieties in polydopamine enriches the interface with calcium ions, facilitating the formation of hydroxyapatite crystals that are aligned to the c-axes, parallel to the polydopamine layer as observed in natural hydroxyapatites in mineralized tissues. This universal surface biomineralization can be an innovative foundation for future tissue engineering.

Amyloid-beta (Abeta) is the major constituent of senile plaques in the brains of Alzheimer's disease patients. In order to develop an efficient in vitro system for studying the interaction of cells with Abeta aggregates, we have prepared a synthetic amyloid lawn by immobilizing Abeta peptides over a functionalized glass surface and subsequently incubating the template in a fresh Abeta solution. On the top of different types of amyloid lawns (e.g. monomeric, oligomeric, and fibrillar), we cultivated PC12 cells, creating physical contacts between the cells and the lawns. Results indicated that cell viability was differentially affected when grown atop different Abeta lawns while cells were well adhered onto the surface of these Abeta lawns. The mode of cell death by Abeta lawn was confirmed to be apoptotic rather than necrotic, showing that cells undergo suicide by just contact with Abeta lawn. While conventional 'solution-based' methods for testing amyloid toxicity suffer from problems such as lot-to-lot variations, continued fibrillation, and heterogeneous population of aggregates, our 'surface-based' lawn system is suitable for high-throughput analysis of amyloid toxicity, which may enable high-throughput screening of potential drug candidates for treating amyloid diseases with the goal of reducing the cell death on the lawn.

Recently discovered evidences suggest that precipitation of Alzheimer's beta-amyloid (Abeta) peptide and the toxicity in Alzheimer's disease (AD) are caused by abnormal interactions with neocortical metal ions, especially Zn2+, Cu2+, and Fe3+. While many studies had focused on the role of a "single" metal ion and its interaction with Abeta peptides, such studies involving "multiple" metal ions have hardly been explored. Here, to explore the nature of codeposition of different metals, two or more metal ions along with Abeta were incubated over a solid template prepared by immobilizing Abeta42 oligomers. The influence of Zn2+,Cu2+, and Fe3+ on Abeta aggregation was investigated by two approaches: co-incubation and sequential addition. Our results using ex situ AFM, ThT-induced fluorescence, and FTIR spectroscopy indicated that the co-incubation of Cu2+, Zn2+, and Fe3+ significantly altered the morphology of aggregates. A concentration dependence study with mixed metal ions suggested that Zn2+ was required at much lower concentrations than Cu2+ to yield nonfibrillar amorphous Abeta deposits. In addition, sequential addition of Zn2+ or Cu2+ on fibrillar aggregates formed by Fe3+ demonstrated that Zn2+ and Cu2+ could possibly change the conformation of the aggregates induced by Fe3+. Our findings elucidate the coexistence of multiple metal ions through their interactions with Abeta peptides or its aggregates.

This study aims to develop bioreducible polyethylenimine (rPEI)/siRNA polyplexes with high stability, high transfection efficiency, and low cytotoxicity for efficient cytoplasmic siRNA delivery. rPEI successfully incorporated siRNA into stable and compact nanocomplexes, and the disulfide linkages in rPEI/siRNA were cleaved under reductive environments, resulting in efficient intracellular translocation and siRNA release. In this study, receptor for advanced glycation end-products (RAGE) was selected as a therapeutic target gene because it is associated with inflammatory responses in ischemia/reperfusion injury. rPEI/siRAGE exhibited high target gene silencing and low cytotoxicity in cardiomyocytes, and the treatment of rPEI/siRAGE reduced the myocardial infarction size.

The clinical applications of therapeutic siRNA remain as a challenge due to the lack of efficient delivery system. In the present study, hyaluronic acid-siRNA conjugate (HA-SS-siRNA)/reducible polyethylenimine (BPEI1.2k-SS) complexes were developed to efficiently deliver the siRNA to HA receptor abundant region with the improved siRNA stability. HA and siRNA were conjugated with disulfide bonds, which are cleavable in cytoplasm. The synthesized HA-SS-siRNA was further complexed with BPEI1.2k-SS, resulting in the formation of spherical nanostructures with approximately 190 nm of size and neutral surface charge. HA-SS-siRNA/BPEI1.2k-SS complexes exhibited the improved stability against serum proteins or polyanions. These complexes were successfully translocated into intracellular region via HA receptor-mediated endocytosis, and silenced target gene expression.

The activation of receptor for advanced glycation end products (RAGE) signaling is mainly associated with myocardial ischemia/reperfusion injury. Thus the blockade of RAGE-ligands axis can be considered as a potential therapeutic strategy to protect myocardial infarction after ischemia/reperfusion injury. Herein, we strengthened the cardioprotective effect with combinatorial treatment of soluble RAGE (sRAGE) and RAGE siRNA (siRAGE) causing more effective suppression of RAGE-mediated signaling transduction. For pharmacological blockade of RAGE, sRAGE, the extracellular ligand binding domain of RAGE, acts as a pharmacological ligand decoy and inhibits the interaction between RAGE and its ligands. For genetic deletion of RAGE, siRAGE suppresses the expression of RAGE by participating in RNA interference mechanism. Therefore, we combined these two RAGE blockade/deletion strategies and investigated the therapeutic effects on rat ischemic and reperfused myocardium. According to our results, based on RAGE expression level analysis and infarct size/fibrosis measurement, co-treatment of sRAGE and siRAGE exhibited synergic cardioprotective effects; thus the newly designed regimen can be considered as a promising candidate for the treatment of myocardial infarction.

A compact electrospray system has been developed using a cone-shaped porous medium. The cone-jet conditions with a stable spraying mode were measured using ethanol and lavender oil, and the average diameter and size distribution of the sprayed droplets were investigated according to the applied voltage. In addition, the spray stability over time was analyzed because the fluid was supplied with a capillary action without the use of a pump. The average diameter of the droplets was 3.6–6.7 μm (ethanol) and 6.4–8.6 μm (lavender oil). We observed that the average particle size clearly increased with the applied voltage; the cause was determined based on the electric stress due to the potential difference (“electric pressure”) between the tip of the porous medium and ground ring. Moreover, the mean droplet size according to the electrical potential was proportional to E0.5 (ethanol) and E0.85 (lavender oil). The penetration time in the porous medium of the proposed system was controlled by the physical properti...

Inflammatory response in myocardial ischemia-reperfusion injury plays a critical role in ventricular remodeling. To avoid deleterious effects of overwhelming inflammation, we blocked the expression of receptor for advanced glycation end-products (RAGE), a key mediator of the local and systemic inflammatory responses, via RNAi mechanism. Herein, a facial amphipathic deoxycholic acid-modified low molecular weight polyethylenimine (DA-PEI) was used as a siRNA delivery carrier to myocardium. The DA-PEI conjugate formed a stable complex with siRNA via electrostatic and hydrophobic interactions. The siRAGE/DA-PEI formulation having negligible toxicity could enhance intracellular delivery efficiency and successfully suppress RAGE expression both in vitro and in vivo. Furthermore, the cardiac administration of siRAGE/DA-PEI reduced apoptosis and inflammatory cytokine release, subsequently led to attenuation of left ventricular remodeling in rat myocardial infarction model. The potential therapeutic effects of RAGE gene silencing on myocardial ischemia-reperfusion injury may suggest that the siRAGE/DA-PEI delivery system can be considered as a promising strategy for treating myocardial infarction.

RNA interference (RNAi) is a naturally occurring regulatory process that controls posttranscriptional gene expression. Small interfering RNA (siRNA), a common form of RNAi-based therapeutics, offers new opportunities for cancer therapy via silencing specific genes, which are associated to cancer progress. However, clinical applications of RNAi-based therapy are still limited due to the easy degradation of siRNA during body circulation and the difficulty in the delivery of siRNA to desired tissues and cells. Thus, there have been many efforts to develop efficient siRNA delivery systems, which protect siRNA from serum nucleases and deliver siRNA to the intracellular region of target cells. Here, the recent advances in siRNA nanocarriers, which possess tumor-targeting ability are reviewed; various nanoparticle systems and their antitumor effects are summarized. The development of multifunctional nanocarriers for theranostics or combinatorial therapy is also discussed.

Poly(ethylene glycol)-coated cross-linked iron oxide nanoparticles (PCIONs) are developed for therapeutic engineering of mesenchymal stem cells (MSCs) and their monitoring via magnetic resonance (MR) imaging at a time. PCIONs successfully combine with plasmid DNA (pDNA) via ionic interaction. Accordingly, PCION/pDNA complexes mediate superior translocations of vascular endothelial growth factor (VEGF) pDNA into intracellular regions of MSCs under external magnetic field, which significantly elevate production of VEGF from MSCs. Genetically engineered MSCs are also clearly visualized via MR imaging after administration to rat cerebrovascular ischemia models, which enable tracking of MSCs migration from injected sites to injured ischemic area.

Graphene-based nanomaterials have received much attention in biomedical applications for drug/gene delivery, cancer therapy, imaging, and tissue engineering. Despite the capacity of 2D carbon materials as a nontoxic and implantable platform, their effect on myogenic differentiation has been rarely studied. We investigated the myotube formation on graphene-based nanomaterials, particularly graphene oxide (GO) and reduced graphene oxide (rGO). GO sheets were immobilized on amine-modified glass to prepare GO-modified glass, which was further reduced by hydrazine treatment for the synthesis of rGO-modified substrate. We studied the behavior, including adhesion, proliferation, and differentiation, of mouse myoblast C2C12 on unmodified, GO-, and rGO-modified glass substrates. According to our analyses of myogenic protein expression, multinucleate myotube formation, and expression of differentiation-specific genes (MyoD, myogenin, Troponin T, and MHC), myogenic differentiation was remarkably enhanced on GO, which resulted from serum protein adsorption and nanotopographical cues. Our results demonstrate the ability of GO to stimulate myogenic differentiation, showing a potential for skeletal tissue engineering applications.

The interactions between cells and materials play critical roles in the success of new scaffolds for tissue engineering, since chemical and physical properties of biomaterials regulate cell adhesion, proliferation, migration, and differentiation. We have developed nanofibrous substrates that possess both topographical cues and electroactivity. The nanofiber scaffolds were fabricated through the electrospinning of polycaprolactone (PCL, a biodegradable polymer) and polyaniline (PANi, a conducting polymer) blends. We investigated the ways in which those properties influenced myoblast behaviors. Neither nanofiber alignment nor PANi concentration influenced cell growth and proliferation, but cell morphology changed significantly from multipolar to bipolar with the anisotropy of nanofibers. According to our analyses of myosin heavy chain expression, multinucleate myotube formation, and the expression of differentiation-specific genes (myogenin, troponin T, MHC), the differentiation of myoblasts on PCL/PANi nanofibers was strongly dependent on both nanofiber alignment and PANi concentration. Our results suggest that topographical cues and the electroactivity of nanofibers synergistically stimulate muscle cell differentiation to make PCL/PANi nanofibers a suitable scaffold material for skeletal tissue engineering.

The conformational change of cellular prion protein (PrP(C)) to its infectious isoform (PrP(Sc)) is a hallmark of prion diseases. We have developed a novel solid surface-based system for efficient prion fibrillation in vitro by immobilizing prion peptides onto a chemically activated solid surface. The self-assembly of prion peptides into fibrils was more highly accelerated on the solid surface than in solution after 72 h of incubation at 37 degrees C. According to our observation using ex situ atomic force microscopy, fibrils were over 200 nm long and 5-8 nm in diameter. Amyloid-like properties of fibrils self-assembled on the solid surface were confirmed by multiple analyses with circular dichroism and amyloid-specific dyes such as Congo red and thioflavin T. The fibril formation of prion peptides was substantially affected by the incubation temperature, and preformed fibrils disassembled after additional heat treatment at 100 Odegrees . The solid surface-based prion fibrillation system developed in the present work may become a useful tool for the in vitro study of prion aggregation. The adoption of this system will allow the efficient investigation of environmental factors and inhibitor screening.

In prion diseases, the posttranslational modification of host-encoded prion protein PrP{sup c} yields a high {beta}-sheet content modified protein PrP{sup sc}, which further polymerizes into amyloid fibrils. PrP106-126 initiates the conformational changes leading to the conversion of PrP{sup c} to PrP{sup sc}. Molecules that can defunctionalize such peptides can serve as a potential tool in combating prion diseases. In microorganisms during stressed conditions, small stress molecules (SSMs) are formed to prevent protein denaturation and maintain protein stability and function. The effect of such SSMs on PrP106-126 amyloid formation is explored in the present study using turbidity, atomic force microscopy (AFM), and cellular toxicity assay. Turbidity and AFM studies clearly depict that the SSMs-ectoine and mannosylglyceramide (MGA) inhibit the PrP106-126 aggregation. Our study also connotes that ectoine and MGA offer strong resistance to prion peptide-induced toxicity in human neuroblastoma cells, concluding that such molecules can be potential inhibitors of prion aggregation and toxicity.

Inspired by nature's strategy for creating organic/inorganic hybrid composite materials, we developed a simple but powerful method to synthesize bone-like peptide/hydroxyapatite nanocomposites using a mussel-mimetic adhesive, polydopamine. We found that polydopamine was uniformly coated in a graphite-like layered structure on the surface of self-assembled diphenylalanine (Phe-Phe, FF) nanowires and enabled the epitaxial growth of c-axis-oriented hydroxyapatite nanocrystals along the nanowires, which is similar to mineralized collagen nanofibers of natural bone. The mineralized peptide nanowires were further organized in relation to each other and then readily hybridized with osteoblastic cells, resulting in the formation of multi-level hierarchical structures. They were found to be nontoxic and enabled efficient adhesion and proliferation of osteoblastic cells by guiding filopoidal extension.

Hydroxyapatite (HAp)/carbon nanotubes (CNTs) hybrid composite materials are successfully synthesized via a biomineralization process that employs poly(dopamine) (PDA), a synthetic mimic of mussel adhesive proteins. Creating bio-inorganic composites for regenerative medicine requires appropriate fillers to enhance their mechanical robustness; for example, natural bones are composed mainly of HAp supported by collagen fibers. In this regard, many efforts have been made to harness HAp as a bone substitute through its integration with reinforcing fibrous materials such as CNTs. We found that the formation of a PDA ad-layer on the surface of CNTs changed the hydrophobic CNTs to become bioactive. This enabled efficient interaction between the CNTs and mineral ions (e.g., Ca2+), which facilitated the mineralization of HAp. CNTs functionalized with PDA (CNT-PDA) highly accelerated the formation of HAp when incubated in a simulated body fluid and exhibited a minimal cytotoxic effect on bone osteoblast cells compared to pristine or carboxylated CNTs. Our results show the potential of CNT-PDA as a scaffold material for bone tissue regeneration and implantation.