Effect of invasome composition on membrane fluidity, vesicle stability and skin interactions

Invasomes have been widely exploited to enhance the percutaneous permeation of drugs. On the other hand, few studies have been dedicated to evaluating how their composition impacts the interaction with the skin, vesicle rigidity and stability, which was the focus of this investigation. Light scattering and spectroscopic techniques were considered for vesicle characterization. The addition of cholesterol (CHOL) into the phosphatidylcholine (PC) vesicles led to increased membrane rigidity (from PC:CHOL 5:0.5) and a concentration-dependent disorder effect on skin domains. Nevertheless, these vesicles were showed to be less stable. Ethanol, in turn, resulted in larger and more flexible vesicles, which can be attributed to its preferential distribution in headgroups of PC. The effect of limonene on membrane rigidity was dependent on the vesicle composition. It reduced the rigidity when few constituents were considered, but an opposite effect was observed for vesicles containing PC, CHOL, ethanol and limonene. Competitive effects of limonene and CHOL by the same domains in PC could explain these findings. Limonene was crucial to obtaining more monodisperse vesicles and it showed a synergistic action with CHOL in the disruption of lipid domains in the skin. Invasomes were more stable than liposomes. CHOL-free invasomes showed to be stable for up to 40 days at room temperature.

Static and photoresponsive dynamic materials to dissect physical regulation of cellular functions

Recent progress in mechanobiology has highlighted the importance of physical cues, such as mechanics, geometry (size), topography, and porosity, in the determination of cellular activities and fates, in addition to biochemical factors derived from their surroundings. In this review, we will first provide an overview of how such fundamental insights are identified by synchronizing the hierarchical nature of biological systems and static materials with tunable physical cues. Thereafter, we will explain the photoresponsive dynamic biomaterials to dissect the spatiotemporal aspects of the dependence of biological functions on physical cues.

Nanoparticle-based strategies to target HIV-infected cells

Antiretroviral drugs employed for the treatment of human immunodeficiency virus (HIV) infections have remained largely ineffective due to their poor bioavailability, numerous adverse effects, modest uptake in infected cells, undesirable drug-drug interactions, the necessity for long-term drug therapy, and lack of access to tissues and reservoirs. Nanotechnology-based interventions could serve to overcome several of these disadvantages and thereby improve the therapeutic efficacy of antiretrovirals while reducing the morbidity and mortality due to the disease. However, attempts to use nanocarriers for the delivery of anti-retroviral drugs have started gaining momentum only in the past decade. This review explores in-depth the various nanocarriers that have been employed for the treatment of HIV infections highlighting their merits and possible demerits.

Halloysite nanotubes - the nano-bio interface

The numerous biological applications of nanoparticles in general and nano-clays in particular are rooted in understanding and harnessing their dynamic nano-bio interface. Among clays, the intrinsically-mesoporous halloysite nanotubes (HNTs) have emerged in recent years as promising nanomaterials. The diverse interactions of these nanotubes with living cells, encompassing electrostatic, van der Waals, and ion exchange, along with cellular response, are crucial in determining the behaviour of HNTs in biological systems. Thus, rational engineering of the nanotube properties allows for vast applications ranging from bacteria encapsulation for bioremediation, through algae flocculation for aquaculture, to intracellular drug delivery. This review summarizes the many aspects of the nano-bio interface of HNTs with different cell types (bacteria, algae and fungi, and mammalian cells), highlighting biocompatibility/bio-adverse properties, interaction mechanisms, and the latest cutting-edge technologies.

Tailoring Iron Oxide Nanoparticles for Efficient Cellular Internalization and Endosomal Escape

Iron oxide nanoparticles (IONs) have been widely explored for biomedical applications due to their high biocompatibility, surface-coating versatility, and superparamagnetic properties. Upon exposure to an external magnetic field, IONs can be precisely directed to a region of interest and serve as exceptional delivery vehicles and cellular markers. However, the design of nanocarriers that achieve an efficient endocytic uptake, escape lysosomal degradation, and perform precise intracellular functions is still a challenge for their application in translational medicine. This review highlights several aspects that mediate the activation of the endosomal pathways, as well as the different properties that govern endosomal escape and nuclear transfection of magnetic IONs. In particular, we review a variety of ION surface modification alternatives that have emerged for facilitating their endocytic uptake and their timely escape from endosomes, with special emphasis on how these can be manipulated for the rational design of cell-penetrating vehicles. Moreover, additional modifications for enhancing nuclear transfection are also included in the design of therapeutic vehicles that must overcome this barrier. Understanding these mechanisms opens new perspectives in the strategic development of vehicles for cell tracking, cell imaging and the targeted intracellular delivery of drugs and gene therapy sequences and vectors.

Regulation of Stem Cell Functions by Micro-Patterned Structures

Micro-patterned surfaces have been broadly used to control the morphology of stem cells for investigation of the influence of physiochemical and biological cues on stem cell functions. Different structures of micro-patterned surfaces can be prepared by photolithography through designing the photomask features. Cell spreading area, geometry, aspect ratio, and alignment can be regulated by the micro-patterned structures. Their influences on adipogenic, osteogenic, and smooth muscle differentiation of the human bone marrow-derived mesenchymal stem cells are compared and investigated in details. Variation of cell morphology can trigger rearrangement of cytoskeleton, generating cytoskeletal mechanical stimulation and consequently inducing differentiation of mesenchymal stem cells into different lineages. This chapter summarizes the latest development of regulation of mesenchymal stem cell morphology by micro-patterns and the influence on the behaviors and differentiation of the mesenchymal stem cells.

Culturing C2C12 myotubes on micromolded gelatin hydrogels accelerates myotube maturation

Background

Skeletal muscle contributes to roughly 40% of lean body mass, and its loss contributes to morbidity and mortality in a variety of pathogenic conditions. Significant insights into muscle function have been made using cultured cells, in particular, the C2C12 myoblast line. However, differentiation of these cells in vitro typically yields immature myotubes relative to skeletal muscles in vivo. While many efforts have attempted to improve the maturity of cultured myotubes, including the use of bioengineered substrates, lack of molecular characterization has precluded their widespread implementation. This study characterizes morphological, molecular, and transcriptional features of C2C12 myotubes cultured on crosslinked, micropatterned gelatin substrates fabricated using previously established methods and compares them to myotubes grown on unpatterned gelatin or traditional plasticware.

Methods

We used immunocytochemistry, SDS-PAGE, and RNAseq to characterize C2C12 myotubes grown on micropatterned gelatin hydrogels, unpatterned gelatin hydrogels, and typical cell culture substrates (i.e., plastic or collagen-coated glass) across a differentiation time course. The ability to form aligned sarcomeres and myofilament protein concentration was assessed. Additionally, the transcriptome was analyzed across the differentiation time course.

Results

C2C12 myotubes grown on micropatterned gelatin hydrogels display an increased ability to form aligned sarcomeres as well as increased contractile protein content relative to myotubes cultured on unpatterned gelatin and plastic. Additionally, genes related to sarcomere formation and in vivo muscle maturation are upregulated in myotubes grown on micropatterned gelatin hydrogels relative to control myotubes.

Conclusions

Our results suggest that growing C2C12 myotubes on micropatterned gelatin hydrogels accelerates sarcomere formation and yields a more fully matured myotube culture. Thus, the use of micropatterned hydrogels is a viable and simple approach to better model skeletal muscle biology in vitro.

Electronic supplementary material

The online version of this article (10.1186/s13395-019-0203-4) contains supplementary material, which is available to authorized users.

Preparation of albendazole-loaded liposomes by supercritical carbon dioxide processing

Supercritical fluid (SCF) technology offers a potential green alternative to organic solvent-based methods for drug formulation. Albendazole (ABZ) has promising anticancer activity when formulated to increase its cellular uptake. Herein, a static volume method was used to determine the solubility of ABZ in supercritical carbon dioxide (scCO₂) for the future development of such ABZ formulations. The solubility of ABZ in scCO₂ (250 bar, 37 °C) was approximately 12 mg/100 mL. The extent of dissolution was measured at various time points to determine when saturation solubility occurred, which was demonstrated from 9 h. In order to determine if scCO₂ processing induced ABZ polymorphism, DSC/TGA, FTIR and XRD were used, which demonstrated no change in its solid state. Following this, ABZ loaded liposomes were manufactured using SCF technology. The liposomes diameter was 167.2 ± 5.3 nm as determined by Zetasizer, and confirmed by cryo-transmission electron microscopy. In conclusion, scCO₂ was used successfully to solubilize ABZ, and to manufacture liposomes of nano-sized range. This study provides insight into use of green technology for future ABZ liposomal formulation without the need for organic solvents.

Multifactorial bottom-up bioengineering approaches for the development of living tissue substitutes

Bottom-up bioengineering utilizes the inherent capacity of cells to build highly sophisticated structures with high levels of biomimicry. Despite the significant advancements in the field, monodomain approaches require prolonged culture time to develop an implantable device, usually associated with cell phenotypic drift in culture. Herein, we assessed the simultaneous effect of macromolecular crowding (MMC) and mechanical loading in enhancing extracellular matrix (ECM) deposition while maintaining tenocyte (TC) phenotype and differentiating bone marrow stem cells (BMSCs) or transdifferentiating neonatal and adult dermal fibroblasts toward tenogenic lineage. At d 7, all cell types presented cytoskeleton alignment perpendicular to the applied load independently of the use of MMC. MMC enhanced ECM deposition in all cell types. Gene expression analysis indicated that MMC and mechanical loading maintained TC phenotype, whereas tenogenic differentiation of BMSCs or transdifferentiation of dermal fibroblasts was not achieved. Our data suggest that multifactorial bottom-up bioengineering approaches significantly accelerate the development of biomimetic tissue equivalents.-Gaspar, D., Ryan, C. N. M., Zeugolis, D. I. Multifactorial bottom-up bioengineering approaches for the development of living tissue substitutes.

Three-dimensional spherical gelatin bubble-based scaffold improves the myotube formation of H9c2 myoblasts

Microenvironmental factors including physical and chemical cues can regulate stem cells as well as terminally differentiated cells to modulate their biological function and differentiation. However, one of the physical cues, the substrate's dimensionality, has not been studied extensively. In this study, the flow-focusing method with a microfluidic device was used to generate gelatin bubbles to fabricate highly ordered three-dimensional (3D) scaffolds. Rat H9c2 myoblasts were seeded into the 3D gelatin bubble-based scaffolds and compared to those grown on 2D gelatin-coating substrates to demonstrate the influences of spatial cues on cell behaviors. Relative to cells on the 2D substrates, the H9c2 myoblasts were featured by a good survival and normal mitochondrial activity but slower cell proliferation within the 3D scaffolds. The cortical actin filaments of H9c2 cells were localized close to the cell membrane when cultured on the 2D substrates, while the F-actins distributed uniformly and occupied most of the cell cytoplasm within the 3D scaffolds. H9c2 myoblasts fused as multinuclear myotubes within the 3D scaffolds without any induction but cells cultured on the 2D substrates had a relatively lower fusion index even differentiation medium was provided. Although there was no difference in actin α 1 and myosin heavy chain 1, H9c2 cells had a higher myogenin messenger RNA level in the 3D scaffolds than those of on the 2D substrates. This study reveals that the dimensionality influences differentiation and fusion of myoblasts.

Biological Tissues as Active Nematic Liquid Crystals

Live tissues can self-organize and be described as active materials composed of cells that generate active stresses through continuous injection of energy. In vitro reconstituted molecular networks, as well as single-cell cytoskeletons show that their filamentous structures can portray nematic liquid crystalline properties and can promote nonequilibrium processes induced by active processes at the microscale. The appearance of collective patterns, the formation of topological singularities, and spontaneous phase transition within the cell cytoskeleton are emergent properties that drive cellular functions. More integrated systems such as tissues have cells that can be seen as coarse-grained active nematic particles and their interaction can dictate many important tissue processes such as epithelial cell extrusion and migration as observed in vitro and in vivo. Here, a brief introduction to the concept of active nematics is provided, and the main focus is on the use of this framework in the systematic study of predominantly 2D tissue architectures and dynamics in vitro. In addition how the nematic state is important in tissue behavior, such as epithelial expansion, tissue homeostasis, and the atherosclerosis disease state, is discussed. Finally, how the nematic organization of cells can be controlled in vitro for tissue engineering purposes is briefly discussed.

Regulation of mesenchymal stem cell functions by micro-nano hybrid patterned surfaces

Micro- and nano-structured substrates have been widely used in the biomedical engineering field. Their precise control of cell morphology makes them promising for investigating various cell behaviors. However, regulation of cell functions using micro-nano hybrid patterns is rarely achieved. Since the cell microenvironment in vivo has complex micro- and nano-structures, it is desirable to use micro-nano hybrid patterns to mimic the microenvironment to control cell morphology and disclose its influence on stem cell differentiation. In this study, poly(vinyl alcohol) (PVA) micro-stripes with different spacings (50 μm, 100 μm and 200 μm) were constructed on polystyrene (PS) nano-grooves to prepare micro-nano hybrid patterns where the direction of the PVA micro-stripes and PS nano-grooves was parallel or orthogonal. Human bone marrow-derived mesenchymal stem cells (hMSCs) cultured on the micro-nano hybrid patterns showed a different cell alignment and elongation dependent on the PVA micro-stripe spacing and orientation of the PS nano-grooves. Comparison of the influence of cell alignment and aspect ratio on differentiation of hMSCs indicated that myogenic differentiation was predominantly regulated by cell alignment and osteogenic differentiation by cell elongation, while adipogenic differentiation was regulated neither by cell alignment nor by cell elongation.

Focal Adhesion Kinase Activation Is Necessary for Stretch-Induced Alignment and Enhanced Differentiation of Myogenic Precursor Cells

Myogenic precursors sense and dynamically respond to mechanical stimulation through complex integrin-mediated mechanotransduction, in which focal adhesion kinase (FAK) is a fundamental intracellular signaling mediator. When skeletal myoblasts are exposed to uniaxial cyclic tensile strain (UCTS), they display uniform alignment and an enhanced rate of differentiation. In this work, we explored the role of FAK activation by using C2C12 myoblasts that were grown on flexible culture plates and exposed to UCTS during the early differentiation phase. After 24 h, the cells oriented perpendicularly to the direction of strain and exhibited an enhanced differentiation profile. Next, the cells were exposed to a strain field that was either kept in the same direction or rotated 90°, in the presence or not of an FAK phosphorylation inhibitor. On reorientation of the strain field by 90°, the cells reassembled their focal adhesions and actin cytoskeleton to regain the perpendicular position with respect to the engaging stress. After blocking the FAK, however, the cells failed to respond to the reoriented strain field and their differentiation was abrogated. Interestingly, when the strain field remained in the same direction, the FAK inhibitor compromised the differentiation, even though there was no evident change in cell orientation. Our data indicate that during exposure to UCTS, the activation of FAK is necessary for the myoblasts to undergo alignment and enhanced differentiation.

Biocompatible 3D printed polymers via fused deposition modelling direct C2C12 cellular phenotype in vitro

The capability to 3D print bespoke biologically receptive parts within short time periods has driven the growing prevalence of additive manufacture (AM) technology within biological settings, however limited research concerning cellular interaction with 3D printed polymers has been undertaken. In this work, we used skeletal muscle C₂C₁₂ cell line in order to ascertain critical evidence of cellular behaviour in response to multiple bio-receptive candidate polymers; polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET) and polycarbonate (PC) 3D printed via fused deposition modelling (FDM). The extrusion based nature of FDM elicited polymer specific topographies, within which C₂C₁₂ cells exhibited reduced metabolic activity when compared to optimised surfaces of tissue culture plastic, however assay viability readings remained high across polymers outlining viable phenotypes. C₂C₁₂ cells exhibited consistently high levels of morphological alignment across polymers, however differential myotube widths and levels of transcriptional myogenin expression appeared to demonstrate response specific thresholds at which varying polymer selection potentiates cellular differentiation, elicits pre-mature early myotube formation and directs subsequent morphological phenotype. Here we observed biocompatible AM polymers manufactured via FDM, which also appear to hold the potential to simultaneously manipulate the desired biological phenotype and enhance the biomimicry of skeletal muscle cells in vitro via AM polymer choice and careful selection of machine processing parameters. When considered in combination with the associated design freedom of AM, this may provide the opportunity to not only enhance the efficiency of creating biomimetic models, but also to precisely control the biological output within such scaffolds.

The next generation cell-penetrating peptide and carbon dot conjugated nano-liposome for transdermal delivery of curcumin

To overcome the problems associated with conventional liposomes in transdermal drug delivery like limited penetration ability and poor stability, in this article we report a new generation of cell penetrating peptide polyarginine containing nano-liposomes conjugated with carbon dots. The newly synthesized, cost-effective liposomic precursors were used for the fabrication of liposomes. The resulting liposomes have a bilayer structure like that of conventional liposomes with much smaller size, higher stability, and high penetration ability. The nano-liposomes show high stability at room temperature for three months without any change in size or encapsulation efficiency. The incorporation of carbon dots also opens up their application in fluorescence cell imaging studies, which is very well supported by the fluorescence microscopic analysis of the liposome skin penetration. The as-prepared nano-liposomes do not show any cytotoxicity for MCF-7 cells, even at high concentrations; however, when drug loaded liposomes are applied, they can kill the cancer cells with a high rate. The synthesized nano-liposomes have the potential to be used as an efficient, stable, biocompatible nanocarrier for transdermal drug delivery.

Heterogeneity of mesenchymal and pluripotent stem cell populations grown on nanogrooves and nanopillars

Surface nanotopographies are a powerful way of manipulating cell morphology and subsequent differentiation.

Understanding the Role of ECM Protein Composition and Geometric Micropatterning for Engineering Human Skeletal Muscle

Skeletal muscle lost through trauma or disease has proven difficult to regenerate due to the challenge of differentiating human myoblasts into aligned, contractile tissue. To address this, we investigated microenvironmental cues that drive myoblast differentiation into aligned myotubes for potential applications in skeletal muscle repair, organ-on-chip disease models and actuators for soft robotics. We used a 2D in vitro system to systematically evaluate the role of extracellular matrix (ECM) protein composition and geometric patterning for controlling the formation of highly aligned myotubes. Specifically, we analyzed myotubes differentiated from murine C2C12 cells and human skeletal muscle derived cells (SkMDCs) on micropatterned lines of laminin compared to fibronectin, collagen type I, and collagen type IV. Results showed that laminin supported significantly greater myotube formation from both cells types, resulting in greater than twofold increase in myotube area on these surfaces compared to the other ECM proteins. Species specific differences revealed that human SkMDCs uniaxially aligned over a wide range of micropatterned line dimensions, while C2C12s required specific line widths and spacings to do the same. Future work will incorporate these results to engineer aligned human skeletal muscle tissue in 2D for in vitro applications in disease modeling, drug discovery and toxicity screening.

Nanofibrous polylactide composite scaffolds with electroactivity and sustained release capacity for tissue engineering

A conveniently fabricated electroactive nanofibrous composite scaffold serves as a sustained drug release system and promotes myoblast differentiation.

Enhanced attachment of human mesenchymal stem cells on nanograined titania surfaces

TiO₂ nanotubes on the nanograined Ti surface improved cell attachment and proliferation together with physical and mechanical properties.

A NIR-remote controlled upconverting nanoparticle: an improved tool for living cell dye-labeling

In living cells, due to the selective permeability and complicated cellular environment, the uptake efficiency and fluorescence decay of organic dyes during dye-labeling may be influenced, which may eventually result in poor fluorescent imaging. In this work, a protocol of UCNs@mSiO2-(FA and Azo) core-shell nanocarriers was designed and prepared successfully. The core-shell nanocarriers were assembled from two parts, including a mesoporous silica shell surface modified by folate (FA) and azobenzene (Azo), and an upconverting nanocrystal (UCN) core. The mesoporous silica shell is used for loading organic dyes and conjugating folate which helps to enhance the cellular uptake of nanocarriers. The UCN core works as a transducer to convert near infrared (NIR) light to local UV and visible light to activate a back-and-forth wagging motion of azobenzene molecules on the surface, while the azobenzene acts as a molecular impeller for propelling the release of organic dyes. The nanocarriers of loading organic dyes can maintain the stability of the fluorescent imaging effect better than free organic dyes. The experimental results show that with the help of the nanoparticle, cell uptake efficiency of the model dyes of rhodamine and 4', 6-diamidino-2-phenylindole (DAPI) was significantly improved. The release of dyes can only be triggered by NIR light exposure and their quantity is highly dependent on the duration of NIR light exposure, thus realizing NIR-regulated dye release spatiotemporally. Our work may open a novel avenue for precisely controlling UCN-based living cell imaging in biotechnology and diagnostics, as well as studying cell dynamics, cell-cell interactions, and tissue morphogenesis.

Highly Ordered 1D Fullerene Crystals for Concurrent Control of Macroscopic Cellular Orientation and Differentiation toward Large-Scale Tissue Engineering

A highly aligned 1D fullerene whisker (FW) scaffold in a centimeter area is fabricated by interfacial alignment. The resulting aligned FW scaffold enables concurrent control over cellular orientation and differentiation to muscle cells. This aligned FW scaffold is made by a facile method, and hence the substrate is a promising alternative to other cell scaffolds for tissue engineering.

Self-assembled binary colloidal crystal monolayers as cell culture substrates

Large-area highly ordered self-assembled binary colloidal crystal (BCC) monolayers are fabricated for mammalian cell culture and biointerface control.

Intracellular delivery of CII TA genes by polycationic liposomes for suppressed immune response of dendritic cells

Construction of an effective nanocomplex for suppression of CII TA proteins can be a potential strategy for inhibiting unwanted immune response.

High-efficient inhibition of recognition in allorejection via a pMyD88/liposomes complex

Data are emerging that the recognition of foreign antigens by Toll/like receptors (TLRs) was predominant in skin graft rejection.

Skeletal muscle tissue engineering: methods to form skeletal myotubes and their applications

Skeletal muscle tissue engineering (SMTE) aims to repair or regenerate defective skeletal muscle tissue lost by traumatic injury, tumor ablation, or muscular disease. However, two decades after the introduction of SMTE, the engineering of functional skeletal muscle in the laboratory still remains a great challenge, and numerous techniques for growing functional muscle tissues are constantly being developed. This article reviews the recent findings regarding the methodology and various technical aspects of SMTE, including cell alignment and differentiation. We describe the structure and organization of muscle and discuss the methods for myoblast alignment cultured in vitro. To better understand muscle formation and to enhance the engineering of skeletal muscle, we also address the molecular basics of myogenesis and discuss different methods to induce myoblast differentiation into myotubes. We then provide an overview of different coculture systems involving skeletal muscle cells, and highlight major applications of engineered skeletal muscle tissues. Finally, potential challenges and future research directions for SMTE are outlined.

Development of an efficient transdermal drug delivery system with TAT-conjugated cationic polymeric lipid vesicles

Conventional liposomes (CLs) have been used as a transdermal drug delivery system for enhancing the delivery of hydrophilic drugs into/through the skin. However, their applications have been constrained by their limited penetration ability and poor stability. In this article, a new kind of transactivating transcriptional activator peptide (TAT)-conjugated polymeric lipid vesicles (TPLVs) formed from amphiphilic lysine-linoleic acid modified dextran (LLD) and cholesterol (Chol) has been prepared successfully. The newly developed TPLVs had a bilayer structure similar to CLs. The TPLVs also have smaller particle size, narrower distribution, higher positive charge and much better stability than the CLs; they remained stable in aqueous solutions for up to 60 days without aggregation. The in vitro and in vivo skin permeation studies revealed that TPLVs delivered a higher amount of drug through the skin than CLs, indicating enhanced drug transdermal activities. The synergetic effects of abovementioned features and the cell-penetrating peptide TAT might have contributed to the improved skin penetration ability of the TPLVs. Similar to CLs, TPLVs began to show limited cytotoxicity against human umbilical vein endothelial cells at a concentration of 200 μg mL^-1. The in vitro release profiles showed that the TPLVs achieved a sustained release of lidocaine. These results suggest that the TPLVs may be utilized as an efficient carrier to replace CLs for transdermal drug delivery.

Engineered skeletal muscle tissue for soft robotics: fabrication strategies, current applications, and future challenges

Skeletal muscle is a scalable actuator system used throughout nature from the millimeter to meter length scales and over a wide range of frequencies and force regimes. This adaptability has spurred interest in using engineered skeletal muscle to power soft robotics devices and in biotechnology and medical applications. However, the challenges to doing this are similar to those facing the tissue engineering and regenerative medicine fields; specifically, how do we translate our understanding of myogenesis in vivo to the engineering of muscle constructs in vitro to achieve functional integration with devices. To do this researchers are developing a number of ways to engineer the cellular microenvironment to guide skeletal muscle tissue formation. This includes understanding the role of substrate stiffness and the mechanical environment, engineering the spatial organization of biochemical and physical cues to guide muscle alignment, and developing bioreactors for mechanical and electrical conditioning. Examples of engineered skeletal muscle that can potentially be used in soft robotics include 2D cantilever-based skeletal muscle actuators and 3D skeletal muscle tissues engineered using scaffolds or directed self-organization. Integration into devices has led to basic muscle-powered devices such as grippers and pumps as well as more sophisticated muscle-powered soft robots that walk and swim. Looking forward, current, and future challenges include identifying the best source of muscle precursor cells to expand and differentiate into myotubes, replacing cardiomyocytes with skeletal muscle tissue as the bio-actuator of choice for soft robots, and vascularization and innervation to enable control and nourishment of larger muscle tissue constructs.

Combined effect of mussel-inspired surface modification and topographical cues on the behavior of skeletal myoblasts

The combined effect of mussel-inspired polydopamine (PDA) surface functionalization and topographical cues on the behavior of skeletal myoblasts is described. On PDA-modified nanofibers, myogenic protein expression and the fusion of myoblasts are increased significantly compared with those on unmodified nanofibers. The multinucleate myotubes on the aligned nanofibers are oriented in a direction parallel to the nanofibers.

Single cell detection using a magnetic zigzag nanowire biosensor

A magnetic zigzag nanowire device was designed for single cell biosensing. Nanowires with widths of 150, 300, 500, and 800 nm were fabricated on silicon trenches by electron beam lithography, electron beam evaporation, and lift-off processes. Magnetoresistance measurements were performed before and after the attachment of a single magnetic cell to the nanowires to characterize the magnetic signal change due to the influence of the magnetic cell. Magnetoresistance responses were measured in different magnetic field directions, and the results showed that this nanowire device can be used for multi-directional detection. It was observed that the highest switching field variation occurred in a 150 nm wide nanowire when the field was perpendicular to the substrate plane. On the other hand, the highest magnetoresistance ratio variation occurred in a 800 nm wide nanowire also when the field was perpendicular to the substrate plane. Besides, the trench-structured substrate proposed in this study can fix the magnetic cell to the sensor in a fluid environment, and the stray field generated by the corners of the magnetic zigzag nanowires has the function of actively attracting the magnetic cells for detection.

Properties and evaluation of quaternized chitosan/lipid cation polymeric liposomes for cancer-targeted gene delivery

Development of high-stability and efficient nonviral vectors with low cytoxicity is important for targeted tumor gene therapy. In this study, cationic polymeric liposomes (CPLs), with similar lipid bilayer structure and high thermal stability, were prepared from polymeric surfactants of quaternized (carboxymethyl)chitosan with different carbon chains (dodecyl, tetradecyl, hexadecyl, and octadecyl). By comparing different factors that influence gene delivery, tetradecyl-quaternized (carboxymethy)chitosan (TQCMC) CPLs, with suitable size (184.4 ± 17.1 nm), ζ potentials (27.5 ± 4.9 mV), and productivity for synthesis TQCMC (weight yield 13.1%), were selected for gene transfection evaluation in various cancer cell lines. Although TQCMC CPLs have lower gene transfection efficiency compared with cationic liposomes (Lipofectamine 2000) in vitro, they displayed higher reporter gene delivery ability for cancer tissues (bearing U87 and SMMC-7721 tumors) in vivo after intravenous injection. TQCMC CPLs also have lower cell cytotoxicity and lower cytokine production or liver injury for BALB/c mice. We conclude that the CPLs are promising gene delivery systems that may be used to target various cancers.

Strategies to improve regeneration of the soft palate muscles after cleft palate repair

Children with a cleft in the soft palate have difficulties with speech, swallowing, and sucking. These patients are unable to separate the nasal from the oral cavity leading to air loss during speech. Although surgical repair ameliorates soft palate function by joining the clefted muscles of the soft palate, optimal function is often not achieved. The regeneration of muscles in the soft palate after surgery is hampered because of (1) their low intrinsic regenerative capacity, (2) the muscle properties related to clefting, and (3) the development of fibrosis. Adjuvant strategies based on tissue engineering may improve the outcome after surgery by approaching these specific issues. Therefore, this review will discuss myogenesis in the noncleft and cleft palate, the characteristics of soft palate muscles, and the process of muscle regeneration. Finally, novel therapeutic strategies based on tissue engineering to improve soft palate function after surgical repair are presented.

Preparation and evaluation of lidocaine hydrochloride-loaded TAT-conjugated polymeric liposomes for transdermal delivery

Transactivation transcriptional activator (TAT) peptides were conjugated on the octadecyl-quaternized, lysine-modified chitosan to form polymeric liposomes (TAT-PLs) with cholesterol for improving transdermal delivery of local anesthetic lidocaine hydrochloride (LID). In this study, the LID loaded TAT-conjugated polymeric liposomes (LID-TAT-PLs) have been successfully prepared. LID-TAT-PLs were characterized by determination of their particle size, polydispersity, morphology, drug encapsulation efficiency, drug release behavior in vitro, and storage-stability. The skin permeation of LID-TAT-PLs was examined using a Franz diffusion cell mounted with depilated mouse skin in vitro, and penetration of TAT-PLs was visualized by confocal laser scanning microscopy (CLSM). The results showed that LID-TAT-PLs were spherical in solution, with substantially smaller mean diameter (154.7±10.7 nm), higher encapsulation efficiency (80.05±2.64%) and better stability in contrast to conventional liposomes (CLs). From the in vitro skin permeation results, transdermal flux of LID-TAT-PLs was approximately 4.17 and 1.75 times higher than that of LID solution and LID CLs (P<0.05). CLSM studies also confirmed that TAT-PLs reached viable layers of the skin. Hence, the results indicate that LID-TAT-PLs are effective and potential alternative for the LID transdermal formulation.

Smart multifunctional core-shell nanospheres with drug and gene co-loaded for enhancing the therapeutic effect in a rat intracranial tumor model

Glioblastoma with high mortality has been one of the most serious cancers threatening human health. Because of the present treatment limitations, there is an urgent need to construct a multifunctional vesicle for enhancing the treatment of in situ malignant glioblastoma. In our study, drug and gene co-loaded magnetic PLGA/multifunctional polymeric liposome (magnetic PLGA/MPLs) core-shell nanospheres were constructed. They were mainly self-assembled from two parts: hydrophobic PLGA cores that can load drugs and magnetic nanocrystals; and polymeric lipid shells anchored with functional molecules such as PEG chains, TAT peptides and RGD peptides that can help the vectors to condense the gene, prolong the circulation time, cross the blood brain barrier and target delivery to the cancer tissue. The results showed that the magnetic PLGA/MPLs nanosphere has a nanosized core-shell structure, can achieve sustained drug release and has good DNA binding abilities. Importantly, compared with the control group and other groups with single functionality, it can co-deliver the drug and gene into the same cell in vitro and show the strongest inhibiting effect on the growth of the in situ malignant glioblastoma in vivo. All of these results indicated that the different functional components of magnetic PLGA/MPLs, can form an organic whole and none of them can be dispensed with. The magnetic PLGA/MPLs nanosphere may be another option for treatment of glioblastoma.

Preparation of biomimetic hydrogels with controlled cell adhesive properties and topographical features for the study of muscle cell adhesion and proliferation

Synthetic substrates with defined chemical and structural characteristics may potentially be prepared to mimic the living ECM to regulate cell adhesion and growth. Hydrogels with cell-adhesive peptides (0.28 ± 0.03 nmol peptide cm(-2) , TTA-R-0.5; and 0.91 ± 0.12 nmol peptide cm(-2) , TTA-R-2.0) and/or micro-scaled topographical patterns (10, 25, and 80 µm grooves) are prepared using enzymatic polymerization. The adherent morphology and proliferation of C2C12 skeletal myoblasts and human aortic smooth muscle cells (hAoSM) on the hydrogels are studied. The newly developed hydrogels may be useful in investigating the roles of cell adhesion and substrate surface properties in the communication of adherent cells with the ECM.

Understanding the cell behavior on nano-/micro-patterned surfaces

Aim: This article reports on studies conducted in the same laboratory on interactions between patterned substrates with different pattern dimensions and chemistries, and various types of cells. Materials & methods: In order to compare the influence of various parameters, bone marrow stromal cells, retinal pigment epithelial cells, human corneal stromal cells (keratocytes), Saos-2 (human osteosarcoma cells), human microvascular endothelial cells and vascular smooth muscle cells were tested on surfaces with different physical patterns and chemical properties. Results: It was observed that cell type and surface topography are more influential than surface chemistry in determining the alignment tendency of a cell on a substrate surface. Low walls (several microns high) could not confine cells into the microgrooves of the films but alignment was still possible if the cells had a natural alignment property. Conclusion: This information is very useful in designing tissue engineering scaffolds and in the long-term success of implants.

Original submitted 30 November 2010; Revised submitted 4 January 2012; Published online 20 July 2012

Local tissue geometry determines contractile force generation of engineered muscle networks

The field of skeletal muscle tissue engineering is currently hampered by the lack of methods to form large muscle constructs composed of dense, aligned, and mature myofibers and limited understanding of structure-function relationships in developing muscle tissues. In our previous studies, engineered muscle sheets with elliptical pores ("muscle networks") were fabricated by casting cells and fibrin gel inside elastomeric tissue molds with staggered hexagonal posts. In these networks, alignment of cells around the elliptical pores followed the local distribution of tissue strains that were generated by cell-mediated compaction of fibrin gel against the hexagonal posts. The goal of this study was to assess how systematic variations in pore elongation affect the morphology and contractile function of muscle networks. We found that in muscle networks with more elongated pores the force production of individual myofibers was not altered, but the myofiber alignment and efficiency of myofiber formation were significantly increased yielding an increase in the total contractile force despite a decrease in the total tissue volume. Beyond a certain pore length, increase in generated contractile force was mainly contributed by more efficient myofiber formation rather than enhanced myofiber alignment. Collectively, these studies show that changes in local tissue geometry can exert both direct structural and indirect myogenic effects on the functional output of engineered muscle. Different hydrogel formulations and pore geometries will be explored in the future to further augment contractile function of engineered muscle networks and promote their use for basic structure-function studies in vitro and, eventually, for efficient muscle repair in vivo.

Exploring N-imidazolyl-O-carboxymethyl chitosan for high performance gene delivery

Chitosan shows good biocompatibility and biodegradability, but the poor water solubility and low transfection efficiency hinder its applications as a gene delivery vector. We here report the detailed synthesis and characterization of a novel ampholytical chitosan derivative, N-imidazolyl-O-carboxymethyl chitosan (IOCMCS), used for high performance gene delivery. After chemical modification, the solubility of the resulting polymer is enhanced, and the polymer is soluble in a wide pH range (4-10). Gel electrophoresis study reveals the strong binding ability between plasmid DNA and the IOCMCS. Moreover, the IOCMCS does not induce remarkable cytotoxicity against human embryonic kidney (HEK293T) cells. The cell transfection results with HEK293T cells using the IOCMCS as gene delivery vector demonstrate the high transfection efficiency, which is dependent on the degree of imidazolyl substitution. Therefore, the IOCMCS is a promising candidate as the DNA delivery vector in gene therapy due to its high solubility, high gene binding capability, low cytotoxicity, and high gene transfection efficiency.

Mechanoregulation of vascularization in aligned tissue-engineered muscle: a role for vascular endothelial growth factor

Skeletal muscle tissue engineering has major promise for regenerative treatment of patients suffering from muscle loss due to, for example, traumatic injury, but faces considerable challenges to progress toward clinical application. In the present study the creation of an aligned prevascularized muscle tissue was addressed. We hypothesized that an aligned vascularized three-dimensional (3D) muscle tissue can be induced in vitro by merely using uniaxial stress. The present study showed that not only do endothelial cells and muscle cells independently align in the direction of uniaxial stress in a hydrogel-based 3D culture system, but also, more importantly, the endothelial cells in the co-cultured 3D constructs organized into vascular structures. Strikingly, in these cultures no additional growth factors were needed to induce vascular formation of the endothelial cells. Vascular endothelial growth factor (VEGF) production by the muscle cells was stimulated by the uniaxial stress that develops in the tissue when constrained in one direction. This stress accompanied by VEGF production appeared to play a key role in the organization of the endothelial cells into vessel-like structures.

Polymeric liposomes-coated superparamagnetic iron oxide nanoparticles as contrast agent for targeted magnetic resonance imaging of cancer cells

The purpose of this study was to use polymeric liposomes (PLs) with a targeting ligand (folate) to coat superparamagnetic iron oxide nanoparticles (SPIONs) and transfer the magnetic nanoparticles from organic phases to aqueous solutions, and further evaluate their efficacy as a magnetic resonance imaging (MRI) contrast agent. The formed nanoparticles exhibited a narrow range of size dispersity (core size of the particles is about 8-10 nm) and relatively high T2 relaxivities (r2 = 164.14 s(-1) mM(-1) for folate-PLs-coated SPIONs). The in vitro tumor cell targeting efficacy of the folate functionalized and PLs-coated SPIONs was evaluated upon observing cellular uptake of magnetite liposomes by HeLa cells, which overexpresses surface receptors for folic acid. In the Prussian blue staining experiments, cells incubated with folate-PLs-coated SPIONs showed much higher intracellular iron density than did the cells incubated with the folate-free PLs-coated SPIONs. Meanwhile, the MTT assay explains the negligible cell cytotoxicity of SPIONs and folate-PLs-coated SPIONs. In HeLa cells, the in vitro MRI study also indicates the better T2-weighted images in folate-PLs-coated SPIONs than in folate-free PLs-coated SPIONs.