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Cardiac patches can help to restore the electrophysiological properties of the heart after myocardial infarction. However, scaffolds for the repair of heart muscle typically require surgical implantation or, if they are injectable, they are not electrically conductive or do not maintain their shape or function. Here, we report the performance, as demonstrated for the repair of infarcted heart muscle in rats and minipigs, of injectable and conductive scaffolds consisting of methacrylated elastin and gelatin, and carbon nanotubes that display shape-memory behaviour, a hierarchical porous structure and a negligible Poisson's ratio. In rats, the implantation of cell-free patches or patches seeded with rat cardiomyocytes onto the myocardium after ligation of the left anterior descending coronary artery led to functional repair after 4 weeks, as indicated by increases in fractional shortening and the ejection fraction, and by a decrease in the infarcted area. We also observed measures of functional recovery in minipigs with infarcted hearts after the delivery of cell-free patches or patches incorporating cardiomyocytes differentiated from human pluripotent stem cells.

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Designing scaffolds with persistent elasticity and conductivity to mimic microenvironments becomes a feasible way to repair cardiac tissue. Injectable biomaterials for cardiac tissue engineering have demonstrated the ability to restore cardiac function by preventing ventricular dilation, enhancing angiogenesis, and improving conduction velocity. However, limitations are still among them, such as poor mechanical stability, low conductivity, and complicated procedure. Here, we developed thermal plastic poly(glycolic acid) surgical suture and mussel-inspired conductive particle's adhesion into a highly elastic, conductive spring-like coils. The polypyrrole (PPy)-coated biospring acted as an electrode and then was assembled into a solid-state supercapacitor. After being injected through a syringe needle (0.33 mm inner diameter), the tangled coils formed an elastically conductive three-dimensional (3-D) network to modulate cardiac function. We found that cardiomyocytes (CMs) grew along the spring coils' track with elongated morphologies and formed highly oriented sarcomeres. The biospring enhanced the CMs' maturation in synchronous contraction accompanied by high expressions of cardiac-specific proteins, α-actinin, and connexin 43 (cx43). After the elastic, conductive biosprings were injected into the myocardial infarction (MI) area, the left ventricular fractional shortening was improved by about 12.6% and the infarct size was decreased by about 34%. Interestingly, the spring can be utilized as a sensor to measure the CMs' contractile force, which was 1.57 × 10-3 ± 0.26 × 10-3 mN (∼4.1 × 106 cells). Accordingly, this study highlights an injectable biospring to form a tangled conductive 3-D network in vivo for MI repair.

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Infection compromises healing process after bone fracture. An anti-bacterial bone graft synthesized from polymer and mineralization components is becoming preferable for its accessibility and low cost and tunable chem-physic properties. In this study, mussel-inspired polydopamine (PDA) was used to synthesize in-situ silver nanoparticles (AgNPs) and mineralization on polyethylene hydrogel (PEG). With dual functions of anti-bacteria and graft mineralization, we found the hydrogel (AgNPs/PDA) promoted bone generation and show significant antibacterial activity. Specifically, the gel upregulated the expression of osteogenic genes of bone sialoprotein gene, alkaline phosphatase, osteocalcin and runt-related transcription factor 2. It also significantly inhibited the growth of Staphylococcus aureus and Escherichia coli. In vivo the AgNPs/PDA gel could repair maxillary bone defect efficiently.

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Compared with conventional 2D cell culture systems, 3D cell culture systems can better mimic the sophisticated internal environment. Hyaluronic acid (HA) is a fundamental element of the extracellular matrix and can be modified in many ways to alter its properties. Herein, in order to develop a 3D hypoxia culture system, we firstly synthesized HA-EDA with HA and ethylene-diamine (EDA) and then wrapped single renal mesangial cell layer-by-layer (LBL) with cationic HA-EDA and anionic HA. Unexpectedly, these wrapped cells formed a 3D hypoxia multi-cellular spheroid after being treated with trypsin. Based on the developed 3D hypoxia microenvironment, we found miR-382 might play a vital role in renal fibrosis. Amazingly, cell autophagy was detected both in 3D spheroid and 3DM cells (cells migrated from the 3D spheroid). However, different from the 3D spheroid, the 3DM cells displayed alleviated accumulation of TGF-ß1 and Fn, which demonstrated the renoprotective role of autophagy in renal fibrosis. The high ratio of CD24+ cells in 3DM cells revealed that cells surviving through the autophagic process could acquire some characterization of progenitor cells via dedifferentiation. The developed 3D multi-cellular spheroid highlighted the role of hypoxia and cell autophagy in renal fibrosis.

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Utilization of the underlying mechanisms of biological systems is the principal endeavor of biomimetics, the primary goal of which is to treat on-going biological processes. From the perspective of tissue engineering, one purpose of biomimetics is to create highly cellular- or tissue-favored environments for bio-defect repair. Marine creatures such as mussels have inspired bioengineers to design ideal cellular substrates, strong adhesives, and other bioengineering materials. Herein, we report a novel mussel shell-derived membrane for wound dressing. Mussel shell in situ manufactured a highly flexible membrane with a regular porous pattern after the direct action of acid (A-shell) followed by base treatment (B-shell). The SEM images display elegantly patterned polygons with nanowalls (about 710 nm). Compared with the A-shell, the B-shell has a more defined and flexible structure. FTIR characterization of the structures indicates that deacetylation occurred on the B-shell. A cellular toxicity study was conducted to determine the optimized processing parameters before applying the wound healing model. The B-shell significantly closed the wound at an early stage (day 10) followed by complete contraction at a later stage (day 21). This is completely consistent with the higher level of α-SMA protein, which accelerates wound contraction in the wound sites. As a key index of the integration between host and guest, a high blood vessel density was detected in both the A-shell and B-shell groups. The treated shells can improve epidermal migration, the formation of granulation tissue, neovascularization and hair follicles, and reduce scar tissue. Our mussel shell-derived membrane could have potential as a wound dressing and other biomedical uses.

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This study developed a kind of magnetic-polymer nanocarrier with folate receptor-targeting and pH-sensitive multifunctionalities to carry doxorubicin (DOX) for treatment of advanced gastric cancer (AGC). Folate-conjugated, pH-sensitive, amphiphilic poly(ß-aminoester) self-assembled with hydrophobic oleic acid-modified iron oxide nanoparticles, and the resulting hydrophobic interaction area is a reservoir for lipophilic DOX (F-P-DOX). Confocal microscopy illustrated that F-P-DOX treatment could keep higher DOX accumulation in cells than P-DOX (without folate conjugation), and therefore get a higher efficiency of DOX internalization at pH 6.5 than at pH 7.4. Electron microscope characterization and real-time polymerase chain reaction revealed cell apoptosis promoted by F-P-DOX. The better efficacy of F-P-DOX on GC than free DOX and P-DOX was determined by MTT assay and xenograft model. Moreover, the accumulation of F-P-DOX in the tumor site was detected by magnetic resonance imaging (MRI). All those observations suggest F-P-DOX could be a promising theranostic candidate for AGC treatment.

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Single-walled carbon nanotubes (SWCNTs) have been used to deliver single-stranded (ssDNA). ssDNA in oligonucleotide can act as an inhibitor of microRNA to regulate cellular functions. However, these ssDNA are difficult to bind carbon nanotubes with low transferring efficiency to cells. To this end, we designed ssDNA with regulatory and functional units to form ssDNA-SWCNT hybrids to study their binding effects and transferring efficiency. The functional unit on ssDNA mimics the inhibitor (MI) of miRNA-382, which plays a crucial role in the progress of many diseases such as renal interstitial fibrosis. After verification of overexpression of miRNA-382 in a coculture system, we designed oligonucleotide sequences (GCG)5-MI, (TAT)5-MI, and N23-MI as regulatory units added to the 5'-terminal end of the functional DNA fragment, respectively. These regulatory units lead to different secondary structures and thus exhibit different affinity ability to SWCNTs, and finally decide their deliver efficacy to cells. Autophagy, apoptosis and necrosis were observed in renal mesangial cells.

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Pelvic organ prolapse (POP) is a serious health issue affecting many adult women. Complications of POP include pelvic pressure, pelvic pain, and problems in emptying their bowels or bladder. Sometimes, POP may even cause urinary outflow obstruction and lead to bladder or kidney infections. Currently, synthetic and naturally derived materials have been chosen for treatment of POP to reduce the high recurrence rates after surgical interventions. However, existing materials for POP treatment cannot meet the clinical requirements in terms of biocompatibility, mechanics, and minimal risk of rejection. Especially, erosion in synthetic polymers and rapid degradation in natural polymers limit their further applications in clinics. To address these concerns, we report a novel POP replacement using core-sheath polystyrene/gelatin electrospun nanofiber mesh. The outside gelatin sheath provides a hydrophilic surface and implantable integrity between host and guest, while the inner PS core offers the necessary mechanical support. The composite mesh shows graft accommodation in pelvic submucosa after implantation in vivo, as shown in hematoxylin-eosin staining and T helper cell phenotype and macrophage phenotype stainings. Qualitative analysis of inducible nitric oxide synthase, arginase, interferon-γ, and interleukin-10 gene expressions also indicates that the implanted composite mesh switches to accommodation mode 2 weeks postimplantation. Thus, these novel core-sheath polystyrene/gelatin nanofibrous membranes are promising in pelvic reconstruction.

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Nanosilver particles (NSPs), are among the most attractive nanomaterials, and have been widely used in a range of biomedical applications, including diagnosis, treatment, drug delivery, medical device coating, and for personal health care. With the increasing application of NSPs in medical contexts, it is becoming necessary for a better understanding of the mechanisms of NSPs' biological interactions and their potential toxicity. In this review, we first introduce the synthesis routes of NSPs, including physical, chemical, and biological or green synthesis. Then the unique physiochemical properties of NSPs, such as antibacterial, antifungal, antiviral, and anti-inflammatory activity, are discussed in detail. Further, some recent applications of NSPs in prevention, diagnosis, and treatment in medical fields are described. Finally, potential toxicology considerations of NSPs, both in vitro and in vivo, are also addressed.

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We report a reducible copolymer self-assembled with superparamagnetic iron oxide nanoparticles (SPIONs) to deliver doxorubicin (DOX) for cancer therapy. The copolymer of reducible polyamidoamine (rPAA) with poly(ethylene glycol)(PEG)/dodecyl amine graft was synthesized by Michael addition. rPAA@SPIONs were formed by the alkyl grafts of reducible copolymers intercalated with the oleic acid layer capped on the surface of magnetite nanocrystals. The intercalating area formed a reservoir for hydrophobic anti-cancer drug (DOX), whilst the PEG moiety in the copolymers helped the nanoparticle well-dispersible in aqueous solution. We employed two-photon excited fluorescence (TPEF) and coherent anti-Stokes Raman (CARS) to investigate drug delivery in intra-cellular structures of live cells, and used Vivaview(®) technique to show real-time inhibition efficacy of nanoparticles in live cells. rPAA@SPIONs present efficiently drug loading with reducible responsibility in vitro tests. Finally, rPAA@SPIONs were tested in mice with xenograft MDA-MB-231 breast tumor though i.v. injection and inhibited tumor growth efficiently. MRI was used to monitor nanoparticles aggregation in tumor site. Histology and Prussian blue on kidney, liver, and heart in mice indicated that DOX/rPAA@SPIONs showed no significant toxicity for mice organs after 24 days treatment.

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In the fabrication of 3-D complex tissues for implantation, layer-by-layer (LBL) electrospun nanofibrous scaffolds have recently received intensive interest. However, poor cell adhesion and cell expansion between the layers in an LBL stack remain important issues. In this study, we report a mussel-inspired, biomimetic approach to functionalize the surface of PCL/gelatin nanofibrous membranes coated with poly (dopamine) (PDA). Our study demonstrates that a PDA coating on electrospun PCL/gelatin nanofibers leads to a significant change in their surface properties and a higher adhesion force. Furthermore, we found that PDA coating promotes the adhesion and growth of adipose stem cells (ADSCs). In 3-D LBL stacked scaffolds, more cells survived in a PAD-coated scaffold than in a non-coated one. The PDA coating was further demonstrated to promote the osteogenic differentiation of ADSCs in LBL paper-stacking membranes. Our study suggests that PDA-coated paper-stacking nanofiber membranes present a facile and economic method for the development of 3D tissue engineering.

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This paper reviews major research and development issues relating to hydrogels as scaffolds for tissue engineering, the article starts with a brief introduction of tissue engineering and hydrogels as extracellular matrix mimics, followed by a description of the various types of hydrogels and preparation methods, before a discussion of the physical and chemical properties that are important to their application. There follows a short comment on the trends of future research and development. Throughout the discussion there is an emphasis on the genetic understanding of bone tissue engineering application.

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By mimicking the native extracellular matrix, electrospun nanofibrous scaffolds (ENSs) can provide both chemical and physical cues to modulate cell adherence and differentiation and to promote tissue regeneration while retaining bioresorbable and biocompatible properties. In this study, ENSs were developed to deliver multiple biomolecules by loading them into the core-sheath structure and/or by conjugating them to the nanofiber surfaces. In this work, poly(L-lactide)-poly(ethylene glycol)-NH(2) and poly(L-lactide) were emulsion electrospun into nanofibers with a core-sheath structure. A model drug, tetracycline hydrochloride, was loaded within the nanofibers. Amino and carboxyl reactive groups were then activated on the fiber surfaces using saturated water vapor exposure and base hydrolysis, respectively. These reactive groups allowed the surface of the ENS to be functionalized with two other bioactive molecules, fluorescein isothiocyanate- and rhodamine-labeled bovine serum albumins, which were used as model proteins. The ENSs were shown to retain their antimicrobial capacity after two functionalization reactions, indicating that multifunctional nanofibers can potentially be developed into functional wound dressings or periodontal membranes or used in more complicated tissue systems where multiple growth factors and anti-infection precautions are critical for the successful implantation and regeneration of tissues.

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This study develops novel pH and reduction dual-sensitive micelles for the anticancer drug doxorubicin (DOX) delivery owing to the fact that the tumor tissues show low pH and high reduction environment. These sub-100 nm micelles present a core-shell structure under physiological conditions, but quickly release the loaded drugs responding to acidic and reductive stimuli. With disulfide bonds in each repeat unit of poly(ß-amino ester)s, the novel copolymer was synthesized via Michael addition polymerization from 2,2'-dithiodiethanol diacrylate, 4,4'-trimethylene dipiperidine, and methoxy-PEG-NH(2). DOX released faster from micelles in a weakly acidic environment (pH 6.5) than at pH 7.4 or in the presence of a higher concentration (5 mM) of reducing agent (DTT). The release is even more effective in a scenario of both stimuli (pH 6.5 and 5 mM DTT). MTT assay showed that the DOX-loaded micelles had a higher cytotoxicity for HepG2 tumor cells than DOX at higher concentrations, and that blank micelles had a very low cytotoxicity to the tumor cells. Confocal microscopy observation showed that the micelles can be quickly internalized, effectively deliver the drugs into nuclei, and inhibit cell growth. These results present the copolymer as a novel and effective pH and reduction dual-responsive nanocarrier to enhance drug efficacy for cancer cells.

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Hepatocyte-targeting and shell cross-linked nanoparticles with lactose moiety on the surface and doxorubicin (DOX) in the core were prepared from lactose-PEG-DOX conjugate. The process consists of the synthesis of a novel α-hydrazine-ω-propargyl poly(ethylene glycol) (PEG) with a double bond in the PEG backbone, followed by the bonding of a lactose molecule containing an azide group to the ω-end of PEG via "click" chemistry, and finally, the conjugation of DOX to the α-end of PEG via an acid-labile, hydrazone linkage. The resultant conjugate can be self-assembled into nanoparticles. Thiolated tri(ethylene glycol) was introduced into the shell of nanoparticles as a cross-linking agent. The release of DOX is more rapid from lactose-PEG-DOX at pH 5.0 than at pH 7.4. Fluorescent microscope studies suggest that the lactose-DOX nanoparticles are internalized by hepatoma cells through a lactose receptor-mediated mechanism, whereas the lactose-free nanoparticles are not endocytosed as rapidly as lactose-DOX nanoparticles. MTT assay also shows that lactose-DOX nanoparticles have a stronger inhibition against hepatoma cells than DOX nanoparticles and pure DOX. FROM THE CLINICAL EDITOR: In this basic science study, a highly efficient targeted doxorubicin delivery method to hepatocytes is presented.

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Nanofibrous membranes are highly soft materials with high surface-to-volume ratios, and therefore can serve as excellent carriers for therapeutic agents that are antibacterial or accelerate wound healing. This article overviews research and development of nanofibrous dressing materials for wound care, in addition to a discussion of natural and synthetic polymers used in fabricating nanofibrous dressing materials, and a description of in vitro and in vivo evaluation methods for the performance and cytotoxicity of these materials. Natural polymers are usually believed to be less cytotoxic than synthetic polymer in wound care. However, most natural polymers exhibit relatively low mechanical strength than synthetic polymers. As a result, they are usually crosslinked or blended with synthetic polymers so as to somewhat affect their biocompatibility.

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Use of the percutaneous route may avoid some of the undesirable side effects that occur following oral administration in estrogen replacement therapy. At present, knowledge of estradiol transdermal properties relating to delivery of drugs in the skin is lacking. One reason is that in the existing transport models of estradiol, the skin is regarded as a single layer. This study revealed a significant difference of effects on estradiol delivery in the 3 sublayers of the skin and has caused us to believe that if we can obtain information about the transfer properties of estradiol in human skin (3 sublayers), we will not only increase our understanding of the estradiol biotransport mechanism, but also benefit clinical application. Accordingly, radioactive 17beta-estradiol was used to clarify the percutaneous absorption of estradiol into the 3 sublayers of the skin (stratum corneum, epidermis, and dermis) and to evaluate the effect of drugs delivered in each sublayer. Based on data thereby obtained, mathematical models were built to further obtain transport parameters (diffusivity, permeability, lag time, and partition coefficients) for the 3 layers of the skin.

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BACKGROUND: Topical drug application has been widely used to manage skin diseases as well as to treat a variety of local and systemic disorders. To evaluate the efficiency of transepidermal drug delivery, an efficient model is needed to study the process of percutaneous transport. MODEL DESCRIPTION: A stochastic model based on Monte Carlo methods and Cellular Automata is presented in this work to study the molecular transport through the stratum corneum of the human skin, which is a typical process in transepidermal drug delivery. METHODS: To validate the model, an in vitro experiment on percutaneous absorption of radioactive 17beta-estradiol was performed. RESULTS AND DISCUSSION: The simulation results agree with the experimental data. CONCLUSION: The use and power of the presented approach in studying the process of transepidermal drug delivery were demonstrated.

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BACKGROUND/PURPOSE: Percutaneous permeation is a frequently used approach in drug delivery, but the detailed physics process in the patch--stratum corneum (SC)--viable epidermis system remains unclear: the influence of the interphases in the multilayered structure has been little studied. METHODS: This paper applied the finite-element method to develop a contact algorithm with an interphase element to account for the interphase barrier on drug diffusion and chemical absorption during a transdermal drug delivery process. A more realistic multilayer structure, including the patch, SC and viable epidermis, are incorporated into the algorithm. Both interphases between the patch and SC, and between SC and viable epidermis are considered. RESULTS: Our study confirms that the interphase transfer coefficients have a direct connection with drug concentration and flux distribution along the diffusion paths. The simulation results suggested a potential for the optimal control of drug diffusion. The partition coefficients and other interphase barrier factors can be incorporated into the model. CONCLUSIONS: The algorithm can deal with complicated geometrical conditions, which is difficult using classical analytical approaches. Furthermore, calibrated against experiments, the model may predict more realistically the drug delivery process and drug distribution profiles so as to assist in the patch and even drug design.

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We describe the development, validation, and application of a novel PDMS-based microfluidic device for imaging leukocyte interaction with a biological substrate at defined shear force employing a parallel plate geometry that optimizes experimental throughput while decreasing reagent consumption. The device is vacuum bonded above a standard 6-well tissue culture plate that accommodates a monolayer of endothelial cells, thereby providing a channel to directly observe the kinetics of leukocyte adhesion under defined shear flow. Computational fluid dynamics (CFD) was applied to model the shear stress and the trajectory of leukocytes within the flow channels at a micron length scale. In order to test this model, neutrophil capture, rolling, and deceleration to arrest as a function of time and position was imaged in the transparent channels. Neutrophil recruitment to the substrate proved to be highly sensitive to disturbances in flow streamlines, which enhanced the rate of neutrophil-surface collisions at the entrance to the channels. Downstream from these disturbances, the relationship between receptor mediated deceleration of rolling neutrophils and dose response of stimulation by the chemokine IL-8 was found to provide a functional readout of integrin activation. This microfluidic technique allows detailed kinetic studies of cell adhesion and reveals neutrophil activation within seconds to chemotactic molecules at concentrations in the picoMolar range.

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