Development of a multifunctional bioreactor to evaluate the promotion effects of cyclic stretching and electrical stimulation on muscle differentiation.

A multifunctional bioreactor was fabricated in this study to investigate the facilitation efficiency of electrical and mechanical stimulations on myogenic differentiation. This bioreactor consisted of a highly stretchable conductive membrane prepared by depositing polypyrrole (PPy) on a flexible polydimethylsiloxane (PDMS) film. The tensile deformation of the PPy/PDMS membrane can be tuned by adjusting the channel depth. In addition, PPy/PDMS maintained its electrical conductivity under continuous cyclic stretching in the strain range of 6.5%-13% for 24 h. This device can be used to individually or simultaneously perform cyclic stretching and electrical stimulation. The results of single stimulation showed that either cyclic stretching or electrical stimulation upregulated myogenic gene expression and promoted myotube formation, where electrical stimulation improved better than cyclic stretching. However, only cyclic stretching can align C2C12 cells perpendicular to the stretching direction, and electrical stimulation did not affect cell morphology. Myosin heavy chain (MHC) immunostaining demonstrated that oriented cells under cyclic stretching resulted in parallel myotubes. The combination of these two stimuli exhibited synergetic effects on both myogenic gene regulation and myotube formation, and the incorporated electrical field did not affect the orientation effect of the cyclic stretching. These results suggested that these two treatments likely influenced cells through different pathways. Overall, the simultaneous application of cyclic stretching and electrical stimulation preserved both stimuli's advantages, so myo-differentiation can be highly improved to obtain abundant parallel myotubes, suggesting that our developed multifunctional bioreactor should benefit muscle tissue engineering applications.

Comparison of Peripheral Blood Inflammatory Indices in Patients with Neovascular Age-related Macular Degeneration and Haemorrhagic Polypoidal Choroidal Vasculopathy.

PURPOSE: To compare the differences in peripheral blood inflammatory indices between patients with neovascular age-related macular degeneration (nAMD) and haemorrhagic polypoidal choroidal vasculopathy (PCV). METHODS: Retrospective, best corrected visual acuity (BCVA), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and monocyte-to-lymphocyte ratio (MLR), were analysed across the nAMD, PCV and normal control (NCG) groups of patients. The ratios' cut-off values for nAMD were calculated. RESULTS: nAMD had a significantly longer duration and better BCVA than PCV (all P < .05). The NLR, MLR and PLR were significantly higher in nAMD than in PCV and NCG (all P < .01), no significant differences between PCV and NCG (all P > .05). The ROC curve analysis revealed that the cut-off values for NLR and MLR were 1.98 and 0.24, respectively, for nAMD. CONCLUSION: NLR, MLR and PLR are significantly high in patients with nAMD. The ability of these inflammatory indicators to distinguish nAMD and PCV is unclear.

Experimental demonstration of noncontact vital-sign measurement using pulse radar.

BACKGROUD: Recently, monitoring the vital-sign with the noncontact method is a popular technology. OBJECTIVE: In this work, we present a fully pulse radar system including front-end sensing and back-end data processing. A series of ultra-wide band sensing pulses is generated and radiated to detect the subject's chest vibration which in turn obtains the required vital-sign signals. METHODS: An artificial plywood with 3 centimeter thickness is placed between a transmitting/receiving antenna of the radar and subject to demonstrate the characteristic of noncontact sensing. The firmware and digital signal processing are also presented in this paper to optimize physiological data quality. RESULTS: The experimental results show that the continuous heart rate and breathing rate can be monitored by this customized system radar module. CONCLUSION: A fully customized ultra-wide band radar for vital-sign application is presented. The radar system plan with wall parameter is also incorporated into the design consideration to meet the FCC requirement and SNR.

Alginate/polycaprolactone composite fibers as multifunctional wound dressings.

We developed a composite wound dressing that provides multifunctional wound care. Alginate and polycaprolactone (PCL) were coelectrospun as composite fibers. Highly absorbent alginate provided a moist environment for wounds and PCL increased cell adhesion. Silver nanoparticles embedded in PCL fibers for long-term release inhibited the growth of microorganisms. In addition, plasmid DNA encoding platelet-derived growth factor-B (PDGF-B) were complexed with polyethylenimine (PEI) to form cationic nanoparticles which were then adsorbed on anionic alginate fibers through electrostatic interaction. As wound cells adhered to composite fibers, they were in situ transfected to express PDGF-B continuously. Moreover, calcium ions in alginate fibers were released into the wound site through ion exchange to accelerate hemostasis. Wound healing experiments demonstrated that PDGF-B gene-loaded composite fibers accelerated wound closure and promoted collagen formation. We expect this comprehensive study offers an ideal multifunctional solution to facilitate wound healing.

The Development of Polylactic Acid/Multi-Wall Carbon Nanotubes/Polyethylene Glycol Scaffolds for Bone Tissue Regeneration Application.

Composite electrospun fibers were fabricated to develop drug loaded scaffolds to promote bone tissue regeneration. Multi-wall carbon nanotubes (MWCNTs) were incorporated to polylactic acid (PLA) to strengthen electrospun nanofibers. To modulate drug release behavior, different ratios of hydrophilic polyethylene glycol (PEG) were added to composite fibers. Glass transition temperature (Tg) can be reduced by the incorporated PEG to enhance the ductility of the nanofibers. The SEM images and the MTT results demonstrated that composite fibers are suitable scaffolds for cell adhesion and proliferation. Dexamethasone (DEX), an osteogenic inducer, was loaded to PLA/MWCNT/PEG fibers. The surface element analysis performed by XPS showed that fluorine of DEX in pristine PLA fibers was much higher than those of the MWCNT-containing fibers, suggesting that the pristine PLA fibers mainly load DEX on their surfaces, whereas MWCNTs can adsorb DEX with evenly distribution in nanofibers. Drug release experiments demonstrated that the release profiles of DEX were manipulated by the ratio of PEG, and that the more PEG in the nanofibers, the faster DEX was released. When rat bone marrow stromal cells (rBMSCs) were seeded on these nanofibers, the Alizarin Red S staining and calcium quantification results demonstrated that loaded DEX were released to promote osteogenic differentiation of rBMSCs and facilitate mineralized tissue formation. These results indicated that the DEX-loaded PLA/MWCNT/PEG nanofibers not only enhanced mechanical strength, but also promoted osteogenesis of stem cells via the continuous release of DEX. The nanofibers should be a potential scaffold for bone tissue engineering application.

Electrical Field-Assisted Gene Delivery from Polyelectrolyte Multilayers.

To sustain gene delivery and elongate transgene expression, plasmid DNA and cationic nonviral vectors can be deposited through layer-by-layer (LbL) assembly to form polyelectrolyte multilayers (PEMs). Although these macromolecules can be released for transfection purposes, their entanglement only allows partial delivery. Therefore, how to efficiently deliver immobilized genes from PEMs remains a challenge. In this study, we attempt to facilitate their delivery through the pretreatment of the external electrical field. Multilayers of polyethylenimine (PEI) and DNA were deposited onto conductive polypyrrole (PPy), which were placed in an aqueous environment to examine their release after electric field pretreatment. Only the electric field perpendicular to the substrate with constant voltage efficiently promoted the release of PEI and DNA from PEMs, and the higher potential resulted in the more releases which were enhanced with treatment time. The roughness of PEMs also increased after electric field treatment because the electrical field not only caused electrophoresis of polyelectrolytes and but also allowed electrochemical reaction on the PPy electrode. Finally, the released DNA and PEI were used for transfection. Polyplexes were successfully formed after electric field treatment, and the transfection efficiency was also improved, suggesting that this electric field pretreatment effectively assists gene delivery from PEMs and should be beneficial to regenerative medicine application.

A novel antimicrobial peptide-derived vehicle for oligodeoxynucleotide delivery to inhibit TNF-α expression.

Indolicidin (IL), an antimicrobial peptide, was investigated as a vehicle to promote oligodeoxynucleotides (ODNs) delivery. To increase charge density, IL was dimerized by adding a cysteine to its C or N terminus, which was denoted as ILC or CIL, respectively. In contrast to IL, cytotoxicity of ILC and CIL was significantly reduced because these dimeric peptides were longer than IL, which restricted their insertions to cell membrane. In contrast to ILC, CIL displayed well loading efficiency. These peptides were applied to deliver ODNs against tumor necrosis factor-α (TNF-α) because TNF-α is a pro-inflammatory cytokine which plays an important role in immunological diseases. Although IL/ODN slightly reduced TNF-α expression, the high cytotoxicity restricted its application window. Furthermore, ILC/ODN was incapable of inducing gene silence due to its low encapsulation efficiency and poor endosomal escape. In contrast, CIL exhibited excellent ODN transportation and the internalized CIL/ODN complexes may escape from endosomes. Therefore, TNF-α expression can be specifically reduced by CIL/ODN complexes, and the silence effect was maintained longer than 14 h. This study provides a useful strategy of peptide vehicle design, which may facilitate the delivery of not only ODN but also other oligonucleotides, including siRNA and miRNA, to promote gene silence application.

The enrichment of cancer stem cells using composite alginate/polycaprolactone nanofibers.

Cancer stem cells (CSCs) are potential platforms to high-throughput screen anti-cancer drugs. However, they are difficult to isolate from cancer cells. Therefore, we proposed to fabricate 3-D scaffolds for CSC enrichment. Alginate is a biocompatible polysaccharide with poor cell adhesion, whereas polycaprolactone (PCL) is relative cell adhesive. These two materials were coelectrospun as composite scaffolds. Cells collected from alginate and composite fibers demonstrated high stemness, epithelial-mesenchymal transition, invasion, drug resistance, and angiogenesis. Interestingly, cells collected from composite fibers with low ratio of PCL were significantly improved their CSC properties compared to those from pure alginate fibers because few PCL fibers spatially separated cell populations to concentrate CSCs. These results suggested that alginate fibers effectively enriched CSCs and composite fibers created an uneven microenvironment to regulate cell morphology and distribution, by which cell-cell interaction was thus manipulated. These tunable scaffolds are potential to isolate CSCs from different tissues to facilitate the cancer research.

The effects of substrate-mediated electrical stimulation on the promotion of osteogenic differentiation and its optimization.

To explore the effect of electrical stimulation (ES) on osteogenesis, a polypyrrole (PPy)-made electrical culture system was developed to provide a direct-current electric field (DCEF). This DCEF device was applied to treat differentiated rat bone marrow stromal cells (rBMSCs) once in different stages of osteo-differentation to investigate its temporal effects. The mineralization results showed that the DCEF treatment not only accelerated cell differentiation but also promoted the saturation levels, and the ES on day 8 was the group demonstrated the optimal result. The gene regulation analysis indicated that the DCEF treatment immediately increased the levels of genes related to osteo-differentiation, especially Runx2. Because Runx2 is a crucial transcriptional factor of osteogenesis, the ES-caused improvement of mineralization was likely contributed by the extension of its expression. Further, different ES modes were investigated of their efficacy on bone matrix deposition. Square waves with different parameters including frequency, offset, amplitude, and duty cycle were systematically examined. In contrast to constant voltage, square waves demonstrated periodical changes of current through substrate to significantly improve mineralization, and the efficiencies highly depended on both frequency and intensity. Through this comprehensive study, DCEF treating condition was optimized, which should be beneficial to its application on osteogenesis promotion. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1607-1619, 2019.

Gene immobilization on alginate/polycaprolactone fibers through electrophoretic deposition to promote in situ transfection efficiency and biocompatibility.

Alginate and polycaprolactone (PCL) were coelectrospun as composite nanofibers for in situ transfection, in which anionic alginate fibers were used to adsorb polyethyleneimine (PEI)/DNA polyplexes and biocompatible PCL fibers were applied to promote cell adhesion. To improve gene immobilization, direct-current electric field (DCEF) was applied to guide cationic polyplexes toward nanofibers on cathode. Fluorescent labeling experiments suggested that the applied DCEF not only accelerated but also increased the saturation levels of gene immobilization. Interestingly, these DCEF also increased the degradation of nanofibers. The water contact angle and Fourier-transform infrared spectrometry results indicated that the degraded component was mainly alginate. It suggested that the DCEF treatment may cause the electrophoresis of calcium ions to destabilize alginates fibers, and thus the degradation rates increased with the applied voltages. This alginate degradation increased the ratio of PCL in composite fibers, so the cell adhesion, viability, and proliferation were improved. Finally, these DCEF-treated fibers were used for substrate-mediated gene delivery. The transfection efficiency highly increased with DCEF when the voltages were lower than 1.5 V. This dynamic scaffold system not only provided a suitable microenvironment for cell ingrowth, but also improved gene immobilization and transfection, and thus promised its therapeutic effect for tissue regeneration.

The control of alginate degradation to dynamically manipulate scaffold composition for in situ transfection application.

In this study, nanofibrous scaffolds were used for in situ transfection application. Polyethylenimine (PEI)/DNA complexes adsorbed to alginate nanofibers, so the more alginate fibers resulted in the higher transfection efficiency. However, alginate was not favorable for cell adhesion. Therefore, poly (ε­caprolactone) (PCL) nanofibers were electrospun with alginate to improve biocompatibility. The in situ transfection results demonstrated that although the incorporated PCL fibers effectively improved cell morphology, the bioactivity and proliferation rates of surface cells were not significantly increased due to the high ratio of alginate fibers. However, the reduction of the alginate ratio may decrease transfection efficiency because the immobilization of nonviral vectors linearly depended on the density of alginate fibers. To maintain transfection efficiency and increase biocompatibility, the stability of alginate fibers were manipulated by adjusting the concentrations of calcium ions during crosslinking. These partially crosslinked alginate fibers were initially intact to allow nanoparticle adsorption for cell uptake, and then gradually degraded in days to create an appropriate environment for cell survival. This dynamic system successfully fulfilled the requirements of both gene delivery and biocompatibility. To our knowledge, this study may be the first one which dynamically regulates scaffold composition for substrate-mediated gene delivery.

A stretchable conductive Polypyrrole Polydimethylsiloxane device fabricated by simple soft lithography and oxygen plasma treatment.

This paper reports a simple method used to fabricate a stretchable conductive polypyrrole (PPy) rough pore-shape polydimethylsiloxane (p-PDMS) device. An abrasive paper is first used to imprint rough micro-structures on the SU-8 micromold. The p-PDMS microchannel is then fabricated using a standard soft-lithography process. An oxygen plasma treatment is then applied to form an irreversible sealing between the microchannel and a blank cover PDMS. The conductive layer is formed by injecting the PPy mixture into the microchannel which polymerizes in the rough pore-shape micro-structures; The PPy/p-PDMS hybrid device shows good electrical property and stretchability. The electrical properties of different geometrical designs of the PPy/p-PDMS microchannel under stretching were investigated, including straight, curved, and serpentine. Mouse embryonic fibroblasts (NIH/3 T3) were also cultured inside the PPy/p-PDMS device to demonstrate good biocompatibility and feasibility using the conductive and stretchable microchannel in cell culture microfluidics applications. Finally, cyclic stretching and bending tests were performed to evaluate the reliability of PPy/p-PDMS microchannel.

Development of an indolicidin-derived peptide by reducing membrane perturbation to decrease cytotoxicity and maintain gene delivery ability.

Indolicidin (IL) is a cationic antimicrobial peptide and our previous study has demonstrated its potential as a cell penetrating peptide (CPP) to promote gene delivery. However, the cytotoxicity of IL arisen from its membrane perturbation capacity may restrict its clinical application. To promote gene delivery safety and efficiency, an almost mirror-symmetric IL derivative, SAP10 (RRWKFFPWRR-CONH2), was designed in this study. All-atom molecular dynamics (MD) simulations were performed to understand the association between SAP10 and model lipid bilayers. By comparison with IL, SAP10 with high positively charged density resisted its deep insertion into lipid bilayers, which thus reduced its perturbation to lipid bilayers and improved biocompatibility. Consequently, we further mixed SAP10, polyethylenimine (PEI) and DNA to form the ternary nanocomplexes for gene delivery investigation. Both IL and SAP10 weakened the interaction between to DNA and PEI, which may be beneficial to promote the dissociation of internalized DNA from the carrier molecules. In vitro experiments demonstrated that the SAP10-associated ternary nanocomplexes highly promoted the transfection efficiency to various cells with low cytotoxicity. The effect of the SAP10 on promoting gene delivery was mainly contributed by the adsorbed peptides on the nanoparticles rather than the free ones. In particular, the dose of SAP10 could be increased to broaden the administration window, which ensured its safety on transfection. Therefore, our results suggested the argument that the designed SAP10 is a safe and an efficient peptide to promote PEI-mediated gene delivery.

The development of an alginate/polycaprolactone composite scaffold for in situ transfection application.

Alginate and polycaprolactone (PCL) were coelectrospun using a dual-jet system to prepare composite nanofibers in defined ratios, and hence both chemical properties and hydrophobicity of scaffolds can be manipulated. These nanofibers were applied in gene immobilization: positively charged polyethyleneimine (PEI)/DNA polyplexes were adsorbed onto anionic alginate fibers, and the higher ratios of alginate resulted in the more immobilized nonviral vectors. Through the incorporation of PCL, biocompatibility of scaffolds was highly improved. Finally, these scaffolds were used for in situ transfection application. Compared to pure alginate fibers, composite fibers not only successfully transferred target genes to adhered cells but also enhanced cell morphology and viability, suggesting that alginate/PCL nanofibers were multifunctional with gene delivery capability and biocompatibility, and the manipulation of their composition can balance and optimize both requirements. To our knowledge, this approach might be the first one using electrostatic interactions to immobilize genes onto nanofibrous scaffolds for in situ transfection application.

The conjugation of indolicidin to polyethylenimine for enhanced gene delivery with reduced cytotoxicity.

Indolicidin (IL), a cationic peptide derived from bovine neutrophils, was grafted onto polyethylenimine (PEI) to investigate the potential of these conjugates as nonviral vectors. To specifically control the conjugation sites, a cysteine residue was added to the C or N terminus of IL, which was denoted as ILC or CIL, respectively. In addition, an IL-derived hydrophilic peptide, SAP10, was also applied for conjugation. Both PEI-ILC and PEI-CIL demonstrated higher transfection efficiency than unmodified PEI; however, PEI-SAP10 was unable to transfect cells. The confocal microscopy results indicated that only PEI-ILC and PEI-CIL successfully delivered DNA into cells. These internalized DNA should be released mainly through the proton sponge effect, whereas the grafted IL may also perturb the endosomal membrane to eventually cause membrane disruption. Finally, we used molecular dynamics simulations to clarify the mechanism of grafted peptides interacting with membranes. The results indicated that the hydrophobic domains of conjugated peptides were essential for gene transportation because the interaction between peptides and the cell membrane was enhanced when these hydrophobic domains entered the hydrocarbon zone of the lipid bilayer. Additionally, tryptophan residues played important roles in stabilizing the insertion of peptide sequences. This study not only developed an effective gene vehicle but also provided useful information for the design of peptide-conjugated carriers for drug delivery applications.

The control of cell orientation using biodegradable alginate fibers fabricated by near-field electrospinning.

For spatially controlling cell alignment, near field electrospinning (NFES) was developed to direct-write alginate fiber patterns. Compared to randomly electrospun fibers, NFES fibers guided the extension of HEK 293T cells and the levels of cell alignment increased with decreasing fiber distances. However, these guiding fibers were unfavorable for cell adhesion and limited cell growth. To preserve cell alignment ability and improve biocompatibility, the stability of patterned alginate fibers was adjusted by regulating the level of ion crosslinking. These partially crosslinked NFES fibers demonstrated parallel line-patterns in the initial stage while gradually degraded with time. The reduction of fiber density increased the available area for cell growth and enhanced cell viability. On the other hand, aligned cells were still found on these degraded patterns, suggesting that cell morphologies were mainly guided during cell seeding. This dynamically controlled fiber pattern system fulfilled the need of controlling cell orientation and biocompatibility, thus was potential to modify scaffold surfaces for tissue engineering application.

The Regulation of Osteogenesis Using Electroactive Polypyrrole Films.

To evaluate the effect of electrical conductivity of biomaterials on osteogenesis, polypyrrole (PPy) was fabricated by oxidative chemical polymerization as substrates for cell culture. Through adjusting the concentrations of monomer and initiator, polypyrrole films with different electrical conductivities were fabricated. These fabricated polypyrrole films are transparent enough for easy optical microscopy. Fourier transform infrared spectroscopy, X-ray spectroscopy and four-point probe were used to assess the microstructures, surface chemical compositions and electrical sheet resistance of films, respectively. Results indicate that higher monomer and initiator concentration leads to highly-branched PPy chains and thus promotes the electron mobility and electrical conductivity. Selected polypyrrole films then were applied for culturing rat bone marrow stromal cells. Cell viability and mineralization assays reveal that not only these films are biocompatible, but also capable of enhancing the calcium deposition into the extra cellular matrix by the differentiated cells.

Virus immobilization on biomaterial scaffolds through biotin-avidin interaction for improving bone regeneration.

To spatially control therapeutic gene delivery for potential tissue engineering applications, a biotin-avidin interaction strategy was applied to immobilize viral vectors on biomaterial scaffolds. Both adenoviral vectors and gelatin sponges were biotinylated and avidin was applied to link them in a virus-biotin-avidin-biotin-material (VBABM) arrangement. The tethered viral particles were stably maintained within scaffolds and SEM images illustrated that viral particles were evenly distributed in three-dimensional (3D) gelatin sponges. An in vivo study demonstrated that transgene expression was restricted to the implant sites only and transduction efficiency was improved using this conjugation method. For an orthotopic bone regeneration model, adenovirus encoding BMP-2 (AdBMP2) was immobilized to gelatin sponges before implanting into critical-sized bone defects in rat calvaria. Compared to gelatin sponges with AdBMP2 loaded in a freely suspended form, the VBABM method enhanced gene transfer and bone regeneration was significantly improved. These results suggest that biotin-avidin immobilization of viral vectors to biomaterial scaffolds may be an effective strategy to facilitate tissue regeneration.

The consideration of indolicidin modification to balance its hemocompatibility and delivery efficiency.

Indolicidin (IL) is an antimicrobial peptide (AMP), which has been utilized as a cell penetrating peptide (CPP) for drug delivery. However, the hemolysis restricts its clinical application. Therefore, we investigated the delivery efficiency and hemocompatibility of IL and its derivatives. The transportation of fluorophore to NIH/3T3 cells could be improved either by in accompany with these peptides or in the form of peptide-conjugates. The hydrophobicity scales of these peptides were calculated according to their residues, which were compared to their effects on hemolysis as well as cell uptake efficiency. The results suggested that the cell penetrability of IL and its derivatives was related to their hydrophobicity scales based on the octanol-interface scale (ΔGoct-if), whereas their hemolysis levels depended on the hydrophobicity scales based on interface (ΔGwif). Consequently, we designed two peptides, IL-R57F89 and SAP10, to validate the correlation. These two peptides had similar ΔGwif; however, the ΔGoct-if of SAP10 was much higher than that of IL-K7F89. Both IL-R57F89 and SAP10 demonstrated extremely low hemolysis. Compared to the limit cell uptake of SAP10, IL-R57F89 greatly promoted the delivery efficiency. These results were consistent to our prediction, suggesting that hydrophobicity scales should be a useful preliminary guidance for AMP-derived CPP design.

Electrophoretic deposition to promote layer-by-layer assembly for in situ gene delivery application.

In this study, layer-by-layer (LbL) assembly of polyelectrolyte was facilitated using electric field assistance (EFA). To elucidate the EFA effects on polyelectrolyte multilayers (PEMs), the electric fields were solely administrated to either chitosan or DNA adsorption. Both DNA and chitosan adsorptions can be augmented under low electric field due to the electrophoretic deposition. However, the ensuing electrochemical reactions on electrode interfered with interactions between multilayers when the bias was larger than 0.5V, leading to retard deposition. Subsequent delivery experiments indicated that EFA during DNA deposition demonstrated superior DNA release. In contrast, no obvious improvements were observed for the groups using the EFA during chitosan deposition. Moreover, water contact angle experiments revealed different effects of electric fields on multilayer structure. Using EFA during DNA deposition led to a layered-form composition, whereas interpenetration of electrolytes was enhanced with the application of the electric field during chitosan deposition. For in vitro experiments, EFA during DNA deposition significantly enhanced in situ transfection performances of PEMs that the transgene expression levels were increased and the periods were extended, suggesting this method is potential to quantitatively and temporally improve substrate-mediated gene delivery.