Thermo-responsive non-woven scaffolds for "smart" 3D cell culture

The thermo‐responsive polymer poly(N‐isopropylacrylamide) has received widespread attention for its in vitro application in the non‐invasive, non‐destructive release of adherent cells on two dimensional surfaces. In this study, 3D non‐woven scaffolds fabricated from poly(propylene) (PP), poly(ethylene terephthalate) (PET), and nylon that had been grafted with PNIPAAm were tested for their ability to support the proliferation and subsequent thermal release of HC04 and HepG2 hepatocytes. Hepatocyte viability and proliferation were estimated using the Alamar Blue assay and Hoechst 33258 total DNA quantification. The assays revealed that the pure and grafted non‐woven scaffolds maintained the hepatocytes within the matrix and promoted 3D proliferation comparable to that of the commercially available Algimatrix? alginate scaffold. Albumin production and selected cytochrome P450 genes expression was found to be superior in cells growing on pure and grafted non‐woven PP scaffolds as compared to cells grown as a 2D monolayer. Two scaffolds, namely, PP‐g‐PNIPAAm‐A and PP‐g‐PNIPAAm‐B were identified as having far superior thermal release capabilities; releasing the majority of the cells from the matrices within 2 h. This is the first report for the development of 3D non‐woven, thermo‐responsive scaffolds able to release cells from the matrix without the use of any enzymatic assistance or scaffold degradation. Biotechnol. Bioeng. 2012; 109:2147–2158. © 2012 Wiley Periodicals, Inc.     

A Three‐Dimensionally Interconnected Carbon Nanotube–Conducting Polymer Hydrogel Network for High‐Performance Flexible Battery Electrodes

High‐performance flexible energy‐storage devices have great potential as power sources for wearable electronics. One major limitation to the realization of these applications is the lack of flexible electrodes with excellent mechanical and electrochemical properties. Currently employed batteries and supercapacitors are mainly based on electrodes that are not flexible enough for these purposes. Here, a three‐dimensionally interconnected hybrid hydrogel system based on carbon nanotube (CNT)‐conductive polymer network architecture is reported for high‐performance flexible lithium ion battery electrodes. Unlike previously reported conducting polymers (e.g., polyaniline, polypyrrole, polythiophene), which are mechanically fragile and incompatible with aqueous solution processing, this interpenetrating network of the CNT‐conducting polymer hydrogel exibits good mechanical properties, high conductivity, and facile ion transport, leading to facile electrode kinetics and high strain tolerance during electrode volume change. A high‐rate capability for TiO₂ and high cycling stability for SiNP electrodes are reported. Typically, the flexible TiO₂ electrodes achieved a capacity of 76 mAh g^–1 in 40 s of charge/discharge and a high areal capacity of 2.2 mAh cm^–2 can be obtained for flexible SiNP‐based electrodes at 0.1C rate. This simple yet efficient solution process is promising for the fabrication of a variety of high performance flexible electrodes.     

Hybrid chitosan–ß‐glycerol phosphate–gelatin nano‐/micro fibrous scaffolds with suitable mechanical and biological properties for tissue engineering

Scaffold‐based tissue engineering is considered as a promising approach in the regenerative medicine. Graft instability of collagen, by causing poor mechanical properties and rapid degradation, and their hard handling remains major challenges to be addressed. In this research, a composite structured nano‐/microfibrous scaffold, made from a mixture of chitosan–ß‐glycerol phosphate–gelatin (chitosan–GP–gelatin) using a standard electrospinning set‐up was developed. Gelatin–acid acetic and chitosan ß‐glycerol phosphate–HCL solutions were prepared at ratios of 30/70, 50/50, 70/30 (w/w) and their mechanical and biological properties were engineered. Furthermore, the pore structure of the fabricated nanofibrous scaffolds was investigated and predicted using a theoretical model. Higher gelatin concentrations in the polymer blend resulted in significant increase in mean pore size and its distribution. Interaction between the scaffold and the contained cells was also monitored and compared in the test and control groups. Scaffolds with higher chitosan concentrations showed higher rate of cell attachment with better proliferation property, compared with gelatin‐only scaffolds. The fabricated scaffolds, unlike many other natural polymers, also exhibit non‐toxic and biodegradable properties in the grafted tissues. In conclusion, the data clearly showed that the fabricated biomaterial is a biologically compatible scaffold with potential to serve as a proper platform for retaining the cultured cells for further application in cell‐based tissue engineering, especially in wound healing practices. These results suggested the potential of using mesoporous composite chitosan–GP–gelatin fibrous scaffolds for engineering three‐dimensional tissues with different inherent cell characteristics. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 163–175, 2016.     

Controlled Synthesis and Energy Applications of One‐Dimensional Conducting Polymer Nanostructures: An Overview

The past decade has witnessed increasing attention in the synthesis, properties, and applications of one‐dimensional (1D) conducting polymer nanostructures. This overview first summarizes the synthetic strategies for various 1D nanostructures of conjugated polypyrrole (PPy), polyaniline (PANI), polythiophene (PTh), poly(p‐phenylenevinylene) (PPV) and derivatives thereof. By using template‐directed or template‐free methods, nanoscale rods, wires/fibers, belts/ribbons, tubes, arrays, or composites have been successfully synthesized. With their unique structures and advantageous characteristics (e.g., high conductivity, high carrier mobility, good electrochemical activity, large specific surface area, short and direct path for charge/ion transportation, good mechanical properties), 1D conducting polymer nanostructures are demonstrated to be very useful for energy applications. Next, their applications in solar cells, fuel cells, rechargeable lithium batteries, and electrochemical supercapacitors are highlighted, with a strong emphasis on recent literature examples. Finally, this review ends with a summary and some perspectives on the challenges and opportunities in this emerging area of research.     

Detailed positron annihilation lifetime spectroscopic investigation of atrazine imprinted polymers grafted onto PE/PP non‐woven fabrics

This study presents the preparation of molecularly imprinted matrices by using radiation‐induced grafting technique onto polyethylene/polypropylene (PE/PP) non‐woven fabrics. Atrazine imprinted polymers were grafted onto PE/PP non‐woven fabrics through the use of methacrylic acid (MAA) and ethylene glycol dimethylacrylate (EGDMA) as the functional monomer and crosslinking agent, respectively. Grafted MIPs were characterized by attenuated total reflectance Fourier transform infra‐red spectroscopy (ATR‐FTIR), X‐ray photoelectron spectroscopy (XPS), elemental analysis, scanning electron microscopy (SEM), and positron annihilation lifetime spectroscopy (PALS). The average diameter of free volume holes was determined as 0.612 nm which correlates very well with the size of template molecule atrazine, 0.512 nm. Binding behaviors were investigated against various factors, such as concentration of template molecule, pH, and contact time. Furthermore, the specific selectivity of grafted MIP on non‐woven fabric was studied by using other common triazine compounds, such as simazine and metribuzine which show structural similarities to atrazine. The specific binding values for atrazine, simazine, and metribuzine were determined as 40%, 2.5%, and 1.5%, respectively.     

Supermacroporous polymer‐based cryogel bioreactor for monoclonal antibody production in continuous culture using hybridoma cells

Cryogel matrices composed of different polymeric blends were synthesized, yielding a unique combination of hydrophilicity and hydrophobicity with the presence or absence of charged surface. Four such cryogel matrices composed of polyacrylamide–chitosan (PAAC), poly(N‐isopropylacrylamide)–chitosan, polyacrylonitrile (PAN), and poly(N‐isopropylacrylamide) were tested for growth of different hybridoma cell lines and production of antibody in static culture. All the matrices were capable for the adherence of hybridoma cell lines 6A4D7, B7B10, and H9E10 to the polymeric surfaces as well as for the efficient monoclonal antibody (mAb) production. PAAC proved to be relatively better in terms of both mAb production and cell growth. Further, PAAC cryogel was designed into three different formats, monolith, disks, and beads, and used as packing material for packed‐bed bioreactor. Long‐term cultivation of 6A4D7 cell line on PAAC cryogel scaffold in all the three formats could be successfully done for a period of 6 weeks under static conditions. Continuous packed‐bed bioreactor was setup using 6A4D7 hybridoma cell line in the three reactor formats. The reactors ran continuously for a period of 60 days during which mAb production and metabolism of cells in the bioreactors were monitored periodically. The monolith bioreactor performed most efficiently over a period of 60 days and produced a total of 57.5 mg of antibody in the first 30 days (in 500 mL) with a highest concentration of 115 μg mL^?1, which is fourfold higher than t‐flask culture. The results demonstrate that appropriate chemistry and geometry of the bioreactor matrix for cell growth and immobilization can enhance the reactor productivity. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2011     

On‐demand three‐dimensional freeform fabrication of multi‐layered hydrogel scaffold with fluidic channels

One of the challenges in tissue engineering is to provide adequate supplies of oxygen and nutrients to cells within the engineered tissue construct. Soft‐lithographic techniques have allowed the generation of hydrogel scaffolds containing a network of fluidic channels, but at the cost of complicated and often time‐consuming manufacturing steps. We report a three‐dimensional (3D) direct printing technique to construct hydrogel scaffolds containing fluidic channels. Cells can also be printed on to and embedded in the scaffold with this technique. Collagen hydrogel precursor was printed and subsequently crosslinked via nebulized sodium bicarbonate solution. A heated gelatin solution, which served as a sacrificial element for the fluidic channels, was printed between the collagen layers. The process was repeated layer‐by‐layer to form a 3D hydrogel block. The printed hydrogel block was heated to 37°C, which allowed the gelatin to be selectively liquefied and drained, generating a hollow channel within the collagen scaffold. The dermal fibroblasts grown in a scaffold containing fluidic channels showed significantly elevated cell viability compared to the ones without any channels. The on‐demand capability to print fluidic channel structures and cells in a 3D hydrogel scaffold offers flexibility in generating perfusable 3D artificial tissue composites. Biotechnol. Bioeng. 2010;105: 1178–1186. © 2009 Wiley Periodicals, Inc.     

MXene—Conducting Polymer Asymmetric Pseudocapacitors

Conducting polymers (CPs) are attractive pseudocapacitive materials which show the highest capacitance under positive potentials in aqueous protic electrolytes. One way to expand their voltage window (thus energy density) in aqueous electrolytes is to manufacture asymmetric supercapacitors using distinctly different anodes. However, CPs lack matching pseudocapacitive anode materials that can perform well in protic electrolytes (e.g., sulfuric acid). 2D titanium carbide (Ti₃C₂T_x), MXene, as a universal pseudocapacitive anode material for a range of CPs, such as polyaniline, polypyrrole, and poly(3,4‐ethylenedioxythiophene) deposited on reduced graphene oxide (rGO) sheets, is reported here. All‐pseudocapacitive organic–inorganic asymmetric devices with MXene cathodes and rGO–polymer anodes can operate in voltage windows up to 1.45 V in 3 m H₂SO₄. Most importantly, these devices show outstanding cycling performance, outperforming many reported asymmetric pseudocapacitors.     

Facile and selective covalent grafting of an RGD‐peptide to electrospun scaffolds improves HUVEC adhesion

The development of a biomimetic surface able to promote endothelialization is fundamental in the search for blood vessel substitutes that prevent the formation of thrombi or hyperplasia. This study aims at investigating the effect of functionalization of poly‐ε‐caprolactone or poly(L‐lactic acid‐co‐?‐caprolactone) electrospun scaffolds with a photoreactive adhesive peptide. The designed peptide sequence contains four Gly‐Arg‐Gly‐Asp‐Ser‐Pro motifs per chain and a p‐azido‐Phe residue at each terminus. Different peptide densities on the scaffold surface were obtained by simply modifying the peptide concentration used in pretreatment of the scaffold before UV irradiation. Scaffolds of poly‐ε‐caprolactone embedded with adhesive peptides were produced to assess the importance of peptide covalent grafting. Our results show that the scaffolds functionalized with photoreactive peptides enhance adhesion at 24 h with a dose‐dependent effect and control the proliferation of human umbilical vein endothelial cells, whereas the inclusion of adhesive peptide in the electrospun matrices by embedding does not give satisfactory results. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.     

Centrifugal seeding of mammalian cells in nonwoven fibrous matrices

Three‐dimensional (3D) cell cultures have many advantages over two‐dimensional cultures. However, seeding cells in 3D scaffolds such as nonwoven fibrous polyethylene terephthalate (PET) matrices has been a challenge task in tissue engineering and cell culture bioprocessing. In this study, a centrifugal seeding method was investigated to improve the cell seeding efficiency in PET matrices with two different porosities (93% and 88%). Both the centrifugal force and centrifugation time were found to affect the seeding efficiency. With an appropriate centrifugation speed, a high 80?90% cell seeding efficiency was achieved and the time to reach this high seeding efficiency was less than 5 min. The seeding efficiency was similar for matrices with different porosities, although the optimal seeding time was significantly shorter for the low‐porosity scaffold. Post seeding cell viability was demonstrated by culturing colon cancer cells seeded in PET matrices for over 5 days. The centrifugal seeding method developed in this work can be used to efficiently and uniformly seed small fibrous scaffolds for applications in 3D cell‐based assays for high‐throughput screening. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Functional 3‐D cardiac co‐culture model using bioactive chitosan nanofiber scaffolds

The in vitro generation of a three‐dimensional (3‐D) myocardial tissue‐like construct employing cells, biomaterials, and biomolecules is a promising strategy in cardiac tissue regeneration, drug testing, and tissue engineering applications. Despite significant progress in this field, current cardiac tissue models are not yet able to stably maintain functional characteristics of cardiomyocytes for long‐term culture and therapeutic purposes. The objective of this study was to fabricate bioactive 3‐D chitosan nanofiber scaffolds using an electrospinning technique and exploring its potential for long‐term cardiac function in the 3‐D co‐culture model. Chitosan is a natural polysaccharide biomaterial that is biocompatible, biodegradable, non‐toxic, and cost effective. Electrospun chitosan was utilized to provide structural scaffolding characterized by scale and architectural resemblance to the extracellular matrix (ECM) in vivo. The chitosan fibers were coated with fibronectin via adsorption in order to enhance cellular adhesion to the fibers and migration into the interfibrous milieu. Ventricular cardiomyocytes were harvested from neonatal rats and studied in various culture conditions (i.e., mono‐ and co‐cultures) for their viability and function. Cellular morphology and functionality were examined using immunofluorescent staining for alpha‐sarcomeric actin (SM‐actin) and gap junction protein, Connexin‐43 (Cx43). Scanning electron microscopy (SEM) and light microscopy were used to investigate cellular morphology, spatial organization, and contractions. Calcium indicator was used to monitor calcium ion flux of beating cardiomyocytes. The results demonstrate that the chitosan nanofibers retained their cylindrical morphology in long‐term cell cultures and exhibited good cellular attachment and spreading in the presence of adhesion molecule, fibronectin. Cardiomyocyte mono‐cultures resulted in loss of cardiomyocyte polarity and islands of non‐coherent contractions. However, the cardiomyocyte‐fibroblast co‐cultures resulted in polarized cardiomyocyte morphology and retained their morphology and function for long‐term culture. The Cx43 expression in the fibroblast co‐culture was higher than the cardiomyocytes mono‐culture and endothelial cells co‐culture. In addition, fibroblast co‐cultures demonstrated synchronized contractions involving large tissue‐like cellular networks. To our knowledge, this is the first attempt to test chitosan nanofiber scaffolds as a 3‐D cardiac co‐culture model. Our results demonstrate that chitosan nanofibers can serve as a potential scaffold that can retain cardiac structure and function. These studies will provide useful information to develop a strategy that allows us to generate engineered 3‐D cardiac tissue constructs using biocompatible and biodegradable chitosan nanofiber scaffolds for many tissue engineering applications. Biotechnol. Bioeng. 2013; 110: 637–647. © 2012 Wiley Periodicals, Inc.     

Application of polyethyleneimine‐modified scaffolds to the regeneration of cartilaginous tissue

In this study, we analyzed the physicochemical and biophysical properties of three‐dimensional scaffolds modified using polyethyleneimine (PEI) and applied these scaffolds to the cultivation of bovine knee chondrocytes (BKCs). PEI was crosslinked in the bulk or on the surface of the ternary scaffolds comprising polyethylene oxide, chitin and chitosan. The results revealed that when the concentration of PEI was less than 300 μg/mL, the cytotoxicity of a scaffold was on the same order in the two method of modification. An increase in the concentration of PEI favored the adhesion of BKCs. When the amount of PEI in scaffolds is fixed, the surface‐modified scaffolds exhibited a higher adhesion efficiency of BKCs than the bulk‐modified scaffolds. For the regeneration of cartilaginous components, a higher amount of PEI in a scaffold yielded larger amounts of proliferated BKCs, secreted glycosaminoglycans, and produced collagen. In addition, the formation of neocartilage in the surface‐modified scaffolds was more effective than that in the bulk‐modified scaffolds. These tissue‐engineered scaffolds, modified by an appropriate concentration of PEI, can be potentially applied to cartilage repair in clinical trials. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Propagation of pseudo-intimal linings of vascular prostheses

Summary In an attempt to develop viable intimal linings for artificial vascular prostheses, an investigation was undertaken of methods to ensure cell deposition and adherence to microfabric-lined devices, and to stimulate cellular propagation on these surfaces. The WI-38 cell was used as a model. Technical procedures developed for seeding, adherence, and growth included: (a) degassing of the microfabrics before seeding to permit penetration of media, (b) centrifugation to seed cells forcibly into the microfabric, (c) containment of cells during the early stages of in vitro cultivation to prevent outgrowth of the newly seeded cells, and (d) perfusion of the cultures on a fixed schedule for removal of waste products and replacement with fresh media. Of the parylene C-coated polypropylene microfabrics tested, the nonvertically drafted, microwave discharge-treated fabrics were decidedly better suited for cell attachment of the WI-38 cell than multiple drafted or maximal drafted fabrics which provided less adequate surfaces for cell attachment. Although the adhesive used in cementing the microfabric to a backing is undoubtedly toxic, parylene C coating protects the cells. Nylon microfabrics tested to date proved deleterious to confluent cell growth. Gold fabrics were highly compatible with the cells. This study was supported by a contract (NIH-NHLI 71-2054) with the Medical Devices Applications Program, National Heart and Lung Institute, Bethesda, Maryland.     

Understanding the Effects of Molecular Dopant on n‐Type Organic Thermoelectric Properties

Molecular doping is a powerful method to fine‐tune the thermoelectric properties of organic semiconductors, in particular to impart the requisite electrical conductivity. The incorporation of molecular dopants can, however, perturb the microstructure of semicrystalline organic semiconductors, which complicates the development of a detailed understanding of structure–property relationships. To better understand how the doping pathway and the resulting dopant counterion influence the thermoelectric performance and transport properties, a new dimer dopant, (N‐DMBI)₂, is developed. Subsequently, FBDPPV is then n‐doped with dimer dopants (N‐DMBI)₂, (RuCp*mes)₂, and the hydride‐donor dopant N‐DMBI‐H. By comparing the UV–vis–NIR absorption spectra and morphological characteristics of the doped polymers, it is found that not only the doping mechanism, but also the shape of the counterion strongly influence the thermoelectric properties and transport characteristics. (N‐DMBI)₂, which is a direct electron‐donating dopant with a comparatively small, relatively planar counterion, gives the best power factor among the three systems studied here. Additionally, temperature‐dependent conductivity and Seebeck coefficient measurements differ between the three dopants with (N‐DMBI)₂ yielding the best thermoelectric properties. The results of this study of dopant effects on thermoelectric properties provide insight into guidelines for future organic thermoelectrics.     

Carbonate fabrics in the modern microbialites of Pavilion Lake: two suites of microfabrics that reflect variation in microbial community morphology,growth habit,and lithification

Modern microbialites in Pavilion Lake, BC, provide an analog for ancient non‐stromatolitic microbialites that formed from in situ mineralization. Because Pavilion microbialites are mineralizing under the influence of microbial communities, they provide insights into how biological processes influence microbialite microfabrics and mesostructures. Hemispherical nodules and micrite–microbial crusts are two mesostructures within Pavilion microbialites that are directly associated with photosynthetic communities. Both filamentous cyanobacteria in hemispherical nodules and branching filamentous green algae in micrite–microbial crusts were associated with calcite precipitation at microbialite surfaces and with characteristic microfabrics in the lithified microbialite. Hemispherical nodules formed at microbialite surfaces when calcite precipitated around filamentous cyanobacteria with a radial growth habit. The radial filament pattern was preserved within the microbialite to varying degrees. Some subsurface nodules contained well‐defined filaments, whereas others contained only dispersed organic inclusions. Variation in filament preservation is interpreted to reflect differences in timing and amount of carbonate precipitation relative to heterotrophic decay, with more defined filaments reflecting greater lithification prior to degradation than more diffuse filaments. Micrite–microbial crusts produce the second suite of microfabrics and form in association with filamentous green algae oriented perpendicular to the microbialite surface. Some crusts include calcified filaments, whereas others contained voids that reflect the filamentous community in shape, size, and distribution. Pavilion microbialites demonstrate that microfabric variation can reflect differences in lithification processes and microbial metabolisms as well as microbial community morphology and organization. Even when the morphology of individual filaments or cells is not well preserved, the microbial growth habit can be captured in mesoscale microbialite structures. These results suggest that when petrographic preservation is extremely good, ancient microbialite growth structures and microfabrics can be interpreted in the context of variation in community organization, community composition, and lithification history. Even in the absence of distinct microbial microfabrics, mesostructures can capture microbial community morphology.     

Non‐Fullerene Acceptor‐Based Bulk Heterojunction Polymer Solar Cells: Engineering the Nanomorphology via Processing Additives

The performance of bulk heterojunction solar cells made from blends of a non‐fullerene acceptor, N,N′‐bis(2‐ethylhexyl)‐2,6‐bis(5″‐hexyl‐[2,2′;5′,2″]terthiophen‐5yl)‐1,4,5,8‐naphthalene diimide (NDI‐3TH), and poly(3‐hexylthiophene) (P3HT) donor is enhanced 10‐fold by using a processing additive in conjunction with an electron‐blocking and a hole‐blocking buffer layers. The power conversion efficiency of P3HT:NDI‐3TH solar cells improves from 0.14% to 1.5% by using a processing additive (1,8‐diiodooctane) at an optimum concentration of 0.2 vol%, which is far below the 2‐3 vol% optimum concentrations found in polymer/fullerene systems. TEM and AFM imaging show that the size and connectivity of the NDI‐3TH domains in the phase‐separated P3HT:NDI‐3TH blends vary strongly with the concentration of the processing additive. These results demonstrate, for the first time, that processing additives can be effective in the optimization of the morphology and performance of bulk heterojunction polymer solar cells based on non‐fullerene acceptors.     

A brief review of extrusion‐based tissue scaffold bio‐printing

Extrusion‐based bio‐printing has great potential as a technique for manipulating biomaterials and living cells to create three‐dimensional (3D) scaffolds for damaged tissue repair and function restoration. Over the last two decades, advances in both engineering techniques and life sciences have evolved extrusion‐based bio‐printing from a simple technique to one able to create diverse tissue scaffolds from a wide range of biomaterials and cell types. However, the complexities associated with synthesis of materials for bio‐printing and manipulation of multiple materials and cells in bio‐printing pose many challenges for scaffold fabrication. This paper presents an overview of extrusion‐based bio‐printing for scaffold fabrication, focusing on the prior‐printing considerations (such as scaffold design and materials/cell synthesis), working principles, comparison to other techniques, and to‐date achievements. This paper also briefly reviews the recent development of strategies with regard to hydrogel synthesis, multi‐materials/cells manipulation, and process‐induced cell damage in extrusion‐based bio‐printing. The key issue and challenges for extrusion‐based bio‐printing are also identified and discussed along with recommendations for future, aimed at developing novel biomaterials and bio‐printing systems, creating patterned vascular networks within scaffolds, and preserving the cell viability and functions in scaffold bio‐printing. The address of these challenges will significantly enhance the capability of extrusion‐based bio‐printing.     

Solution‐Processable Conjugated Polymers as Anode Interfacial Layer Materials for Organic Solar Cells

In recent years, solution‐processed conjugated polymers have been extensively used as anode interfacial layer (AIL) materials in organic solar cells (OSCs) due to their excellent film‐forming property and low‐temperature processing advantages. In this review, the authors focus on the recent advances in conjugated polymers as AIL materials in OSCs. Several of the main classes of solution‐processable conjugated polymers, including poly(3,4‐ethylenedioxythiophene):(styrenesulfonate), polyaniline, polythiophene, conjugated polyelectrolytes, sulfonated poly(diphenylamine), and crosslinked polymers as AIL materials are discussed in depth, and the mechanisms of these AIL materials in enhancing OSC performances are also elucidated. The structure–property relationships of various conjugated polymer AIL materials are analyzed, and some important design rules for such materials toward high efficiencies and stable OSCs are presented. In addition, some chemical and physical approaches to optimize the photoelectronic and physic properties of conjugated polymer AIL materials, which improve their performance in modifying OSCs, are also highlighted. Considering the significance of tandem OSCs, the relevant applications of conjugated polymer AIL materials in constructing interconnection layers for tandem OSCs are also mentioned. Finally, a brief summary is presented and some perspectives to help researchers understand the current challenges and opportunities in this area are proposed.     

Post‐transcriptional regulation of α‐smooth muscle actin determines the contractile phenotype of Dupuytren's nodular cells

The objective was to study Dupuytren's myofibroblast cells in constrained collagen matrices in order to more closely emulate their in vivo environment and, to correlate their contractility with α‐smooth muscle actin (α‐SMA) expression and determine if dermal fibroblasts regulate Dupuytren's myofibroblast phenotype. Isotonic and isometric force contraction by cells isolated from Dupuytren's nodules, palmar and non‐palmar skin fibroblasts was measured in collagen matrices. The effect of co‐culturing nodule cells with dermal fibroblasts on isometric contraction was examined. Isometric contraction was correlated with levels of α‐SMA mRNA by pcr and protein by Western blotting, and α‐SMA distribution assessed by immunofluorescence. Dupuytren's nodule cells exhibited similar levels of isotonic contraction to both palmar and non‐palmar dermal fibroblasts. However, nodule cells generated high levels of isometric force (mean: 3.5 dynes/h), which continued to increase over 24 h to a maximum of 173 dynes. In contrast, dermal fibroblasts initially exhibited low levels of contraction (mean: 0.5 dynes/h) and reached tensional homeostasis on average after 15 h (range: 4–20 h), with a maximum force of 52 dynes. Although all three cell types had similar α‐SMA mRNA levels, increased levels of α‐SMA protein were observed in nodule cells compared to dermal fibroblasts. α‐SMA localised to stress fibres in 35% (range: 26–50%) of nodule cells compared to only 3% (range:0–6%) of dermal fibroblasts. Co‐cultures of Dupuytren's cells and dermal fibroblasts showed no contractile differences. The contractile phenotype of Dupuytren's myofibroblasts is determined by increased α‐SMA protein distributed in stress fibres, not by cellular mRNA levels. Dupuytren's cell contractility is not influenced by dermal fibroblasts. J. Cell. Physiol. 224: 681–690, 2010. © 2010 Wiley‐Liss, Inc.