Comparison of mesenchymal stem cells released from poly( N -isopropylacrylamide) copolymer film and by trypsinization

Photothermal release and recovery of mesenchymal stem cells from substrates functionalized with gold nanorods

Mesenchymal stem cell therapies show great promise in regenerative medicine. However, to generate clinically relevant numbers of these stem cells, significant in vitro expansion of the cells is required before transplantation into the affected wound or defect. The current gold standard protocol for recovering in vitro cultured cells involves treatment with enzymes such as trypsin which can affect the cell phenotype and ability to interact with the environment. Alternative enzyme free methods of adherent cell recovery have been investigated, but none match the convenience and performance of enzymatic detachment. In this work we have developed a synthetically simple, low cost cell culture substrate functionalized with gold nanorods that can support cell proliferation and detachment. When these nanorods are irradiated with biocompatible low intensity near infrared radiation (785 nm, 560 mWcm^-2) they generate localized surface plasmon resonance induced nanoscale heating effects which trigger detachment of adherent mesenchymal stem cells. Through simulations and thermometry experiments we show that this localized heating is concentrated at the cell-nanorod interface, and that the stem cells detached using this technique show either similar or improved multipotency, viability and ability to differentiate into clinically desirable osteo and adipocytes, compared to enzymatically harvested cells. This proof-of-principle work shows that photothermally mediated cell detachment is a promising method for recovering mesenchymal stem cells from in vitro culture substrates, and paves the way for further studies to scale up this process and facilitate its clinical translation. STATEMENT OF SIGNIFICANCE: New non-enzymatic methods of harvesting adherent cells without damaging or killing them are highly desirable in fields such as regenerative medicine. Here, we present a synthetically simple, non-toxic, infra-red induced method of harvesting mesenchymal stem cells from gold nanorod functionalized substrates. The detached cells retain their ability to differentiate into therapeutically valuable osteo and adipocytes. This work represents a significant improvement on similar cell harvesting studies due to: its simplicity; the use of clinically valuable stem cells as oppose to immortalized cell lines; and the extensive cellular characterization performed. Understanding, not just if cells live or die but how they proliferate and differentiate after photothermal detachment will be essential for the translation of this and similar techniques into commercial devices.

Three-Dimensional Printable Conductive Semi-Interpenetrating Polymer Network Hydrogel for Neural Tissue Applications

Intrinsically conducting polymers (ICPs) are widely used to fabricate biomaterials; their application in neural tissue engineering, however, is severely limited because of their hydrophobicity and insufficient mechanical properties. For these reasons, soft conductive polymer hydrogels (CPHs) are recently developed, resulting in a water-based system with tissue-like mechanical, biological, and electrical properties. The strategy of incorporating ICPs as a conductive component into CPHs is recently explored by synthesizing the hydrogel around ICP chains, thus forming a semi-interpenetrating polymer network (semi-IPN). In this work, a novel conductive semi-IPN hydrogel is designed and synthesized. The hybrid hydrogel is based on a poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide) hydrogel where polythiophene is introduced as an ICP to provide the system with good electrical properties. The fabrication of the hybrid hydrogel in an aqueous medium is made possible by modifying and synthesizing the monomers of polythiophene to ensure water solubility. The morphological, chemical, thermal, electrical, electrochemical, and mechanical properties of semi-IPNs were fully investigated. Additionally, the biological response of neural progenitor cells and mesenchymal stem cells in contact with the conductive semi-IPN was evaluated in terms of neural differentiation and proliferation. Lastly, the potential of the hydrogel solution as a 3D printing ink was evaluated through the 3D laser printing method. The presented results revealed that the proposed 3D printable conductive semi-IPN system is a good candidate as a scaffold for neural tissue applications.

Evaluation of Strategies Aimed at Improving Liver Progenitor Cell Rolling and Subsequent Adhesion to the Endothelium

Adult-derived human liver stem/progenitor cells (ADHLSCs) are a promising alternative to orthotopic liver transplantation in the treatment of inborn errors of metabolism. However, as is the case with many mesenchymal stromal cells, ADHLSCs have shown a low level of engraftment, which could be explained by the fact that they lack expression of selectin ligand and LFA-1 and only slightly express VLA- 4, molecules that have been shown to be involved in cell adhesion to the endothelium. In this paper, we have investigated strategies to increase their rolling and adhesion during the homing process by (1) adding a selectin ligand (Sialyl Lewis X) to their surface using biotinyl-N-hydroxy-succinimide–streptavidin bridges, and (2) protecting the adhesion proteins from trypsinization-induced damage using a thermosensitive polymer for cell culture and a nonenzymatic cell dissociation solution (CDS) for harvest. Despite increasing adhesion of ADHLSCs to E-selectin during an adhesion test in vitro performed under shear stress, the addition of Sialyl Lewis X did not increase adhesion to endothelial cells under the same conditions. Cultivating cells on a thermosensitive polymer and harvesting them with CDS increased their adhesion to endothelial cells under noninflammatory conditions, compared to the use of trypsin. However, we were not able to demonstrate any improvement in cell adhesion to the endothelium following culture on polymer and harvest with CDS, suggesting that alternative methods of improving engraftment still need to be evaluated.

Towards Physiologic Culture Approaches to Improve Standard Cultivation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are of great interest for their use in cell-based therapies due to their multipotent differentiation and immunomodulatory capacities. In consequence of limited numbers following their isolation from the donor tissue, MSCs require extensive expansion performed in traditional 2D cell culture setups to reach adequate amounts for therapeutic use. However, prolonged culture of MSCs in vitro has been shown to decrease their differentiation potential and alter their immunomodulatory properties. For that reason, preservation of these physiological characteristics of MSCs throughout their in vitro culture is essential for improving the efficiency of therapeutic and in vitro modeling applications. With this objective in mind, many studies already investigated certain parameters for enhancing current standard MSC culture protocols with regard to the effects of specific culture media components or culture conditions. Although there is a lot of diversity in the final therapeutic uses of the cells, the primary stage of standard isolation and expansion is imperative. Therefore, we want to review on approaches for optimizing standard MSC culture protocols during this essential primary step of in vitro expansion. The reviewed studies investigate and suggest improvements focused on culture media components (amino acids, ascorbic acid, glucose level, growth factors, lipids, platelet lysate, trace elements, serum, and xenogeneic components) as well as culture conditions and processes (hypoxia, cell seeding, and dissociation during passaging), in order to preserve the MSC phenotype and functionality during the primary phase of in vitro culture.

Fabrication and characterization of thermoresponsive composite carriers: PNIPAAm-grafted glass spheres

Processing capacity and product yield of three-dimensional (3D) smart responsive carriers are markedly superior to those of two-dimensional substrates with the same compositions due to the special structure; therefore, more attempts have been made to develop the 3D intelligent systems in recent decades. A novel preparation strategy of thermoresponsive glass sphere-based composite carriers was reported in this study. First, PNIPAAm copolymers were synthesized by free-radical polymerization of N-isopropylacrylamide (NIPAAm), hydroxypropyl methacrylate (HPM), and 3-trimethoxysilypropyl methacrylate (TMSPM). Then, the copolymer solution was sprayed on the surfaces of glass spheres using a self-made bottom-spray fluidized bed reactor, and the bonding between copolymers and glass spheres was fabricated by thermal annealing to form PNIPAAm copolymer/glass sphere composite carriers. The coating effects of PNIPAAm copolymers on sphere surfaces were investigated, including characteristic functional groups, surface microstructure, grafting density, equilibrium swelling, as well as biocompatibility and potential application for cell culture. The results show that the temperature-responsive PNIPAAm copolymers can be linked to the surfaces of glass spheres by bottom-spray coating technology, and the copolymer layers can be formed on the sphere surfaces. The composite carriers have excellent thermosensitivity and favorable biocompatibility, and they are available for effective cell adhesion and spontaneous cell detachment by the use of smart responsiveness.

Dual drug delivery system based on pH-sensitive silk fibroin/alginate nanoparticles entrapped in PNIPAM hydrogel for treating severe infected burn wound

Herein, the pH-sensitive vancomycin (VANCO) loaded silk fibroin-sodium alginate nanoparticles (NPs) embedded in poly(N-isopropylacrylamide) (PNIPAM) hydrogel containing epidermal growth factor (EGF) are introduced for treating chronic burn wound infections. The hybrid system was developed to control the release rates of an antibiotic and growth factor for optimal treatment of burn infections. VANCO had a pH responsive release behavior from the nanoparticle (NP) and showed higher release rate in an alkaline pH compared to the neutral pH during 10 d. About 30% of EGF was also released from the hydrogel within 20 d. The released VANCO and EGF preserved their bioactivity more than ∼ 80%. The suitable physico-chemical properties and cellular behaviors of PNIPAM hydrogel supported the proliferation and growth of the fibroblast cells. Furthermore, the higher re-epithelialization with good wound contraction rate, neovascular formation, and expression of transforming growth factor-beta were observed in S. aureus infected rat burn wound by using the hydrogel containing VANCO and EGF compared with untreated wounds and hydrogel alone. The wound infection was also significantly reduced in the groups treated with the hydrogels containing VANCO. Overall, in vitro and in vivo results suggested that developed hybrid system would be a promising construct to treat severe wound infection.

Preparation and Characterization of Thermoresponsive Poly(N-Isopropylacrylamide) for Cell Culture Applications

Poly(N-isopropylacrylamide) (PNIPAAm) is a typical thermoresponsive polymer used widely and studied deeply in smart materials, which is attractive and valuable owing to its reversible and remote "on-off" behavior adjusted by temperature variation. PNIPAAm usually exhibits opposite solubility or wettability across lower critical solution temperature (LCST), and it is readily functionalized making it available in extensive applications. Cell culture is one of the most prospective and representative applications. Active attachment and spontaneous detachment of targeted cells are easily tunable by surface wettability changes and volume phase transitions of PNIPAAm modified substrates with respect to ambient temperature. The thermoresponsive culture platforms and matching thermal-liftoff method can effectively substitute for the traditional cell harvesting ways like enzymatic hydrolysis and mechanical scraping, and will improve the stable and high quality of recovered cells. Therefore, the establishment and detection on PNIPAAm based culture systems are of particular importance. This review covers the important developments and recommendations for future work of the preparation and characterization of temperature-responsive substrates based on PNIPAAm and analogues for cell culture applications.

Mechanical and physicochemical behavior of a 3D hydrogel scaffold during cell growth and proliferation

Some of the essential properties for cellular scaffolding are the capability to maintain the three-dimensional (3D) structure, good adhesion, and adequate elastic modulus during cell growth, migration, and proliferation. Biocompatible synthetic hydrogels are commonly used as cellular scaffolds because they can mimic the natural extracellular matrices (ECMs). However, it is possible that the physicochemical and mechanical behavior of the scaffold changes during cell proliferation and loses the scaffold properties but this is rarely monitored. In this work, the physicochemical and mechanical properties of a macroporous soft material based on poly(N-isopropyl acrylamide) (PNIPAM) have been studied during a period of 75 days at culture condition while bovine fetal fibroblasts (BFF) were grown within the matrix. The interconnected macroporous hydrogel was obtained by cryogelation at −18 °C. The swelling capacity of the scaffold was not altered during cell proliferation but changes in the mechanical properties were observed, beginning with the high elastic modulus (280 kPa) that progressively decreased until mechanical stability (40 kPa) was achieved after 20 culture days. It was observed that the matrix–cell interactions together with collagen production favor normal cellular processes such as cell morphology, adhesion, migration, and proliferation. Therefore, the observed behavior of macroporous PNIPAM as a 3D scaffold during cell growth indicates that the soft matrix is cytocompatible for a long time and preserves the suitable properties that can be applied in tissue engineering and regenerative medicine.

3D cell scaffold based on macroporous PNIPAM is cytocompatible and preserves the cell viability for more than 75 culture days.

Cytotoxicity and bioadhesive properties of poly-N-isopropylacrylamide hydrogel

Several hydrogel surfaces present properties that simulate the mechanical and physicochemical features of extracellular matrix (ECM), providing a platform that mimic the native cellular milieus. Poly-N-isopropylacrylamide (PNIPAM) hydrogels are receiving attention in biomedical field due to their thermosensibility and soft texture. However, more extensive biocompatibility and cellular interactions studies with cell lines are needed. Therefore, the aim of this study is focus on evaluating the biocompatibility of PNIPAM through cytotoxicity, genotoxicity, and proliferation tests in murine preadipose cells (3T3-L1), human embryonic kidney cells (HEK293) and human carcinoma-derived cells (A549) in presence of hydrogel surfaces. Bioadhesive capacity above PNIPAM surfaces was also analyzed. MTT and neutral red uptake assays shown non-cytotoxic effect of PNIPAM in the studied cell lines. Genotoxicity was evaluated by the single-cell gel electrophoresis assay, where DNA damages were not detected. [³H]-thymidine staining allowed to corroborate that cell proliferation had progressed correctly. Adopted morphologies for each cell line over PNIPAM were similar to cell growing observed on polystyrene, indicating that the surfaces favor the cell attachment during 5 days' culture. The good biocompatibility of PNIPAM surfaces make it an interesting scaffold with clinical potential in tissue regeneration engineering, and a possible adipose and kidney tissue-engineered construct.

Development of thermo-responsive polycaprolactone macrocarriers conjugated with Poly(N-isopropyl acrylamide) for cell culture

Poly(N-isopropyl acrylamide) (PNIPAAm) is a well-known 'smart' material responding to external stimuli such as temperature. PNIPAAm was successfully conjugated to polycaprolactone (PCL) bead surfaces through amidation reaction. Functionalization steps were characterized and confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and Energy Dispersion Spectroscopy. PNIPAAm-conjugated PCL allowed human dermal fibroblast cells (HDF) and mesenchymal stem cells (MSC) to adhere, spread, and grow successfully. By reducing the temperature to 30 °C, more than 70% of HDF were detached from PNIPAAm-conjugated PCL macrocarriers with 85% viability. The cell detachment ratio by trypsin treatment was slightly higher than that induced by reduced temperature, however, cell detachment from PNIPAAm-conjugated macrocarriers by lowering the temperature significantly reduced cell death and increased both cell viability and the recovery potential of the detached cells. HDF attachment and detachment were also observed by Live-Dead staining and phase contrast imaging. The expression of extracellular matrix proteins such as Laminin and Fibronectin was also affected by the trypsinization process but not by the reduced temperature process. Taken together, our results showed that thermo-responsive macrocarriers could be a promising alternative method for the non-invasive detachment of cells, in particular for tissue engineering, clinical applications and the use of bioreactors.

Stability of a biodegradable microcarrier surface: physically adsorbed versus chemically linked shells

Mesenchymal stem cells (MSCs) have gained increasing interest for tissue engineering and cellular therapy. MSC expansion on microcarriers (MCs) in stirred bioreactors has emerged as an attractive method for their scaled up production. Some MCs have been developed based on polyesters as a hydrophobic biodegradable core. However, most of these MCs are formulated by an emulsion/organic solvent evaporation (E/E) process using poly(vinyl alcohol) as a shell steric stabilizer, which is biocompatible but not degradable in vivo. Moreover, in most of these MCs, the polymer shell is only physically adsorbed at the particle surface. To the best of our knowledge, no study deals with the stability of such a shell when the MCs are in contact with competitive surfactants or with proteins contained in the culture medium. In this study, fully in vivo bioresorbable dextran-covered polylactide-based MCs were formulated using an E/E process, which allowed to control their surface chemistry. Different dextran derivatives with alkyne or ammonium groups were firstly synthesised. Then, on the one hand, some MCs (non-clicked MCs) were formulated with a physically adsorbed polysaccharide shell onto the core. On the other hand, the polysaccharide shell was linked to the core via in situ CuAAC click-chemistry carried out during the E/E process (clicked MCs). The stability of such coverage was first studied in the presence of competitive surfactants (sodium dodecyl sulfate-SDS, or proteins contained in the culture medium) using nanoparticles (NPs) exhibiting the same chemical composition (core/shell) as MCs. The results revealed the total desorption of the dextran shell for non-clicked NPs after treatment with SDS or the culture medium, while this shell desorption was greatly decreased for clicked NPs. A qualitative study of this shell stability was finally carried out on MCs formulated using a new fluorescent dextran-based surfactant. The results were in agreement with those observed for NPs, and showed that non-clicked MCs are characterized by poor shell stability in contact with a competitive surfactant, which could be quite an issue during MSC expansion. In contrast, clicked MCs possess better shell stability, which allow a better control of the MC surface chemistry, especially during cell culture.

Poly(N-isopropylacrylamide) modified polydopamine as a temperature-responsive surface for cultivation and harvest of mesenchymal stem cells

A thermo-responsive surface was fabricated by depositing poly(N-isopropylacrylamide) (PNIPAAm) onto polydopamine coated cell culture substrata through free radical polymerization for the purpose of culturing and harvesting human mesenchymal stem cells (hMSCs). Human MSCs were cultured onto the PNIPAAm-g-polydopamine coated surface and harvested by changing from physiological to ambient temperature. The produced PNIPAAm-g-polydopamine surface was characterized by atomic force microscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance, water contact angle measurement, differential scanning calorimetry, and cell culture studies. Our results revealed that hMSCs could be detached from the PNIPAAm-g-polydopamine surface within 60 min after switching the temperature from 37 °C to room temperature. The detached hMSCs were able to proliferate on the PNIPAAm-g-polydopamine coated surface for further growth and harvest.

Near infrared dye-labelled polymeric micro- and nanomaterials: in vivo imaging and evaluation of their local persistence

The use of micro- and nanomaterials as carriers of therapeutic molecules can enhance the efficiency of treatments while avoiding side effects thanks to the development of controlled drug delivery systems. The binding of a dye to a drug or to a drug carrier has opened up a wide range of possibilities for an effective in vivo optical tracing of drug biodistribution by using non-invasive real-time technologies prior to their potential use as therapeutic vectors. Here, we describe the fluorescent tagging of polymeric micro- and nanomaterials based on poly(lactic-co-glycolic) acid and on the thermoresponsive poly(N-isopropylacrylamide) with the fluorescent probe IR-820 which was chemically modified for its covalent coupling to the materials. The chemical modification of the dye and the polymers yielded micro- and nanoparticulated labelled materials to be potentially used as drug depots of different therapeutic molecules. In vitro biological studies revealed their reduced cytotoxicity. A spatiotemporal in vivo micro- and nanoparticle tracking allowed the evaluation of the biodistribution of materials showing their local persistence and high biocompatibility after pathological studies. These results underline the suitability of these materials for the local, sustained, not harmful and/or on-demand drug delivery and the remarkable importance of evaluating the biodistribution of materials and tissue persistence for their use as local drug depots.

Physicochemical properties of ionic and non-ionic biocompatible hydrogels in water and cell culture conditions: Relation with type of morphologies of bovine fetal fibroblasts in contact with the surfaces

Cationic, anionic and non-ionic hydrogels having acrylamide polymer backbones were synthesized via free radical polymerization with N,N-methylenebisacrylamide (BIS) as crosslinker. The chemical structures of the hydrogels were characterized by Fourier Transform Infrared Spectroscopy (FTIR). Physicochemical properties such as swelling kinetic, maximum swelling capacity, volume phase transition temperature (VPTT) and wettability (static water contact angle) of hydrogels swollen in aqueous and cell culture medium, at room and cell culture temperatures were studied. In order to correlate the surface properties of the hydrogels and cellular adhesivity of bovine fetal fibroblasts (BFFs), cellular behaviour was analyzed by inverted fluorescence optical microscopy and atomic force microscopy (AFM). MTT assay demonstrated that the number of viable cells in contact with hydrogels does not significantly change in comparison to a control surface. Flattened and spindle-shaped cells and cell spheroids were the adopted morphologies during first days of culture on different hydrogels. Cell spheroids were easily obtained during the first 5days of culture in contact with PNIPAM-co-20%HMA (poly (N-isopropylacrylamide-co-20%N-acryloyl-tris-(hydroxymethyl)aminomethane)) hydrogel surface. After 15days of culture all hydrogels showed high adhesion and visual proliferation. According to obtained results, non-ionic and hydrophilic surfaces with moderated wettability induce the formation of BFFs cell spheroids. These hydrogel surfaces could be used in clinical and biochemical treatments at laboratory level to cell growth and will allow generating the base for future biotechnologic platform.

Selective Photomechanical Detachment and Retrieval of Divided Sister Cells from Enclosed Microfluidics for Downstream Analyses

Considerable evidence suggests that self-renewal and differentiation of cancer stem-like cells, a key cell population in tumorgenesis, can determine the outcome of disease. Though the development of microfluidics has enhanced the study of cellular lineage, it remains challenging to retrieve sister cells separately inside enclosed microfluidics for further analyses. In this work, we developed a photomechanical method to selectively detach and reliably retrieve target cells from enclosed microfluidic chambers. Cells cultured on carbon nanotube-polydimethylsiloxane composite surfaces can be detached using shear force induced through irradiation of a nanosecond-pulsed laser. This retrieval process has been verified to preserve cell viability, membrane proteins, and mRNA expression levels. Using the presented method, we have successfully performed 96-plex single-cell transcriptome analysis on sister cells in order to identify the genes altered during self-renewal and differentiation, demonstrating phenomenal resolution in the study of cellular lineage.

Single-Cell Isolation of Circulating Tumor Cells from Whole Blood by Lateral Magnetophoretic Microseparation and Microfluidic Dispensing

This paper introduces a single-cell isolation technology for circulating tumor cells (CTCs) using a microfluidic device (the "SIM-Chip"). The SIM-Chip comprises a lateral magnetophoretic microseparator and a microdispenser as a two-step cascade platform. First, CTCs were enriched from whole blood by the lateral magnetophoretic microseparator based on immunomagnetic nanobeads. Next, the enriched CTCs were electrically identified by single-cell impedance cytometer and isolated as single cells using the microshooter. Using 200 μL of whole blood spiked with 50 MCF7 breast cancer cells, the analysis demonstrated that the single-cell isolation efficiency of the SIM-Chip was 82.4%, and the purity of the isolated MCF7 cells with respect to WBCs was 92.45%. The data also showed that the WBC depletion rate of the SIM-Chip was 2.5 × 10(5) (5.4-log). The recovery rates were around 99.78% for spiked MCF7 cells ranging in number from 10 to 90. The isolated single MCF7 cells were intact and could be used for subsequent downstream genetic assays, such as RT-PCR. Single-cell culture evaluation of the proliferation of MCF7 cells isolated by the SIM-Chip showed that 84.1% of cells at least doubled in 5 days. Consequently, the SIM-Chip could be used for single-cell isolation of rare target cells from whole blood with high purity and recovery without cell damage.

Preservation of osteoblasts and BM-MSCs biological properties after consecutive passages with the thermal-liftoff method

Thermo-responsive surfaces based on PNIPAAm provide a novel way to harvest cells with temperature reduction.

The likely role of proteolytic enzymes in unwanted differentiation of stem cells in culture

Tissue engineering aims at developing the necessary technological strategies for replacement or regeneration tissues. However, the number of cells required is much greater than the number obtained from a cell source. Expanding the cells' number in cell culture for a long period is required until the necessary amount of cells is obtained. While in culture, cells often go unwanted differentiation. Little attention has been given to the use of proteolytic enzymes in cell passage. Review the importance of extracellular matrix and surface proteins for cell behavior and the possible mechanisms of cellular changes that may occur due to the use of proteolytic enzymes is an essential issue. Possible alternative to replace these enzymes in cell passage has also been developed.

Nanothin Coculture Membranes with Tunable Pore Architecture and Thermoresponsive Functionality for Transfer-Printable Stem Cell-Derived Cardiac Sheets

Coculturing stem cells with the desired cell type is an effective method to promote the differentiation of stem cells. The features of the membrane used for coculturing are crucial to achieving the best outcome. Not only should the membrane act as a physical barrier that prevents the mixing of the cocultured cell populations, but it should also allow effective interactions between the cells. Unfortunately, conventional membranes used for coculture do not sufficiently meet these requirements. In addition, cell harvesting using proteolytic enzymes following coculture impairs cell viability and the extracellular matrix (ECM) produced by the cultured cells. To overcome these limitations, we developed nanothin and highly porous (NTHP) membranes, which are ∼20-fold thinner and ∼25-fold more porous than the conventional coculture membranes. The tunable pore size of NTHP membranes at the nanoscale level was found crucial for the formation of direct gap junctions-mediated contacts between the cocultured cells. Differentiation of the cocultured stem cells was dramatically enhanced with the pore size-customized NTHP membrane system compared to conventional coculture methods. This was likely due to effective physical contacts between the cocultured cells and the fast diffusion of bioactive molecules across the membrane. Also, the thermoresponsive functionality of the NTHP membranes enabled the efficient generation of homogeneous, ECM-preserved, highly viable, and transfer-printable sheets of cardiomyogenically differentiated cells. The coculture platform developed in this study would be effective for producing various types of therapeutic multilayered cell sheets that can be differentiated from stem cells.

Thermo-responsive poly(N-isopropylacrylamide)-grafted hollow fiber membranes for osteoblasts culture and non-invasive harvest

Hollow fiber membrane (HFM) culture system is one of the most important bioreactors for the large-scale culture and expansion of therapeutic cells. However, enzymatic and mechanical treatments are traditionally applied to harvest the expanded cells from HFMs, which inevitably causes harm to the cells. In this study, thermo-responsive cellulose acetate HFMs for cell culture and non-invasive harvest were prepared for the first time via free radical polymerization in the presence of cerium (IV). ATR-FTIR and elemental analysis results indicated that the poly(N-isopropylacrylamide) (PNIPAAm) was covalently grafted on HFMs successfully. Dynamic contact angle measurements at different temperatures revealed that the magnitude of volume phase transition was decreased with increasing grafted amount of PNIPAAm. And the amount of serum protein adsorbed on HFMs surface also displayed the same pattern. Meanwhile osteoblasts adhered and spread well on the surface of PNIPAAm-grafted HFMs at 37 °C. And Calcein-AM/PI staining, AB assay, ALP activity and OCN protein expression level all showed that PNIPAAm-grafted HFMs had good cell compatibility. After incubation at 20 °C for 120 min, the adhering cells on PNIPAAm-grafted HFMs turned to be round and detached after being gently pipetted. These results suggest that thermo-responsive HFMs are attractive cell culture substrates which enable cell culture, expansion and the recovery without proteolytic enzyme treatment for the application in tissue engineering and regenerative medicine.

cGMP-compliant transportation conditions for a prompt therapeutic use of marrow mesenchymal stromal/stem cells

We recently described conditions for safe 18-h manufacturer-to-patient transportation of freshly harvested hBM-MSC expanded under cGMP protocols using human platelet lysate (hPL), that allowed prompt use as an advanced therapeutic medicinal product. Here we outline important considerations when comparing different transportation conditions, highlighting that although cell transportation may involve a reduction in viability, this did not undermine the ultimate bone-forming regenerative potential of the cGMP-hBM-MSC population.

Thermoresponsive substrates used for the expansion of human mesenchymal stem cells and the preservation of immunophenotype

The facile regeneration of undifferentiated human mesenchymal stem cells (hMSCs) from thermoresponsive surfaces facilitates the collection of stem cells avoiding the use of animal derived cell detachment agents commonly used in cell culture. This communication proposes a procedure to fabricate coatings from commercially available pNIPAm which is both affordable and a significant simplification on alternative approaches used elsewhere. Solvent casting was used to produce films in the micrometer range and successful cell adhesion and proliferation was highly dependent on the thickness of the coating produced with 1 μm thick coatings supporting cells to confluence. 3T3 cell sheets and hMSCs were successfully detached from the cast coatings upon temperature reduction. Furthermore, results indicate that the hMSCs remained undifferentiated as the surface receptor profile of hMSCs was not altered when cells were detached in this manner.

Generation of tissue constructs for cardiovascular regenerative medicine: from cell procurement to scaffold design

The ability of the human body to naturally recover from coronary heart disease is limited because cardiac cells are terminally differentiated, have low proliferation rates, and low turn-over rates. Cardiovascular tissue engineering offers the potential for production of cardiac tissue ex vivo, but is currently limited by several challenges: (i) Tissue engineering constructs require pure populations of seed cells, (ii) Fabrication of 3-D geometrical structures with features of the same length scales that exist in native tissue is non-trivial, and (iii) Cells require stimulation from the appropriate biological, electrical and mechanical factors. In this review, we summarize the current state of microfluidic techniques for enrichment of subpopulations of cells required for cardiovascular tissue engineering, which offer unique advantages over traditional plating and FACS/MACS-based enrichment. We then summarize modern techniques for producing tissue engineering scaffolds that mimic native cardiac tissue.