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With the emergence of microscale biotechnology, such as biomicroelectromechanical systems ("Bio-MEMS") and microfluidic-based microchips for sensing and diagnostics, polydimethylsiloxane (PDMS)-based elastomers have become very popular materials. [1] PDMS elastomers possess several features that are well suited for these applications: mechanical stability and elasticity, chemical inertness, optical transparency, gas permeability, ease of fabrication, and biocompatibility. [1d, 2] However, the extremely hydrophobic nature of PDMS often limits its applicability (e.g. poor aqueous fluid flow and nonspecific adhesion of biomolecules). [2] Various methods have been proposed to modify the PDMS surface to impart hydrophilicity, for example, UV or plasma treatment to oxidize the surface [3] and coating the surface with hydrophilic polymers. [4] However, the treated PDMS surfaces often recover their hydrophobic traits due to the migration of unreacted PDMS oligomers to the surface and the rearrangement of PDMS polymer chains. [2b, 5] We suggest that coating PDMS with hydrophilic materials would be more effective than the molecular level modifications. Hydrogels, which are networks of cross-linked polymers taking up large amounts of water, are therefore considered promising materials. Hydrogels can also be designed to present functionalities for specific purposes, such as in vitro cell culture, cell encapsulation, and molecular capture and release. [6] Therefore, PDMS coated with hydrogels with desired properties would significantly enhance the performance of PDMS-based devices. However, it is a significant challenge to attain and sustain the adhesion between hydrogel and PDMS, due to the stark discrepancy between the bulk properties of PDMS substrates and hydrogels.To meet this challenge, we describe a unique approach to tailor hydrogel adhesion to a PDMS substrate. Alginate, a naturally derived polysaccharide, was covalently linked to the PDMS surface. This attached alginate acted as a "glue" to allow the strong, permanent adhesion of the hydrogel onto the PDMS surface by 1) imparting hydrophilicity to improve compatibility with hydrogels, and 2) providing functional groups for the stable conjugation of hydrogels. The resulting hydrogel-coated PDMS substrate was used in the following two applications: 1) it served as an in vitro cell culture platform to study cellular behavior in response to cyclic mechanical strain, and 2) it was used in a microfluidic device with hydrogel-filled channels.The PDMS surface was chemically grafted with alginate following a series of modification steps: [7] step 1: oxidation to present hydroxy groups (OH-PDMS, Figure 1 a); step 2: silanization using 3-aminopropyltriethoxysilane to present primary amino groups (NH 2 -PDMS); and step 3: conjugation of alginate by carbodiimide-mediated amide coupling between amino groups on the PDMS surface and carboxylic acid groups of alginate (alginate-PDMS). The successive modifications of PDMS were confirmed with FTIR spectroscopy ( Figure S1 and Table...

An integrated multimodal optical microscope is demonstrated for high-resolution, structural and functional imaging of engineered and natural skin. This microscope incorporates multiple imaging modalities including optical coherence (OCM), multi-photon (MPM), and fluorescence lifetime imaging microscopy (FLIM), enabling simultaneous visualization of multiple contrast sources and mechanisms from cells and tissues. Spatially co-registered OCM/MPM/FLIM images of multi-layered skin tissues are obtained, which are formed based on complementary information provided by different modalities, i.e., scattering information from OCM, molecular information from MPM, and functional cellular metabolism states from FLIM. Cellular structures in both the dermis and epidermis, especially different morphological and physiological states of keratinocytes from different epidermal layers, are revealed by mutually-validating images. In vivo imaging of human skin is also investigated, which demonstrates the potential of multimodal microscopy for in vivo investigation during engineered skin engraftment. This integrated imaging technique and microscope show the potential for investigating cellular dynamics in developing engineered skin and following in vivo grafting, which will help refine the control and culturing conditions necessary to obtain more robust and physiologically-relevant engineered skin substitutes. Multimodal microscopy images of a microporous 3D hydrogel scaffold seeded with 3T3 fibroblasts. Representative spatially co-registered images were generated based on different methodologies including optical coherence (OCM), multiphoton (MPM), and fluorescence lifetime imaging (FLIM) microscopy.

Hydrogel trifft Silicon: Die chemische Funktionalisierung einer Polydimethylsiloxan(PDMS)‐Oberfläche mit einem „klebenden“ Polysaccharid induziert eine starke dauerhafte Adhäsion zwischen dem Hydrogel und PDMS. Das hydrogelbeschichtete Siliconsubstrat war von Nutzen für die kontrollierte Organisation von Zellen unter mechanischer Streckung (siehe Bild) und zum Aufbau gelgefüllter Mikrofluidikeinheiten.

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Composite materials based on the coupling of conductive organic polymers and carbon nanotubes have shown that they possess properties of the individual components with a synergistic effect. Multi-wall carbon nanotube (MWCNT)/ polymer composites are hybrid materials that combine numerous mechanical, electrical and chemical properties and thus, constitute ideal biomaterials for a wide range of regenerative medicine applications. Although, complete dispersion of CNT in a polymer matrix has rarely been achieved, in this study we have succeeded high dispersibility of CNT in POSS-PCU and POSS-PCL, novel polymers based on polyprolactone and polycarbonate polyurethane (PCU) and poly(caprolactoneurea)urethane both having incorporated polyhedral oligomeric silsesquioxane (POSS). We report the synthesis and characterization of a novel biomaterial that possesses unique properties of being electrically conducting and thus being capable of electronic interfacing with tissue. To this end, POSS-PCU/MWCNT composite can be used as a biomaterial for the development of nerve guidance channels to promote nerve regeneration and POSS-PCL/MWCNT as a substrate to increase electronic interfacing between neurons and micro-machined electrodes for potential applications in neural probes, prosthetic devices and brain implants.

Multi-wall carbon nanotube (MWCNT)/polymer composites are hybrid materials that combine numerous mechanical, electrical and chemical properties and thus, constitute ideal biomaterials for a wide range of regenerative medicine applications. Although, complete dispersion of MWCNT in a polymer matrix has rarely been achieved, in this study we have studied the dispersibility of MWCNT in POSS-PCU, a novel polymer based on polyprolactone and polycarbonate polyurethane (PCU) with an incorporated polyhedral oligomeric silsesquioxane (POSS). Furthermore, we developed a computational model that can visualise MWCNTs in order to predict the range of dispersibility and provide a 3-D mathematical model that can predict the chemical concentration for ideal nanocomposites.

Introduction Human hematopoietic stem cell transplantation (HSCT) has been used to treat a range of hematological and immunological disorders. As a result, the demand for hematopoietic stem cells (HSC) in clinical applications is increasing. Amniotic fluid stem cells (AFSC) serve as a potential alternative cell source for therapy. Amniotic fluid can be derived by amniocentesis or therapeutic amniodrainage. AFSC are multi-potent, have low risk of tumorigenicity, can be expanded and do not have legal or ethical limitations. The significant hematopoietic activity of murine AFSC led us to explore the potential of human AFSC (CD117/c-Kit+) towards hematopoietic differentiation and to reconstitution in vivo. Methods Human AFSC (2nd and 3rd trimester) and cord blood HSC (CB-HSC; control) were selected for CD117 and CD34 respectively using a MoFlo XDP sorter. Sorted cells (104 in 200μl PBS) were injected intravenously into sub-lethally irradiated NOD-SCID/IL2rγnull (NSG) mice (n=6/group). Hematopoietic engraftment of human cells (% of human CD45+ within total CD45+) and multi-lineage reconstitution (myeloid: CD13, CD14, CD15 and lymphoid: CD3, CD4 and CD8) were assessed at 16 weeks in blood, bone marrow (BM) and spleen by flow cytometry. For subsequent secondary transplants, BM mononuclear cells (MNC) derived from BM harvested from primary recipients of mice were intravenously injected into secondary recipients (1.5x107 MNC in 200μl PBS). Hematopoietic engraftment was assessed at 16 weeks post-transplantation (n=6/group). For further analysis of human donor cell engraftment, Q-PCR was performed on spleen samples harvested from primary and secondary recipients using oligonucleotide primers specific for human ALU repeat sequences; Immunohistochemistry was carried out using anti-human CD45 antibody and detected with a commercially available kit (Dako EnVision Plus, Dako). Results are expressed as mean±SEM, and statistical analysis was performed using 1-way ANOVA with Bonferroni post-hoc tests. Results Human AFSC engrafted the hematopoietic system of NSG mice at levels similar to the ones achieved with CB-HSC (blood: AFSC 7.5±1.3% vs. CB-HSC 6.1±2.2%, p=0.6; BM: AFSC 46.3±7.9% vs. CB-HSC 38.3±8.2%, p=0.6; spleen: AFSC 39.6±9.3% vs. CB-HSC 34.7±10.5%, p=0.7). Similarly, at 16 weeks following secondary transplantation, human donor cell engraftment was comparable between groups in blood (AFSC 11.5 ± 3.9% vs. CB-HSC 16.9 ± 3.9%, p=0.3) and other hematopoietic tissues. Q-PCR and immunohistochemistry confirmed donor cell engraftment in AFSC and CB-HSC groups. Importantly, there were no differences between groups in multi-lineage differentiation at 16 weeks post primary and secondary transplantation. Conclusion Human CD117/c-Kit+ AFSC have functional, multi-lineage hematopoietic potential that is similar to the current "gold-standard" stem cell source for hematopoietic transplantation. The ease of isolation during early gestation, as well as their gene-engineering and expansion potential make human AFSC a novel autologous fetal cell source for pre- and post-natal therapy of inherited hematological disorders. Disclosures No relevant conflicts of interest to declare.