Comparing physicochemical properties of printed and hand cast biocements designed for ligament replacement

In order to combat the low regenerative capabilities of ligaments, full `bone to bone' replacements are required, which will integrate with bone while providing a smooth transition to the replacement soft tissue (tissues surrounding organs in the body, not being bone). This study investigated the use of three-dimensional powder printing technology to form calcium phosphate brackets, previously used for forming bespoke scaffold geometries, to 95±0·1% accuracy of their original computer aided design. The surface and internal structures of the printed samples were characterised both chemically and morphologically and compared with hand moulded cements in the dry state and after 3 days of immersion in phosphate buffered saline. X-ray diffraction, Raman spectroscopy and SEM all showed the presence of brushite in the hand moulded samples and brushite and monetite within the printed samples. Furthermore, the printed structures have a higher level of porosity in the dry state in comparison to the hand moulded samples (36±2·2% compared to 24±0·7%) despite exhibiting a compressive strength of almost double the hand cast material. Although the compressive strength of the printed cements decreases after the 3 day immersion, there was no significant difference between the printed and hand moulded cements under the same conditions. Three-dimensional powder printing technology has enabled the manufacture of bespoke calcium phosphate brackets with properties similar to those reported for hand moulded cements

Silsesquioxane polymer as a potential scaffold for laryngeal reconstruction

Cancer, disease and trauma to the larynx and their treatment can lead to permanent loss of structures critical to voice, breathing and swallowing. Engineered partial or total laryngeal replacements would need to match the ambitious specifications of replicating functionality, outer biocompatibility, and permissiveness for an inner mucosal lining. Here we present porous polyhedral oligomeric silsesquioxane-poly(carbonate urea) urethane (POSS-PCUU) as a potential scaffold for engineering laryngeal tissue. Specifically, we employ a precipitation and porogen leaching technique for manufacturing the polymer. The polymer is chemically consistent across all sample types and produces a foam-like scaffold with two distinct topographies and an internal structure composed of nano- and micro-pores. While the highly porous internal structure of the scaffold contributes to the complex tensile behaviour of the polymer, the surface of the scaffold remains largely non-porous. The low number of pores minimise access for cells, although primary fibroblasts and epithelial cells do attach and proliferate on the polymer surface. Our data show that with a change in manufacturing protocol to produce porous polymer surfaces, POSS-PCUU may be a potential candidate for overcoming some of the limitations associated with laryngeal reconstruction and regeneration

Functionalized α-Helical Peptide Hydrogels for Neural Tissue Engineering.

This is the final version of the article. Available from the American Chemical Society via the DOI in this record.Trauma to the central and peripheral nervous systems often lead to serious morbidity. Current surgical methods for repairing or replacing such damage have limitations. Tissue engineering offers a potential alternative. Here we show that functionalized α-helical-peptide hydrogels can be used to induce attachment, migration, proliferation and differentiation of murine embryonic neural stem cells (NSCs). Specifically, compared with undecorated gels, those functionalized with Arg-Gly-Asp-Ser (RGDS) peptides increase the proliferative activity of NSCs; promote their directional migration; induce differentiation, with increased expression of microtubule-associated protein-2, and a low expression of glial fibrillary acidic protein; and lead to the formation of larger neurospheres. Electrophysiological measurements from NSCs grown in RGDS-decorated gels indicate developmental progress toward mature neuron-like behavior. Our data indicate that these functional peptide hydrogels may go some way toward overcoming the limitations of current approaches to nerve-tissue repair.This work was supported by the Biotechnology and Biological Sciences Research Council (H01716X, D.N.W. and M.A.B.); the European Research Council (StG243261, BS; and ADG340764, D.N.W.); the Royal Society (UF051616, B.S.); the Medical Research Council (G1100623, A.D.R.); and the Engineering and Physical Sciences Research Council (Bristol Chemical Synthesis Centre for Doctoral Training, EP/G036764/1, K.L.H.). D.N.W. holds a Royal Society Wolfson Research Merit Award

Host macrophage response to injectable hydrogels derived from ECM and α-helical peptides

Tissue engineering materials play a key role in how closely the complex architectural and functional characteristics of native healthy tissue can be replicated. Traditional natural and synthetic materials are superseded by bespoke materials that cross the boundary between these two categories. Here we present hydrogels that are derived from decellularised extracellular matrix and those that are synthesised from de novo α-helical peptides. We assess in vitro activation of murine macrophages to our hydrogels and whether these gels induce an M1-like or M2-like phenotype. This was followed by the in vivo immune macrophage response to hydrogels injected into rat partial-thickness abdominal wall defects. Over 28 days we observe an increase in mononuclear cell infiltration at the hydrogel-tissue interface without promoting a foreign body reaction and see no evidence of hydrogel encapsulation or formation of multinucleate giant cells. We also note an upregulation of myogenic differentiation markers and the expression of anti-inflammatory markers Arginase1, IL-10, and CD206, indicating pro-remodelling for all injected hydrogels. Furthermore, all hydrogels promote an anti-inflammatory environment after an initial spike in the pro-inflammatory phenotype. No difference between the injected site and the healthy tissue is seen after 28 days, indicating full integration. These materials offer great potential for future applications in regenerative medicine and towards unmet clinical needs

Effect of plasma surface modification on the biocompatibility of UHMWPE

In this paper active screen plasma nitriding (ASPN) is used to chemically modify the surface of UHMWPE. This is an unexplored and new area of research. ASPN allows the homogeneous treatment of any shape or surface at low temperature; therefore, it was thought that ASPN would be an effective technique to modify organic polymer surfaces. ASPN experiments were carried out at 120 °C using a dc plasma nitriding unit with a 25% N2 and 75% H2 atmosphere at 2.5 mbar of pressure. UHMWPE samples treated for different time periods were characterized by nanoindentation, FTIR, XPS, interferometry and SEM. A 3T3 fibroblast cell line was used for in vitro cell culture experiments. Nanoindentation of UHMWPE showed that hardness and elastic modulus increased with ASPN treatment compared to the untreated material. FTIR spectra did not show significant differences between the untreated and treated samples; however, some changes were observed at 30 min of treatment in the range of 1500–1700 cm−1 associated mainly with the presence of N−H groups. XPS studies showed that nitrogen was present on the surface and its amount increased with treatment time. Interferometry showed that no significant changes were observed on the surfaces after the treatment. Finally, cell culture experiments and SEM showed that fibroblasts attached and proliferated to a greater extent on the plasma-treated surfaces leading to the conclusion that ASPN surface treatment can potentially significantly improve the biocompatibility behaviour of polymeric materials

Hadronic B decays: Supersymmetric enhancement and a simple spectator model

Two aspects of hadronic B decays are investigated. Firstly, the supersymmetric enhancement of hadronic b decays by gluino penguin processes is studied through their effect on the Wilson coefficients of the effective Hamiltonian. Secondly, hadronization of the final state quarks is studied through a simple phase space spectator model.Comment: 24 pages, REVTEX, minor additional text and some references adde

Seaweed polysaccharide-based hydrogels used for the regeneration of articular cartilage

This manuscript provides an overview of the in vitro and in vivo studies reported in the literature focusing on seaweed polysaccharides based hydrogels that have been proposed for applications in regenerative medicine, particularly, in the field of cartilage tissue engineering. For a better understanding of the main requisites for these specific applications, the main aspects of the native cartilage structure, as well as recognized diseases that affect this tissue are briefly described. Current available treatments are also presented to emphasize the need for alternative techniques. The following part of this review is centered on the description of the general characteristics of algae polysaccharides, as well as relevant properties required for designing hydrogels for cartilage tissue engineering purposes. An in-depth overview of the most well known seaweed polysaccharide, namely agarose, alginate, carrageenan and ulvan biopolymeric gels, that have been proposed for engineering cartilage is also provided. Finally, this review describes and summarizes the translational aspect for the clinical application of alternative systems emphasizing the importance of cryopreservation and the commercial products currently available for cartilage treatment.Authors report no declarations of interest. Authors thank the Portuguese Foundation for Science and Technology (FCT) for the PhD fellowship of Elena G. Popa (SFRH/BD/64070/2009) and research project (MIT/ECE/0047/2009). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no REGPOT-CT2012-316331-POLARIS

Assessing Cellular Response to Functionalized alpha-Helical Peptide Hydrogels

No abstract available

α-Helical Peptides on Plasma-Treated Polymers Promote Ciliation of Airway Epithelial Cells

Airway respiratory epithelium forms a physical barrier through intercellular tight junctions, which prevents debris from passing through to the internal environment while ciliated epithelial cells expel particulate-trapping mucus up the airway. Polymeric solutions to loss of airway structure and integrity have been unable to fully restore functional epithelium. We hypothesized that plasma treatment of polymers would permit adsorption of α-helical peptides and that this would promote functional differentiation of airway epithelial cells. Five candidate plasma compositions are compared; Air, N2, H2, H2:N2 and Air:N2. X-ray photoelectron spectroscopy shows changes in at% N and C 1s peaks after plasma treatment while electron microscopy indicates successful adsorption of hydrogelating self-assembling fibres (hSAF) on all samples. Subsequently, adsorbed hSAFs support human nasal epithelial cell attachment and proliferation and induce differentiation at an air-liquid interface. Transepithelial measurements show that the cells form tight junctions and produce cilia beating at the normal expected frequency of 10-11 Hz after 28 days in culture. The synthetic peptide system described in this study offers potential superiority as an epithelial regeneration substrate over present “gold-standard” materials, such as collagen, as they are controllable and can be chemically functionalised to support a variety of in vivo environments. Using the hSAF peptides described here in combination with plasma-treated polymeric surfaces could offer a way of improving the functionality and integration of implantable polymers for aerodigestive tract reconstruction and regeneration