Decellularized cartilage as a chondroinductive material for cartilage tissue engineering

Cartilage defects, whether caused by osteoarthritis, joint trauma, or other disease, have provoked a wide variety of tissue engineering scaffold strategies in recent years. Traditionally, cartilage tissue engineering scaffolds have utilized synthetic polymer components to form hydrogels or other porous matrices. However, components found within the extracellular matrix (ECM) such as collagen, glycosaminoglycans (GAGs), and ECM-based matrices have emerged as an essential subset of biomaterials for tissue engineering scaffolds. The objective of this research was to develop and evaluate decellularized cartilage (DCC) as a chondroinductive material for cartilage tissue engineering applications. This work was successful in developing a decellularization method for hyaline cartilage fragments that removed 99% of cells, while retaining 87% of GAGs and also in determining a method to produce a homogenous nanopowder of DCC. Additionally, this research was the first to examine the ability of DCC to induce chondrogenesis in stem cells by quantifying gene expression of chondrogenic markers. The results demonstrate for the first time that DCC can indeed upregulate chondrogenic markers and may be a new chondroinductive material that can provide microenvironmental cues and signaling to promote stem cell differentiation in cartilage regeneration

Tuning mechanical performance of poly(ethylene glycol) and agarose interpenetrating network hydrogels for cartilage tissue engineering

Hydrogels are attractive for tissue engineering applications due to their incredible versatility, but they can be limited in cartilage tissue engineering applications due to inadequate mechanical performance. In an effort to address this limitation, our team previously reported the drastic improvement in the mechanical performance of interpenetrating networks (IPNs) of poly(ethylene glycol) diacrylate (PEG-DA) and agarose relative to pure PEG-DA and agarose networks. The goal of the current study was specifically to determine the relative importance of PEG-DA concentration, agarose concentration, and PEG-DA molecular weight in controlling mechanical performance, swelling characteristics, and network parameters. IPNs consistently had compressive and shear moduli greater than the additive sum of either single network when compared to pure PEG-DA gels with a similar PEG-DA content. IPNs withstood a maximum stress of up to 4.0 MPa in unconfined compression, with increased PEG-DA molecular weight being the greatest contributing factor to improved failure properties. However, aside from failure properties, PEG-DA concentration was the most influential factor for the large majority of properties. Increasing the agarose and PEG-DA concentrations as well as the PEG-DA molecular weight of agarose/PEG-DA IPNs and pure PEG-DA gels improved moduli and maximum stresses by as much as an order of magnitude or greater compared to pure PEG-DA gels in our previous studies. Although the viability of encapsulated chondrocytes was not significantly affected by IPN formulation, glycosaminoglycan (GAG) content was significantly influenced, with a 12-fold increase over a three-week period in gels with a lower PEG-DA concentration. These results suggest that mechanical performance of IPNs may be tuned with partial but not complete independence from biological performance of encapsulated cells

The effects of polydispersity and metastability on crystal growth kinetics

We investigate the effect of metastable gas-liquid (G-L) separation on crystal growth in a system of either monodisperse or slightly size-polydisperse square well particles, using a simulation setup that allows us to focus on the growth of a single crystal. Our system parameters are such that, inside the metastable G-L binodal, a macroscopic layer of the gas phase "coats" the crystal as it grows, consistent with experiment and theoretical free energy considerations. Crucially, the effect of this metastable G-L separation on the crystal growth rate depends qualitatively on whether the system is polydisperse. We measure reduced polydispersity and qualitatively different local size ordering in the crystal relative to the fluid, proposing that the required fractionation is dynamically facilitated by the gas layer. Our results show that polydispersity and metastability, both ubiquitous in soft matter, must be considered in tandem if their dynamical effects are to be understood.Comment: Published in Soft Matter. DOI: 10.1039/C3SM27627

Femtosecond fluorescence up-conversion spectroscopy of a rotation-restricted azobenzene after excitation to the S1 state

Femtosecond time-resolved fluorescence up-conversion spectroscopy has been used in a study of the photo- induced isomerization reactions of a rotation-restricted trans-azobenzene (trans-AB) derivative capped by a crown ether (1), a chemically similar open derivative (2), and unsubstituted trans-AB (3) after excitation to the S 1 (np*) state at l ¼ 475 nm in dioxane solution. The observed biexponential temporal fluorescence profiles for 1 and 2 were almost indistinguishable within experimental error. The fitted fast fluorescence decay times (2s) for the two compounds were t 1 (1) ¼ (0.79 0.20) and t 1 (2) ¼ (1.05 0.20) ps, compared to t 1 (3) ¼ (0.37 0.06) ps. The second decay components could be described with t 2 (1) ¼ (20.3 9.5) resp. t 2 (2) ¼ (19.0 6.0) ps, vs. t 2 (3) ¼ (3.26 0.85) ps. The very similar lifetimes strongly suggest that trans–cis isomerization of 1 and 2 after S 1 excitation is governed by the same mechanism. Since 1 cannot isomerize by a simple large-amplitude rotation of one of the phenyl rings about the central NN bond, the isomerization dynamics of both ABs should be better described as ‘‘inversion’’ at the N atom(s) rather than large-amplitude ‘‘rotation’’

Intermolecular vibrational energy redistribution in DCO (X^2A'): Classical-Quantum correspondence, dynamical assignments of highly excited states, and phase space transport

Intermolecular dynamics of highly excited DCO (X^2A') is studied from a classical-quantum perspective using the effective spectroscopic Hamiltonian proposed recently by Trollch and Temps (Z. Phy. Chem. 215, 207 (2001)). This work focuses on the polyads P = 3 and P = 4 corresponding to excitation energies E_v ~ 5100 cm^-1 and 7000 cm^-1 respectively. The majority of states belonging to these polyads are dynamically assigned, despite extensive stochasticity in the classical phase space, using the recently proposed technique of level velocities. A wavelet based time-frequency analysis is used to reveal the nature of phase space transport and the relevant dynamical bottlenecks. The local frequency analysis clearly illustrates the existence of mode-specific IVR dynamics i.e., differing nature of the IVR dynamics ensuing from CO stretch and the DCO bend bright states. In addition the role of the weak Fermi resonance involving the CO stretch and DCO bend modes is investigated. A key feature of the present work is that the techniques utilized for the analysis i.e., parametric variations and local frequency analysis are not limited by the dimensionality of the system. This study, thus, explores the potential for understanding IVR in large molecules from both time domain and frequency domain perspectives.Comment: 15 pages, 8 low resolution figures (including 2 color figures). submitted to PCC

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

Telling Stories

This thesis project is composed as a hypertext-based Website in which the pages are nonfiction stories about family. In large part, the text itself adheres to the literary tradition of family memoir, exploring themes of dysfunction, communication, and family history. However, this project deviates substantially from traditional memoir in terms of form. The hypertext space within which the stories exist allows for building of individualized narratives by the user through semantic linking. Through this hypertext space, I provide the possibility for representing my family through various lenses and media

Ultrafast Z -> E photoisomerisation of structurally modified furylfulgides

Renth F, Siewertsen R, Strübe F, Mattay J, Temps F. Ultrafast Z -> E photoisomerisation of structurally modified furylfulgides. Physical Chemistry Chemical Physics. 2014;16(36):19556-19563.Femtosecond broadband transient absorption spectroscopy has been used in a comparative study of the ultrafast photo-induced Z -> E isomerisation reactions of four photochromic furylfulgides with selected structural motifs in n-hexane as solvent. The results show that all studied Z-fulgides exhibit fast and direct processes along barrierless excited-state pathways involving a conical intersection (CI) between the S-1 and S-0 electronic states. The excited-state lifetimes range from tau(1) = 0.18 ps for the methyl derivative to tau(1) = 0.32 ps for the benzofurylfulgide. The impulsive rise of the absorption by vibrationally hot Z- and E-isomers back in the electronic ground state following electronic deactivation and isomerisation indicates that the initially prepared wave packet persists even after passage of the CI. Furthermore, the results provide qualitative evidence for a quickly dephasing vibrational coherence in the electronic ground state. In contrast to the significant changes observed for the corresponding E- and C-isomers [Renth et al., Int. Rev. Phys. Chem., 2013, 32, 1-38], the excited-state dynamics of the Z-isomers is not affected by varied sterical hindrance from methyl and isopropyl substituents at the central hexatriene unit, or by intramolecular bridging, and remains unaltered upon extension of the pi-electron system in a benzannulated furyl fulgide