Rigidity of poly-L-glutamic acid scaffolds: Influence of secondary and supramolecular structure

An overview of substrate stiffness guided cellular response and its applications in tissue regeneration

Cell-matrix interactions play a critical role in tissue repair and regeneration. With gradual uncovering of substrate mechanical characteristics that can affect cell-matrix interactions, much progress has been made to unravel substrate stiffness-mediated cellular response as well as its underlying mechanisms. Yet, as a part of cell-matrix interaction biology, this field remains in its infancy, and the detailed molecular mechanisms are still elusive regarding scaffold-modulated tissue regeneration. This review provides an overview of recent progress in the area of the substrate stiffness-mediated cellular responses, including 1) the physical determination of substrate stiffness on cell fate and tissue development; 2) the current exploited approaches to manipulate the stiffness of scaffolds; 3) the progress of recent researches to reveal the role of substrate stiffness in cellular responses in some representative tissue-engineered regeneration varying from stiff tissue to soft tissue. This article aims to provide an up-to-date overview of cell mechanobiology research in substrate stiffness mediated cellular response and tissue regeneration with insightful information to facilitate interdisciplinary knowledge transfer and enable the establishment of prognostic markers for the design of suitable biomaterials.

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Substrate stiffness physically determines cell fate and tissue development.

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Rational design of scaffolds requires the understanding of cell-matrix interactions.

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Substrate stiffness depends on scaffold molecular-constituent-structure interaction.

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Substrate stiffness-mediated cellular responses vary in different tissues.

Evaluation of formation and proportion of secondary structure in γ-polyglutamic acid by terahertz time-domain spectroscopy

The study of secondary structure is essential for understanding peptides and proteins. Here, we measured the terahertz (THz) spectra of γ-polyglutamic acid (γ-PGA) dominated by α-helix and random coil (RC) respectively. The α-helix has two absorption peaks in the THz region, but no absorption peak is observed in the RC conformation. We believe this is because the hydrogen bonding effect leads to a higher orientation in the helix-dominated γ-PGA. At lower pH, the absorption intensity of γ-PGA increases with the induction time. Similar changes were obtained in the Fourier infrared spectroscopy (FTIR). Through the correlation analysis of THz and IR spectroscopy, it is found that the characteristic peak at 1.2 THz can be used as a sensitive indicator of the intermediate conformation of the α-helical structure. In addition, the transformation of α-helix-RC conformation is related to the peak intensity at 1.99 THz (R² = 0.991), which preliminarily indicates that terahertz time-domain spectroscopy (THz-TDS) has the potential to become a new effective method for characterizing and evaluating secondary structure.

Fluorescence properties of aurone derivatives: an experimental and theoretical study with some preliminary biological applications

In this paper, we explored the fluorescence properties of eight aurone derivatives bearing methoxy groups and bromine atoms as substituents in the benzene rings.

The cold neutron chopper spectrometer at the Spallation Neutron Source-A review of the first 8 years of operation

The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. Experiments are being routinely performed with the sample at extreme conditions: T ≲ 0.05 K, p ≳ 2 GPa, and B = 8 T can be achieved individually or in combination. In particular, CNCS is in a position to advance the state of the art with inelastic neutron scattering under pressure, and some of the recent accomplishments in this area will be presented in more detail.

Tumor delivery of liposomal doxorubicin prepared with poly-L-glutamic acid as a drug-trapping agent

CONTEXT

Poly-l-glutamic acid (PGA) is an anionic polymer with a large number of carboxyl groups that can interact electrostatically with cationic drugs such as doxorubicin (DOX).

OBJECTIVE

For stable encapsulation of DOX into liposomes, we prepared triethylamine (TEA)-PGA-liposomes using PGA as an internal trapping agent.

METHODS

We prepared TEA-PGA-liposomes by remote loading of DOX with a TEA gradient into preformed liposomes prepared with 1, 2, or 4 mg/mL PGA (molecular weights 4800, 9800, and 20 500), and evaluated their biodistribution and antitumor effects on Lewis lung carcinoma (LLC) tumor-bearing mice.

RESULTS

TEA-PGA-liposomes using the higher the molecular weight or concentration of PGA showed a slower release of DOX from the liposomes. TEA-PGA-liposomes prepared with a high concentration of PGA could enhance DOX accumulation in tumors and prolonged DOX circulation in the serum, indicating that DOX may be retained stably in the liposomal interior by interaction with PGA. Furthermore, injection of TEA-PGA-liposomes prepared with 4 mg/mL of PGA₉₈₀₀ or 2 mg/mL PGA₂₀₅₀₀ strongly inhibited tumor growth in LLC tumor-bearing mice.

CONCLUSIONS

PGA may be a potential trapping agent for liposomal DOX for tumor drug delivery.

Elasticity and Inverse Temperature Transition in Elastin

Elastin is a structural protein and biomaterial that provides elasticity and resilience to a range of tissues. This work provides insights into the elastic properties of elastin and its peculiar inverse temperature transition (ITT). These features are dependent on hydration of elastin and are driven by a similar mechanism of hydrophobic collapse to an entropically favorable state. Using neutron scattering, we quantify the changes in the geometry of molecular motions above and below the transition temperature, showing a reduction in the displacement of water-induced motions upon hydrophobic collapse at the ITT. We also measured the collective vibrations of elastin gels as a function of elongation, revealing no changes in the spectral features associated with local rigidity and secondary structure, in agreement with the entropic origin of elasticity.