Effects of Low-Energy X-rays and UV Radiation on Fibroblast Cells

https://tigerprints.clemson.edu/csrp/1003/thumbnail.jp

Devices that cooperate with ultrasound probes for muscoskeletal evaluations and related systems and methods

Adaptors for ultrasound probes can have an adaptor body can have an open lower end that allows a distal end of the ultrasound probe to extend therethrough to contact skin of a patient. The adaptor can include a plurality of spaced apart resilient members held by the adaptor body that, in operation, are able to change in length such that the resilient members translate from a first longer length to a second shorter length when the probe applies compressive force to the target tissue

Modeling and measurement of intermolecular interaction forces between cartilage ECM macromolecules

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 143-151).The mechanical properties of cartilage tissue depend largely on the macromolecules that make up its extracellular matrix (ECM). Aggrecan is the most abundant proteoglycan in articular cartilage. It is composed of a core protein with highly charged, densely packed glycosaminoglycan (GAG) side chains, which are responsible for [approximately] 50% of the equilibrium compressive stiffness of the tissue. Using atomic force microscopy (AFM) and high resolution force spectroscopy (HRFS), it is now possible to directly measure nanoscale interactions between ECM macromolecules in physiologically relevant aqueous solution conditions. In order to interpret these data and compare them to macroscopic tissue measurements, a combination of experiments and theoretical modeling must be used. In this thesis, a new molecular-scale continuum Poisson-Boltzmann (PB)-based model was developed to predict the intermolecular interactions between GAG macromolecules by taking into account nanoscale space varying electric potential and fields between neighboring GAGs. A rod-like charge density distribution describing the time averaged space occupied by a single GAG chain was formulated. The spacing and size of the rods greatly influenced the calculated force even when the total charge was kept constant. The theoretical simulations described HRFS experimental data of the normal interaction force between two surfaces chemically end-grafted with an array of GAGs ("brushes") more accurately than simpler models which approximate the GAG charge as a homogeneous volume or planar surface charge. Taken together, these results highlight the importance of nonuniform molecular-level charge distribution on the measured GAG interaction forces. Normal interaction forces between aggrecan macromolecules were measured using contact mode AFM imaging and by HRFS.(cont.) The aggrecan molecules were end-grafted to gold-coated substrates and probe tips to achieve brush-like layers at physiologically relevant densities. Both colloidal probe tips (2.5[micro]m radius) and sharper probe tips ([approximately] 25-50nm radius) were used. The measured normal forces were predominantly repulsive and showed a strong ionic strength dependence reflecting the importance of repulsive electrostatic interactions. These aggrecan-aggrecan forces were much larger than those previously measured between brushes composed only of a single layer of GAG chains isolated from aggrecan molecules. The measured aggrecan normal force interactions were then compared to the predictions of the PB charged rod model for GAG electrostatic interactions and to measurements of the equilibrium compressive modulus of intact cartilage tissue. At near physiological bath conditions (0.1M NaCl), the PB electrostatic model closely predicted the values of the measured force for nanomechanical strains < 0.4, using model parameter values that were all fixed to their known values from the literature. At higher strains, the measured normal forces were higher than those predicted by the model, qualitatively consistent with the likelihood that other nonelectrostatic interactions were becoming more important. A compressive stiffness was also calculated from the measured aggrecan-aggrecan nanomechanical force data, and was found to be [approximately] 50% of the modulus of native intact cartilage. This is consistent with previous reports suggesting that aggrecan-associated electrostatic interactions account for approximately half of the tissue modulus.by Delphine Marguerite Denise Dean.Ph.D

Identifying SARS-CoV-2 Variants of Concern through Saliva- Based RT-qPCR by Targeting Recurrent Mutation Sites

SARS-CoV-2 variants of concern (VOCs) continue to pose a public health threat which necessitates a real-time monitoring strategy to complement whole genome sequencing. Thus, we investigated the efficacy of competitive probe RT-qPCR assays for six mutation sites identified in SARS-CoV-2 VOCs and, after validating the assays with synthetic RNA, performed these assays on positive saliva samples. When compared with whole genome sequence results, the SD69-70 and ORF1aD3675-3677 assays demonstrated 93.60 and 68.00% accuracy, respectively. The SNP assays (K417T, E484K, E484Q, L452R) demonstrated 99.20, 96.40, 99.60, and 96.80% accuracies, respectively. Lastly, we screened 345 positive saliva samples from 7 to 22 December 2021 using Omicron-specific mutation assays and were able to quickly identify rapid spread of Omicron in Upstate South Carolina. Our workflow demonstrates a novel approach for low-cost, real-time population screening of VOCs

Molecular Adhesion between Cartilage Extracellular Matrix Macromolecules

In this study, we investigated the molecular adhesion between the major constituents of cartilage extracellular matrix, namely, the highly negatively charged proteoglycan aggrecan and the type II/IX/XI fibrillar collagen network, in simulated physiological conditions. Colloidal force spectroscopy was applied to measure the maximum adhesion force and total adhesion energy between aggrecan end-attached spherical tips (end radius R ≈ 2.5 μm) and trypsin-treated cartilage disks with undamaged collagen networks. Studies were carried out in various aqueous solutions to reveal the physical factors that govern aggrecan–collagen adhesion. Increasing both ionic strength and [Ca2+] significantly increased adhesion, highlighting the importance of electrostatic repulsion and Ca2+-mediated ion bridging effects. In addition, we probed how partial enzymatic degradation of the collagen network, which simulates osteoarthritic conditions, affects the aggrecan–collagen interactions. Interestingly, we found a significant increase in aggrecan–collagen adhesion even when there were no detectable changes at the macro- or microscales. It is hypothesized that the aggrecan–collagen adhesion, together with aggrecan–aggrecan self-adhesion, works synergistically to determine the local molecular deformability and energy dissipation of the cartilage matrix, in turn, affecting its macroscopic tissue properties.National Science Foundation (U.S.) (Grant CMMI-0758651)National Institutes of Health (U.S.) (Grant AR60331)United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship (Grant N00244-09-1-0064))Shriners of North AmericaDrexel University (Faculty Start-up Grant

A Leishmania secretion system for the expression of major ampullate spidroin mimics

Spider major ampullate silk fibers have been shown to display a unique combination of relatively high fracture strength and toughness compared to other fibers and show potential for tissue engineering scaffolds. While it is not possible to mass produce native spider silks, the potential ability to produce fibers from recombinant spider silk fibers could allow for an increased innovation rate within tissue engineering and regenerative medicine. In this pilot study, we improved upon a prior fabrication route by both changing the expression host and additives to the fiber pulling precursor solution to improve the performance of fibers. The new expression host for producing spidroin protein mimics, protozoan parasite Leishmania tarentolae, has numerous advantages including a relatively low cost of culture, rapid growth rate and a tractable secretion pathway. Tensile testing of hand pulled fibers produced from these spidroin-like proteins demonstrated that additives could significantly modify the fiber’s mechanical and/or antimicrobial properties. Cross-linking the proteins with glutaraldehyde before fiber pulling resulted in a relative increase in tensile strength and decrease in ductility. The addition of ampicillin into the spinning solution resulted in the fibers being able to inhibit bacterial growth

Targeting of NAT10 enhances healthspan in a mouse model of human accelerated aging syndrome.

Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare, but devastating genetic disease characterized by segmental premature aging, with cardiovascular disease being the main cause of death. Cells from HGPS patients accumulate progerin, a permanently farnesylated, toxic form of Lamin A, disrupting the nuclear shape and chromatin organization, leading to DNA-damage accumulation and senescence. Therapeutic approaches targeting farnesylation or aiming to reduce progerin levels have provided only partial health improvements. Recently, we identified Remodelin, a small-molecule agent that leads to amelioration of HGPS cellular defects through inhibition of the enzyme N-acetyltransferase 10 (NAT10). Here, we show the preclinical data demonstrating that targeting NAT10 in vivo, either via chemical inhibition or genetic depletion, significantly enhances the healthspan in a Lmna G609G HGPS mouse model. Collectively, the data provided here highlights NAT10 as a potential therapeutic target for HGPS