Biology subjects

Roeder, R. K.

Publications and source records attributed to Roeder, R. K..

3 recordsLinked to original sources

bioRxiv2022

Methacrylate-Modified Gold Nanoparticles Enable Non-Invasive Monitoring of Photocrosslinked Hydrogel Scaffolds

Photocrosslinked hydrogels, such as methacrylate-modified gelatin (gelMA) and hyaluronic acid (HAMA), are widely utilized as tissue engineering scaffolds and/or drug delivery vehicles, but lack a suitable means for non-invasive, longitudinal monitoring of surgical placement, biodegradation, and drug release. Therefore, we developed a novel photopolymerizable X-ray contrast agent, methacrylate-modified gold nanoparticles (AuMA NPs), to enable covalent-linking to methacrylate-modified hydrogels (gelMA and HAMA) in one-step during photocrosslinking and non-invasive monitoring by X-ray micro-computed tomography (micro-CT). Hydrogels exhibited a linear increase in X-ray attenuation with increased Au NP concentration to enable quantitative imaging by contrast-enhanced micro-CT. The enzymatic and hydrolytic degradation kinetics of gelMA-Au NP hydrogels were longitudinally monitored by micro-CT for up to one month in vitro, yielding results that were consistent with concurrent measurements by optical spectroscopy and gravimetric analysis. Importantly, AuMA NPs did not disrupt the hydrogel network, rheology, mechanical properties, and hydrolytic stability compared with gelMA alone. GelMA-Au NP hydrogels were thus able to be bioprinted into well-defined three-dimensional architectures supporting endothelial cell viability and growth. Overall, AuMA NPs enabled the preparation of both conventional photopolymerized hydrogels and bioprinted scaffolds with tunable X-ray contrast for noninvasive, longitudinal monitoring of placement, degradation, and NP release by micro-CT.

bioengineering↗

bioRxiv2020

Quantitative Molecular Imaging of Breast Microcalcification Composition using Photon-Counting Spectral Computed Tomography

Mammographic screening for breast cancer is unable to distinguish molecular differences between hydroxyapatite (HA) microcalcifications (cals) that are associated with malignancy and calcium oxalate (CaOx) cals that are benign. Therefore, the objective of this study was to investigate quantitative material decomposition of model breast cals of clinically-relevant composition and size using spectral photon-counting computed tomography (PCCT). Model cals composed of HA, CaOx, and dicalcium phosphate (DCP) were treated as materials containing spatially coincident elemental compositions of calcium (Ca), phosphorus (P), and oxygen (O). Elemental decomposition was performed using constrained maximum-likelihood estimation in the image domain. Images were acquired with a commercial, preclinical PCCT system (MARS Bioimaging) with five energy bins selected to maximize counts at low photon energies and spectral differences between Ca and P. Elemental concentrations of Ca and P within the each cal composition were accurately identified and quantified with a root-mean-squared error < 12%. HA and CaOx cals, < 1 mm is size, were accurately discriminated by the measured P content with an area under the receiver operating characteristic curve (AUC) > 0.9. The mole fraction of P, P/(Ca+P), was able to discriminate all three cal compositions with AUC > 0.8 for cals < 1 mm is size and AUC = 1 for cals > 2 mm in size. The overall accuracy for the classification of cal types and quantification of P was robust against different assumptions in the elemental decomposition calibration, but quantification of Ca was improved with assumptions that most accurately accounted for the molar volume of each element within cal compositions. Thus, PCCT enabled quantitative molecular imaging of breast cal composition, which is not possible with current clinical molecular imaging modalities.

bioengineering↗

bioRxiv2019

Mineral deposition and vascular invasion of hydroxyapatite reinforced collagen scaffolds seeded with human adipose-derived stem cells

Collagen-based scaffolds reinforced with hydroxyapatite (HA) are an attractive choice for bone tissue engineering because their composition mimics that of bone. We previously reported the development of compression-molded collagen-HA scaffolds that exhibited high porosity, interconnected pores, and mechanical properties that were well-suited for surgical handling and fixation. The objective of this study was to investigate the use of these novel collagen-HA scaffolds in combination with human adipose-derived stem cells (hASCs) as a template for bone formation in a subcutaneous athymic mouse model. Cell-seeded constructs were pre-treated with either control or osteogenic media. Cell-free and collagen-only groups were included, as was a clinically approved bone void filler as a control for the material. After 8 weeks implantation, cell-free collagen-HA scaffolds and those that were pre-seeded with osteogenically differentiated hASCs supported bone formation and vascular invasion at comparable rates. HA-reinforcement allowed collagen constructs to maintain their implanted shape, provided for improved cell-tissue-scaffold integration, and resulted in a more organized tissue when pre-treated in an osteogenic induction medium. Scaffold type and pre-treatment also determined osteoclast activity and therefore potential remodeling of the constructs. Results suggest that it may be necessary to match the scaffold with a particular cell type and cell-specific pre-treatment to achieve optimal bone formation.

bioengineering↗