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The relationship between molecular structure and water dynamics is a fundamental yet often neglected subject in the field of hydrogels for drug delivery, bioprinting, as well as biomaterial science and tissue engineering & regenerative medicine (TE&RM). Water is a fundamental constituent of hydrogel systems and engages via hydrogen bonding with the macromolecular network. The methods and techniques to measure and reveal the phenomena and dynamics of water within hydrogels are still limited. In this work, differential scanning calorimetry (DSC) was used as a quantitative method to analyze freezable (including free and freezable bound) and non-freezable bound water within gelatin methacrylate (GelMA) hydrogels. Nuclear magnetic resonance (NMR) is a complementary method for the study of water behavior and can be used to measure the spin-relaxation of water hydrogen nuclei, which is related to water dynamics. In this research, nuclear magnetic resonance relaxometry was employed to investigate the molecular state of water in GelMA hydrogels using spin–lattice (T1) and spin–spin (T2) spin-relaxation time constants. The data displays a trend of increasing bound water content with increasing GelMA concentration. In addition, T2 values were further applied to calculate microviscosity and translational diffusion coefficients. Water relaxation under various chemical environments, including different media, temperatures, gelatin sources, as well as crosslinking effects, were also examined. These comprehensive physical data sets offer fundamental insight into biomolecule transport within the GelMA hydrogel system, which ultimately are important for drug delivery, bioprinting, as well as biomaterial science and TE&RM communities. [ABSTRACT FROM AUTHOR]

Purpose: Single‐sided portable NMR (pNMR) has previously been demonstrated to be suitable for quantification of mammographic density (MD) in excised breast tissue samples. Here we investigate the precision and accuracy of pNMR measurements of MD ex vivo as compared with the gold standards. Methods: Forty‐five breast‐tissue explants from 9 prophylactic mastectomy patients were measured. The relative tissue water content was taken as the MD‐equivalent quantity. In each sample, the water content was measured using some combination of three pNMR techniques (apparent T2, diffusion, and T1 measurements) and two gold‐standard techniques (computed microtomography [μCT] and hematoxylin and eosin [H&E] histology). Pairwise correlation plots and Bland–Altman analysis were used to quantify the degree of agreement between pNMR techniques and the gold standards. Results: Relative water content measured from both apparent T2 relaxation spectra, and diffusion decays exhibited strong correlation with the H&E and μCT results. Bland–Altman analysis yielded average bias values of −0.4, −2.6, 2.6, and 2.8 water percentage points (pp) and 95% confidence intervals of 13.1, 7.5, 11.2, and 11.8 pp for the H&E – T2, μCT – T2, H&E – diffusion, and μCT – diffusion comparison pairs, respectively. T1‐based measurements were found to be less reliable, with the Bland–Altman confidence intervals of 27.7 and 33.0 pp when compared with H&E and μCT, respectively. Conclusion: Apparent T2‐based and diffusion‐based pNMR measurements enable quantification of MD in breast‐tissue explants with the precision of approximately 10 pp and accuracy of approximately 3 pp or better, making pNMR a promising measurement modality for radiation‐free quantification of MD. [ABSTRACT FROM AUTHOR]

Background: Increased mammographic density (MD) is a strong and independent risk factor for breast cancer. Lifetime oestrogenic exposure is associated with increased MD, however androgenic effects on MD have not been widely investigated. Methods: We studied the effect of 17 β -oestradiol (E2) alone or in combination with an androgen receptor (AR) agonist (5 α -dihydrotestosterone [DHT]) or a selective AR modulator (Enobosarm), in modulating MD as measured via single-sided Portable NMR in a patient-derived explant (PDE) model of normal human mammary tissue. Results: We observed an upward trend in explants treated with E2 alone in 3/6 cases, an effect which appeared to be somewhat influenced by menopausal status. Co-treatment of E2 with the AR agonists DHT or Enobosarm however effected a downward trend in regards to MD. E2 significantly upregulated the ER regulated genes (ERGs) CELSR2 and AR , and the AR regulated genes SEC14L2 and GRPC5A, whereas E2 in combination with AR agonist Enobosarm downregulated ERGs SERPINA3, ATP6V1B1, TFF1 and PR regulated gene RANK. Only GREB1 and CLIC6 were upregulated by E2 and downregulated by the combination of E2 with Enobosarm. DHT + E2 exhibited no significant difference in expression of ER, AR or PR genes examined, compared with the effect of E2 alone. A negative trend was observed between ER protein levels and MD increase in PDEs. Since ER protein gets degraded upon hormone activation, this observation supports active ER signalling in the promotion of MD. Conclusions: Collectively, these findings supports the utility of single-sided Portable NMR for the measurement of MD in explanted human mammary tissue to detect MD change in response to exogenous hormone treatments. A mechanism through which activation of AR may reduce MD as a potential mechanism for reducing breast cancer risk associated to high MD is discussed. [ABSTRACT FROM AUTHOR]

A theory is presented for radiation damping (RD) in the toroid cavity nuclear magnetic resonance detector, a cylindrically symmetric inhomogeneous-rf field detector in which the magnitude of B[sub 1] is inversely proportional to the distance from the cylindrical symmetry axis. The equations of motion of the magnetization components are obtained and discussed. Numerical simulations of conventional- and composite-pulse experiments are presented, along with a discussion of the effects of RD on the evolution of magnetization. Preliminary simulations of RD in the presence of inhomogeneous line broadening are also presented. The signature effect of radiation damping in the TCD is the winding or unwinding of magnetization gratings that has recently been observed by other researchers. The observed magnitude of the effect is linked to the effective filling factor, which currently appears to be limited by the stray inductance of the detection circuit. The results are of interest in connection with recent findings regarding the interaction of RD with the dipolar demagnetizing field. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

[super 1]H and [super 13]C NMR spectroscopy was used to understand the centrifugation and inhomogeneous broadening mechanism was employed to obtain NMR line shapes of the lipid and aqueous species in bicontinuous cubic phase (BCP) samples. The mechanism of the inhomogeneous broadening involves a spatially nonuniform diamagnetically induced magnetic field determined by the mesoscopic structure and the diamagnetic susceptibilities of the two BCD domains that could be applied to probe compositional uniformity and microscopic organization of BCP samples.