Abstract
1H spin−lattice nuclear magnetic resonance relaxation experiments were performed for five kinds of dermal fillers based on hyaluronic acid. The relaxation data were collected over a broad frequency range between 4 kHz and 40 MHz, at body temperature. Thanks to the frequency range encompassing four orders of magnitude, the dynamics of water confined in the polymeric matrix was revealed. It is demonstrated that translation diffusion of the confined water molecules exhibits a two‐dimensional character and the diffusion process is slower than diffusion in bulk water by 3–4 orders of magnitude. As far as rotational dynamics of the confined water is concerned, it is shown that in all cases there is a water pool characterized by a rotational correlation time of about 4×10−9 s. In some of the dermal fillers a fraction of the confined water (about 10 %) forms a pool that exhibits considerably slower (by an order of magnitude) rotational dynamics. In addition, the water binding capacity of the dermal fillers was quantitatively compared.
Highlights
The unique advantage of Nuclear magnetic resonance (NMR) relaxometry lies, in the ability of revealing the time scale of the motion, and its mechanism;[1,2,6,7,8,9,10,11,12,13,14,15] the key to this ability is as follows: Protons (1H nuclei) placed in an external magnetic field can assume two quantum states characterized by the magnetic spin quantum number m 1⁄4 1=2 that correspond to the parallel and anti-parallel orientations of the 1H magnetic moment with respect to the magnetic field
Water dynamics in five kinds of dermal filler has been investigated by means of NMR relaxometry
It has been assumed that the exchange lifetime for both pools of confined water are much faster than the corresponding relaxation contributions, and both the dipolar relaxation constants, Cintra and CintraðextraÞ include the Pq and Pq(extra) factors, respectively
Summary
H spin-lattice relaxation originates from 1H-1H magnetic dipoledipole interactions. In the present case, taking into account the prevailing water content, the relaxation reflects dynamics of different pools of water in the system. ÐwÞ, stems from intermolecular and intramolecular H- H dipole-dipole interactions modulated by translational and rotational dynamics of water molecules, respectively. According to spin relaxation theory, the relaxation rates are given as linear combinations of spectral density functions characterizing the dynamical process leading to the fluctuations of the corresponding dipole-dipole interactions and the relaxation, i. After subtracting the contribution to the overall relaxation originating from bulk water, the relaxation rate R1 ðwÞ is given (under the assumption of 2D translation diffusion of the confined water) as [Eq (6)]: inter ttrans 4. The form of the spectral density, Jinter ðwÞ, associated with translation diffusion of the confined water molecules depends on the dimensionality of the diffusion. Bulk where Rconf ðwÞ and R1 ðwÞ denote the relaxation contributions associated with the confined and free pools of water, while w is (3). Figure 1. 1H magnetization versus time for dermal filler labeled as DF1–DF5 for different resonance frequencies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
