Direct and Real-Time Quantification Of Bortezomib Release From Alginate Microparticles Using Boron (11B) Nuclear Magnetic Resonance Spectroscopy

Rheological analysis of a novel phenylboronic acid-closomer gel

This study aims to characterize the rheological behavior of a novel phenylboronic acid (PBA)-based closomer nanoconjugate (Closogel) with potential application in pharmaceutical formulation. PBA was used as a cross-linking agent and model (antiviral) drug. The PBA loaded Closogel chemical structure was analyzed by boron (¹¹B) NMR and Fourier transform infrared (FTIR) spectroscopy. The Closogel and control hydroxyethyl cellulose (HEC) gel were analyzed under oscillatory and continuous shear rheometry followed by mathematical modeling to characterize the gel flow behavior. The chemical analysis confirmed the existence of characteristic borate esters peaks and Boron chemical shifts within Closogel spectra. Due to its more flexible molecular structure, undiluted Closogel exhibited lower, yield stress, viscosity and relaxation time (30 Pa &163 Pa.s & 0.21 s vs 45 Pa &301 Pa.s & 0.39 s for HEC). Both Closogel and HEC gels exhibited a thixotropic behavior. The plastic undiluted and pseudoplastic 2.5 % w/v aqueous Closogels were more viscous than elastic (tan (δ) > 1) in the linear viscoelastic range. The Herschel-Bulkley model showed a significant fitting to all experimental data (R² > 0.95). The 0.25 % w/v aqueous Closogel nearly exhibited a Newtonian behavior with a flow index of 0.93. These data suggest that PBA loaded Closomer-based gels have similar rheological behavior, with lower complex modulus than that of HEC gels, and they can be a promising platform used for delivery of topical antiviral or other bioactive agents.

In-cell NMR: Why and how?

NMR spectroscopy has been applied to cells and tissues analysis since its beginnings, as early as 1950. We have attempted to gather here in a didactic fashion the broad diversity of data and ideas that emerged from NMR investigations on living cells. Covering a large proportion of the periodic table, NMR spectroscopy permits scrutiny of a great variety of atomic nuclei in all living organisms non-invasively. It has thus provided quantitative information on cellular atoms and their chemical environment, dynamics, or interactions. We will show that NMR studies have generated valuable knowledge on a vast array of cellular molecules and events, from water, salts, metabolites, cell walls, proteins, nucleic acids, drugs and drug targets, to pH, redox equilibria and chemical reactions. The characterization of such a multitude of objects at the atomic scale has thus shaped our mental representation of cellular life at multiple levels, together with major techniques like mass-spectrometry or microscopies. NMR studies on cells has accompanied the developments of MRI and metabolomics, and various subfields have flourished, coined with appealing names: fluxomics, foodomics, MRI and MRS (i.e. imaging and localized spectroscopy of living tissues, respectively), whole-cell NMR, on-cell ligand-based NMR, systems NMR, cellular structural biology, in-cell NMR… All these have not grown separately, but rather by reinforcing each other like a braided trunk. Hence, we try here to provide an analytical account of a large ensemble of intricately linked approaches, whose integration has been and will be key to their success. We present extensive overviews, firstly on the various types of information provided by NMR in a cellular environment (the "why", oriented towards a broad readership), and secondly on the employed NMR techniques and setups (the "how", where we discuss the past, current and future methods). Each subsection is constructed as a historical anthology, showing how the intrinsic properties of NMR spectroscopy and its developments structured the accessible knowledge on cellular phenomena. Using this systematic approach, we sought i) to make this review accessible to the broadest audience and ii) to highlight some early techniques that may find renewed interest. Finally, we present a brief discussion on what may be potential and desirable developments in the context of integrative studies in biology.

Research Progress of NMR in Natural Product Quantification

In the fields of medicine and health, traditional high-performance liquid chromatography or UV-visible spectrophotometry is generally used for substance quantification. However, over time, nuclear magnetic resonance spectroscopy (NMR) has gradually become more mature. Nuclear magnetic resonance spectroscopy has certain advantages in the quantitative analysis of substances, such as being nondestructive, having a high flux and short analysis time. Nuclear magnetic resonance spectroscopy has been included in the pharmacopoeiae of various countries. In this paper, the principle of nuclear magnetic resonance spectroscopy and the recent progress in the quantitative study of natural products by NMR are reviewed, and its application in the quantitative study of natural products is proposed. At the same time, the problems of using NMR alone to quantify natural products are summarized and corresponding suggestions are put forward.

Fluorine (19F) Nuclear Magnetic Resonance Spectroscopy For Real Time Maraviroc Analysis From Microparticulate Systems

Real time analysis of pharmaceuticals in controlled release nano and microsystems remains a challenge. It is hypothesized that fluorine 19 nuclear magnetic resonance (¹⁹F qNMR) can be used for real time quantification and in vitro release of maraviroc (MVC). The release of maraviroc was analyzed in simulated body fluids from spray dried sodium alginate microspheres (MS) using the ¹⁹F qNMR method. Calibration produced a linearity curve in concentration range (0.42 mg/ml - 15 mg/ml), and the limits of detection and quantification values were 0.97 mg/ml and 2.93 mg/ml, respectively. The method was confirmed to be specific, accurate, precise, and robust (%RSE > 2%). MVC was successfully microencapsulated (18% w/w) as evidenced by the FT-IR spectra and SEM images. The MS had an average diameter of 2.522 ± 0.15 μm, with a zeta potential of - 61.31 ± 2.1 mV. Overall, the ¹⁹F qNMR method enabled a direct and real time quantification of MVC for an efficient drug release kinetics. This approach could be potentially used to quantify fluorinated drug potency, purity, and stability, and evaluate in vitro release kinetic from different formulations.