A nuclear magnetic resonance study of water in aggrecan solutions

Decoupling Protein Concentration and Aggregate Content Using Diffusion and Water NMR

Protein-based biopharmaceutical drugs, such as monoclonal antibodies, account for the majority of the best-selling drugs globally in recent years. For bioprocesses, key performance indicators are the concentration and aggregate level for the product being produced. In water NMR (wNMR), the use of the water transverse relaxation rate [R2(1H2O)] has been previously used to determine protein concentration and aggregate level; however, it cannot be used to separate between them without using an additional technique. This work shows that it is possible to "decouple" these two key characteristics by recording the water diffusion coefficient [D(1H2O)] in conjunction with R2(1H2O), even in the event of overlap in either D(1H2O) or R2(1H2O). This method is demonstrated on three different systems, following appropriate D(1H2O) or R2(1H2O) calibration data acquisition for a protein of interest. Our method highlights the potential use of benchtop NMR as an at-line process analytical technique.

Nanoceria Aggregate Formulation Promotes Buffer Stability, Cell Clustering, and Reduction of Adherent Biofilm in Streptococcus mutans

Streptococcus mutans is one of the key etiological factors in tooth-borne biofilm development that leads to dental caries in the presence of fermentable sugars. We previously reported on the ability of acid-stabilized nanoceria (CeO2-NP) produced by the hydrolysis of ceric salts to limit biofilm adherence of S. mutans via non-bactericidal mechanism(s). Herein, we report a chondroitin sulfate A (CSA) formulation (CeO2-NP-CSA) comprising nanoceria aggregates that promotes resistance to bulk precipitation under a range of conditions with retention of the biofilm-inhibiting activity, allowing for a more thorough mechanistic study of its bioactivity. The principal mechanism of reduced in vitro biofilm adherence of S. mutans by CeO2-NP-CSA is the production of nonadherent cell clusters. Additionally, dose-dependent in vitro human cell toxicity studies demonstrated no additional toxicity beyond that of equimolar doses of sodium fluoride, currently utilized in many oral health products. This study represents a unique approach and use of a nanoceria aggregate formulation with implications for promoting oral health and dental caries prevention as an adjunctive treatment.

NMR techniques in studying water in biotechnological systems

Different NMR methodologies have been considered in studying water as a part of the structure of heterogeneous biosystems. The current work mostly describes NMR techniques to investigate slow translational dynamics of molecules affecting anisotropic properties of polymers and biomaterials. With these approaches, information about organized structures and their stability could be obtained in conditions when external factors affect biomolecules. Such changes might include rearrangement of macromolecular conformations at fabrication of nano-scaffolds for tissue engineering applications. The changes in water-fiber interactions could be mirrored by the magnetic resonance methods in various relaxations, double-quantum filtered (DQF), 1D and 2D translational diffusion experiments. These findings effectively demonstrate the current state of NMR studies in applying these experiments to the various systems with the anisotropic properties. For fibrous materials, it is shown how NMR correlation experiments with two gradients (orthogonal or collinear) encode diffusion coefficients in anisotropic materials and how to estimate the permeability of cell walls. It is considered how the DQF NMR technique discovers anisotropic water in natural polymers with various cross-links. The findings clarify hydration sites, dynamic properties, and binding of macromolecules discovering the role of specific states in improving scaffold characteristics in tissue engineering processes. Showing the results in developing these NMR tools, this review focuses on the ways of extracting information about biophysical properties of biomaterials from the NMR data obtained.

Effect of long-term heat exposure on rheological and intrinsic water characteristics of bone-derived beef stocks

Bone-derived protein stocks are used in food industry to enhance taste of soups, sauces, and a range of other products. Both during commercial manufacturing and when used for culinary purposes, the stocks may be exposed to high temperatures for an extended time period. The present study investigated the effect of retention at 90°C for 0, 3, 6, 9, 24, 48, 72, and 168 hr on the functional attributes of concentrated bone-derived beef stocks (57% Dry matter (DM)). Visual inspection and rheological analyses showed that during increasing heat exposure, the gel strength as well as viscosity of the concentrated stocks decreased incrementally and significantly (P > 0.001). Nuclear magnetic resonance (NMR) relaxation measurements conducted on the beef stocks also revealed strong effects of heat exposure on the transverse (T₂ ) relaxation time, which increased incrementally and significantly (P > 0.001) with longer heat exposure. Thus, the present study demonstrated that heat-induced changes in rheological properties of bone-derived beef stocks can be ascribed to changes in intrinsic water-protein interactions and water attributes as a result of heat-induced protein modifications. In conclusion, the study proves that NMR relaxometry is a valuable tool for monitoring changes in intrinsic water mobility that are manifested in modified functional attributes of concentrated beef stocks.

Distribution of Gadolinium in Rat Heart Studied by Fast Field Cycling Relaxometry and Imaging SIMS

Research on microcirculatory alterations in human heart disease is essential to understand the genesis of myocardial contractile dysfunction and its evolution towards heart failure. The use of contrast agents in magnetic resonance imaging is an important tool in medical diagnostics related to this dysfunction. Contrast agents significantly improve the imaging by enhancing the nuclear magnetic relaxation rates of water protons in the tissues where they are distributed. Gadolinium complexes are widely employed in clinical practice due to their high magnetic moment and relatively long electronic relaxation time. In this study, the behavior of gadolinium ion as a contrast agent was investigated by two complementary methods, relaxometry and secondary ion mass spectrometry. The study examined the distribution of blood flow within the microvascular network in ex vivo Langendorff isolated rat heart models, perfused with Omniscan® contrast agent. The combined use of secondary ion mass spectrometry and relaxometry allowed for both a qualitative mapping of agent distribution as well as the quantification of gadolinium ion concentration and persistence. This combination of a chemical mapping and temporal analysis of the molar concentration of gadolinium ion in heart tissue allows for new insights on the biomolecular mechanisms underlying the microcirculatory alterations in heart disease.