Concept: Differential scanning calorimetry
Much physiological and behavioral evidence has been provided suggesting that insect Odorant Binding Proteins (OBPs) are indispensable for odorant recognition and thus appealing targets for structure-based discovery and design of novel host-seeking disruptors. Despite the fact that more than 60 putative OBP-encoding genes have been identified in the malaria vector Anopheles gambiae, the crystal structures of only six of them are known. It is therefore clear that OBP structure determination constitutes the bottle-neck for structure-based approaches to mosquito repellent/attractant discovery. Here, we describe the three dimensional structure of an Anopheles gambiae “Plus-C” group OBP, AgamOBP48, which exhibits the second highest expression levels in female antennae. This structure represents the first example of a 3D domain-swapped dimer in dipteran species. A combined binding site is formed at the dimer interface by equal contribution of each monomer. Structural comparisons with the monomeric AgamOBP47 revealed that the major structural difference between the two “Plus-C” proteins localizes in their N- and C-terminal regions and their concerted conformational change may account for monomer-swapped dimer conversion and, furthermore, the formation of novel binding pockets. Using a combination of gel filtration chromatography, differential scanning calorimetry and analytical ultracentrifugation, we demonstrate the AgamOBP48 dimerization in solution. Eventually, molecular modelling calculations were used to predict the binding mode of the most potent synthetic ligand of AgamOBP48 known so far, discovered by ligand- and structure-based virtual screening. The structure-aided identification of multiple OBP-binders represents a powerful tool to be employed in the effort to control the vector-borne diseases transmission.
In the present study, novel ultradeformable liposomes (menthosomes; MTS), deformable liposomes (transfersomes; TFS) and conventional liposomes (CLP) were compared in their potential for transdermal delivery of meloxicam (MX). MTS, TFS and CLP were investigated for size, size distribution, zeta potential, elasticity, entrapment efficiency and stability. In vitro skin permeation using hairless mice skin was evaluated. Vesicular morphology was observed under freeze-fractured transmission electron microscopy (FF-TEM). Intrinsic thermal properties were performed using differential scanning calorimetry (DSC) and X-ray diffraction. The skin permeation mechanism was characterized using confocal laser scanning microscopy (CLSM). The results indicated that the difference in physicochemical characteristics of MTS, TFS and CLP affected the skin permeability. MTS and TFS showed higher flux of MX than CLP. CLSM image showed deformable vesicles mechanism for delivery of MX across the hairless mice skin. Our study suggested that ultradeformable and deformable liposomes (MTS and TFS) had a potential to use as transdermal drug delivery carriers for MX.
We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures.
Improved methods for the accurate identification of both the presence and severity of cervical intraepithelial neoplasia (CIN) and extent of spread of invasive carcinomas of the cervix (IC) are needed. Differential scanning calorimetry (DSC) has recently been shown to detect specific changes in the thermal behavior of blood plasma proteins in several diseases. This methodology is being explored to provide a complementary approach for screening of cervical disease. The present study evaluated the utility of DSC in differentiating between healthy controls, increasing severity of CIN and early and advanced IC. Significant discrimination was apparent relative to the extent of disease with no clear effect of demographic factors such as age, ethnicity, smoking status and parity. Of most clinical relevance, there was strong differentiation of CIN from healthy controls and IC, and amongst patients with IC between FIGO Stage I and advanced cancer. The observed disease-specific changes in DSC profiles (thermograms) were hypothesized to reflect differential expression of disease biomarkers that subsequently bound to and affected the thermal behavior of the most abundant plasma proteins. The effect of interacting biomarkers can be inferred from the modulation of thermograms but cannot be directly identified by DSC. To investigate the nature of the proposed interactions, mass spectrometry (MS) analyses were employed. Quantitative assessment of the low molecular weight protein fragments of plasma and urine samples revealed a small list of peptides whose abundance was correlated with the extent of cervical disease, with the most striking plasma peptidome data supporting the interactome theory of peptide portioning to abundant plasma proteins. The combined DSC and MS approach in this study was successful in identifying unique biomarker signatures for cervical cancer and demonstrated the utility of DSC plasma profiles as a complementary diagnostic tool to evaluate cervical cancer health.
While ∼75% of commercially utilized polymers are semicrystalline, the generally low mechanical modulus of these materials, especially for those possessing a glass transition temperature below room temperature, restricts their use for structural applications. Our focus in this paper is to address this deficiency through the controlled, multiscale assembly of nanoparticles (NPs), in particular by leveraging the kinetics of polymer crystallization. This process yields a multiscale NP structure that is templated by the lamellar semicrystalline polymer morphology and spans NPs engulfed by the growing crystals, NPs ordered into layers in the interlamellar zone [spacing of [Formula: see text] (10-100 nm)], and NPs assembled into fractal objects at the interfibrillar scale, [Formula: see text] (1-10 μm). The relative fraction of NPs in this hierarchy is readily manipulated by the crystallization speed. Adding NPs usually increases the Young’s modulus of the polymer, but the effects of multiscale ordering are nearly an order of magnitude larger than those for a state where the NPs are not ordered, i.e., randomly dispersed in the matrix. Since the material’s fracture toughness remains practically unaffected in this process, this assembly strategy allows us to create high modulus materials that retain the attractive high toughness and low density of polymers.
Ice repellent coatings have been studied and keenly sought after for many years, where any advances in the durability of such coatings will result in huge energy savings across many fields. Progress in creating anti-ice and anti-frost surfaces has been particularly rapid since the discovery and development of slippery, liquid infused porous surfaces (SLIPS). Here we use SLIPS-coated differential scanning calorimeter (DSC) pans to investigate the effects of the surface modification on the nucleation of supercooled water. This investigation is inherently different from previous studies which looked at the adhesion of ice to SLIPS surfaces, or the formation of ice under high humidity conditions. Given the stochastic nature of nucleation of ice from supercooled water, multiple runs on the same sample are needed to determine if a given surface coating has a real and statistically significant effect on the nucleation temperature. We have cycled supercooling to freezing and then thawing of deionized water in hydrophilic (untreated aluminum), hydrophobic, superhydrophobic, and SLIPS-treated DSC pans multiple times to determine the effects of surface treatment on the nucleation and subsequent growth of ice. We find that SLIPS coatings lower the nucleation temperature of supercooled water in contact with statistical significance and show no deterioration or change in the coating performance even after 150 freeze-thaw cycles.
Monoclonal antibodies (mAbs) are the fastest growing class of biopharmaceuticals reflecting their diverse applications in research and the clinic. The correct glycosylation of mAbs is required to elicit effector functions such as complement-dependent and antibody-dependent cell-mediated cytotoxicity, although these may be undesirable for the treatment of certain chronic diseases. To gain insight into the properties of glycan-deficient mAbs, we generated and characterized six different aglycosylated human IgG1 mAbs (carrying the N297A mutation) and compared them to their glycosylated counterparts. We found no differences in solubility or heterogeneity, and all mAbs the remained stable in stress tests at 4 and 37 °C. Surface plasmon resonance spectroscopy showed no differences in binding affinity, and the in vivo terminal serum half-life and plasma clearance were similar in rats. However, differential scanning calorimetry revealed that the aglycosylated mAbs contained a less stable C(H)2 domain and they were also significantly more susceptible to pH-induced aggregation. We conclude that aglycosylated mAbs are functionally equivalent to their glycosylated counterparts and could be particularly suitable for certain therapeutic applications, such as the treatment of chronic diseases.
In recent years, amorphous formulations and other special dosage forms of drug products have been investigated to achieve adequate solubility and disintegration. We have evaluated the distribution of crystalline and amorphous states of a drug product using Nanothermal analysis (Nano-TA) and Raman imaging methods. Compared to conventional differential scanning calorimetry, Nano-TA can be used to more rapidly characterize the crystalline and amorphous states of model formulations, including their ingredient distributions, without any sample preparation. In the current study, imaging maps obtained for specific model formulations were evaluated on the basis of their visual appearance and the physicochemical properties of the active pharmaceutical ingredient (API). In addition, the crystalline and amorphous states of the model formulations were distinguished by Raman mapping. Nano-TA was found to be useful for the characterization of crystalline and amorphous states of APIs and the distribution of other ingredients. This technology could be used to monitor the changes in crystalline forms of drug substances and dosage forms during processing. In addition, Nano-TA can be used to characterize amorphous states.
Abstract The objective of this study was to improve the dissolution rate and to enhance the stability of a poorly water-soluble and low glass-trasition temperature (T(g)) model drug, fenofibrate, in low molecular weight grades of hydroxypropylcellulose matrices produced by hot-melt extrusion (HME). Percent drug loading had a significant effect on the extrudability of the formulations. Dissolution rate of fenofibrate from melt extruded pellets was faster than that of the pure drug (p < 0.05). Incorporation of sugars within the formulation further increased the fenofibrate release rates. Differential scanning calorimetry results revealed that the crystalline drug was converted into an amorphous form during the HME process. Fenofibrate is prone to recrystallization due to its low T(g). Various polymers were evaluated as stabilizing agents among which polyvinylpyrrolidone 17PF and amino methacrylate copolymer exhibited a significant inhibitory effect on fenofibrate recrystallization in the hot-melt extrudates. Subsequently immediate-release fenofibrate tablets were successfully developed and complete drug release was achieved within 5 min. The dissolution profile was comparable to that of a currently marketed formulation. The hot-melt extruded fenofibrate tablets were stable, and exhibited an unchanged drug release profile after 3-month storage at 40°C/75% RH.
The purpose of this study was to develop a raloxifene-loaded solid dispersion with enhanced dissolution rate and bioavailability via spray-drying technique. Solid dispersions of raloxifene (RXF) were prepared with PVP K30 at weight ratios of 1:4, 1:6 and 1:8 using a spray-drying method, and characterized by differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and solubility and dissolution tests. The bioavailability of the solid dispersion in rats was also evaluated compared to those of RXF powder and commercial product. Results showed that the RXF-loaded solid dispersion was in amorphous form with increased solubility and dissolution rate. The absorption of RXF from solid dispersion resulted in approximately 2.6-fold enhanced bioavailability compared to pure drug. Moreover, RXF-loaded solid dispersion gave similar AUC, C(max) and T(max) values to the commercial product, suggesting that it was bioequivalent to the commercial product in rats. These findings suggest that an amorphous solid dispersion of RXF could be a viable option for enhancing the oral bioavailability of RXF.