Differential Scanning Calorimetry Scans Research Articles

DSC examination of cartilage damage of patients undergoing shoulder replacement

Shoulder replacement is a viable surgical treatment for comminuted proximal humerus fractures and shoulder osteoarthritis. Proper evaluation of hyaline cartilage is essential for the right choice of prosthesis; however, there are only a limited number of studies available investigating the cartilage of glenohumeral joint of patients undergoing shoulder replacement. We hypothesized that differential scanning calorimetry (DSC) could determine the grade of cartilage damage in patients undergoing reversed shoulder replacement, providing insights into the structural changes of the human cartilage samples. Sample of hyaline cartilage of glenohumeral joint was harvested during reversed shoulder replacement of orthopaedic and trauma patients. Thermal parameters were measured using DSC, and radiological examination of glenohumeral joint was also done prior to surgery. We have found that changes in thermal characteristics and DSC scans clearly indicate the severity of osteoarthritis and cartilage damage. The denaturation temperature range and the half-width of the heat flow curves were significantly wider in the orthopaedic samples compared to the control and traumatic ones. The calorimetric enthalpy (ΔHcal) exhibited significant differences in both pathologic samples, compared to the control. The melting temperatures (Tm) show that structural change caused by orthopaedic condition is greater than the effect of traumatic. Therefore, differential scanning calorimetry could help to determine the grade of cartilage damage in orthopaedic and trauma patients undergoing reversed shoulder replacement.

Structure and properties of nano- and polycrystalline Mn-doped CuCr2Se4 obtained by ceramic method and high-energy ball milling

Chemical compounds with a general formula CuCr2–xMnxSe4 (x = 0.1, 0.2) were successfully synthesized in polycrystalline form, using solid state reaction method, and as nanoparticles, using high-energy ball milling. The influence of manganese and grain size on their structure, magnetic and thermal properties was investigated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), magnetic measurements (SQUID, high magnetic fields) and DSC (Differential Scanning Calorimetry). Electronic structures of obtained compounds were determined using XANES (X-ray Near Edge Absorption Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy). X-ray studies confirmed that the spinel phase forms only for x = 0.1, 0.2. The obtained compounds crystallize with the space group Fd3¯m. The results of magnetic measurements for poly- and nanocrystalline compounds showed that the polycrystalline compounds are ferromagnets with the Curie temperature of TC =352 K for x = 0.1 and TC =342 K for x = 0.2, and the Curie-Weiss temperature of θCW =362 K for x = 0.1 and θCW =354 K for x = 0.2. Whereas the nanoparticles CuCr2–xMnxSe4 (x = 0.1, 0.2) revealed a superparamagnetic character with blocking temperature of TB ≈ 25 K for both compounds.The XANES and XPS data indicate the Cr ions are trivalent (Cr3+). Mn ions are trivalent and tetravalent (Mn3+ and Mn4+), which implies small amount of the Cu ions change the valency from divalency to monovalency (Cu2+ and Cu1+). DSC/TG analysis indicates that the presence of Mn ions in the CuCr2Se4 crystal lattice affects the stability and resistance of the doped compounds in comparison with the pure CuCr2Se4. Decreasing the grain size leads to a decrease in melting temperature.

Calorimetric observation of lysozyme degradation at elevated temperature in water and DMSO-water mixtures

The reversibility of protein denaturation is an essential factor for biotechnology. Previous differential scanning calorimetry (DSC) studies demonstrated the development of the low-temperature shoulder on the calorimetric denaturation peak of lysozyme in successive heating-cooling cycles, which implies irreversible denaturation. However, this effect was not thoroughly investigated. In the present work, we have quantitatively studied the effect of incubation at the elevated temperature on the state of lysozyme in water and mixtures of water with dimethyl sulfoxide (DMSO) using DSC. The changes to the state of the lysozyme molecule indicated by DSC thermograms were also evaluated by circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) techniques. It is noted that with the increase of duration or temperature of incubation, the low-temperature peak on DSC thermograms grows, while the height of the unfolding peak of native structure decreases. The increase in the height of the low-temperature peak in DSC scans correlates with the development of the sideband associated with the absorption of the carboxyl group in the infrared spectra. This result suggests that the low-temperature endothermic peak corresponds to the unfolding of the deamidated protein. At the same time, DLS measurements indicate absence of aggregation, while FTIR and CD data demonstrate that deamidated protein maintains a native-like structure. The evaluation of the DSC thermograms allowed to determine the rates and activation energy of the degradation of protein molecules at the elevated temperatures. The addition of DMSO slows down the protein degradation but has little effect on the apparent activation energy of the process.

Thermal shrinkage and heat capacity of monolithic polymeric physical aerogels

Monolithic physical aerogels based on semicrystalline linear polymers are suitable for molecular separation, catalysis, and thermal insulation. These low-density materials generally exhibit thermal shrinkage in their pre-melting region. Differential Scanning Calorimetry (DSC) shows that aerogel thermal shrinkages occur with relevant step decreases of heat capacity (ΔCp < 0). For physical aerogels based on the thermodynamically stable β form of syndiotactic polystyrene (sPS), a positive heat capacity step associated with glass transition (Tg) and a negative heat capacity step associated with thermal shrinkage are well separated. As for poly (2,6-dimethyl-1,4-phenylene)oxide (PPO), which exhibits the rather unique closeness of Tg and Tm, the two phenomena are superimposed and a regular increase of heat capacity with porosity, going from positive to progressively more negative values is observed. Negative heat capacity steps are not present for thermal shrinkage of polymer foams, which exhibit high porosity but the low surface area. On the basis of the present study, simple and fast DSC scans allow accurate evaluation of temperatures of thermal shrinkage of monolithic physical polymer aerogels.

Isothermal crystallization kinetics of (Cu60Zr25Ti15)99.3Nb0.7 bulk metallic glass

This paper reports the crystallization kinetics of (Cu60Zr25Ti15)99.3Nb0.7 bulk metallic glass under isothermal conditions. Differential scanning calorimetry (DSC) has been employed for isothermal annealing at ten different temperatures prior to the onset of crystallization (To) temperature. X-ray diffraction and transmission electron microscopy have been used to confirm the amorphous structure of the as cast sample. Crystallized volume fractions (x) are calculated from the exothermic peaks of DSC scans. Crystallized volume fractions (x) against time show sigmoidal type of curves as well as the curves become steeper at higher annealing temperatures. Continuous heating transformation diagram has been simulated to understand the stability of the bulk metallic glass. Crystallization kinetics parameters are calculated using Arrhenius and Johnson–Mehl–Avrami equations. Activation energy (Ea) and Avrami exponential factor (n) have exhibited strong correlation with crystallized volume fraction (x). The average activation energy for isothermal crystallization is found to be 330 ± 30 kJ/mol by Arrhenius equation. Nucleation activation energy (Enucleation) is found to be higher than that of growth activation energy (Egrowth). The Avrami exponential factor (n) indicates about the diffusion controlled mechanism of the nucleation and three-dimensional growth.

Influence of PCL on the epoxy workability, insights from thermal and spectroscopic analyses

Epoxy compound based on diglycidyl ether of bisphenol A (DGEBA), methyl tetrahydrophthalic anhydride (MTHPA) as hardener and 2,4,6-tris (dimethylaminomethyl) phenol (DEH 35) as catalyzer, at 100/87/5 as fixed concentration was successfully processed. Aiming workable thermoset, thermoplastic Polycaprolactone (PCL) was added at 10, 20 and 30 phr contents to the epoxy compound. Analyses of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and optical microscopy (OM) were conducted in order to obtain evidences from chemical interactions, curing kinetics and phase separation. From FTIR spectra partially miscibility between Epoxy and PCL can be assumed, mainly due to the hydrogen bonding between PCL carbonyl and epoxy hydroxyl, whereas after reaching epoxy's solubility limit PCL segregates and it is suggested separated phases take place through spinodal decomposition (Kinloch et al., 1994) [1] and nucleation and growth (NG) mechanisms which depend on temperature and raw material concentrations, as illustrated in OM images. Curing kinetics followed through released heat during DSC scans, indicated decreased crosslinking density upon PCL addition, as also lower Tg related to neat epoxy. Overcoming epoxy brittle fracture, rough surface fracture images with toughening character were captured from epoxy/PCL. Evidences of workable epoxy/PCL compounds are provided and related results presented in this work offer reliable tools to determine the exact aimed degree of crosslinking widening processing window to desired application.

Relationship Between Geometric and Aerodynamic Particle Size Distributions in the Formulation of Solution and Suspension Metered-Dose Inhalers.

The relationship between the geometric particle size distribution (GPSD) and the aerodynamic particle size distribution (APSD) of commercial solution and suspension metered-dose inhaler (MDI) formulations was assessed to clarify the use of GPSD to estimate the APSD. The size distribution of particles discharged from four suspension and four solution MDIs was measured using the Inas®100 light-scattering spectrometer and a Next Generation Impactor. The conversion factor was calculated by measuring the GPSD and APSD of MDIs. The morphology and physical properties of MDIs were studied using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Six of the eight MDIs showed similar conversion factor profiles, irrespective of their composition and formulation types. Applying the conversion factor obtained from one of the six MDIs resulted in a particle size distribution comparable to each APSD except for some formulations. The two other solution MDIs, which contained citric acid, had much higher and variable conversion factors. SEM images and DSC scans of the solids obtained by nebulization of the solutions containing beclomethasone and/or citric acid showed the formation of a paste-like amorphous solid. These results indicated that APSD of solution and suspension MDIs that form rigid particles may be estimated by using the conversion factor and GPSD. Contrarily, the estimation is more difficult in formulations that tend to lose the particle structure during the measurement.

Studies on Semi-crystalline Poly Lactic Acid (PLA) as a Hydrophobic Coating Material on Kraft Paper for Imparting Barrier Properties in Coated Abrasive Applications

This study investigated and explored the possible use of bio-based Poly lactic acid (PLA) as a barrier coating material on natural Kraft paper to fabricate coated abrasive products and to replace the conventional, non-biodegradable, synthetic polymer based barrier coating materials. PLA was coated on the Kraft paper using a solution coating process. The barrier properties of the PLA-treated Kraft paper were accordingly tested for application as a backing material in coated abrasive products. The concentration of PLA in solution was systematically increased from 5 wt% to 25 wt%. The coating thickness and coating weights were increased quantitatively with increasing solution concentrations. The morphology of the coating was characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), contact angle, and surface roughness measurements. The mechanical properties of the PLA coating applied Kraft paper were quantified by measuring the tensile strength, bursting strength, air porosity and Cobb value in order to find its suitability as coated abrasive product. The thermal analysis carried out using DSC scan indicated the semi-crystalline nature of PLA. The coating’s analysis for air and water resistance indicated that the air and water resistance increased with increase in PLA coating thickness. The data from different studies revealed that the PLA coating with a coating weight of 9 g m−2 appeared to be the most ideal concentration over the untreated or other lower PLA g m−2 treated backing materials and proved to possess superior overall barrier properties that are essentially needed for the fabrication of coated abrasive products.

Uniformity of the glassy state of iron-based metallic glassy particles and reproducibility of fabricating microparts

The uniformity of the glassy state of [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glassy particles prepared using our own developed technique, called the pulsated orifice ejection method (POEM), was investigated. Differential scanning calorimetry (DSC) results revealed that the thermal histories of the particles prepared from the same batch were almost identical. This suggested that the particles with the same size/volume possessed almost the same glassy state and had advantages as raw materials for microparts. The fabricated final product using our proposed process, termed as micro viscous flow processing, where a single particle is compressed with a precise jig under strictly controlled processing conditions, was confirmed to maintain a fully amorphous structure. DSC scans of each micropart traced nearly the same path, which indicated that their glassy states were still almost identical after processing. The precise control of the temperature and applied load enable the final products to achieve almost the same thermal histories and also geometric shapes. This is the first report that proves the high reproducibility of fabricating Fe-based metallic glassy microparts with high quality. Our proposed sequential process may shed light on a new fabrication technique of microparts using metallic glasses.

Kinetics of Cr clustering in a Cu-Cr-Zr alloy processed by equal-channel angular pressing: A DSC study

The kinetics of Cr clustering process in a commercial Cu-1Cr-0.1 Zr (wt.%) alloy processed by equal channel angular pressing (ECAP) via route BC at room temperature for 1, 8 and 16 passes, has been investigated using Differential Scanning Calorimetry (DSC). The DSC scan results showed that the Cr clustering peak temperature reaction increases with increasing the heating rate and decreased with the imposed strain. The activation energy of clustering was estimated using Kissinger, Boswell and Ligero analytical methods. The obtained values were in the range of ∼137 and 144 kJ/mol. The Avrami parameter n was around unity which corresponds to a process of grain boundary nucleation after site saturation.

DNA:chitosan complex, known as a drug delivery system, can create a porous scaffold

Supramolecular structure can be formed using noncovalent interactions based on the self-assembly processes. DNA is a good example for supramolecular materials because it is able to form supramolecular structure by forming specific hydrogen bonds between its base pairs. Moreover, DNA as an anionic medium can bind with oppositely charged materials to form complex structures of various shapes and properties. This work is focused on a foam complex that is formed between negatively charged DNA and positive chitosan. Various characterizations —Fourier transformed infrared spectroscopy (FTIR), Small and Wide-angle X-ray scattering (SAXS and WAXS), scanning electron microscope (SEM), texture analyzer and differential scanning calorimetry (DSC) — are used to study the properties of this dried scaffold. The FTIR spectra presented the chemical structure of DNA and chitosan. While the SAXS power law decay has revealed that an increasing of chitosan content smoothens the surface of the structure, on the other hand, the roughness is much higher when the DNA content is increased. The melting point of the foam from the DSC scan has been identified. The mechanical property of foam is suitable for the application of scaffold, and there is no cytotoxicity of foam to the cell. It is expected that this type of biomaterial could be used in several applications such as functional material and as a drug delivery material.

Thermal analysis studies on the compatibility of furosemide with solid state and liquid crystalline excipients

In the context of the present study, the thermal behavior of furosemide and the solid state excipients, sodium alginate, poly(ethylene oxide), poly(vinylpyrrolidone), lactose mono-hydrate and magnesium stearate, using Differential Scanning Calorimetry (DSC), was probed. It was found that the thermal behavior of these solid-state pharmaceutical excipients and furosemide correlates nicely with the literature relevant data. Regarding the furosemide-excipients mixtures, the DSC scans appear as a compilation of the thermal curves of each excipient. This suggests that the formulations containing these mixtures, may retain their stability over time. This information, which arises from the cooperativity of materials, their thermal stability and behavioris very helpful for the research and development of safe and effective pharmaceutical formulations. DSC experiments were also carried out with chimeric bilayers (called ?liposomes?), composed of hydrogenated soy phosphatidylcholine (HSPC) and poly(n-butylacrylate)-b-poly(acrylic acid) block copolymer with 70 % content of poly(acrylic acid (PnBA-b-PAA 30/70) with the addition of furosemide at the molar ratio of 9:0.1:1.0 in the system HSPC:PnBA-b-PAA 30/70:furosemide. Chimeric liposomal systems were characterized as ?fluid-like? by their DSC curves, which may be potentially translated as an easy way for release of furosemide from the advanced delivery system.

Silver Nano-Coating of Liquid Wood for Nanocomposite Manufacturing

The green composites from renewable resources are being increasingly studied because of their potential to provide benefits to the natural environment. Biotechnologies such as liquid wood injection moulding have several merits into account. Liquid wood is a thermoplastic material made from byproducts of the wood pulp industry. The liquid wood is in the form of pellets, which for processing will be melted and injected, just like plastics. This study is set to explore the potential advantages of combining liquid wood with silver nanoparticles. The use of silver-nanoparticles as antimicrobial agent is being evaluated for biomedical devices as well as furniture in many public places. In order to solve manufacturing problems in handling and spreading nano-particles in injection moulding products, an innovative methodology has been used. Plastic pellets are coated by Physical vapor deposition (PVD) with a nanometric layer of metallic silver. This continuous nanofilm produces silver nanoparticles during the plastification stage of the injection moulding process. Nano-coating fragmentation allows to distribute silver nano-platelets in the polymer matrix with very low contents and incomparable homogeneity. PVD coating has been optimized to take into account the nature of the raw material to process, mainly in terms of high-water content and small pellet size. Differential scanning calorimetry (DSC) on liquid wood granules coated with silver showed that no alteration has been produced in PVD. In fact, DSC scans show that no interaction is present between the polymer structure and the metal coating. These studies allow also a preliminary evaluation of the properties belongs of the new biomaterial, while opening for discussion the potential applications and future use in a wide variety of areas such as: bioengineering, medical and others.

Crystallization and kinetics studies of $$\hbox {Ti}_{{20}}\hbox {Zr}_{{20}}\hbox {Cu}_{60-x}\hbox {Ni}_{{x}}$$ ($$x = 10, 20, 30$$ and 40) metallic glasses

Synthesis and characterization of $$\hbox {Ti}_{{20}}\hbox {Zr}_{{20}}\hbox {Cu}_{60-x}\hbox {Ni}_{{x}}$$ ( $$x = 10, 20, 30$$ and 40) metallic glasses are reported in this paper. Glassy ribbons are produced by rapid quenching using the standard copper wheel roller technique in argon atmosphere. Their structural characterization is carried out by X-ray diffraction (XRD) and thermal behaviour (crystallization) study by differential scanning calorimetry (DSC). Results of XRD on both sides of each ribbon sample confirmed that each sample was indeed amorphous/glassy as only a very broad peak in XRD pattern was observed. Metallic glass $$\hbox {Ti}_{{20}}\hbox {Zr}_{{20}}\hbox {Cu}_{{50}}\hbox {Ni}_{{10}}$$ shows three crystallization peaks in non-isothermal DSC scans while other three samples show only a single crystallization peak. The activation energy of crystallization for each sample has been calculated using three available models, namely, those of Kissinger, Augis–Bennett and Ozawa. All the three models gave nearly similar activation energies for a given sample within 10%.

Freezing/melting of water in the confined nanospace of carbon materials: Effect of an external stimulus

Abstract Freezing/melting behavior of water confined in the nanopores of activated carbon materials has been evaluated using differential scanning calorimetry (DSC) at different water loadings, and after the application of an external stimulus. Under atmospheric pressure conditions, the DSC scans show a depression in the freezing/melting point of confined water compared to the bulk system. Interestingly, water confined in narrow micropores (pores below 0.7 nm) does not exhibit any phase transition, i.e. it is non-freezable water. Inelastic neutron scattering (INS) data confirm the presence of a distorted molecular assembly in narrow micropores, whereas synchrotron X-ray powder diffraction data (SXRPD) demonstrate the non-freezable nature of the water confined in these narrow-constrictions. Similar experiments under high-pressure CH4 give rise to a completely different scenario. Under high-pressure conditions methane hydrates are formed with a water-to-hydrate yield of 100% for the under-saturated and saturated samples, i.e. in the presence of an external stimulus even water in narrow micropores is prone to experience a liquid-to-solid phase transition. These results confirm the beneficial role of carbon as a host structure to promote nucleation and growth of methane hydrates with faster kinetics and a higher yield compared to the bulk system and to other porous materials.

Compositional dependence of thermal transport and optical properties of Se85 Ge15-x Pbx (0≤ x ≤10) chalcogenide glassy alloys

In the present work, the ratio of germanium (Ge) to lead (Pb) is varied keeping the concentration of selenium(Se) fixed in the glassy system, Se85 Ge15-x Pbx (0 ≤ x ≤ 10) to optimize the thermal transport and optical properties. The differential scanning calorimetry (DSC) measurements were carried out in the non-isothermal mode to know glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm). DSC scans of some samples(4 ≤ x ≤ 10) exhibit two glass transition temperatures (Tg), which indicates the presence of co-existing phases in glassy samples. The values of effective thermal conductivity (λe),effective thermal diffusivity(χe) and volumetric heat capacity(QCp) have been determined using transient plane source (TPS) measurements. These parameters show a non-monotonous behavior with the variation of Pb content in the prepared series. These results are explained in terms of chemical bond approach, changes in thermal transfer processes and mechanism of phonon scattering under transitions from dilute to concentrated solid solution. Band gap and Urbach energy have been estimated using Uv–Vis spectroscopy. Optical band gap (~0.65 eV) is minimum for the sample having 4 at.% of Pb. A signature of exciton formation is obtained for this critical composition. Results are explained using structural defect model and by degree of disorder induced, as indicated by a change in intensity and position of the Raman peak corresponding to Se–Se bonds.

Orientational glass, orientationally disordered crystal and crystalline polymorphism: A further study on the thermal behavior and molecular mobility in levoglucosan

Levoglucosan has very particular features in its phase diagram. On the one hand it has two crystalline phases, one orientationally ordered (ORC), stable at room temperature, which is transformed by heating in an orientationally disordered crystal (ODIC), a plastic crystal. On the other hand, it is difficult to form the structural glass by cooling down from the isotropic liquid, but it is easy to form the orientational glass (O-G) of levoglucosan by cooling from the ODIC phase. The stability of the O-G and ODIC phases allowed the study of the orientational glass transition, O-G → ODIC, by differential scanning calorimetry (DSC) and thermally stimulated depolarization currents (TSDC) with the determination of the respective dynamic fragility. In this context a critical analysis of the procedures using the effect of the DSC scanning rate on the temperature location of the DSC glass transition signal was performed.Two polymorphs of levoglucosan, not yet described in the literature, were discovered. These crystalline ORC forms are converted into an ODIC phase by heating, as happens with the most stable polymorph (as received). The three ORCs show ORC → ODIC transitions that differ greatly in temperature, enthalpy, and entropy of transition. We must therefore consider four levoglucosan polymorphs, three ORCs and one ODIC.TSDC was also used to study the secondary relaxations in the levoglucosan orientational glass, and it was possible to identify a β-type mobility (Johari-Goldstein) in addition to fast relaxations. Finally, the two dielectric techniques, dielectric relaxation spectroscopy (DRS) and TSDC, were compared in their ability to provide relevant information on the secondary mobility.

Thermally Induced Denaturing Energetics of Human Blood Plasma Albumin by Differential Scanning Calorimetry (DSC) as an Indicator for Breast Cancer Diagnosis in Female Patients.

Cancerous invasion yields unusual metabolisms providing a significant amount of peptide albuminomes that modulate albumin stability via binding. The study aimed at the investigation of the thermal stability of human plasma albumin with breast cancer of various stages by means of differential scanning calorimetry (DSC). Blood plasma was drawn from 11 female breast cancer patients and 50 healthy volunteers of homogeneous demographics. Plasma samples and their albumin-enriched fractions were subjected to DSC scanning between 37 and 90°C at 5°C/min rate. For normal blood plasma, a characteristic signature of DSC tracing was observed. And, the deconvolution of DSC thermograms revealed the recognition of thermal transition of albumin. It was found that denaturing temperature of albumin increased with increasing breast cancer staging which implied the increase in albuminome/peptide abundance produced by cancerous invasion. The analysis of albumin denaturing energetics based on rational approximation of the simple Lumry-Eyring model demonstrated that thermal transition of free albumin and albuminome-bound form attained energetic levels expressed as apparent activation energy (Eapp ± s.e.) of 132.68 ± 14.21 and 46.76 ± 8.42Kcal/mol corresponded to the schemes dominated by irreversible alteration and by reversible unfolding, respectively. Thus, Eapp value may indicate the degrees of cancerous invasion. It was proposed that Eapp may be used as an indicator to diagnose and assess the prognosis of breast cancer.

Differential Scanning Calorimetry Analyses of Idebenone-Loaded Solid Lipid Nanoparticles Interactions with a Model of Bio-Membrane: A Comparison with In Vitro Skin Permeation Data.

Differential scanning calorimetry (DSC) has emerged as a helpful technique both to characterize drug delivery systems and to study their interactions with bio-membranes. In this work, we compared idebenone (IDE)-loaded solid lipid nanoparticle (SLN) interactions with bio-membranes assessed by DSC with previous in vitro skin penetration data to evaluate the feasibility of predicting IDE skin penetration using DSC analyses. In vitro interactions experiments were performed using multi-lamellar liposomes as a model of bio-membrane. Enthalpy changes (ΔH) and transition temperature (Tm) were assessed during nine repeated DSC scans to evaluate IDE-loaded SLN–bio-membrane interactions over time. Analyzing ΔH and Tm values for each scan, we observed that the difference of ΔH and Tm values between the first and the last scan seemed to be related to SLN ability to locate IDE in the epidermis and in the stratum corneum, respectively. Therefore, the results of this study suggest the possibility of qualitatively predicting in vitro IDE skin penetration from IDE-loaded SLN utilizing the calorimetric parameters obtained from interaction experiments between the carriers under investigation and a model of bio-membrane.

Environmental adjustments of the cooperativity in M13 phage thermal denaturation

The filamentous bacteriophage M13 has been widely used in phage display and as a scaffold for nanostructures. Although M13 is loosely described as a thermo-resistant virus, no thorough studies of its thermostability have been reported so far. By using differential scanning calorimetry (DSC), we characterized the thermal stability of M13 in aqueous buffer and in the presence of ethanol. M13 was found to be very thermostable indeed, being resistant to the combined effects of temperature and high ethanol content. Upon thermal denaturation, several subunits of the major coat protein apparently undergo a cooperative conformational change, leading to the formation of residual β-strand conformation. Furthermore, the cooperativity of the denaturation process changes drastically with pH and ethanol concentration, indicating that P8 moieties are able to adjust its intermolecular packing in response to the environment. Deconvolution of DSC scans allowed the estimation of the number of P8 molecules comprising one cooperative unit.