Differential Scanning Microcalorimetry Research Articles

Structural and Thermodynamic Characteristics of Potato Starches Depending on the Plant Genotype and Conditions of Their Cultivation

The creation of new highly productive forms of potato by genetic engineering methods raises the question about the quality of transgenic tubers, which first of all relates to the properties of important storage compound such as starch. The article presents the results of studies aiming to the analysis of morphology, structure, and thermodynamic parameters of starch extracted from the potato tubers expressing the tms1 auxin biosynthesis gene from Agrobacterium tumefaciens and characterized by increased productivity in vitro. The transformed and control plants were cultivated in vitro on artificial sterile medium, as well as in vivo in the soil. The methods of scanning electron microscopy, wide-angle X-ray scattering, and differential scanning microcalorimetry were used in the work. It was established that the transformation of plants with the construction with the tms1 gene under the control of the patatin gene promoter causes significant changes in a number of thermodynamic parameters of starch, first of all an increase in the thickness of crystalline lamella and melting temperature, which apparently reflects the increase in the structural ordering of the main starch fraction (approximately 90%) in the tubers of these transformants. Along with this, the effect of accumulating fractions with a less ordered structure in the starch composition, correlating with the ectopic expression of the tms1 auxin biosynthesis gene, was established. At the same time, the B type of the polymorphic structure of starch remains unchanged. However, the detected changes mainly affected starch of the plants, cultivated in vitro. The starch of transgenic plants cultivated in the soil differs little in its basic characteristics from the starch of nontransgenic control plants.

Synthesis and behaviour of PEG-b-PDEAm block copolymers in aqueous solution

Well-defined double hydrophilic block copolymers (DHBCs) of poly(ethylene glycol)-block-poly(N,N-diethylacrylamide) (PEG-b-PDEAm) were synthesized via a reversible addition-fragmentation chain-transfer (RAFT) polymerization of N,N-diethylacrylamide (DEAm) using dithioester terminated PEG of different chain lengths as macro-chain transfer agents. Controlled molecular weight and narrow molecular weight distribution were achieved as proven by size exclusion chromatography (SEC). Cloud points (CP) were determined via turbidity measurements with ultraviolet-visible spectroscopy (UV–vis) and LCST by differential scanning micro-calorimetry (micro-DSC). They range from 32 to 40 °C depending on the PDEAm length block and its concentration. Above the LCST, fluorescence spectroscopy and dynamic light scattering (DLS) demonstrated that the PEG-b-PDEAm copolymers self-organized into large aggregates. More interestingly, copolymers pre-aggregated at relatively high concentrations below the LCST.

Role of Lipid Environment in the Pore-Forming Activity of Cecropin A

Cecropin A (CecA) is a well-known antimicrobial peptide produced by Hyalophore cecropia. It was found that cecropin A forms ion channels of different conductance and selectivity in planar lipid bilayers in the presence of negatively charged DOPS. Here the pore-forming activity of CecA in lipid bilayer of different lipid composition formed by the Montall and Muller technique in the absence and in the presence of alkaloids was studied. We found that one-side addition of CecA up to 5 µM led to the destabilization of lipid bilayers composed of POPC:POPG (50:50 mol %) or POPC:POPE:POPG (25:25:50 mol %). At the same time 2 µM of CecA induced the step-like current fluctuations corresponding to the openings and closures of transmembrane pores in POPC:TOCL – membranes (50:50 mol %). Increasing of CecA concentration up to 5 µM enhanced the macroscopic conductance. Introduction of piperine or capsaicin to the membrane bathing solution up to 400 µM caused dramatic reduction in multichannel conductance induced by CecA. Using differential scanning microcalorimetry we showed that piperine and capsaicin decreased the maximum temperature of the main transition of DPPC at molar ratio to lipid of 1:10 on 3.6 and 5.7 °C respectively. Analyzing the data we suggested that regulation of CecA induced macroscopic conductance is due to the changes in the elastic properties of the membrane at alkaloid adsorption. The study was supported by the Russian Foundation of Science (# 19-14-00110) and Russian Foundation of Basic Research (# 18-34-20047)

Light-assisted drying for anhydrous preservation of biological samples: optical characterization of the trehalose preservation matrix.

Protein-based drugs have been developed to treat a variety of conditions and assays use immobilized capture proteins for disease detection. Freeze-drying is currently the standard for the preservation of proteins, but this method is expensive and requires lengthy processing times. Anhydrous preservation in a trehalose amorphous solid matrix offers a promising alternative to freeze-drying. Light assisted drying (LAD) is a processing method to create an amorphous trehalose matrix. Proteins suspended in a trehalose solution are dehydrated using near-infrared laser light. The laser radiation accelerates drying and as water is removed the trehalose forms a protective matrix. In this work, LAD samples are characterized to determine the crystallization kinetics of the trehalose after LAD processing and the distribution of amorphous trehalose in the samples. These characteristics influence the long-term stability of the samples. Polarized light imaging revealed that LAD processed samples are stable against crystallization during low-humidity storage at room temperature. Scanning white light interferometry and Raman spectroscopy indicated that trehalose was present across samples in an amorphous form. In addition, differential scanning microcalorimetry was used to measure the thermodynamic characteristics of the protein lysozyme after LAD processing. These results demonstrate that LAD does not change the properties of this protein.

Effects of Salinity on Formation Behavior of Methane Hydrate in Montmorillonite

In marine sediments, seawater influences the phase behavior of natural gas hydrate. As a porous medium, the water distribution and physical properties of montmorillonite are influenced by the salt ions in seawater. In this work, the bound-water content in, and crystal structure of, montmorillonite is measured to investigate the effect of salt ions on the water distribution in montmorillonite. It can be determined from the results that the bound-water content in montmorillonite decreases as the salt-ion concentration increases. Salt ions affect the intercalation of water molecules in montmorillonite, and they then inhibit the expansion effect of montmorillonite. Next, the phase behaviors of methane hydrate in montmorillonite with NaCl solution are investigated using high-pressure micro-differential scanning calorimetry. The phase behavior of hydrate in montmorillonite with NaCl solution is discussed. In montmorillonite with NaCl solution, the phase equilibrium temperatures and the conversion rate of methane hydrate both decrease with increasing NaCl concentration. The results show that methane hydrate in montmorillonite is influenced not only by the phase-equilibrium effect of salt ions, but also by the formation effect of the salt ions on the bound-water content in montmorillonite.

The effect of two formulations of carbon enterosorbents on oxidative stress indexes and molecular conformation of serum albumin in experimental animals exposed to CCl4

The liver failure means inability to perform its normal synthetic, biotransformation and excretory functions. The disturbance of metabolic processes leads to the development of "metabolic endogenous intoxication" resulting in oxidative stress. Oxidative stress initiates the processes of oxidation of amino acid residues of blood plasma proteins causing the changes in their structure and functions. The effect of administration of highly activated porous carbonic enterosorbents on oxidative stress manifestations and molecular conformation of serum albumin in blood of experimental animals with acute liver failure induced by carbon tetrachloride (CCl4) needs to be investigated. Two forms of activated carbonic enterosorbents such as AC1 (primary beads with the range of diameters of 125–250 μm) and AC2 (secondary granules prepared from micronized AC1 having the mean particle size of ~1 μm) derived from phenol-formaldehyde resin were used in rat model with CCl4 intoxication. The total level of reactive oxygen species (ROS) in blood plasma, the activity of catalase (CAT) in blood hemolysates; the content of reduced glutathione (GSH) in liver homogenates, and the level of oxidative modification of proteins (OMP) such as aldehyde-dinitrophenylhydrazone (A-DNPH) and ketone-dinitrophenylhydrazone (K-DNPH) derivatives in blood plasma and liver homogenates were determined. In addition, the level of pro/antioxidant ratio in blood hemolysates and the content of lipid peroxidation product - malondialdehyde (MDA), in blood plasma and liver were determined. Melting thermograms of blood plasma proteins (BPP) and molecular conformation changes of serum albumin were analyzed by biophysical methods (differential scanning microcalorimetry and spectrofluorimetry). The extent of CCl4-induced oxidative damage in blood and liver of experimental animals was shown to be less expressed for AC1 in comparison with AC2 enterosorbent. However, AC2 used in the form of secondary granules positively influenced some biophysical properties of albumin molecule (temperature of melting, shape of melting endotherm and intrinsic fluorescence) after rats exposure to CCl4. In general, administration of both AC1 and AC2 led to the reduction of oxidative stress manifestations and partial restoration of native molecular conformation of serum albumin. These observations are promising in terms of achieving recovery of detoxification potential of organism after severe liver injury.

Global aviation biofuels market expected to grow $131 bn by 2025

Meibomian gland secretions (or meibum) are produced by holocrine meibomian glands and are secreted in melted form onto the ocular surface of humans and animals to form a protective tear film lipid layer (TFLL). Its protective effect strongly depends on the composition and, hence, thermotropic behavior of meibum. The goal of our study was to quantitatively evaluate the melting characteristics of human meibum and model lipid mixtures using differential scanning microcalorimetry. Standard calorimetric parameters, e.g. changes in calorimetric enthalpy, transition temperatures Tm, cooperativity of melting, etc. were assessed. We found that thermotropic behavior of meibum resembled that of relatively simple mixtures of unsaturated wax esters, but showed a lower change in calorimetric enthalpy, which can be indicative of a looser packing of lipids in meibum compared with pure standards and their simple mixtures. The cooperativity of melting of meibomian lipids was comparable to that of an equimolar mixture of four oleic-acid based wax esters. We demonstrated that the phase transitions in meibum start at about 10–15 °C and end at 35–36 °C, with Tm being about 30 °C. The highly asymmetrical shape of the thermotropic peak of meibum is important for the physiology and biophysics of TFLL.

Properties of Micellar Solutions of Sodium Decyl Sulfate at Relatively High Concentrations

Heat capacities of aqueous solutions of anionic surfactant sodium decyl sulfate in the 0.28–0.42 mol kg−1 range of molar concentrations and the 278–363 K range of temperatures are studied via precision adiabatic differential scanning microcalorimetry. Specific and apparent heat capacities of solutions at intervals of 0.01 mol kg−1, partial molar heat capacities of the solute and the solvent, and excess partial molar heat capacities are plotted as functions of concentration and temperature. The Kraft boundary is determined. Analysis of the characteristic changes in the above properties reveals structural changes in sodium decyl sulfate micelles that correspond to their shape transforming from cylindrical to plate-like in the region of the third critical micelle concentration.

Physicochemical and Biological Characterization of RTXM83, a New Rituximab Biosimilar.

RTXM83 is a rituximab biosimilar with proven clinical safety and efficacy. It is the first rituximab biosimilar developed and approved in South America and is currently marketed in several Latin American, Middle Eastern and African countries. The aim of this study was to present the physicochemical and biological characterization studies utilized to demonstrate the similarity between RTXM83 and its reference product. Primary and higher order protein structures were analysed using peptide mapping with liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS), fluorescence spectroscopy and circular dichroism, and micro-differential scanning calorimetry, among other techniques. Charge variants were determined by cation-exchange chromatography (CEX)and capillary isoelectric focusing(cIEF). Glycosylation and glycoforms distribution were analysed using MS, normal phase high-performance liquid chromatography (NP-HPLC) and high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). Size variants were evaluated by size-exclusion chromatography (SEC), sedimentation velocity analytical ultracentrifugation (SV-AUC), dynamic light scattering (DLS), and capillary electrophoresis-sodium dodecyl sulfate (CE-SDS). Biological characterization included binding assays for complement C1q, CD20, and several Fc receptors (FcRs), as well as potency determination for in vitro apoptosis induction, complement-dependent cytotoxicity (CDC), and antibody-dependent cell-mediated cytotoxicity (ADCC). RTXM83 and the reference product showed identical primary sequences and disulfide bridge patterns, and similarity at higher order protein structures, post-translational modification profiles (amino acid modifications, charge variants, and glycosylation) and levels of purity and process-related impurities. Functional studies demonstrated that RTXM83 is similar to the reference product regarding the three known mechanisms of action of rituximab: CDC, ADCC, and apoptosis induction. Binding affinities to CD20, complement component C1q, and different FcRs were also equivalent. RTXM83 is similar to its reference product in all critical quality attributes.

SIMULTANEOUS EFFECTS OF Cd(II) AND Pb(II) IONS AND γ-IRRADIATION ON STABILITY OF Spirulina platensis

Effect of toxic metal ions Cd(II) and Pb(II) on cyanobacterium (blue-green algae) Spirulina platensis intact cells have been studied with optical and differential scanning microcalorimetry (DSC) methods after 7.2 kGy 137 Cs gamma irradiation and without irradiation. It is shown that the addition of metal ions causes a decrease in optical absorption spectra band intensities. In the case of irradiation, the absorption band intensity decreases higher than without irradiation. The binding constant of Pb(II) with Spirulina platensis is calculated for nutrition medium with pH 9.2. DSC data show that Cd(II) and Pb(II) ions do not change the integral heat of absorption (Δ H m ) that equals to 24.6 J g -1 . In the case of irradiation, the DSC melting curve profile changes significantly and Δ H m decreases two times, which indicates that 50 % of proteins are denaturated. The DSC method also gives a possibility to evaluate C-phycocyanin content from deconvoluted heat absorption peak at 50 °C, which equals to 35.5 %. In case of irradiated wet mass, sub-cultured wet mass, and wet mass re-irradiated with the same dose, contents of Spirulina platensis ingredients – C-phycocyanin, chlorophyll, and carotenoids – increase as a result of the simultaneous effect of the metal ions and irradiation.

Kinetic promotion of mixed methane-THF hydrate by additives: Opportune to energy storage

Natural gas storage in the form of clathrate hydrates (Solidified natural gas; SNG) is an innovative and an extremely safe approach. Application of environmentally benign additives to enhance the hydrate formation kinetics is highly promising and possesses significant research potential. In this work, we elucidate the influence of hydrophilic/hydrophobic eco-friendly additives on the kinetics of mixed methane-tetrahydrofuran hydrates along with morphological observation. Further, the mixed methane-THF hydrates formed were characterized employing a high-pressure micro-differential scanning calorimetry (µ-DSC). Enhanced kinetics and microscale analysis in presence of these additives present salient information to aid the commercial deployment of SNG technology.

Microcalorimetry and fluorescence show stable peptide nucleic acid (PNA) duplexes in high organic content solvent mixtures.

The selectivity of nucleic acid hybridisation can be exploited to template chemical reactions, enabling materials discovery by chemical evolution. However, to date the range of reactions that can be used has been limited to those that are compatible with aqueous media, since the addition of organic co-solvents can have a large impact on the stability of nucleic acid duplexes. Peptide nucleic acids (PNAs) are promising in this regard because previous studies have suggested they may be stable as duplexes in high organic content solvent mixtures. Here, we use micro-differential scanning calorimetry (micro-DSC) to confirm for the first time that double-stranded PNA (dsPNA) is stable in N,N-dimethylformamide (DMF)/water mixtures up to 95 vol% DMF. Using fluorescence, we corroborate these results and show that the isothermal annealing of PNA in high DMF content solution is also rapid. These findings suggest that PNA could enable the use of a range of water-sensitive chemistries in nucleic acid templating applications.

PEGylated NiPAM microgels: synthesis, characterization and colloidal stability.

The objective of this work is to synthesize highly stable thermoresponsive microgels that could be used in diverse applications. To achieve this, N-isopropylacrylamide (NiPAM) based microgels were first synthesized by surfactant-free precipitation polymerization of NiPAM in the presence of poly(ethylene glycol)methacrylate (PEG) as a macro-comonomer and methylenebisacrylamide (MBA) as a chemical crosslinker. By combining a complete set of techniques such as dynamic light scattering (DLS), scanning electron microscopy (SEM), zetametry, 1H NMR and micro-differential scanning calorimetry (μDSC), we clearly demonstrate that (i) the incorporation of the PEG chains controls the size and the polydispersity of the NiPAM-based microgels, whereas the thermal behavior in solution (enthalpy, volume phase transition temperature (VPTT)) remains almost the same as for pure NiPAM microgels; (ii) the PEG chains are mainly located on the microgel periphery; and (iii) the presence of the PEG chains strongly increases the colloidal stability of microgels in electrolyte solutions at high temperatures.

The Mechanisms of Action of Triindolylmethane Derivatives on Lipid Membranes.

The effects of new synthetic antibacterial agents – tris(1-pentyl-1H-indol-3-yl)methylium chloride (LCTA-1975) and (1-(4-(dimethylamino)-2,5-dioxo-2,5-dihydro-1H-pyrrol-3-yl)-1H-indol-3-yl)bis(1-propyl- 1H-indol-3-yl)methylium chloride (LCTA-2701 – on model lipid membranes were studied. The ability of the tested agents to form ion-conductive transmembrane pores, influence the electrical stability of lipid bilayers and the phase transition of membrane lipids, and cause the deformation and fusion of lipid vesicles was investigated. It was established that both compounds exert a strong detergent effect on model membranes. The results of differential scanning microcalorimetry and measuring of the threshold transmembrane voltage that caused membrane breakdown before and after adsorption of LCTA-1975 and LCTA-2701 indicated that both agents cause disordering of membrane lipids. Synergism of the uncoupling action of antibiotics and the alkaloid capsaicin on model lipid membranes was shown. The threshold concentration of the antibiotic that caused an increase in the ion permeability of the lipid bilayer depended on the membrane lipid composition. It was lower by an order of magnitude in the case of negatively charged lipid bilayers than for the uncharged membranes. This can be explained by the positive charge of the tested agents. At the same time, LCTA-2701 was characterized by greater efficiency than LCTA-1975. In addition to its detergent action, LCTA-2701 can induce ion-permeable transmembrane pores: step-like current fluctuations corresponding to the opening and closing of individual ion channels were observed. The difference in the mechanisms of action might be related to the structural features of the antibiotic molecules: in the LCTA-1975 molecule, all three substituents at the nitrogen atoms of the indole rings are identical and represent n-alkyl (pentyl) groups, while LCTA-2701 contains a maleimide group, along with two alkyl substituents (n-propyl). The obtained results might be relevant to our understanding of the mechanism of action of new antibacterial agents, explaining the difference in the selectivity of action of the tested agents on the target microorganisms and their toxicity to human cells. Model lipid membranes should be used in further studies of the trends in the modification and improvement of the structures of new antibacterial agents.

Physicochemical and thermodynamic properties of the {1-alkyl-1-methylpiperidinium bromide [C1Cn=2,4PIP][Br], or 1-butylpyridinium bromide, [C4Py][Br], or tri(ethyl)butylammonium bromide [N2,2,2,4] [Br] + water} binary systems

This work is a continuation of our comprehensive study of ionic liquids, ILs (including organic salts with melting temperature above 100 °C) and their aqueous solutions as a novel alternative working pair for the absorption heat pump. A series of organic salts: 1-ethyl-1-methyl-piperidinium bromide, [C1C2PIP][Br], 1-butyl-1-methyl-piperidinium bromide, [C1C4PIP][Br], 1-butylpyridinium bromide, [C4Py][Br] and tri(ethyl)butylammonium bromide, [N2,2,2,4][Br] have been synthesized. The structures of compounds have been confirmed using NMR spectra. The basic thermal characterization of pure organic salts, including temperature and enthalpy of phase transition (Ttr, ΔtrH), temperature and enthalpy of melting (Tfus, ΔfusH) have been measured using a differential scanning microcalorimetry technique (DSC). The physico-chemical properties that are: density (ρ) and dynamic viscosity (η) of the tested binary systems have been determined at wide temperature and composition range. From experimental densities data, the apparent molar volumes (Vϕ,1) were calculated. In order to obtain limiting apparent molar volumes (Vϕ,10), the concentration dependence of apparent molar volumes was correlated with Redlich–Mayer type equation. Additionally, the limiting molar expansibilities (Eϕ0) and isobaric thermal expansion coefficients (αP) have been calculated. Temperature dependence of the dynamic viscosity has been correlated using VFT equation. The solid−liquid phase equilibria (SLE) have been determined using a dynamic method and correlated using NRTL equation. The influence of the alkyl chain length in the piperidinium cation substituent, as well as the cation structure, on investigated properties are presented and discussed.

Role of the Drying Technique on the Low-Acyl Gellan Gum Gel Structure: Molecular and Macroscopic Investigations

The effect of three drying processes (freeze, oven and supercritical CO2 drying) on CP Kelco low-acyl gellan gum gel was investigated, highlighting the role of the water removal mechanism (i.e. sublimation, evaporation and solvent replacement/extraction) and the process parameters on the gel structure, rather than focusing on the drying kinetics. It is the first time that a research paper not only compares the drying methods but also discusses and investigates how the molecular and macroscopic levels of gellan gum are affected during drying. Specifically, the dried gel structures were characterised by bulk density and shrinkage analyses as well as scanning electron microscope (SEM) and micro-computed tomography (μCT) microscopy. Micro-differential scanning calorimetry (μDSC) was used in a novel way to investigate the effect of the drying technique on the polymer disorder chains by partial melting of the gel. The resulting water uptake during rehydration was influenced by the obtained dried structure and, therefore, by the employed drying process. It was found that freeze-dried (FD) structures had a fast rehydration rate, while both oven-dried (OD) and supercritical CO2-dried (scCO2D) structures were slower. After 30 min, FD samples achieved a normalised moisture content (NMC) around 0.83, whereas OD and scCO2D samples around 0.33 and 0.19, respectively. In this context, depending on the role of the specific hydrocolloid in food (i.e. gelling agent, thickener, carrier), one particular dried-gel structure could be more appropriate than another.Graphical abstractFrom left to right: unprocessed hydrogels; μ-CT images of dried gels and unprocessed hydrogel; DSC curves after drying process

Ionic Liquids as Efficient Extractants for Quercetin from Red Onion (Allium cepa L.)

The solubility of Quercetin in alcohols, esters and in 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM][TFA] ionic liquid (IL) using the dynamic method was measured at constant pH in a range of temperature 233-373 K and compare to the literature data. The experimental solubility data have been correlated by means of commonly known GE models,UNIQUAC and NRTL with the assumption that the systems studied here present simple eutectic behaviour. The basic thermal properties of Quercetin, i.e., fusion temperature and the enthalpy of fusion have been measured with differential scanning microcalorimetry technique (DSC).The application of alcohols, esters and ionic liquids (ILs) as alternatives to conventional organic solvents in the liquid-liquid extraction of Quercetin from different medicinal plants, flowers and frozen red onion (Allium cepa L.) was investigated. The parameters affecting the extraction yield using ILs such as chemical structures of the IL cation and anion, the phase volume ratio of extracting solvent, time of extraction and the Quercetin form of sample and concentration were evaluated. Specific Quercetin composition was performed through HPLC measurements. Using the most effective ILs in extraction, the 14.3±0.1g.kg-1 and 5.9±0.1g.kg-1of Quercetin from frozen pure red onion was obtained with N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate, [N2,2,1,2OCH3][BF4] and 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM][TFA], respectively.

Complexation of lysozyme with lambda carrageenan: Complex characterization and protein stability

In a previous work, we reported that interaction of lysozyme (Lys) with kappa carrageenan (kCG) is governed by both electrostatic interactions and secondary forces, and lead to formation of asymmetric complex particles with an irregular localization of biopolymers without formation of a single center of binding. In this work we characterize complexation of lysozyme with strongly charged lambda carrageenan (lCG) and study protein stability within complex at different composition, pH and ionic strength (I) by a combination of a few main experimental techniques: turbidimetric titration, dynamic and electrophoretic light scattering, differential scanning microcalorimetry (DSMC), fluorescence and circular dichroism measurements. Complexation is governed by only electrostatic interactions, exhibits extremely low (7⋅10−4) qOnset values and lead to formation of swarm of large complex aggregates consisting of hundreds of very small separate particles. At pH 7 and I = 0.01 a stoichiometric lCG/Lys composition is equal to 0.309:1 (wt/wt) or 1:119 (mole/mole). It shift monotonically in the direction of higher lCG content with increase I values. The effect of I on stability of the complex formed has nonmonotonic character displaying a maximum at I ≈ 0.08. Complexation leads to a spectacular increase in the helix content and blue shift for Lys in the presence of lCG that probably reflects a more hydrophobic nonpolar environment of surface exposed tryptophan residues. It also significantly decreases thermal stability of Lys within complex in a wide range of pH suggesting that lCG has a higher affinity for the unfolded state than for the native state of Lys.

Studying the colloidal behavior of chimeric liposomes by cryo-TEM, micro-differential scanning calorimetry and high-resolution ultrasound spectroscopy

The investigation of colloidal properties of nanosystems represents a fundamental issue for the development of nanotechnology-based medicines. The aim of this study is to combine various techniques in order to characterize more comprehensively chimeric nanovesicles composed of block or gradient block copolymers with different architectures and compositions. Several chimeric systems were prepared and the impact of the block [poly(ε-caprolactone)−poly(ethylene oxide); PEO-b-PCL] and gradient block [poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline); MPOx] copolymers on the physicochemical and morphological characteristics of conventional 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes was examined. Light scattering techniques and cryo-TEM were used for the physicochemical and morphological characterization of the prepared systems. The size and the morphology were strongly related to the architecture and the composition of the polymeric compounds. Micro differential scanning calorimetry and high-resolution ultrasound spectroscopy were used for investigating the interactions between the DPPC lipids and the polymeric guest. An increase in the main transition temperature was observed for the prepared chimeric systems in comparison to DPPC liposomes. In conclusion, a detailed characterization of the colloidal behavior of chimeric liposomes can benefit from the combination of the aforementioned techniques that operate synergistically, giving information on their physicochemical and morphological characteristics as well as on their thermotropic behavior.

Preparation of an ethylene glycol-based block copolymer consisting of six different temperature-responsive blocks

An ethylene glycol-based hexa-block copolymer with six different temperature-responsive blocks was prepared via a reversible addition-fragmentation chain transfer (RAFT) polymerization. 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methacrylate (OEGMA) were selected as the ethylene glycol-based monomers. Each block of the hexa-block copolymer has a different OEGMA content and thus exhibits a different lower critical solution temperature (LCST). The structures of the block copolymers are similar to gradient copolymers. The molecular weights of the copolymers increased with the number of blocks (first block (P(MEO2MA)): 2800 g/mol, di-block copolymer: 7400 g/mol, tri-block copolymer: 12,000 g/mol, tetra-block copolymer: 18,500 g/mol, penta-block copolymer: 26,800 g/mol, and hexa-block copolymer: 40,400 g/mol) with relatively narrow molecular weight distributions (1.18–1.42). Each block exhibits a different LCST in aqueous solution owing to their different OEGMA contents. To the best of our knowledge, this is the first report of a block copolymer containing more than four types of temperature-responsive blocks. The temperature-responsive properties of the prepared block copolymers were investigated by UV-vis spectroscopy, micro-differential scanning calorimetry, and scanning electron microscopy. An ethylene glycol-based hexa-block copolymer with six different temperature-responsive blocks was prepared via a reversible addition-fragmentation chain transfer (RAFT) polymerization. 2-(2-Methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methacrylate (OEGMA) were selected as the ethylene glycol-based monomers. Each block exhibits a different LCST in aqueous solution owing to their different OEGMA contents.