Biexponential Equation Research Articles

Formulation of gastroresistant tablets containing sodium alendronate-loaded blend microparticles

<p>Sodium alendronate is an antiresorptive drug used for the treatment of postmenopausal osteoporosis. However, its oral administration is associated with low bioavailability and gastroesophageal irritation. This work aimed at developing tablets containing sodium alendronate-loaded microparticles by direct compression to achieve a safe and effective form. The parameters evaluated were average weight, hardness, thickness and drug content. <italic>In vitro</italic> release tests were carried out using simulated gastric and intestinal fluids, and the profiles were analyzed through the Korsmeyer-Peppas mono- or biexponential dependent approaches. Tablets presented adequate average weight, thickness, good mechanical properties and drug content close to 100%. Moreover, the formulation released less than 11% of sodium alendronate in gastric fluid, exhibiting a good gastroresistance. At pH 6.8, almost 100% of the drug was released in 12h, showing a prolonged profile. The mathematical modeling indicated that the experimental data was better fitted to the biexponential equation. Furthermore, a good correlation coefficient was obtained for the Korsmeyer-Peppas model and the release exponent suggested that the drug dissolution was driven by anomalous transport. In conclusion, the microparticulated tablets can be considered a promising alternative for oral delivery of sodium alendronate.</p>

Investigation of Apparent Diffusion Coefficient from Ultra-high b-Values in Parkinson's Disease.

To assess brain damage in Parkinson's disease (PD) based on apparent diffusion coefficient (ADC) data obtained from ultra-high b-values. Eighteen PD patients and 18 controls received diffusion-weighted imaging (DWI) with standard b-values (0, 1,000 s/mm(2)) and 15 b-values (0-5,000 s/mm(2)). Standard ADC (ADCst) maps were calculated from standard b-values, while maps of pure diffusion coefficients (D), pseudo-diffusion coefficients (D(*)), and ultra-high ADCs (ADCuh) were calculated from the 15 b-values using a tri-component model. In this model, D and D(*) values were quantified with a bi-exponential equation using b-values less than 2,000 s/mm(2), while ADCuh was quantified by fitting the signals at ultra-high b-values (2,000-5,000 s/mm(2)) to the mono-exponential equation. ADCst, ADCuh, D, and D(*) of the globus pallidus (GP), putamen (P), and substantia nigra (SN) were compared between PD patients and normal control subjects. ADCuh of the GP, P, and SN was significantly lower in PD patients than those in control subjects (P < 0.001), while ADCst, D, and D(*) of the GP, P and SN were not different between the two groups (P > 0.05). ADCuh may be a useful measurement for evaluating brain damage in PD patients. • DWI with ultra-high b-values may provide new insight into Parkinson's disease pathology • ADC calculated using ultra-high b-values is different between PD and controls • ADC uh may be associated with water transportation by aquaporins.

Development of optimum feeding rate model for white sturgeon (Acipenser transmontanus)

Abstract Establishing the optimum feeding rate (OFR; % body weight per day) for a cultured fish is a significant step toward the success of the aquaculture operation. Therefore, the objectives of this study were 1) the estimation of OFR for 19 datasets with different initial body weights by applying broken-line and quadratic regression models and 2) an investigation of potential OFR prediction models using 19 estimated OFRs from objective 1. Objective 1) Nineteen datasets were obtained from five published studies (14 datasets) and one unpublished study (5 datasets) which were carried out to evaluate the effects of feeding rate on growth performance in white sturgeon of initial body weights varying from 0.05 g to 764 g. Each dataset, containing feeding rate (independent variable) and specific growth rate (% body weight increase per day; dependent variable) was used to estimate OFR by one-slope straight broken-line, two-slope straight broken-line, quadratic broken-line, and quadratic models for each body weight class. Calculations of model selection criteria, including the adjusted coefficient of correlation, Akaike information criterion, and corrected Akaike information criterion were performed to compare model performance on OFR estimation for each dataset. Three models (two-slope straight broken-line, quadratic broken-line, and quadratic models) were considered acceptable for the estimation of OFR, and the three sets of estimated OFRs obtained by these models were used in objective 2. Objective 2) Several regression models, including polynomial models of order from 1 to 6, a simple exponential model with a constant, and a bi-exponential model, were fitted to each set of the 19 estimated OFRs against transformed initial body weights. A power function model was also fitted to the estimated OFRs against untransformed initial body weights. The model selection criteria for objective 2 were the same as those for objective 1. Overall model performance on the estimation of OFR for the 19 datasets shows that the quadratic broken-line model performed best, followed by the quadratic, two-slope straight broken-line, and one-slope straight broken-line models. Given the overall performance of model fitness to the sets of the OFR estimates, the bi-exponential regression model emerged as the most favorable one. As a result, the bi-exponential model equation. OFR % body weight per day = 0.00344 ± 0.0123 e − 5.684 ± 2.309 ln ( body weight ) + 8.695 ± 0.606 e − 0.549 ± 0.065 ln ( body weight ) obtained by fitting the estimated OFRs derived from the quadratic broken-line model analysis, can be used to predict the OFR for white sturgeon from about 0.05 g to 800 g.

Self-Emulsifying Pellets: Relations Between Kinetic Parameters of Drug Release and Emulsion Reconstitution—Influence of Formulation Variables

The effects of surfactant type and content on the kinetics of emulsion reconstitution and release of drugs differing in lipophilicity from self-emulsifying microcrystalline cellulose pellets were studied. Furosemide and propranolol were the drugs, medium-chain triglyceride was the oil, and Cremophors ELP, RH40, and RH60 were the surfactants. Pellets were prepared by extrusion/spheronization with emulsions (75% water and 25%, w/w, oil/surfactant/drug). Stability of the emulsions was evaluated from changes in the back-scattered light, and re-emulsification and drug release from light transmittance and UV spectroscopy, respectively. Emulsion stability increased because of the incorporation of the drugs. Re-emulsification depended only on the surfactant content and was expressed by a simple power equation (Ra2 > 0.945, Q(2) > 0.752). Drug release was expressed by two biexponential equations (Ra2 > 0.989, Q(2) > 0.699 and Ra2 > 0.947, Q(2) > 0.693) implying initial burst and terminal slow release phase and by the linear form (Lineweaver-Burke) of Michaelis-Menten equation (Ra2 > 0.726, Q(2) > 0.397). Relationships exist between the rate constants of the equations describing emulsion reconstitution and drug release, for propranolol compositions (R(2) = 0.915), and for compositions of both drugs with less hydrophilic ELP and RH40 (R(2) = 0.511), and also, among dissolution efficiency, drug solubility in oil/surfactant, and emulsion reconstitution ability, indicating the importance of drug solubilization in oil/surfactant and re-emulsification ability on drug release.

Determination of Optimum Values of Descriptors to Set Filters for Synthetic Tri-Pyrrole Derivatives (Prodiginines) Against Multi Drug Resistant Strain of &lt;i&gt;Plasmodium Falciparum&lt;/i&gt;

In the present study, we have carried out extensive non-linear Quantitative-Structure Activity Relationship (QSAR) analysis to correlate in vitro anti-malarial activity against multi drug resistant strain of Plasmodium falciparum. Forty-three synthetic prodiginines with different structural features were used for their potential antimalarial activity. Linear, bilinear, biexponential and parabolic equations were developed. These equations were compared to determine the optimum values of descriptors for very useful and easily interpretable descriptors. The optimum values of these descriptors could be helpful in finding and optimizing a good lead compound. Obtained correlations reveal that various factors like lipophilicity, molecular weight and number of bonds have non-linear relation with the anti-malarial activity.

Irrigation of a Mediterranean soil under field conditions with urban wastewater: Effect on pesticide behaviour

The use of wastewater for irrigation in arid or semiarid regions, where shortage of fresh water restricts agricultural production, has been well established in the last decades. However, the effect of this irrigation practice on the retention on soil of pesticides applied for pest control has been mostly approached by laboratory assays. More realistic approaches are needed because soil pollution with pesticides may cause a serious risk to the environment and to human health due to direct exposure or through the food chain. Therefore in this study a field experiment was run with three pesticides with contrasting properties: the insecticide thiacloprid and the herbicides chlorotoluron and pendimethalin. Three different treatments were considered: non-amended soil irrigated with well water (WL), with treated wastewater (TW) and organic-amended soil (3.2kg per plot) irrigated with treated wastewater (F+TW). Pesticide decay kinetic models showed that chlorotoluron residues were adequately explained by the bi-exponential first-order equation whereas the other two pesticides were fitted to a single first-order equation. The short-term pesticide persistence (DT50) was always higher for TW, reflecting that irrigation with TW slightly increased pesticide persistence in surface soil. Addition of an organic fertilizer (F+TW) did not modify the long-term thiacloprid persistence (DT90) with respect to irrigation with TW, decreased that of pendimethalin (almost 10 days) but increased that of chlorotoluron (12 days). The biological soil indicators measured showed contradictory results, with soil respiration increasing and dehydrogenase activity decreasing with TW irrigation.

Computational Antioxidant Capacity Simulation (CAOCS): A Novel Framework of Antioxidant Capacity Profiling

Abstract Inconsistent ranking is a well-known drawback of antioxidant capacity (AOC) profiling methodologies that use free-radical species as oxidant. This problem leads to assay results that are not biorelevant. Linear free energy relationships (LFER) theory predicts proton transfer (PT) kinetics as a surrogate for biorelevant hydrogen atom transfer (HAT) kinetics. Computational antioxidant capacity simulation (CAOCS), based on real-time proton transfer kinetics modeling (PTKM) of polyphenols and phenol-like small molecules, inspired a novel AOC profiling methodology. Kinetic data acquired by incremental addition of resorcinol to an oxidized probe (phenol red), was fitted to mono-exponential decay equation (MED). Absorbance decay data from strongly antioxidant phenol-like molecules (e.g. ascorbic acid) and a new chromogenic probe (phenolphthalein) was fitted to MED and bi-exponential decay equation. The preferred model and corresponding best-fit rate constant (K ptt) was identified by comparison of fits, using Akaike’s Information Criterion (AICc). Photometric phenolphthalein assay (PPA)-derived metric was normalized with photometric phenol red assay (PPRA) results by using a function developed from proton concentration differential between phenolphthalein and phenol red, with respect to decay threshold to plateau (assay endpoint) interval. pKa dependence of the CAOCS’ metric is a signature of structure–function relationships, and hence, biorelevance. It is shown, unambiguously, that a combination of two phenolic probe molecules, an analytical system devoid of free radicals, and statistical identification of preferred exponential decay fit to PT kinetics data, constitutes a novel algorithm for AOC profiling of polyphenols and phenol-like molecules. This methodology holds a promise of utility in quality assurance of dietary supplements.

An optoelectronic sensing device for CO detection in air based on a binuclear rhodium complex

The design, fabrication and validation of an optoelectronic sensor implemented in an easy-to-use portable device for the selective and sensitive detection of CO in air is reported herein. The system is based on the colour changes observed in the binuclear rhodium complex of formula [Rh2[(C6H4)P(C6H5)2]2(O2CCF3)2] (CF3CO2H)2 (1) upon coordinating CO molecules in axial positions. Complex 1 is used supported on cellulose chromatography paper. In this support, colour changes to the naked eye are observed for CO concentrations above 50ppm. The probe is also implemented in a simple portable optoelectronic device. The cellulose support containing probe 1 in this device is placed inside a small dark chamber, is illuminated with a tricolour LED emitting at 624, 525 and 470nm, respectively corresponding to red (R), green (G) and blue (B) light, and reflected light is detected by a photodiode. With a transimpedance amplifier, the current generated by the photodiode is transformed into a voltage compatible with the 10-bit analogue-to-digital converter (ADC) port. Colour changes are measured as the distance d between the R, G and B data of the blank (probe without CO) and that for a certain CO concentration. Typical calibration curves are fitted using a bi-exponential equation. This system offers a typical response time of a few minutes (ca. 7min) and a limit of detection of 11ppm. The probe in the cellulose supports is also highly reversible. The optoelectronic device is portable (dimensions 14×8.5×3.5cm; weighs approximately 270g) and is powered by AA batteries. In addition, no variations in experimental parameter d upon exposure to CO2, N2, O2, Ar, water-saturated air and vapours of chloroform, hexane, ethanol, acetone, methane, toluene or formaldehyde are observed. Besides, colour changes are found for acetonitrile vapour, NO and NO2, but only at high concentrations. For validation purposes, the device was used to determine the CO present in the 4-shed accumulated smoke of two cigarette types after passing smokers’ lungs.

Fluorescence Modulation and Photochromism in Azobismaleimide Derivatives

A fluorophore-photochrome system incorporating an aryleneimine type fluorophore and an azobismaleimide photochrome was developed and the photochemical properties of this system were investigated. The photoisomerization of trans-azoaromatic chromophore leads to the increase of the fluorescence intensity of fluorophore. The cis azobismaleimide isomers revert photochemically to the trans form and the emission intensity decreases. The fluorescence intensity of the imine fluorophore can be modulated under irradiation with UV and visible (436nm) light due to reversible trans-cis-trans photoisomerization of azobismaleimide partner. The photoisomerization kinetics was obeyed a first-order relationship with a rate constant of 1.95 × 10(-2)s(-1) for azobismaleimide/imine fluorophore system and for polyazothioetherimide/imine derivative the kinetics was described by a biexponential equation.

Effect of ionic liquids alkyl chain length on horseradish peroxidase thermal inactivation kinetics and activity recovery after inactivation

The effects of different alkyl chain lengths of ionic liquids 1-ethyl-, 1-butyl- and 1-hexyl-3-methylimidazolium chloride, on the catalytic activity, thermal stability and deactivation kinetics of horseradish peroxidase were studied in the temperature range of 45-85 °C. The presence of 1-ethyl- and 1-butyl-ionic liquids up to 25% (w/v) did not affect significantly the enzyme activity at 25 °C, whereas the addition of 1-hexyl-solvent resulted in lower activity of enzyme. Typical biphasic deactivation profiles were obtained and adequately fitted by a bi-exponential equation. When increasing ionic liquids concentration up to 25% (w/v), the second phase of deactivation became more prominent, till leading to apparent first-order kinetics. Occurrence of activity regain, following thermal deactivation was found, reaching up 60-80% of the initial activity, especially in 1-hexyl-3-methylimidazolium chloride. Activity regain was particularly noticeable in the first phase of deactivation. Temperature sensitivity of the Soret band maxima indicated that the enzyme prepared in buffer or 1-hexyl-3-methylimidazolium chloride had similar conformational changes in the haem region, but no correlations were found with activity decrease.

Experimental pharmacokinetics of niferidil upon intravenous administration

The kinetics of niferidil concentration change in blood serum, organs, and urine of rats was studied after i.v. administration at a dose of 5 mg/kg. The blood concentration profile was shown to be described by a bi-exponential equation corresponding to a two-compartment model. Niferidil disappeared quickly from the blood pool with a distribution half-life of 5.13 min. The elimination half-life from blood was 23.3 min. Niferidil penetrated rapidly into organs such as the liver, kidneys, and heart. The concentration calculated per gram of organ 30 min after i.v. administration was six times greater than that in blood (in 1 mL). Accumulation in these organs was not observed. The elimination half-life from the organs was about 1 h. Niferidil was not detected in brain tissue. Niferidil was excreted after i.v. administration unchanged in urine in small amounts. About 10% of the injected dose was eliminated after 24 h. Niferidil was not found in feces.

Dynamics of regional lung aeration determined by electrical impedance tomography in patients with acute respiratory distress syndrome

Background: Lung tissue of patients with acute respiratory distress syndrome (ARDS) is heterogeneously damaged and prone to develop atelectasis. During inflation, atelectatic regions may exhibit alveolar recruitment accompanied by prolonged filling with air in contrast to regions with already open alveoli with a fast increase in regional aeration. During deflation, derecruitment of injured regions is possible with ongoing loss in regional aeration. The aim of our study was to assess the dynamics of regional lung aeration in mechanically ventilated patients with ARDS and its dependency on positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT). Methods: Twelve lung healthy and twenty ARDS patients were examined by EIT during sustained step increases in airway pressure from 0, 8 and 15 cm H2O to 35 cm H2O and during subsequent step decrease to the corresponding PEEP. Regional EIT waveforms in the ventral and dorsal lung regions were fitted to bi-exponential equations. Regional fast and slow respiratory time constants and the sizes of the fast and slow compartments were subsequently calculated. Results: ARDS patients exhibited significantly lower fast and slow time constants than the lung healthy patients in ventral and dorsal regions. The time constants were significantly affected by PEEP and differed between the regions. The size of the fast compartment was significantly lower in ARDS patients than in patients with healthy lung under all studied conditions. Conclusion: These results show that regional lung mechanics can be assessed by EIT. They reflect the lower respiratory system compliance of injured lungs and imply more pronounced regional recruitment and derecruitment in ARDS patients.

Dynamics of regional lung aeration determined by electrical impedance tomography in patients with acute respiratory distress syndrome

BackgroundLung tissue of patients with acute respiratory distress syndrome (ARDS) is heterogeneously damaged and prone to develop atelectasis. During inflation, atelectatic regions may exhibit alveolar recruitment accompanied by prolonged filling with air in contrast to regions with already open alveoli with a fast increase in regional aeration. During deflation, derecruitment of injured regions is possible with ongoing loss in regional aeration. The aim of our study was to assess the dynamics of regional lung aeration in mechanically ventilated patients with ARDS and its dependency on positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT).MethodsTwelve lung healthy and twenty ARDS patients were examined by EIT during sustained step increases in airway pressure from 0, 8 and 15 cm H2O to 35 cm H2O and during subsequent step decrease to the corresponding PEEP. Regional EIT waveforms in the ventral and dorsal lung regions were fitted to bi-exponential equations. Regional fast and slow respiratory time constants and the sizes of the fast and slow compartments were subsequently calculated.ResultsARDS patients exhibited significantly lower fast and slow time constants than the lung healthy patients in ventral and dorsal regions. The time constants were significantly affected by PEEP and differed between the regions. The size of the fast compartment was significantly lower in ARDS patients than in patients with healthy lung under all studied conditions.ConclusionThese results show that regional lung mechanics can be assessed by EIT. They reflect the lower respiratory system compliance of injured lungs and imply more pronounced regional recruitment and derecruitment in ARDS patients.

Antagonism of Trichoderma harzianum ETS 323 on Botrytis cinerea Mycelium in Culture Conditions

ABSTRACT Previous studies have shown that the extracellular proteins of Trichoderma harzianum ETS 323 grown in the presence of deactivated Botrytis cinerea in culture include a putative l-amino acid oxidase and have suggested the involvement of this enzyme in the antagonistic mechanism. Here, we hypothesized that the mycoparasitic process of Trichoderma spp. against B. cinerea involves two steps; that is, an initial hyphal coiling stage and a subsequent hyphal coiling stage, with different coiling rates. The two-step antagonism of T. harzianum ETS 323 against B. cinerea during the mycoparasitic process in culture was evaluated using a biexponential equation. In addition, an l-amino acid oxidase (Th-l-AAO) was identified from T. harzianum ETS 323. The secretion of Th-l-AAO was increased when T. harzianum ETS 323 was grown with deactivated hyphae of B. cinerea. Moreover, in vitro assays indicated that Th-l-AAO effectively inhibited B. cinerea hyphal growth, caused cytosolic vacuolization in the hyphae, and led to hyphal lysis. Th-l-AAO also showed disease control against the development of B. cinerea on postharvest apple fruit and tobacco leaves. Furthermore, an apoptosis-like response, including the generation of reactive oxygen species, was observed in B. cinerea after treatment with Th-l-AAO, suggesting that Th-l-AAO triggers programmed cell death in B. cinerea. This may be associated with the two-step antagonism of T. harzianum ETS 323 against B. cinerea.

One Single-Time-Point Kidney Uptake From OctreoScan Correlates With Number of Desintegrations Measured Over 72 Hours and Calculated for the 6.7 Hours Half-Life Nuclide 177Lu

In somatostatin receptor-targeted therapy, renal toxicity is an expected side effect, and therefore pretherapeutic dosimetry based on a measured kinetics is preferable. In contrast, a convenient one single-time-point scan might also reveal relevant information on expected dose to organs. However, very early time points might not reflect the true retention by the renal cortex and therefore be of limited value to predict dose for the long-lived 177Lu. Dosimetry with 111In-octreotide was performed in 24 patients, and the number of disintegrations (ND) were calculated for 177Lu. Uptake values for each time point were correlated with ND. The fitting algorithm was best with biexponential equations in 18 patients. Mean biologic half-life of the alpha component was 6 hours (+/-12 hours) and for the beta component 82 hours (+/-38 hours). For the early time points, correlation with ND was generally poor. For later time points, correlation increased markedly after 4 hours (4 hours: r = 0.83, 72 hours: r = 0.93) and were also capable of predicting dosimetry to some extent. In conclusion, thorough quantification of the 4 hours single-time-point scans seems to be enough to predict the expected renal dose for radionuclide therapies to some degree.

Photochromic behavior of naphthopyran in styrene–butadiene–styrene elastomer thin films: Effect of stretching of film and linker

AbstractThermoplastic elastomers of styrene–butadiene–styrene (SBS) triblock copolymers containing grafts of naphthopyran as side‐chain polymer were prepared by polymerization of naphthopyran acrylate monomer with a solution of SBS in tetrahydrofuran. Thin films of all grafted SBS polymers displayed photochromism, the decoloration kinetics of naphthopyran in the films was modeled by fitting biexponential equations to the photochromic decay curves after UV light irradiation. Stretching of the grafted SBS film at room temperature affected the fading rate constant k1 of the naphthopyran. The length of linker between photochromic naphthopyran moiety and the acrylate unit in monomer also affected the fading rate constant k1 of the naphthopyran in SBS elastomers. This study presents an example of tuning the photochromic properties of naphthopyran via two approaches, polymer structure, and stretching of films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and characterization of Biochanin A loaded solid lipid nanoparticles

Biochanin A, the predominant isoflavones found in plants, had proved its human health benefits. The purpose of this research was to study whether Biochanin A (BCA) loaded solid lipid nanoparticles (SLN) could improve solution and prolong the half‐life of BCA. BCA‐SLN was prepared by emulsion evaporation and low temperature solidification technique, and freeze‐dried powders were developed to improve stability.The mean particle sizes, zeta potential, entrapment efficiency (EE), and drug loading capacity (DL) of BCA was 176.0 nm, −18.7 ± 0.26, 97.15 ± 0.28%, and 6.38 ± 0.04%, respectively. The results of differential scanning calorimetry (DSC) and X‐ray diffraction analysis (XRD) indicated that the BCA was wrapped and absorbed in the nanoparticles. The solution of preparation is much higher than the untreated BCA.Results of stability of SLN showed a relatively short‐term stability after storage at 4°C and 25°C for 15 days. Drug release of untreated BCA and BCA‐SLN was fit into the Biexponential equations and Weibull equations, respectively, and SLN showed sustained release properties. But after freeze‐dried, stability was improved, and the EE and DL had a slightly decrease. The mean particle size was slightly increased, but the structure was not changed. In conclusion, SLN systems can represent an effective strategy to change the poor aqueous solubility and prolong the half‐time of BCA.

Release characteristics of doxycycline chitosan nanoparticles freeze-dried powderin vitroandin vivo

This paper is to study the release characteristics of doxycycline (DC) raw material drug and doxycycline chitosan nanoparticles (DC-CS-NPs) freeze-dried powder in vitro and in vivo by ultraviolet spectrophotometry and ultra performance liquid chromatography, respectively. Results showed that the release behaviors of DC raw material drug were simulated the most in the zero order dynamic equation in artificial gastric juice, artificial intestinal juice and pH 7.4 buffer phosphate. The release of DC raw material drug was fast which could completely dissolve in one hour; The DC-CS-NPs freeze-dried powder had a significant slow-release characteristic. The release behaviors were simulated the most in the biexponential equation. The drug released fast in the early stage while it released slowly later. The order of release speed of DC-CS-NPs freeze-dried powder from fast to slow was pH 2.0 artificial gastric juice, pH 3.0 artificial gastric juice, pH 4.0 artificial gastric juice, artificial intestinal juice and pH 7.4 buffer phosphate. When DC raw material drug became DC-CS-NPs freeze-dried powder, after a single oral administration at a dose of 20 mg/kg at (25±1) ℃, the double-peak phenomenon of plasma in channel catfish was turned into single-peak, and the pharmacokinetic parameters of DC-CS-NPs freeze-dried powder were changed. Compared to DC raw material drug, the peak concentration (Cmax) decreased. The peak time (Tmax) and terminal elimination half-life (T1/2β) prolonged. The area under concentration-time curve (AUC) was larger. The DC-CS-NPs freeze-dried powder will become an ideal DC new formulation.

PHBV/PCL Microparticles for Controlled Release of Resveratrol: Physicochemical Characterization, Antioxidant Potential, and Effect on Hemolysis of Human Erythrocytes

Microparticles of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL) containing resveratrol were successfully prepared by simple emulsion/solvent evaporation. All formulations showed suitable encapsulation efficiency values higher than 80%. PHBV microparticles revealed spherical shape with rough surface and presence of pores. PCL microparticles were spherically shaped with smooth surface. Fourier-transformed infrared spectra demonstrated no chemical bond between resveratrol and polymers. X-ray powder diffraction patterns and differential scanning calorimetry analyses indicated that microencapsulation led to drug amorphization. These PHBV/PCL microparticles delayed the dissolution profile of resveratrol. Release profiles were better fitted to biexponential equation. The hypochlorous-acid-scavenging activity and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation discoloration assay confirmed that the antioxidant activity of PHBV/PCL microparticles was kept, but was dependent on the microparticle morphology and dissolution profile. Resveratrol-loaded PHBV/PCL microparticles showed no cytotoxic effect on red blood cells.

Influence of polymer polarity on photochromic behavior of naphthodipyran doped in different polymeric matrixes

AbstractPhotochromic polymer films were prepared by doping the naphthodipyran into different polymers such as Polyvinylpyrrolidone (PVP), styrene‐butadiene‐styrene (SBS) triblock copolymer, and polymethyl methacrylate (PMMA) at different concentrations. The kinetics of the photochromism/decoloration in the thin films was quantified by fitting biexponential equations to their photochromic decay curves after UV irradiation. The results show that the fastest decoloration process was in SBS, and the slowest one was in PVP. The DSC results indicate that Tg of polymeric matrix has no obvious effect on the decoloration rate of naphthodipyran. The decreasing order of the decoloration constant of naphthodipyran was consistent with increasing polarity of polymer matrixes as PVP &gt; PMMA &gt; SBS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012