pH-Dependent Solubility and Dissolution Behavior of Carvedilol—Case Example of a Weakly Basic BCS Class II Drug

The objective of this study was to investigate the pH-dependent solubility and dissolution of weakly basic Biopharmaceutical Classification Systems (BCS) class II drugs, characterized by low solubility and high permeability, using carvedilol, a weak base with a pK _a value of 7.8, as a model drug. A series of solubility and in vitro dissolution studies was carried out using media that simulate the gastric and intestinal fluids and cover the physiological pH range of the GI from 1.2 to 7.8. The effect of ionic strength, buffer capacity, and buffer species of the dissolution media on the solubility and dissolution behavior of carvedilol was also investigated. The study revealed that carvedilol exhibited a typical weak base pH-dependent solubility profile with a high solubility at low pH (545.1–2591.4 μg/mL within the pH range 1.2–5.0) and low solubility at high pH (5.8–51.9 μg/mL within the pH range 6.5–7.8). The dissolution behavior of carvedilol was consistent with the solubility results, where carvedilol release was complete (95.8–98.2% released within 60 min) in media simulating the gastric fluid (pH 1.2–5.0) and relatively low (15.9–86.2% released within 240 min) in media simulating the intestinal fluid (pH 6.5–7.8). It was found that the buffer species of the dissolution media may influence the solubility and consequently the percentage of carvedilol released by forming carvedilol salts of varying solubilities. Carvedilol solubility and dissolution decreased with increasing ionic strength, while lowering the buffer capacity resulted in a decrease in carvedilol solubility and dissolution rate.     

制剂技术在提高BCS IV类药物生物利用度中的应用及此类药物体内外相关性研究现状

随着组合化学和高通量筛选在药物发现中的广泛应用，新候选药物不断涌现，其中不乏各种BCS IV类药物，而该类药物凸显的低溶解性/低渗透性极大地阻碍了其进一步的临床开发与应用。因此，如何有效提高该类药物生物利用度，已成为药剂学研究者长期以来广泛关注并致力于解决的课题。分类综述制剂技术在改善BCS IV类药物溶解性/渗透性方面的应用研究，并简介该类药物的体内外相关性研究进展。     

Using pH Gradient Dissolution with <Emphasis Type="Italic">In-Situ</Emphasis> Flux Measurement to Evaluate Bioavailability and DDI for Formulated Poorly Soluble Drug Products

This study described a pH-gradient dissolution method combined with flux measurements as an in vitro tool for assessing the risk of bioavailability reduction due to drug-drug interactions (DDI) caused by acid reducing agents (ARAs). The device incorporates absorption chambers into USP II dissolution vessels, with fiber optic UV-probes monitoring concentration in situ. Dosage forms of Genentech BCS class II drugs, GDC-0810, GDC-0941, and compound A, were tested by starting the dissolution in either pH 1.6 or pH 4.0 media then converting to FaSSIF after 30 min. GDC-0810 showed no significant difference in flux between the two conversion experiments. A supersaturation phase was observed for GDC-0941 in the pH 1.6 experiments after media conversion to FaSSIF; however, it did not appear to occur in the pH 4.0 experiment due to low drug solubility at pH 4.0, resulting in a 95% decrease in flux compared to pH 1.6 experiment. The extent of flux reduction and the total accumulated API mass in the absorption chamber agreed well with the 89% reduction in mean Cmax and the 82% reduction in mean AUC from dog PK study between animals treated with pentagastrin and famotidine. Testing of the compound A optimized formulation tablets showed a 25% reduction in flux and in vitro absorbed amount by changing pH 1.6 to 4.0, correlating well with the AUC decrease in clinical studies. Good correlation between in vitro data and in vivo PK data demonstrated the applicability of the method for formulators to develop drug products mitigating DDI from ARAs.     

High-throughput sequencing of <Emphasis Type="Italic">Prunus ferganensis</Emphasis> indicates that it is a geographical population of <Emphasis Type="Italic">P. persica</Emphasis>

Peach belongs to the genus Prunus, which includes Prunus persica and its relative species, P. mira, P. davidiana, P. kansuensis, and P. ferganensis. Of these, P. ferganensis have been classified as a species, subspecies, or geographical population of P. persica. To explore the genetic difference between P. ferganensis and P. persica, high-throughput sequencing was used in different peach accessions belonging to different species. First, low-depth sequencing data of peach accessions belonging to four categories revealed that similarity between P. ferganensis and P. persica was similar to that between P. persica accessions from different geographical populations. Then, to further detect the genomic variation in P. ferganensis, the P. ferganensis accession “Xinjiang Pan Tao 1” and the P. persica accession “Xia Miao 1” were sequenced with high depth, and sequence reads were assembled. The results showed that the collinearity of “Xinjiang Pan Tao 1” with the reference genome “Lovell” was higher than that of “Xia Miao 1” and “Lovell” peach. Additionally, the number of genetic variants, including single nucleotide polymorphisms (SNPs), structural variations (SVs), and the specific genes annotated from unmapped sequence in “Xia Miao 1” was higher than that in “Xinjiang Pan Tao 1” peach. The data showed that there was a close distance between “Xinjiang Pan Tao 1” (P. ferganensis) and reference genome which belong to P. persica, comparing “Xia Miao 1” (P. persica) and reference ones. The results accompany with phylogenetic tree and structure analysis confirmed that P. ferganensis should be considered as a geographic population of P. persica rather than a subspecies or a distinct species. Furthermore, gene ontology analysis was performed using the gene comprising large-effect variation to understand the phenotypic difference between two accessions. The result revealed that the pathways of gene function affected by SVs but SNPs and insertion-deletions markedly differed between the two peach accessions.     

Action of Angiotensins and Synthetic Renin Substrate on Isolated Rat Colon

AIKEN and Vane have reported¹ the independent actions of angiotensin I (AI) and angiotensin II (AII) on various isolated smooth muscle preparations, including rat colon. Tney showed that the apparent contractile action of AI on these preparations depended primarily on its in situ conversion to All by “converting enzyme” and that when the activity of the enzyme was inhibited by a pentapeptide extracted from Bothrops jararaca venom, the residual contractile action, probably due to unchanged AI, was very small. I have investigated the action of synthetic tetradecapeptide renin substrates (TPRS) on rat colon, in the light of the known actions of AI and All.     

Coamorphous Loratadine-Citric Acid System with Enhanced Physical Stability and Bioavailability

Coamorphous systems using citric acid as a small molecular excipient were studied for improving physical stability and bioavailability of loratadine, a BCS class II drug with low water solubility and high permeability. Coamorphous loratadine-citric acid systems were prepared by solvent evaporation technique and characterized by differential scanning calorimetry, X-ray powder diffraction, and Fourier transform infrared spectroscopy. Solid-state analysis proofed that coamorphous loratadine-citric acid system (1:1) was amorphous and homogeneous, had a higher T _g over amorphous loratadine, and the intermolecular hydrogen bond interactions between loratadine and citric acid exist. The solubility and dissolution of coamorphous loratadine-citric acid system (1:1) were found to be significantly greater than those of crystalline and amorphous form. The pharmacokinetic study in rats proved that coamorphous loratadine-citric acid system (1:1) could significantly improve absorption and bioavailability of loratadine. Coamorphous loratadine-citric acid system (1:1) showed excellently physical stability over a period of 3 months at 25°C under 0% RH and 25°C under 60% RH conditions. The improved stability of coamorphous loratadine-citric acid system (1:1) could be related to an elevated T _g over amorphous form and the intermolecular hydrogen bond interactions between loratadine and citric acid. These studies demonstrate that the developed coamorphous loratadine-citric acid system might be a promising oral formulation for improving solubility and bioavailability of loratadine.     

Design,Characterization, and <Emphasis Type="Italic">In Vivo</Emphasis> Pharmacokinetics of Tacrolimus Proliposomes

The objective of this study was to develop proliposomal formulation for a poorly bioavailable drug, tacrolimus. Proliposomes were prepared by thin film hydration method using different lipids such as hydrogenated soy phosphatidylcholine (HEPC), soy phosphatidylcholine (SPC), distearyl phosphatidylcholine (DSPC), dimyristoylphosphatidylcholine (DMPC), and dimyristoylphosphatidylglycerol sodium (DMPG) and cholesterol in various ratios. Proliposomes were evaluated for particle size, zeta potential, in vitro drug release, in vitro permeability, and in vivo pharmacokinetics. In vitro drug release was carried out in purified water using USP type II dissolution apparatus. In vitro drug permeation was studied using parallel artificial membrane permeation assay (PAMPA) and everted rat intestinal perfusion techniques. In vivo pharmacokinetic studies were conducted in male Sprague-Dawley (SD) rats. Among the different formulations, proliposomes with drug/DSPC/cholesterol in the ratio of 1:2:0.5 demonstrated the desired particle size and zeta potential. Enhanced drug release was observed with proliposomes compared to pure tacrolimus in purified water after 1 h. Tacrolimus permeability across PAMPA and everted rat intestinal perfusion models was significantly higher with proliposomes. The optimized formulation of proliposomes indicated a significant improvement in the rate and absorption of tacrolimus. Following a single oral administration, a relative bioavailability of 193.33% was achieved compared to pure tacrolimus suspension.     

Nomenclature for Isolated Chloroplasts

THE nomenclature used to describe the “intactness” or degree of breakage of isolated chloioplasts has been most confusing in the past few years. This resulted chiefly from reports that chloroplasts should be isolated carefully and rapidly to obtain high rates of CO₂ fixation (50–250 µmol/mg chlorophyll/h). This type of chloroplast cannot translocate NADP, ferricyanide or ADP through its intact limiting membrane or envelope. “Class I” chloroplasts, as seen by phase contrast microscopy, had previously been considered to be similar to the in vivo situation. Unfortunately, in vitro they showed only low rates of CO₂ a fixation and easily transported NADP, ferricyanide and ADP into the chloroplast.     

Genetic structure of diploid-polyploid complex of spined loach genus <Emphasis Type="Italic">Cobitis</Emphasis> (<Emphasis Type="Italic">Cypriniformes,Cobitidae</Emphasis>) in the Lower Danube

The extremely high diversity of spined loach biotypes in the Lower Danube has been detected by biochemical genetic investigation and cytometric analysis of 358 specimens collected in the riverbed and shallow channels. Along with two diploid species (C. elongatoides and C. “tanaitica”), six hybrid forms were revealed, namely, diploid C. elongatoides-“tanaitica”; triploid C. 2 elongatoides-“tanaitica,” C. elongatoides-2 “tanaitica,” and C. 2 elongatoides-species-1; and tetraploid C. 3 elongatoides-“tanaitica” and C. elongatoides-species-2-2 “tanaitica.” In addition, specimens with recombinant genotypes were also found. In spite of the apomictic mode of reproduction, the polyploids did not possess clonal structure, but according to the level of polymorphism and the genotype distribution, they were isomorphous to parental diploid species. Thus, in contrast to the polyploidy in Cobitids of the Dnieper, which have appeared in the basin due to the expansion, the polyploids of the Lower Danube are autochthonous and were derived by crossing with local diploid species. The process is apparently proceeds without any limitations.     

A DNA-based pattern classifier with <Emphasis Type="Italic">in vitro</Emphasis> learning and associative recall for genomic characterization and biosensing without explicit sequence knowledge

Background

Genetic material extracted from in situ microbial communities has high promise as an indicator of biological system status. However, the challenge is to access genomic information from all organisms at the population or community scale to monitor the biosystem’s state. Hence, there is a need for a better diagnostic tool that provides a holistic view of a biosystem’s genomic status. Here, we introduce an in vitro methodology for genomic pattern classification of biological samples that taps large amounts of genetic information from all genes present and uses that information to detect changes in genomic patterns and classify them.

Results

We developed a biosensing protocol, termed Biological Memory, that has in vitro computational capabilities to “learn” and “store” genomic sequence information directly from genomic samples without knowledge of their explicit sequences, and that discovers differences in vitro between previously unknown inputs and learned memory molecules. The Memory protocol was designed and optimized based upon (1) common in vitro recombinant DNA operations using 20-base random probes, including polymerization, nuclease digestion, and magnetic bead separation, to capture a snapshot of the genomic state of a biological sample as a DNA memory and (2) the thermal stability of DNA duplexes between new input and the memory to detect similarities and differences. For efficient read out, a microarray was used as an output method. When the microarray-based Memory protocol was implemented to test its capability and sensitivity using genomic DNA from two model bacterial strains, i.e., Escherichia coli K12 and Bacillus subtilis, results indicate that the Memory protocol can “learn” input DNA, “recall” similar DNA, differentiate between dissimilar DNA, and detect relatively small concentration differences in samples.

Conclusions

This study demonstrated not only the in vitro information processing capabilities of DNA, but also its promise as a genomic pattern classifier that could access information from all organisms in a biological system without explicit genomic information. The Memory protocol has high potential for many applications, including in situ biomonitoring of ecosystems, screening for diseases, biosensing of pathological features in water and food supplies, and non-biological information processing of memory devices, among many.

     

Soy Protein Microparticles for Enhanced Oral Ibuprofen Delivery: Preparation,Characterization, and <Emphasis Type="Italic">In Vitro</Emphasis> Release Evaluation

The objective of this work was to evaluate soy protein isolate (SPI) and acylated soy protein (SPA) as spray-drying encapsulation carriers for oral pharmaceutical applications. SPI acylation was performed by the Schotten–Baumann reaction. SPA, with an acylation rate of 41%, displayed a decrease in solubility in acidic conditions, whereas its solubility was unaffected by basic conditions. The drug encapsulation capacities of both SPI and SPA were tested with ibuprofen (IBU) as a model poorly soluble drug. IBU-SPI and IBU-SPA particles were obtained by spray-drying under eco-friendly conditions. Yields of 70 to 87% and microencapsulation efficiencies exceeding 80% were attained for an IBU content of 20 to 40% w/w, confirming the excellent microencapsulation properties of SPI and the suitability of the chemical modification. The in vitro release kinetics of IBU were studied in simulated gastrointestinal conditions (pH 1.2 and pH 6.8, 37°C). pH-sensitive release patterns were observed, with an optimized low rate of release in simulated gastric fluid for SPA formulations, and a rapid and complete release in simulated intestinal fluid for both formulations, due to the optimal pattern of pH-dependent solubility for SPA and the molecular dispersion of IBU in soy protein. These results demonstrate that SPI and SPA are relevant for the development of pH-sensitive drug delivery systems for the oral route.     

In vitro evaluation of the prebiotic effect of red and white grape polyphenolic extracts

Nowadays, the strong relationship between diet and health is well known. Although the primary role of diet is to provide nutrients to fulfill metabolic requirements, the use of foods to improve health and the state of well-being is an idea increasingly accepted by society in the last three decades. During the last years, an important number of scientific advances have been achieved in this field and, although in some situations, it is difficult to establish a distinction between “harmful” and “good” bacteria, experts agree in classifying the genera Bifidobacterium and Lactobacillus as beneficial bacteria. Thus, several strategies can be used to stimulate the proliferation of these beneficial intestinal bacteria, being one of them the consumption of prebiotics. The development of new prebiotics, with added functionality, is one of the most serious challenges shared not only by the scientific community but also by the food industry. The objective of this work was to evaluate the potential prebiotic effect of red and white grape residues, both obtained during the winemaking process. For such purpose, an in vitro study with pure cultures of Lactobacillus and Bifidobacterium was first conducted. Secondly, a study with mixed cultures using human fecal inocula was carried out in a simulator of the distal part of the colon. The obtained results showed an increase in the Lactobacillus and Bifidobacterium population, indicating that these ingredients are serious candidates to be considered as prebiotics.     

Snake fauna (Reptilia: Serpentes) from the Early/Middle Miocene of Sandelzhausen and Rothenstein 13 (Germany)

The Early/Middle Miocene (European Land Mammal Zone MN5) localities of Sandelzhausen and Rothenstein 13 in southern Germany have yielded remains of about 13 ophidian taxa: Eoanilius sp. (Aniliidae), Bavarioboa ultima (Boidae), “Coluber” sp., ?Telescopus sp., Natrix sp., cf. Natrix sp., cf. “Neonatrix” sp., unidentified “colubrines” and “natricines” (Colubridae), Naja sp., an unidentified elapid (Elapidae), Vipera sp. (“Oriental viper”), Vipera sp. (“aspis complex”) (Viperidae). Both faunas document a transitional phase from those reported from several late Early and Middle Miocene sites of Central and Western Europe. The climates of Sandelzhausen and Rothenstein 13, as indicated by ophidian fossils, were warm, although not tropical or subtropical.     

Use of Macrophytes in Assessing the Ecological Status of Small River (by the Example of the Okhta River,St. Petersburg)

Hydrochemical and hydrobiological characteristics have been studied at 13 sites in the Okhta River within the precincts of St. Petersburg in 2010. The Water Pollution Index (WPI), calculated according to hydrochemical parameters, characterizes the river water quality as “very polluted” to “extremely polluted.” According to the Pantle–Buck–Sláde?ek Saprobity Index, obtained on the basis of macrozoobenthos characteristics, polysaprobic and α-mesosaprobic zones can be distinguished in the watercourse. The species richness of river macrophytes is low (18 species). The Macrophyte Water Quality Index makes it possible to assess water quality in the range from “polluted” to “very polluted” water. Macrophyte trophic indexes MTR, IBMR and TIM indicate a high trophy level in the watercourse sites. Based on the analysis of hydrochemical materials and the data on macrozoobenthos and macrophytes, the general tendency is similar: deterioration of water quality downstream. Macrophyte characteristics reflect changes in hydrochemical parameters downstream the river course. А strong correlation (r =–0.76) is found between the Macrophyte Water Quality Index and WPI. The possibility of using the data on macrophytes in small rivers for assessing water quality is demonstrated.     

Acyclovir-Polyethylene Glycol 6000 Binary Dispersions: Mechanistic Insights

The dissolution and subsequent oral bioavailability of acyclovir (ACY) is limited by its poor aqueous solubility. An attempt has been made in this work to provide mechanistic insights into the solubility enhancement and dissolution of ACY by using the water-soluble carrier polyethylene glycol 6000 (PEG6000). Solid dispersions with varying ratios of the drug (ACY) and carrier (PEG6000) were prepared and evaluated by phase solubility, in vitro release studies, kinetic analysis, in situ perfusion, and in vitro permeation studies. Solid state characterization was done by powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) analysis, and surface morphology was assessed by polarizing microscopic image analysis, scanning electron microscopy, atomic force microscopy, and nuclear magnetic resonance analysis. Thermodynamic parameters indicated the solubilization effect of the carrier. The aqueous solubility and dissolution of ACY was found to be higher in all samples. The findings of XRD, DSC, FTIR and NMR analysis confirmed the formation of solid solution, crystallinity reduction, and the absence of interaction between the drug and carrier. SEM and AFM analysis reports ratified the particle size reduction and change in the surface morphology in samples. The permeation coefficient and amount of ACY diffused were higher in samples in comparison to pure ACY. Stability was found to be higher in dispersions. The results suggest that the study findings provided clear mechanical insights into the solubility and dissolution enhancement of ACY in PEG6000, and such findings could lay the platform for resolving the poor aqueous solubility issues in formulation development.     

The role of visual information in maintaining postural stability after the maximum exercise for the upper and lower limb muscles

The postural stability on a seesaw generating anterior–posterior instability with the eyes open (EO) and then the eyes closed (EC) in young healthy subjects (n = 28) before and 6 min after the maximum bicycle exercise (Wingate test) performed using lower limbs (“leg exercise”) or upper limbs (“hand exercise”) was investigated. It was found that “hand exercise” caused the same increase in average velocity (V, mm/s) and in the average range of sway of the centre of pressure (Qy, mm) as “leg exercise.” However, the duration of V recovery (EC: 2 min 30 s and 50 s; EO: 60 s and 40 s after “leg exercise” and “hand exercise,” respectively) and Qy (EC: 1 min 10 s and 30 s after “leg exercise” and “hand exercise,” respectively; EO: no changes from baseline) was shorter after “hand exercise.” In the presence of visual information, the increment in V decreased more than 2 times after “leg exercise” (+100.5% and + 40.5%, p < 0.01 for EC and EO, respectively) and after “hand exercise” (+73.0% and +30.3%, p < 0.01 for EC and EO, respectively). Moreover, Qy after both exercises remained at the initial level under EO conditions but significantly increased under EC conditions (+42.8%, p < 0.01 after “leg exercise” and +40.3%, p < 0.01 after “hand exercise”). Thus, the maximum exercise for the muscles of the upper limbs causes the same reduction in postural stability as analogous exercise for the muscles of the lower limbs, but the recovery period after “hand” exercise was shorter. The presence of visual information allows the baseline maintenance of postural stability and significantly reduces the strain of postural regulation while standing on a movable support after the maximum “leg exercise” and “hand exercise.”     

Oxidation-induced modification of the fibrinogen polypeptide chains

By using the mass-spectrometry method, the oxidative modifications of the fibrinogen Aα, Bβ, and γ polypeptide chains induced by its oxidation have been studied. The αC-region has been proven to be the most vulnerable target for the oxidizer (ozone) as compared with the other structural elements of the Aα chain. The Bβ chain mapping shows that the oxidative sites are localized within all the structural elements of the chain in which the β-nodule exhibits high susceptibility to oxidation. The γ chains are the least vulnerable to the oxidizer action. The results obtained demonstrate convincingly that the self-assembly centers dealing with interactions of knob “A”: hole “a” are not involved in oxidative modification. It is concluded that the numerous oxidative sites revealed are mainly responsible for inhibiting lateral aggregation of protofibrils. The part of amino acid residues subjected to oxidation is supposed to carry out the antioxidant function.