Controlled Release of Salicylic Acid from Biodegradable Cross-Linked Polyesters

The purpose of this work was to develop a family of crosslinked poly(xylitol adipate salicylate)s with a wide range of tunable release properties for delivering pharmacologically active salicylic acid. The synthesis parameters and release conditions were varied to modulate polyester properties and to understand the mechanism of release. Varying release rates were obtained upon longer curing (35% in the noncured polymer to 10% in the cured polymer in 7 days). Differential salicylic acid loading led to the synthesis of polymers with variable cross-linking and the release could be tuned (100% release for the lowest loading to 30% in the highest loading). Controlled release was monitored by changing various factors, and the release profiles were dependent on the stoichiometric composition, pH, curing time, and presence of enzyme. The polymer released a combination of salicylic acid and disalicylic acid, and the released products were found to be nontoxic. Minimal hemolysis and platelet activation indicated good blood compatibility. These polymers qualify as ``bioactive'' and ``resorbable'' and can, therefore, find applications as immunomodulatory resorbable biomaterials with tunable release properties.

Amperometric acetylcholinesterase biosensor for pesticides monitoring utilising iron oxide nanoparticles and poly(indole-5-carboxylic acid)

A new electrochemical sensing device was constructed for determination of pesticides. In this report, acetylcholinesterase was bioconjugated onto hybrid nanocomposite, i.e. iron oxide nanoparticles and poly(indole-5-carboxylic acid) (Fe(3)O(4)NPs/Pin5COOH) was deposited electrochemically on glassy carbon electrode. Fe(3)O(4)NPs was showed as an amplified sensing interface at lower voltage which makes the sensor more sensitive and specific. The enzyme inhibition by pesticides was detected within concentrations ranges between 0.1-60 and 1.5-70 nM for malathion and chlorpyrifos, respectively, under optimal experimental conditions (sodium phosphate buffer, pH 7.0 and 25 degrees C). Biosensor determined the pesticides level in water samples (spiked) with satisfactory accuracy (96%-100%). Sensor showed good storage stability and retained 50% of its initial activity within 70 days at 4 degrees C.

Solubilities of 10-undecenoic acid and geraniol in supercritical carbon dioxide

The solubilities of 10-undecenoic acid and geraniol in supercritical carbon dioxide were measured at 308, 313,323 and 333K, and at pressures of 10-18 MPa. Solubilities (in mole fraction),ranged from 0.4 x 10(-3) to 17.4 x 10(-3) for 10-undecenoic acid and 2.7 x 10(-3) to 25 x 10(-3) for geraniol, respectively. The AARD was around 11% and 5% for these models for 10-undecenoic acid and geraniol, respectively. The solubilities of both compounds showed retrograde behavior wherein the solubilities decrease with temperature at isobaric conditions. The solubility of geraniol was higher than 10-undecenoic acid at all investigated temperatures and pressures. The data were found to be self consistent based on the Mendez-Santiago model. New models based on association theory using van Laar and Margules activity coefficient models for solute in liquid phase were derived, and used to correlate the solubilities. (C) 2015 Elsevier B.V. All rights reserved.

Controlled release kinetics of p-aminosalicylic acid from biodegradable crosslinked polyesters for enhanced anti-mycobacterial activity

Unlike conventional polymeric drug delivery systems, where drugs are entrapped in polymers, this study focuses on the incorporation of the drug into the polymer backbone to achieve higher loading and sustained release. Crosslinked, biodegradable, xylitol based polyesters have been synthesized in this study. The bioactive drug moiety, p-aminosalicylic acid (PAS), was incorporated in xylitol based polyesters to impart its anti-mycobacterial activity. To understand the influence of the monomer chemistry on the incorporation of PAS and its subsequent release from the polymer, different diacids have been used. Controlled release profiles of the drug from these polyesters were studied under normal physiological conditions. The degradation of the polyesters varied from 48% to 76% and the release of PAS ranged from 54% to 65% of its initial loading in 7 days. A new model was developed to explain the release kinetics of PAS from the polymer that accounted for the polymer degradation and drug concentration. The thermal, mechanical, drug release and cytocompatibility properties of the polymers indicate their suitability in biomedical applications. The released products from these polymers were observed to be pharmacologically active against Mycobacteria. The high drug loading and sustained release also ensured enhanced efficacy. These polymers form biocompatible, biodegradable polyesters where the sustained release of PAS may be tailored for potential treatment of mycobacterial infections. Statement of significance In the present work, we report on novel polyesters with p-aminosalicylic acid (PAS) incorporated in the polymer backbone. The current work aims to achieve controlled release of PAS and ensures the delivered PAS is stable and pharmacologically active. The novelty of this work primarily involves the synthetic chemistry of polymerization and detailed analysis and efficacy of active PAS delivery. A new kinetic model has been developed to explain the PAS release profiles. These polymers are biodegradable, cytocompatible and anti-mycobacterial in nature. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Physical insights into salicylic acid release from poly(anhydrides)

Salicylic acid (SA) based biodegradable polyanhydrides (PAHs) are of great interest for drug delivery in a variety of diseases and disorders owing to the multi-utility of SA. There is a need for the design of SA-based PAHs for tunable drug release, optimized for the treatment of different diseases. In this study, we devised a simple strategy for tuning the release properties and erosion kinetics of a family of PAHs. PAHs incorporating SA were derived from related aliphatic diacids, varying only in the chain length, and prepared by simple melt condensation polymerization. Upon hydrolysis induced erosion, the polymer degrades into cytocompatible products, including the incorporated bioactive SA and diacid. The degradation follows first order kinetics with the rate constant varying by nearly 25 times between the PAH obtained with adipic acid and that with dodecanedioic acid. The release profiles have been tailored from 100% to 50% SA release in 7 days across the different PAHs. The release rate constants of these semi-crystalline, surface eroding PAHs decreased almost linearly with an increase in the diacid chain length, and varied by nearly 40 times between adipic acid and dodecanedioic acid PAH. The degradation products with SA concentration in the range of 30-350 ppm were used to assess cytocompatibility and showed no cytotoxicity to HeLa cells. This particular strategy is expected to (a) enable synthesis of application specific PAHs with tunable erosion and release profiles; (b) encompass a large number of drugs that may be incorporated into the PAH matrix. Such a strategy can potentially be extended to the controlled release of other drugs that may be incorporated into the PAH backbone and has important implications for the rational design of drug eluting bioactive polymers.

Length of concentrate finishing affects the fatty acid composition of grass-fed andgenetically lean beef: an emphasis on trans-18:1 and conjugated linoleic acid profiles

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Proximate composition and fatty acid and cholesterol content of 22 species of northwest Atlantic finfish

The moisture, fat, ash, fatty acid profile, and cholesterol content are reported for cooked and raw fillets from 22 species of finfish found in the Northwest Atlantic. All but nine species had 1%or less fat. Ocean perch and a spring sampling of mackerel and wolffiSh had about 2% fat, followed by yellowfin tuna, whiting, silver hake, butterfish, and a summer -sampling of mackerel and wolffish with a range of 3-7% fat. Herring had a range of 5-12% fat representing a winter sampling on the low end and summer sampling on the high end of the range. Bluefin tuna (a summer sampling) contained the most fat with a high of 23% fat. Omega-3 fatty acids were present in excess of omega-6 fatty acids. The fattier fISh supplied the most omega-3 fatty acids per gram of tissue. The mean cholesterol content for all species was 57 ± 16 mg/l00 g raw tissue. Finfish from the Northwest Atlantic would appear to fit into the regime for a healthy heart, being low in fat and cholesterol and rich in omega-3 fatty acids.(PDF file contains 42 pages.)

Synthesis of (±)-7,8-epoxy-4-basmen-6-one by a transannular cyclization strategy

The first synthesis of the cembranoid natural product (±)-7,8-epoxy-4-basmen-6- one (1) is described. Key steps of the synthetic route include the cationic cyclization of the acid chloride from 15 to provide the macrocycle 16, and the photochemical transannular radical cyclization of the ester 41 to form the tricyclic product 50. Product 50 was transformed into 1 in ten steps. Transition-state molecular modeling studies were found to provide accurate predictions of the structural and stereochemical outcomes of cyclization reactions explored experimentally in the development of the synthetic route to 1. These investigations should prove valuable in the development of transannular cyclization as a strategy for synthetic simplification.

Engineering nucleic acid mechanisms for regulation and readout of gene expression : conditional Dicer substrate formation and sensitive multiplexed northern blots

Nucleic acids are most commonly associated with the genetic code, transcription and gene expression. Recently, interest has grown in engineering nucleic acids for biological applications such as controlling or detecting gene expression. The natural presence and functionality of nucleic acids within living organisms coupled with their thermodynamic properties of base-pairing make them ideal for interfacing (and possibly altering) biological systems. We use engineered small conditional RNA or DNA (scRNA, scDNA, respectively) molecules to control and detect gene expression. Three novel systems are presented: two for conditional down-regulation of gene expression via RNA interference (RNAi) and a third system for simultaneous sensitive detection of multiple RNAs using labeled scRNAs.

RNAi is a powerful tool to study genetic circuits by knocking down a gene of interest. RNAi executes the logic: If gene Y is detected, silence gene Y. The fact that detection and silencing are restricted to the same gene means that RNAi is constitutively on. This poses a significant limitation when spatiotemporal control is needed. In this work, we engineered small nucleic acid molecules that execute the logic: If mRNA X is detected, form a Dicer substrate that targets independent mRNA Y for silencing. This is a step towards implementing the logic of conditional RNAi: If gene X is detected, silence gene Y. We use scRNAs and scDNAs to engineer signal transduction cascades that produce an RNAi effector molecule in response to hybridization to a nucleic acid target X. The first mechanism is solely based on hybridization cascades and uses scRNAs to produce a double-stranded RNA (dsRNA) Dicer substrate against target gene Y. The second mechanism is based on hybridization of scDNAs to detect a nucleic acid target and produce a template for transcription of a short hairpin RNA (shRNA) Dicer substrate against target gene Y. Test-tube studies for both mechanisms demonstrate that the output Dicer substrate is produced predominantly in the presence of a correct input target and is cleaved by Dicer to produce a small interfering RNA (siRNA). Both output products can lead to gene knockdown in tissue culture. To date, signal transduction is not observed in cells; possible reasons are explored.

Signal transduction cascades are composed of multiple scRNAs (or scDNAs). The need to study multiple molecules simultaneously has motivated the development of a highly sensitive method for multiplexed northern blots. The core technology of our system is the utilization of a hybridization chain reaction (HCR) of scRNAs as the detection signal for a northern blot. To achieve multiplexing (simultaneous detection of multiple genes), we use fluorescently tagged scRNAs. Moreover, by using radioactive labeling of scRNAs, the system exhibits a five-fold increase, compared to the literature, in detection sensitivity. Sensitive multiplexed northern blot detection provides an avenue for exploring the fate of scRNAs and scDNAs in tissue culture.

Design and analysis of nucleic acid reaction pathways

Nucleic acids are a useful substrate for engineering at the molecular level. Designing the detailed energetics and kinetics of interactions between nucleic acid strands remains a challenge. Building on previous algorithms to characterize the ensemble of dilute solutions of nucleic acids, we present a design algorithm that allows optimization of structural features and binding energetics of a test tube of interacting nucleic acid strands. We extend this formulation to handle multiple thermodynamic states and combinatorial constraints to allow optimization of pathways of interacting nucleic acids. In both design strategies, low-cost estimates to thermodynamic properties are calculated using hierarchical ensemble decomposition and test tube ensemble focusing. These algorithms are tested on randomized test sets and on example pathways drawn from the molecular programming literature. To analyze the kinetic properties of designed sequences, we describe algorithms to identify dominant species and kinetic rates using coarse-graining at the scale of a small box containing several strands or a large box containing a dilute solution of strands.

Acid precipitation and its effects on aquatic systems in the English Lake District

There is no evidence of an increase in the acidity (lower pH or alkalinity) of water-bodies in the Lake District over the last 50 years. Brown trout occur in acid streams and upland tarns where pH is 4.5-5.2 throughout the year. Their occurrence in such waters in Britain and Ireland has been known for most of this century and there is no previous evidence of harmful effects on salmonid fisheries, though numbers of fish are naturally low. However, many benthic invertebrates that are common in hill-streams where pH is above 5.7 do not occur in more acid streams. This phenomenon occurs in the headwaters of several western rivers in Cumbria. It is not a recent response to "acid rain". Harmful effects of pH are undoubtedly more pronounced in waters that are poor in other dissolved ions. Low concentrations of sodium, potassium, calcium and chloride are especially important and may limit the distributions of some aquatic animals even where pH is above 5.7. The concentration of sulphate ions is usually relatively high but this is not important to the fauna; concentrations are at least two times higher in productive alkaline water-bodies than they are in unproductive acid waters.

I. The 3.7 Å crystal structure of horse heart ferricytochrome C. II. The application of the Karle-Hauptman tangent formula to protein phasing

I. The 3.7 Å Crystal Structure of Horse Heart Ferricytochrome C.

The crystal structure of horse heart ferricytochrome c has been determined to a resolution of 3.7 Å using the multiple isomorphous replacement technique. Two isomorphous derivatives were used in the analysis, leading to a map with a mean figure of merit of 0.458. The quality of the resulting map was extremely high, even though the derivative data did not appear to be of high quality.

Although it was impossible to fit the known amino acid sequence to the calculated structure in an unambiguous way, many important features of the molecule could still be determined from the 3.7 Å electron density map. Among these was the fact that cytochrome c contains little or no α-helix. The polypeptide chain appears to be wound about the heme group in such a way as to form a loosely packed hydrophobic core in the molecule.

The heme group is located in a cleft on the molecule with one edge exposed to the solvent. The fifth coordinating ligand is His 18 and the sixth coordinating ligand is probably neither His 26 nor His 33.

The high resolution analysis of cytochrome c is now in progress and should be completed within the next year.

II. The Application of the Karle-Hauptman Tangent Formula to Protein Phasing.

The Karle-Hauptman tangent formula has been shown to be applicable to the refinement of previously determined protein phases. Tests were made with both the cytochrome c data from Part I and a theoretical structure based on the myoglobin molecule. The refinement process was found to be highly dependent upon the manner in which the tangent formula was applied. Iterative procedures did not work well, at least at low resolution.

The tangent formula worked very well in selecting the true phase from the two possible phase choices resulting from a single isomorphous replacement phase analysis. The only restriction on this application is that the heavy atoms form a non-centric cluster in the unit cell.

Pages 156 through 284 in this Thesis consist of previously published papers relating to the above two sections. References to these papers can be found on page 155.

Fatty acid composition of three species of Hypnea (Gigartinales, Rhodophyta) from Karachi coast

Hypnea musciformis (Wulf.) Lamour., H. pannosa J. Ag. and H. valentiae (Turn.) Mont., collected from the northern Arabian Sea coast of Pakistan, have been investigated for their fatty acid compositions through GC-MS. Palmitic acid was present in largest quantity (55-57%) and oleic was the major (7.6-8.4%) unsaturated fatty acid. Pentacosanoic and hexacosenoic acids are being reported for the first time from any species of Hypnea. The three species differed remarkably due to their habitat ecology.