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Chitosan nanoparticles (CS NPs) showed promising results in drug, vaccine and gene delivery for the treatment of various diseases. The considerable attention towards CS was owning to its outstanding biological properties, however, the main challenge in the application of CS NPs was faced during their size-controlled synthesis. Herein, ionic gelation reaction between CS and sodium tripolyphosphate (TPP), a widely used and safe CS cross-linker for biomedical application, was exploited by a microfluidic approach based on a staggered herringbone micromixer (SHM) for the synthesis of TPP cross-linked CS NPs (CS/TPP NPs). Screening design of experiments was applied to systematically evaluate the main process and formulative factors affecting CS/TPP NPs physical properties (mean size and size distribution). Effectiveness of the SHM-assisted manufacturing process was confirmed by the preliminary evaluation of the biological performance of the optimized CS/TPP NPs that were internalized in the cytosol of human mesenchymal stem cells through clathrin-mediated mechanism. Curcumin, selected as a challenging model drug, was successfully loaded into CS/TPP NPs (EE% > 70%) and slowly released up to 48 h via the diffusion mechanism. Finally, the comparison with the conventional bulk mixing method corroborated the efficacy of the microfluidics-assisted method due to the precise control of mixing at microscales., Competing Interests: The authors declare no conflict of interest.

Background: Periodontitis is an inflammatory disease with a bacterial etiology that affects the supporting structures of the teeth and is a major cause of tooth loss. The objective of this study was to investigate the drug loading and in vitro release of minocycline from novel calcium polyphosphate microspheres intended for use in treating periodontitis. Methods: Calcium polyphosphate coacervate, produced by a precipitation reaction of calcium chloride and sodium polyphosphate solutions, was loaded with minocycline and subsequently used to produce microspheres by an emulsion/solvent extraction technique. Microspheres classified by size were subjected to a 7-day elution in a Tris-buffer solution under dynamic conditions. The physicochemical characteristics of the drug-loaded microspheres were investigated using scanning electron microscopy, particle size analysis, Phosphorus-31 Nuclear Magnetic Resonance spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Drug loading and release were determined using ultraviolet -visible (UV/VIS) spectrophotometry. Results: Minocycline-loaded calcium polyphosphate microspheres of varying size were successfully produced, with small and large microspheres having volume mean diameters of 22 ± 1 µm and 193 ± 5 µm, respectively. Polyphosphate chain length and calcium to phosphorus mole ratio remained stable throughout microsphere production. Drug loading was 1.64 ± 0.16, 1.35 ± 0.55, and 0.84 ± 0.14 weight% for the coacervate and large and small microspheres, respectively, corresponding to mean encapsulation efficiencies of 81.7 ± 12.2 % and 50.9 ± 3.9 % for the large and small microspheres. Sustained drug release was observed in vitro over a clinically relevant 7-day period, with small and large microspheres exhibiting similar elution profiles. Antibiotic release generally followed microsphere degradation as measured by Ca and P ion release. Conclusions: This study demonstrated successful drug loading of calcium polyphosphate microspheres with minocycline. Furthermore, in vitro sustained release of minocycline over a 7-day period was observed, suggesting potential utility of this approach for treating periodontitis.

Stavudine remains a useful replacement option for treatment for HIV + children. WHO reduced the adult dose to 30 mg twice daily, which maintains efficacy and lowers mitochondrial toxicity. We explored intracellular stavudine triphosphate levels in children receiving a reduced dose of 0.5 to 0.75 mg/kg of body weight twice daily to investigate whether a similar dose optimization can safely be made. A population pharmacokinetic model was developed to describe the pharmacokinetics of intracellular stavudine triphosphate in 23 HIV + children and 24 HIV + adults who received stavudine at 0.5 mg/kg and 20 mg twice daily for 7 days, respectively. Simulations were employed to optimize the pediatric dosing regimen to match exposures in adults receiving the current WHO-recommended dose of 30 mg twice daily. A biphasic disposition model with first-order appearance and disappearance described the pharmacokinetics of stavudine triphosphate. The use of allometric scaling with fat-free mass characterized well the pharmacokinetics in both adults and children, and no other significant effect could be detected. Simulations of 30 mg twice daily in adults predicted median (interquartile range [IQR]) stavudine triphosphate minimum drug concentration ( C min ) and maximum drug concentration ( C max ) values of 13 (10 to 19) and 45 (38 to 53) fmol/10 6 cells, respectively. Targeting this exposure, simulations in HIV + children were used to identify a suitable weight-band dosing approach (0.5 to 0.75 mg/kg), which was predicted to achieve median (IQR) C min and C max values of 13 (9 to 18) and 49 (40 to 58) fmol/10 6 cells, respectively. Weight-band dosing using a stavudine dose of 0.5 to 0.75 mg/kg is proposed, and it shows comparable exposures to adults receiving the current WHO-recommended dose of 30 mg twice daily. Our pharmacokinetic results suggest that the decreased stavudine dose in children >2 years would have a reduced toxic effect while retaining antiretroviral efficacy., (Copyright © 2018 Innes et al.)

Yeasts Cryptococcus humicola accumulated cadmium, cobalt, and iron (~ 50, 17, and 4% of the content in the medium, respectively) from the medium containing glucose, phosphate, and 2 mmol/L of metal salts. The effects of metal absorption on the levels of orthophosphate (Pi) and inorganic polyphosphate (polyP) varied for the metals under study. The levels of Pi and polyP increased in the case of cadmium and cobalt, respectively. In the case of iron, no changes in the levels of Pi and polyP were observed. Multiple DAPI-stained polyP inclusions were observed in the cytoplasm of cadmium-containing cells. The intensity of DAPI staining of the cell wall especially increased in case of cobalt and iron accumulation.

The present investigation deals with preparation and characterization of anti-migraine zolmitriptan (ZMT) nanostructured polymeric carriers for nose to brain drug targeting. The drug-loaded colloidal nanocarriers of ZMT were prepared by modified ionic gelation of cationic chitosan with anionic sodium tripolyphosphate and characterized for particle size, zeta potential, and entrapment efficiency. Further, in order to investigate nose to brain drug targeting, biodistribution, and brain kinetics studies were performed using 99m technetium radiolabeled nanocarriers ( 99m Tc-ZMTNP) in Swiss albino mice. The results were compared with intranasal pure drug solution ( 99m Tc-ZMT) and intravenous nanocarriers ( 99m Tc-ZMTNP). A single photon emission computerized tomography (SPECT) radioimaging studies were also carried out to visualize and confirm brain uptake of nanocarriers. The optimized nanocarriers showed particle size of 161 nm, entrapment efficiency of 80.6%, and zeta potential of + 23.7 mV. The pharmacokinetic parameters, C max , and AUC 0-∞ values for ZMT concentration in the brain expressed as percent radioactivity per gram of brain in intranasal and intravenous route of administration were calculated. The brain C max and AUC 0-∞ values found in three groups, intranasal 99m Tc-ZMTNP, intranasal 99m Tc-ZMT, and intravenous 99m Tc-ZMTNP were (0.427 and 1.889), (0.272 and 0.7157), and (0.204 and 0.9333), respectively. The higher C max values of intranasal 99m Tc-ZMTNP suggests better brain uptake as compared to other routes of administration. The significant higher values of nose to brain targeting parameters namely, drug targeting index (5.57), drug targeting efficiency (557.08%), and nose to brain drug direct transport (82.05%) confirmed drug targeting to brain via nasal route. The coupled bimodal SPECT-CT scintigrams confirm the brain uptake of intranasal 99m Tc-ZMTNP demonstrating major radioactivity accumulation in brain. This study conclusively demonstrated the greater uptake of ZMT-loaded nanocarriers by nose to brain drug targeting, which proves promising drug delivery system.

Introduction: Complex mechanisms underlie dry eye (DE) symptom provocation. In particular, corneal hypersensitivity may provoke symptoms in short tear break-up time (BUT) DE characterized by tear film instability. We hypothesized that improved tear film stability may alleviate corneal sensitivity in patients with short tear BUT DE. Therefore, we investigated the effect of topical diquafosol tetrasodium (DQS) on corneal sensitivity in unstable tear film DE., Methods: This prospective, randomized study included 27 subjects (age: 39.1 ± 8.4 years; range: 25-59 years) with short tear BUT DE, defined based on the presence of DE symptoms and tear film instability. Subjects were randomly divided into DQS (3% DQS, 12 subjects) and artificial tear (AT; preservative-free AT, 15 subjects) groups. Subjects applied the medication 6 times a day for 5 weeks. The perception of touch (S-touch) and pain (S-pain) sensitivity was measured using a Cochet-Bonnet esthesiometer. Tear evaluation, corneal sensitivity, and DE symptoms were compared before and after DQS or AT administration. The correlation between the improvement degrees of corneal sensitivity and DE symptoms following medication was analyzed., Results: DQS significantly improved tear BUT and tear meniscus height (TMH) scores (p < 0.05), while AT significantly improved tear BUT (p < 0.05) but not TMH score. Mean S-pain and DE symptom scores were lower after medication use in the DQS (S-pain and DE symptoms: p  < 0.05) and AT groups (S-pain: p  = 0.05; DE symptoms: p  < 0.05). However, S-touch did not change significantly in either group. A positive correlation was observed between the improvement degrees of S-pain and DE symptoms in the overall subjects studied., Conclusion: Both DQS and AT alleviate corneal hypersensitivity and DE symptoms in eyes with short tear BUT DE. However, DQS seems to be more effective to adjust tear environment, leading to the normalization of corneal sensitivity and DE symptoms., Trial Registration: UMIN Clinical Trials Registry Identifier, UMIN000014536.

Purpose: To evaluate the immediate effect of 3% diquafosol ophthalmic solution on tear MUC5AC concentration, periodic acid-Schiff (PAS)-positive goblet cells, and tear film stability in normal and keratoconjunctivitis sicca (KCS) rat models., Methods: Rats were divided into normal and KCS groups. 3% of diquafosol solution was instilled into the right eye and normal saline into the left eye in both groups. To determine the peak time of tear MUC5AC concentration, tears were collected after 3% diquafosol instillation every 5 min up to 20 min. The tear film stability and the numbers of PAS-positive goblet cells were compared in both models., Results: After diquafosol instillation, tear MUC5AC concentration increased steadily for 15 min, at which point the MUC5AC concentration reached its peak. In both normal and KCS groups, the MUC5AC concentration at 15 min was higher after instillation of 3% diquafosol solution (17.77 ± 2.09 ng/ml in the normal group, 9.65 ± 3.51 ng/ml in the KCS group) than that after saline instillation (13.74 ± 2.87 ng/ml in the normal group, 8.19 ± 3.99 ng/ml in the KCS group) (p = 0.018 for both). The corneal wetting ability was significantly longer after instillation of 3% diquafosol solution compared with that after instillation of normal saline in the normal group (p = 0.018). The percentage of PAS-positive goblet cells after the instillation of 3% diquafosol solution was significantly lower than that after instillation of normal saline in both models (p = 0.018 for both)., Conclusions: Diquafosol ophthalmic solution was effective in stimulating mucin secretion in both normal and KCS rat models, and the peak time of tear MUC5AC concentration was 15 min after diquafosol instillation. The increased tear MUC5AC concentration was accompanied by improved tear film stability and a decreased percentage of PAS-positive goblet cells.

Background: There has been increased attention given to polymeric nanoparticles as protein carriers. In this regard, chitosan/tripolyphosphate (TPP) nanoparticles are considered to be a simple and efficient carrier. However, to have an ideal protein release profile, we need to optimize the properties of the carrier., Methods: This study examined the influence of 4 critical process parameters on the physicochemical characteristics of final nanoparticles. Chitosan-based nanoparticles were produced by ionic gelation, and then the size, polydispersity and zeta potential of those resulting nanoparticles were evaluated. Subsequently, the encapsulation efficiency of bovine serum albumin as model protein was investigated., Results: The morphologies of nanoparticles were characterized using field emission scanning electron microscopy (FE-SEM). Linear mathematical models were presented for each response through 3 levels using Central Composite Design with the help of design of experiments software, and formulation optimization was performed., Conclusions: Such research will serve as a basic study in protein loading into TPP cross-linked chitosan nanoparticles.

The metabolic conversion of nucleoside analogues into their triphosphates often proceeds insufficiently. Rate-limitations can be at the mono-, but also at the di- and triphosphorylation steps. We developed a nucleoside triphosphate (NTP) delivery system (TriPPPro-approach). In this approach, NTPs are masked by two bioreversible units at the γ-phosphate. Using a procedure involving H-phosphonate chemistry, a series of derivatives bearing approved, as well as potentially antivirally active, nucleoside analogues was synthesized. The enzyme-triggered delivery of NTPs was demonstrated by pig liver esterase, in human T-lymphocyte cell extracts and by a polymerase chain reaction using a prodrug of thymidine triphosphate. The TriPPPro-compounds of some HIV-inactive nucleoside analogues showed marked anti-HIV activity. For cellular uptake studies, a fluorescent TriPPPro-compound was prepared that delivered the triphosphorylated metabolite to intact CEM cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Introduction: Dry eye is a multifactorial disease of the ocular surface causing ocular discomfort and visual impairment for the patient. A variety of topical and systemic drugs are available to treat dry eye. Conventional treatments are limited to tear supplementation or improvement of ocular surface inflammation by the use of corticosteroids or cyclosporine A. Treatment of severe dry eye associated with Sjögren's syndrome (SS) is even more challenging and is designed to improve the quality and quantity of tear fluid. Diquafosol tetrasodium , a P2Y2 purinergic receptor agonist, acts via a novel mechanism by activating P2Y2 receptors of the ocular surface., Areas Covered: The aim of this review is to summarize the pharmacokinetics, and pharmacological and clinical data of 3% diquafosol tetrasodium ophthalmic solution in patients with dry eye, particularly SS. The mechanisms of impaired ocular surface due to severe dry eye, as defined by the International Dry Eye Workshop, are analyzed., Expert Opinion: Diquafosol tetrasodium provides a novel mode of action in dry eye syndrome, including SS, by stimulating the quantity and quality of tear fluid secretion via various mechanisms. In clinical trials, 3% Diquafosol tetrasodium ophthalmic solution demonstrated a good safety profile and exhibited efficacy with clinical improvement of the ocular surface in dry eye including SS.

The purpose of this study was to investigate the permeability of exendin-4-loaded chitosan nanoparticles using the Madin Darby canine kidney (MDCK) cell monolayer as an in vitro model and the rat intestine as an ex vivo model of the human intestinal barrier. A series of formulations of sodium tripolyphosphate (TPP) and chitosan with different molecular weights and degrees of deacetylation was evaluated. The formulation consisting of 0.1% TPP and 0.2% chitosan (400 kDa, 95% degree of deacetylation), which gave optimized monodispersed particle size (303.1±10.36 nm), zeta potential (18.37±1.15 mV) and encapsulation efficiency (38.0±2.6%), was used for further analysis. After determining their biocompatibility, the transport potential of drug-loaded chitosan nanoparticles was evaluated and compared with free exendin-4 using both MDCK cell monolayers and different rat intestinal segments. Mechanisms underlying enhanced transport of exendin-4 in the cell model were also explored. Compared with free exendin-4, the absorption of optimized chitosan nanoparticles was enhanced by 4.7-fold in MDCK cell monolayers and by 2.0-2.78-fold in different rat intestinal segments, with no significant difference between the duodenum, jejunum and ileum. As supported by confocal laser scanning microscopic analysis, the lower enhancement of absorption in the intestine compared to the cell monolayer likely resulted from the chitosan nanoparticle-mediated opening of cellular tight junctions and not through intracellular transport. These findings suggest that the potential application of chitosan nanoparticles as delivery carriers of exendin-4 is limited and may need further modifications.

Background: The active metabolites of tenofovir (TFV) and emtricitabine (FTC) in peripheral blood mononuclear cells (PBMCs) have been used as markers of long-term antiretroviral (ARV) adherence. However, the process of isolating PBMCs is expensive, complex, and not feasible in many settings. We compared concentrations of TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP) in the upper layer packed cells (ULPCs) obtained after whole blood centrifugation to isolated PBMCs as a possible alternative marker of adherence., Methods: Ten HIV+ adults with HIV RNA <50 copies/mL on a TDF/FTC-containing regimen provided 5 paired PBMC and ULPC samples over 6 hours. TFV-DP and FTC-TP concentrations were analyzed by liquid chromatography/mass spectrometry. Partial areas under the curve were calculated using noncompartmental methods and Spearman Rank Correlations (rho) between PBMC and ULPC were determined., Results: The median (25th-75th percentile) concentration of TFV-DP in PBMCs was 143 (103-248) fmol/10(6) cells and in ULPC was 227 (160-394) fmol/10(6) cells (rho = 0.65; P < 0.0001). The concentration of FTC-TP in PBMCs was 6660 (5650-10,000) fmol/10(6) cells and in ULPC was 19.0 (12.0-27.8) fmol/10(6) cells (rho = 0.55; P < 0.0001). Compared to PBMCs, ULPC TFV-DP was 64% higher and FTC-TP was 99.7% lower. ULPC concentrations of TFV-DP and FTC-TP in one additional subject receiving a single dose of TDF/FTC were only 0.05% and 25%, of the other 10 subjects, respectively., Conclusions: ULPC concentrations significantly correlated with PBMC concentrations. Preliminary single-dose data suggest some discrimination between intermittent versus consistent dosing. ULPC concentrations of TFV-DP and FTC-TP should be further investigated as a simply collected surrogate measure of ARV adherence.

A system for delivery of analogues of 2'-deoxyribonucleoside triphosphate (dNTP) based on SiO(2) nanoparticles was proposed. A simple and versatile method was developed for the preparation of SiO(2)-dNTP conjugates using the 'click'-reaction between premodified nanoparticles containing the azido groups and dNTP containing the alkyne-modified γ-phosphate group. The substrate properties of SiO(2)-dNTP were tested using Klenow fragment and HIV reverse transcriptase. Nucleoside triphosphates being a part of the SiO(2)-dNTP nanocomposites were shown to be incorporated into the growing DNA chain. The rate of polymerization with the use of SiO(2)-dNTP or common dNTP in case of HIV reverse transcriptase differed insignificantly. It was shown by confocal microscopy that the proposed SiO(2)-dNTP nanocomposites bearing the fluorescent label penetrate into cells and even into cellular nuclei., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Among the most promising of the new therapies being developed for the treatment of Cystic Fibrosis (CF) are those targeted at increasing mucosal hydration on the surface of the airways. One of these therapies, P2Y(2) receptor agonists, bypasses the defective CFTR chloride channel, and activates an alternative chloride channel. This activation results in an increase in airway surface epithelial hydration, and through these actions and effects on cilia beat frequency, increases mucociliary clearance. The pharmacology of P2Y(2) agonists has been confirmed in several preclinical and clinical studies. Denufosol tetrasodium is a novel second-generation, metabolically stable, selective P2Y(2) receptor agonist currently in Phase 3 clinical development. In radiolabelled deposition studies of P2Y(2) agonists in healthy non-smokers and smokers, approximately 7mg of a 40-mg nebulizer (PARI LC Star) load was deposited in the lungs. In a pharmacokinetic study in healthy volunteers, very limited systemic exposure was observed when doses of 200mg of denufosol were nebulized. Thus, it appears that high concentrations of denufosol can be achieved in the airways with very low systemic absorption. Denufosol has been generally well-tolerated in healthy volunteers and patients with CF. The most common adverse events were in the respiratory system, with cough having the highest frequency. Doses of 20-60mg have been evaluated in Phase 2 trials of up to 28 days duration, and superiority relative to placebo on FEV1 has been observed in patients with relatively normal lung function (FEV1 greater than or equal to 75% of predicted). The first Phase 3 trial is a comparison of denufosol 60mg and placebo in 350 patients with CF with FEV1 at study entry greater than or equal to 75% of predicted.

Purpose: To investigate the safety and efficacy of diquafosol tetrasodium, a P2Y2 receptor agonist that stimulates fluid and mucin secretion on the ocular surface, as a novel topical treatment of dry eye disease., Methods: Subjects with dry eye (n=527) were evaluated in a randomized, double-masked, parallel-group trial comparing 24 weeks of treatment with 2 concentrations of diquafosol (1% and 2%) versus placebo instilled 4 times daily. Corneal staining, conjunctival staining, Schirmer tests, and subjective symptoms of dry eye were evaluated. Use of artificial tears was permitted as necessary., Results: Subjects treated with 2% diquafosol had significantly lower corneal staining scores compared with placebo at the 6-week, primary efficacy time point (P<0.001), and superiority continued throughout the 24-week study. Reductions in corneal staining were observed as early as after 2 weeks of treatment, were maintained throughout the 24-week study, and were observed to worsen slightly (toward baseline) when diquafosol treatment was discontinued (week 25). Results for conjunctival staining were consistent with those observed for corneal staining. Schirmer scores at week 6 were significantly higher with diquafosol treatment than with placebo (P

The ophthalmic formulation of diquafosol tetrasodium (INS365), a P2Y2 receptor agonist, is targeted to treat dry eye disease through rehydration of the ocular surface. Existing pharmacological therapies for dry eye disease are limited, therefore, approval of this medication is anticipated. This review summarises key findings during development and in clinical trials including clinical effectiveness and safety. The relevance of P2Y2 receptor technology to dry eye disease and the disease process is discussed.

Inspire, in collaboration with Allergan and Santen, is developing an eye-drop formulation of diquafosol tetrasodium (INS-365), a second-generation uridine nucleotide analog P2Y, receptor agonist for the potential treatment of dry eye disease. In June 2003, Inspire submitted an NDA for the treatment of dry eye, and in July 2003 the FDA granted the NDA Priority Review status. FDA action is expected in December 2003, and in January 2003 launch was expected in the first half of 2004.

The microbial community structures of anaerobic-aerobic activated sludges, which are dominated with polyphosphate-accumulating bacteria (PABs) and glycogen-accumulating bacteria (GABs), were investigated by quinone profile method and dual staining DAPI (4',6-diamidino-2-phenylindol dihydrochloride) with fluorescent in situ hybridization (FISH). For both activated sludges, the predominant bacterial groups were the beta subclass of the Proteobacteria that contained mainly Q-8 as analyzed by the quinone profile method and gram-positive bacteria with a high DNA G+C content based on FISH. A 16S rRNA-targeted oligonucleotide probe (MP2) specific for M. phosphovorus, a known polyphosphate-accumulating bacterium, was also applied to PABs and GABs-enriched activated sludge to evaluate their possible role in the enhanced biological phosphorus removal (EBPR) process. Interestingly, the bacteria that hybridized with the probe specific to M. phosphovorus in the sludge dominated with PABs represent about 6.9% of the total microorganisms. In the sludge dominated with GABs, these bacteria were about 1.9%. These results suggest its possible involvement in the EBPR process.

Two methods that physically separate polyphosphate-accumulating organisms (PAO) from other organisms in activated sludge were developed. The first method used 4'6-diamidino-2-phenylindole dihydrochloride (DAPI) to selectively stain PAO. When excited with light at 340 nm, polyphosphate granules in DAPI-stained cells fluoresce yellow while cells without polyphosphate fluoresce blue. This difference in fluorescent response was used to separate PAO from non-PAO using flow cytometry. The second method consisted of a simple gradient centrifugation to physically separate PAO from non-PAO based on their density differences. Both methods produced cell suspensions with an increased PAO concentration. From an average PAO concentration of approximately 14% in a full-scale process, the DAPI-flow cytometry method produced sorted samples with PAO representing more than 70% of the total cells, while the density gradient method produced an approximate 43 to 48% PAO enrichment. The physical enrichment methods described herein should facilitate the identification and study of PAO that are relevant in full-scale enhanced biological phosphorus removal processes.

This study demonstrated that temperature is an important factor in determining the outcome of competition between polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating non-poly-P organisms (GAOs) and the resultant stability of enhanced biological phosphorus removal (EBPR) systems. At 20 degrees C and a 10-day sludge age, PAOs were dominant in the anaerobic/aerobic (A/O) SBR, however, at 30 degrees C and a 10-day sludge age, GAOs were dominant in the A/O SBR. For kinetic batch studies, the anaerobic specific acetate uptake rate of GAO-dominated sludge (1.34 x 10(-3) mg C/mg VSS x minute) was higher than the rate of PAO-dominated sludge (0.89 x 10(-3) mg C/mg VSS x minute) at 30 degrees C, leading to the eventual failure of EBPR processes at high temperatures.

Targeting of drugs to the colon, following oral administration, can be accomplished by the use of modified, biodegradable polysaccharides as vehicles. In a previous study, a crosslinked low swelling guar gum (GG) hydrogel was synthesized by reacting it with trisodium trimetaphosphate (STMP). In the present study the functioning of GG crosslinked products (GGP) as possible colon-specific drug carriers was analyzed by studying (a) the release kinetics of pre-loaded hydrocortisone from GGP hydrogels into buffer solutions with, or without GG degrading enzymes (alpha-galactosidase and beta-mannanase) and (b) direct measurements of the polymers' degradation in the cecum of conscious rats. The effect of GG diet on alpha-galactosidase and beta-mannanase activity in the cecum of the rat and GGP degradation was also measured. It was found that the product GGP-0.1 (loosely crosslinked with 0.1 equivalents of STMP) was able to prevent the release of 80% of its hydrocortisone load for at least 6 h in PBS, pH=6.4. When a mixture of alpha-galactosidase and beta-mannanase was added to the buffer solution, an enhanced hydrocortisone release was observed. In-vivo degradation studies in the rat cecum showed that despite the chemical modification of GG, it retained its enzyme-degrading properties in a crosslinker concentration-dependent manner. Eight days of GG diet prior to the study increased alpha-galactosidase activity in the cecum of the rat three-fold, compared to its activity without the diet. However, this increase in the enzyme activity was unable to improve the degradation of the different GGP products. The overall alpha-galactosidase activity in the rat cecum was found to be extracellular, while the activity of beta-mannanase was found to be bacterial cell-wall associated. It is concluded that because CG crosslinked with STMP can be biodegraded enzymatically and is able to retard the release of a low water-soluble drug, this polymer could potentially be used as a vehicle for colon-specific drug delivery.

Guar gum (GG) was crosslinked with increasing amounts of trisodium trimetaphosophate (STMP) to reduce its swelling properties for use as a vehicle in oral delivery formulations, especially drug delivery systems aimed at localizing drugs in the distal portions of the small bowel. Swelling of GG in artificial gastrointestinal fluids was reduced from 100 to 120-fold (native GG) to 10-35-fold depending on the amount of crosslinker used, showing a bell-shape dependency. As a result of the crosslinking procedure GG lost its non-ionic nature and became negatively charged. This was demonstrated by methylene blue (MB) adsorption studies and swelling studies in sodium chloride solutions with increasing concentrations in which the hydrogels' network collapsed. The adsorption of MB was also used to characterize the degree of the GG crosslinking, from which the effective network density was calculated. In addition, effective network density was calculated from elasticity measurements. Both measurements showed that the crosslinking density (but not swelling) of the new products was linearly dependent on the amount of STMP used in the reaction.

Fundamental to the caries process and its inhibition is an understanding of the composition and structural relationships of dental mineral. These have received greater study in recent years, leading to a better understanding of the processes involved. Fluoride has been the most successful of the anti-caries agents to date, and many studies have concentrated on this ion. The anti-caries action of fluoride has been only partially explained by the early finding that fluoride-treated mineral was less soluble, and this criterion is now less widely accepted. The dissolutive process of caries is inhibited by fluoride, monofluorophosphate, trimetaphosphate, and zinc. However, only the first three of these show anti-caries activity. The presence of fluoride during in vivo and in vitro caries is conducive to the formation of an apparently intact surface zone. Current evidence is that this zone reforms during the caries process, thus acquiring fluoride and having larger crystallites compared with sound enamel. Trimetaphosphate also favors the formation of a surface zone. There is a clear beneficial involvement of fluoride, even at low levels, in the process of lesion remineralization. It is highly probable that this process results from re-growth of residual enamel crystallites rather than de novo precipitation of calcium phosphates. Levels of fluoride found in saliva can interact with dental mineral. Although zinc has been shown to adsorb upon apatite mineral and to restrict subsequent crystal growth, it does not appear to affect the action of fluoride, including remineralization, adversely. This may be due to the fact that the uptake of zinc is reversible.(ABSTRACT TRUNCATED AT 250 WORDS)

On the basis of studies aimed at the substantiation of MAC for cyclophos in soil it was established, that subthreshold amounts of cyclophos according to the water-migration and air-migration indexes of harmfulness equal 0.03 mg per 1 kg of absolutely dry soil, according to the general sanitary index--0.1 mg/kg. Since cyclophos destruction period in plants is relatively short (8 days), there is no danger of translocation of the pesticide from soil in amounts exceeding the maximum allowable level for cyclophos in food stuffs. The pesticide migration in the system soil-plant was not determined. The water migration and air-migration indexes are the limiting indexes of harmfulness for cyclophos. 0.03 mg/kg is recommended as the maximum allowable concentration of cyclophos in soil.

The incubation of polyphosphates with the ribosomal fraction of Sulfolobus acidocaldarius leads to the covalent attachment of phosphate to threonine residue(s) of a single 40,000 Mr protein. The hydrolysis kinetics of this protein showed that polyphosphate might be the modifying group. The reaction requires 2 mM Mn2+ ions and is time-dependent. ATP strongly inhibits the transfer of phosphate from polyphosphate, indicating that this process is catalyzed by an enzyme differing from the well-known protein kinases.

Technetium-99m has been suggested as an alternative radiolabel for white cells, and while its physical characteristics are nearly ideal, its stability and site of localization in this procedure are unclear. We examined these parameters by radiolabeling 10(8) neutrophils from rat peritoneum with 74 to 370 MBq technetium-99m-Sn-pyrophosphate. We found that the percentage of initial activity bound to neutrophils was quite variable, possibly because the radiolabel associated with several subfractions: 19.8 +/- 11.5% (mean +/- s.d.) with nuclei and plasma membranes, 25.6 +/- 3.9% with mitochondria, 26.6 +/- 9.8% with microsomes, and 29.2 +/- 6.9% with cytosol. Approximately 80-90% of the radioactivity associated with neutrophils was not bound to protein and only about one-half of the activity localized to cell membranes was removable over 4 hr by pepsin digestion. We concluded that the variable labeling efficiency was due to the radiolabel's rather loose association with several cellular subfractions rather than specific binding to a unique substrate.