Preparation and evaluation of chitosan-based nanogels/gels for oral delivery of myricetin.

A novel nanogel/gel based on chitosan (CS) for the oral delivery of myricetin (Myr) was developed and evaluated comprehensively. The particle size of the obtained Myr-loaded CS/ß-glycerol phosphate (ß-GP) nanogels was in the range of 100-300nm. The rheological tests showed that the sol-gel transition happened when the nanogels were exposed to physiological temperatures, and 3D network structures of the gelatinized nanogels (gels) were confirmed by Scanning Electron Microscopy. Myr was released from CS/ß-GP nanogel/gel in acidic buffers via a Fickian mechanism, and this release was simultaneously accompanied by swelling and erosion. Moreover, the nanogel/gel exhibited no cytotoxicity by MTT assay, and the oral bioavailability of Myr in rats was improved with an accelerated absorption rate after Myr was loaded into CS/ß-GP nanogel/gel. In summary, all of the above showed that CS/ß-GP nanogel/gel was an excellent system for orally delivering Myr.

Formulation and evaluation of thermosensitive biogels for nose to brain delivery of doxepin.

Thermoreversible biogels can serve as effective systems for delivery of drugs through nose with increased nasal residence time. The objective of this study was to use chitosan and glycerophosphate based thermoreversible systems for delivery of doxepin to brain through intranasal administration. Formulations were prepared by admixture of suitable dilutions of chitosan and glycerophosphate with or without polyethylene glycol, followed by addition of the antidepressant doxepin hydrochloride. Both systems were evaluated for gelling characteristics, rheology, mucoadhesion, in vitro release, and ex vivo permeation through sheep nasal mucosa. In vivo efficacy was evaluated in Swiss albino mice through the forced swim test. Nasal tissues of mice subjected to repeated exposure to formulation were evaluated histopathologically. Both formulations gelled rapidly at 37°C, returned to sol state on cooling, and exhibited thixotropy. Addition of polyethylene glycol decreased the glycerophosphate content required for gelation and rendered the formulation isotonic. Both gels showed good mucoadhesion, enhanced drug permeation, and provided prolonged in vitro release at 37°C. Efficacy of the formulation in treated groups was inferred from the measured pharmacodynamic parameter and histopathological reports of formulation treated groups showed no significant local toxicity. The biogels could be potential systems for effective drug delivery to brain via nose.

Efficacy, pharmacokinetics, and biodistribution of thermosensitive chitosan/ß-glycerophosphate hydrogel loaded with docetaxel.

Docetaxel (DTX) is a widely used anticancer drug for various solid tumors. However, its poor solubility in water and lack of specification are two limitations for clinical use. The aim of the study was to develop a thermosensitive chitosan/ß-glycerophosphate (C/GP) hydrogel loaded with DTX for intratumoral delivery. The in vitro release profiles, in vivo antitumor efficacy, pharmacokinetics, and biodistribution of DTX-loaded C/GP hydrogel (DTX-C/GP) were evaluated. The results of in vitro release study demonstrated that DTX-C/GP had the property of controlled delivery for a reasonable time span of 3 weeks and the release period was substantially affected by initial DTX strength. The antitumor efficacy of DTX-C/GP was observed at 20 mg/kg in H22 tumor-bearing mice. It was found that the tumor volume was definitely minimized by intratumoral injection of DTX-C/GP. Compared with saline group, the tumor inhibition rate of blank gel, intravenous DTX solution, intratumoral DTX solution, and DTX-C/GP was 2.3%, 29.8%, 41.9%, and 58.1%, respectively. Further, the in vivo pharmacokinetic characteristics of DTX-C/GP correlated well with the in vitro release. DTX-C/GP significantly prolonged the DTX retention and maintained a high DTX concentration in tumor. The amount of DTX distributed to the normal tissues was minimized so that the toxicity was effectively reduced. In conclusion, DTX-C/GP demonstrated controlled release and significant efficacy and exhibited potential for further clinical development.

Glycerophosphate is interchangeable with inorganic phosphate in terms of safety and serum pharmacokinetics.

OBJECTIVE: The primary aim of the present investigation was to determine and compare the pharmacokinetic (PK) profiles of inorganic phosphate in serum and urine after intravenous administration of sodium glycerophosphate and inorganic sodium phosphate. Additionally, study product safety profiles were evaluated. SUBJECTS AND METHODS: In total, 27 healthy, white volunteers (17 male/10 female) were enrolled in this double-blinded, randomized, 2-sequence, crossover study and were assigned to receive an organic test drug (sodium glycerophosphate) and an inorganic reference preparation (sodium phosphate) on 2 occasions. Validated analytical methods were used, and concentrations of total inorganic phosphate in serum and urine were determined over 24 h following a single 4-hour continuous intravenous infusion of test and reference drugs at a dose of 80 mmol. Study days were separated by washout periods of 7 days. An analysis of variance, based on population means and 90% confidence intervals (CIs), was used for testing bioequivalence (BE; range 0.8-1.25) between investigational products. RESULTS: The geometric means of the ratio of the point estimates and corresponding 90% CIs for the area under the concentration-versus-time curve of inorganic serum phosphate from 0 to 24 h (AUC(0-24)), the phosphate's maximum concentration in serum (C(max)) and the total amount of inorganic phosphate excreted in urine over 24 h corrected for individual baseline values (Ae(0-24 bc)) were estimated. The test/reference ratios for inorganic phosphate were 1.04 (CI 1.00-1.07), 0.85 (CI 0.84-0.87) and 0.84 (CI 0.77-0.92) for AUC(0-24), C(max) in serum and Ae(0-24 bc) in urine, respectively. Hence, standard BE criteria were met for AUC(0-24) and C(max) in serum, while Ae(0-24 bc) marginally failed to demonstrate BE. After drug administration, a total of 15 subjects reported the occurrence of at least 1 treatment emergent adverse event (AE). All AEs were classified as mild to moderate in severity, and the two treatment groups were equally affected. No serious AEs occurred. CONCLUSION: The serum PK profiles of inorganic phosphate were almost superimposable following intravenous administration of equimolar doses of test and reference drugs. Thus, we conclude that the two study drugs are essentially similar in terms of serum PK profiles, safety and tolerability.

Glycerophosphate does not interact with components of parenteral nutrition.

BACKGROUND/AIMS: The primary objective of this study was to determine and compare the pharmacokinetic (PK) profiles of inorganic phosphate in the serum after continuous administration of pure glycerophosphate and glycerophosphate contained in total parenteral nutrition (TPN) emulsions. This approach was selected to identify potential PK interactions between TPN components and glycerophosphate. METHODS: The serum PK profile of inorganic phosphate after continuous intravenous administration of a sodium glycerophosphate containing TPN emulsion was determined in 10 healthy, white (5 male/5 female) volunteers. A pure sodium glycerophosphate formulation served as reference. Standard criteria of bioequivalence were applied. Subjects were enrolled in the double-blinded study and were randomly allocated to receive the test and reference preparations on two occasions in a 2-sequence crossover study design. The volunteers received 1/3 of the maximum recommended body weight- (BW) adjusted intravenous daily dosage (13.3 ml/kg BW) of the test drug over a period of 8 h. The amount of total phosphate (0.101 mmol/kg) and duration of administration were identical for the test and reference drugs. Study days were separated by washout periods of at least 88 h. Serum concentrations of total inorganic phosphate were measured serially over a 36-hour period using a validated method. A statistical mixed ANOVA, based on population averages, was used for testing bioequivalence between these study preparations. RESULTS: The 90% confidence intervals (90% CIs) of inorganic phosphate in serum were calculated for the test/reference ratios of the area under the time-concentration curve from time 0 to 36 h (AUC0₋36), the maximum concentration (C(max)) and the concentration 5 min before the end of infusion (C(ss)) for a bioequivalence range from 0.80 to 1.25. The mean test/reference ratios fell completely within the 90% CIs with values of 1.016 (90% CI 1.005-1.028), 1.013 (90% CI 0.981-1.047) and 0.932 (90% CI 0.886-0.980) for AUC(0-36), C(max) and C(ss), respectively. In total, 3 mild adverse events in the reference group were detected after starting intravenous infusion, while no adverse events were observed in the test group after treatment. CONCLUSION: Primary PK parameters were within the defined bioequivalence range of 0.8-1.25. Thus, inorganic phosphate levels were essentially similar between the two investigational medicinal products tested in the present study. These findings confirm the concept that nutritional components of the test drug do not significantly interact with glycerophosphate. The two study preparations proved to be safe during the investigation.

Mechanism of action of beta-glycerophosphate on bone cell mineralization.

Experiments were performed to determine whether beta-glycerophosphate (beta-GP) promoted mineralization in vitro by modulating bone cell metabolic activity and/or serving as a local source of inorganic phosphate ions (Pi). Using MC3T3-E1, ROS 17/2.8, and chick osteoblast-like cells in the presence of beta-GP or Pi, we examined mineral formation, lactate generation, alkaline phosphatase (AP) activity, and protein and phospholipid synthesis. Neither beta-GP nor Pi modulated any of the major biosynthetic activities of the bone cells. Thus, we found no change in the levels of phospholipids, and the total protein concentration remained constant. Measurement of lactate synthesis showed that beta-GP did not effect the rate of anaerobic glycolysis. Evaluation of medium Pi levels clearly indicated that beta-GP was hydrolyzed by bone cells; within 24 hours, almost 80% of 10 mM beta-GP was hydrolyzed. It is likely that this local increase in medium Pi concentration promoted rapid mineral deposition. Chemical, energy dispersive X-ray, and Fourier transform infrared analysis of the mineral formed in the presence of beta-GP showed that it was nonapatitic; moreover, mineral particles were also seen in the culture medium itself. Experiments performed with a cell-free system indicated that mineral particles formed spontaneously in the presence of AP and beta-GP and were deposited into a collagen matrix. We conclude that medium supplementation with beta-GP or Pi should not exceed 2 mM. If this value is exceeded, then there will be nonphysiological mineral deposition in the bone cell culture.

In vivo behaviour of low molecular weight iron complexes.

The in vivo distribution in mice of ferric citrate, ferric beta-glycerophosphate and ferric lactate complexes has been studied. There is a relationship between the 59Fe uptake by various tissues and the physicochemical characteristics of the complexes. Ferric lactate seems a useful preparation for iron deficiency therapy.

Nucleotide sequence of the ugp genes of Escherichia coli K-12: homology to the maltose system.

The nucleotide sequence of the ugp genes of Escherichia coli K-12, which encode a phosphate-limitation inducible uptake system for sn-glycerol-3-phosphate and glycerophosphoryl diesters, was determined. The genetic organization of the operon differed from previously published results. A single promoter, containing a putative pho box, was detected by S1-nuclease mapping. The promoter is followed by four open reading frames, designated ugpB, A, E and C, which encode a periplasmic binding protein, two hydrophobic membrane proteins and a protein that is likely to couple energy to the transport system, respectively. The sequences of the proteins contain the characteristics of several other binding protein-dependent transport systems, but they seem to be particularly closely related to the maltose system.