Initial experience of laparoscopic retroperitoneal partial nephrectomy in an academic hospital in Malaysia

Laparoscopic retroperitoneal partial nephrectomy (LRPN) is a technically demanding kidney surgery due to the limited space and unfamiliar approach in the retroperitoneal space. The aim of this study is to review the outcome of our initial experience in performing this procedure. All patients who underwent LRPN between 2019 to 2022 were included in this retrospective review. A total of 23 patients underwent LRPN. The mean operating time was 178±43 minutes and mean warm ischemia time was 20±5 minutes. The average estimated blood lost was 89±68ml and the mean postoperative hospital stay was 3.6±0.8 days. Two patients (11.1%) had positive margin and no local recurrence was seen after mean follow up of 15.8±12.0 months. Our initial experience on LRPN showed promising results to perform partial nephrectomy safely and effectively.

Development of an Add-On Device Using 3D Printing for the Enhancement of Drug Administration Efficiency of Dry Powder Inhalers (Accuhaler)

The goal of this study was to develop an add-on device for dry powder inhalers (Accuhaler) via 3D printing to improve drug administration efficiency in patients with limited inspiratory capacity, including young children, the elderly, and those with chronic obstructive pulmonary disease. With salmeterol xinafoate and fluticasone propionate as model active pharmaceutical ingredients (API), the emitted API doses were used to assess the effectiveness of the add-on device. The APIs were quantified by an HPLC assay validated for specificity, range, linearity, accuracy, and precision. The motor power of the add-on device could be regulated to moderate fan speed and the air flow in the assembled device. When 50–100% of the fan motor power of the add-on device was used, the emitted dose from the attached dry powder inhaler (DPI) was increased. A computational fluid dynamics application was used to simulate the air and particle flow in the DPI with the add-on device in order to elucidate the operating mechanism. The use of the add-on device combined with a sufficient inhalation flow rate resulted in a larger pressure drop and airflow velocity at the blister pocket. As these characteristics are associated with powder fluidization, entrainment, and particle re-suspension, this innovative add-on device might be utilized to enhance the DPI emitted drug dose for patients with low inspiratory rates and to facilitate the provision of adequate drug doses to achieve the treatment outcomes.

A Comprehensive Survey of Phenolic Constituents Reported in Monofloral Honeys around the Globe

The aim of this review is to provide a comprehensive overview of the large variety of phenolic compounds that have to date been identified in a wide range of monofloral honeys found globally. The collated information is structured along several themes, including the botanical family and genus of the monofloral honeys for which phenolic constituents have been reported, the chemical classes the phenolic compounds can be attributed to, and the analytical method employed in compound determination as well as countries with a particular research focus on phenolic honey constituents. This review covers 130 research papers that detail the phenolic constituents of a total of 556 monofloral honeys. Based on the findings of this review, it can be concluded that most of these honeys belong to the Myrtaceae and Fabaceae families and that Robinia (Robinia pseudoacacia, Fabaceae), Manuka (Leptospermum scoparium, Myrtaceae), and Chestnut (Castanea sp., Fagaceae) honeys are to date the most studied honeys for phenolic compound determination. China, Italy, and Turkey are the major honey phenolic research hubs. To date, 161 individual phenolic compounds belonging to five major compound groups have been reported, with caffeic acid, gallic acid, ferulic acid and quercetin being the most widely reported among them. HPLC with photodiode array detection appears to be the most popular method for chemical structure identification.

Villous adenoma of the prostatic urethra

Primary villous adenoma originating from the urinary tract is an infrequent entity. We present a rare case of villous adenoma arising from a prostatic urethra with no sign of malignant transformation. Villous adenoma should be considered as one of the differential diagnoses of urethral lesions, especially if it has similar magnetic resonance imaging features as its colonic counterpart. Due to its potential for malignant transformation, its complete resection is mandatory.

A randomised controlled trial of a novel tramadol chewable tablet: pharmacokinetics and tolerability in children

Tramadol is a bitter atypical opioid analgesic drug and is prescribed to treat postoperative pain in children. However, in many countries there is no licensed paediatric tramadol formulation available. We have formulated a novel chewable chocolate-based drug delivery system for the administration of tramadol to children. This pilot, single-centre, open-label, randomised clinical study assessed the taste tolerability and comparative population pharmacokinetics of the novel tramadol chewable tablet against a compounded tramadol hydrochloride oral liquid, at a dose of 1 mg.kg^-1 . A 5-point facial hedonic scale was used by the children, parents and nurses to assess tolerability. One hundred and forty-one children aged 3-16 years were given tramadol 30 min before general anaesthesia. Blood samples were taken following the induction of anaesthesia and for up to 5 h following tramadol administration. Tramadol and its active metabolite O-desmethyltramadol were analysed using reversed-phase high-performance liquid chromatography. A population pharmacokinetic model was built using non-linear mixed effects modelling. The relative bioavailability for the tablet was 1.25 times higher (95%CI 1.16-1.35) than for tramadol hydrochloride oral liquid, while the absorption rate constant for the tablet was significantly lower (1.97 h^-1 vs. 3.34 h^-1 , p < 0.001). Larger inter-individual variability in absorption rates were observed with the liquid tramadol. The tramadol chewable tablet was more acceptable in taste to children when assessed by the children, parents and nurses (all p < 0.001). We conclude that the novel tramadol chewable tablet has favourable acceptability and more reliable relative bioavailability in children compared with tramadol hydrochloride oral liquid.

HPLC-UV assay of tramadol and O-desmethyltramadol in human plasma containing other drugs potentially co-administered to participants in a paediatric population pharmacokinetic study

Multimodal analgesia is employed in paediatric pain management to maximise analgesia and minimise side effects. Tramadol is dosed at 1-1.5 mg/kg to treat severe pain in children but the assay for tramadol in plasma samples for pharmacokinetic and toxicology studies does not often consider concurrently administered medications. In this study we developed and validated an HPLC-UV method to quantify tramadol and its main metabolite (O-desmethyltramadol) in human plasma in the presence of seven potentially interfering drugs. Sample preparation method was developed by combining liquid-liquid extraction and protein precipitation. Chromatographic separation was achieved on a BDS-Hypersil-C18 column (5 µm, 250 × 4.6 mm) using a double gradient method. The limit of quantification was 6.7 ng/ml for both tramadol and ODT. The precision and accuracy were in compliance with ICH guidelines. This method was successfully employed to analyse the blood samples of 137 paediatric participants in a tramadol pharmacokinetic trial.

Tracheotomy: an alternative for tracheobronchial foreign body removal

A 6 years old girl accidentally aspirated a plastic whistle while playing. Computed Tomography of thorax showed foreign body at carina level. Rigid bronchoscope under general anesthesia was attempted but unable to extract the whistle through vocal cord. Tracheostomy was later performed and foreign body was removed.

Application of multiple stepwise spinning disk processing for the synthesis of poly(methyl acrylates) coated chitosan-diclofenac sodium nanoparticles for colonic drug delivery

The production of pharmaceutical nanoparticles by the spinning disk processing (SDP) technique has advantages in terms of its scalability and its capacity to produce readily tunable nanoparticles of narrow size distribution. In this study, we successfully developed a novel multiple stepwise SDP technique to develop aggregates of uniformly sized poly(methyl acrylates)-coated chitosan-diclofenac sodium nanocores (CS-PMA NPs) for colonic drug delivery. The processing conditions were optimized using the Box-Behnken design. SEM and TEM micrographs showed the optimized system to consist of 10 μm-sized agglomerates of CS-PMA NPs, the latter measuring 10nm in diameter. High drug entrapment of 88% was attained. Potential colon-targeted drug release from the CS-PMA NPs was demonstrated, with retardation of drug release in simulated gastrointestinal fluids and over 90% of the drug load released into simulated colonic fluid within 8 h. Drug uptake from CS-PMA NPs into Caco-2 cells was threefold higher than that from a control drug solution, with no apparent cytotoxicity observed at the NP doses administered. The collective data suggest that the SDP is a robust manufacturing method that can potentially be used to scale up the production of composite nanoparticulate colon-targeted drug delivery systems.

Cytotoxicity of monodispersed chitosan nanoparticles against the Caco-2 cells

Published toxicology data on chitosan nanoparticles (NP) often lack direct correlation to the in situ size and surface characteristics of the nanoparticles, and the repeated NP assaults as experienced in chronic use. The aim of this paper was to breach these gaps. Chitosan nanoparticles synthesized by spinning disc processing were characterised for size and zeta potential in HBSS and EMEM at pHs 6.0 and 7.4. Cytotoxicity against the Caco-2 cells was evaluated by measuring the changes in intracellular mitochondrial dehydrogenase activity, TEER and sodium fluorescein transport data and cell morphology. Cellular uptake of NP was observed under the confocal microscope. Contrary to established norms, the collective data suggest that the in vitro cytotoxicity of NP against the Caco-2 cells was less influenced by positive surface charges than by the particle size. Particle size was in turn determined by the pH of the medium in which the NP was dispersed, with the mean size ranging from 25 to 333 nm. At exposure concentration of 0.1%, NP of 25 ± 7 nm (zeta potential 5.3 ± 2.8 mV) was internalised by the Caco-2 cells, and the particles were observed to inflict extensive damage to the intracellular organelles. Concurrently, the transport of materials along the paracellular pathway was significantly facilitated. The Caco-2 cells were, however, capable of recovering from such assaults 5 days following NP removal, although a repeat NP exposure was observed to produce similar effects to the 1st exposure, with the cells exhibiting comparable resiliency to the 2nd assault.

Uptake and cytotoxicity of chitosan nanoparticles in human liver cells

Despite extensive research into the biomedical and pharmaceutical applications of nanoparticles, and the liver being the main detoxifying organ in the human body, there are limited studies which delineate the hepatotoxicity of nanoparticles. This paper reports on the biological interactions between liver cells and chitosan nanoparticles, which have been widely recognised as biocompatible. Using the MTT assay, human liver cells were shown to tolerate up to 4h of exposure to 0.5% w/v of chitosan nanoparticles (18±1 nm, 7.5±1.0 mV in culture medium). At nanoparticle concentrations above 0.5% w/v, cell membrane integrity was compromised as evidenced by leakage of alanine transaminase into the extracellular milieu, and there was a dose-dependent increase in CYP3A4 enzyme activity. Uptake of chitosan nanoparticles into the cell nucleus was observed by confocal microscopic analysis after 4h exposure with 1% w/v of chitosan nanoparticles. Electron micrographs further suggest necrotic or autophagic cell death, possibly caused by cell membrane damage and resultant enzyme leakage.

Design, synthesis, characterization and in-vivo activity of a novel salmon calcitonin conjugate containing a novel PEG-lipid moiety

Objectives

The aim of the study was to explore (1) the synthesis of a novel poly(ethylene glycol) modified lipid (PEG-lipid, PL) containing a chemically active tri-block linker, ε-maleimido lysine (Mal), and its conjugation with salmon calcitonin (sCT), and (2) the biophysical properties and activity of the resulting conjugate, Mal-PL-sCT, relative to the control, 2PEG-Mal-sCT, which comprises sCT conjugated with α-palmitoyl-N-ε-maleimido-l-lysine at cysteine 1 and cysteine 7, and PEG moieties at lysine 11 and lysine 18 via a conventional stepwise method.

Methods

The PEG-lipid was obtained by condensing palmitic acid derivative of ε-maleimido lysine with methoxy poly(ethylene glycol) amine. Under reductive conditions, the PEG-lipid readily reacted with sCT to yield the resultant compound, Mal-PL-sCT.

Key findings

Dynamic light scattering analyses suggested that Mal-PL-sCT and 2PEG-Mal-sCT exhibited robust helical structures with a high tendency to aggregate in water. Both compounds were more stable against intestinal degradation than sCT, although Mal-PL-sCT was less stable than 2PEG-Mal-sCT. However, 2PEG-Mal-sCT did not possess hypocalcaemic activity while Mal-PL-sCT retained the hypocalcaemic activity of sCT when it was subcutaneously injected in the rat model. Multiple functional groups may be conjugated to a peptide via a tri-block linker without the risk of obliterating the intrinsic bioactivity of the peptide.

Conclusions

The resultant novel PEG-lipid has a potential role to optimize protein and peptide delivery.

Mutant p53 mediates survival of breast cancer cells

Background:

p53 is the most commonly mutated tumour-suppressor gene in human cancers. Unlike other tumour-suppressor genes, most p53 cancer mutations are missense mutations within the core domain, leading to the expression of a full-length mutant p53 protein. Accumulating evidence has indicated that p53 cancer mutants not only lose tumour suppression activity but also gain new oncogenic activities to promote tumourigenesis.

Methods:

The endogenous mutant p53 function in human breast cancer cells was studied using RNA interference (RNAi). Gene knockdown was confirmed by quantitative PCR and western blotting. Apoptosis was evaluated by morphological changes of cells, their PARP cleavage and annexin V staining.

Results:

We show that cancer-associated p53 missense mutants are required for the survival of breast cancer cells. Inhibition of endogenous mutant p53 by RNAi led to massive apoptosis in two mutant p53-expressing cell lines, T47D and MDA-MB-468, but not in the wild-type p53-expressing cells, MCF-7 and MCF-10A. Reconstitution of an RNAi-insensitive mutant p53 in MDA-MB-468 cells completely abolished the apoptotic effects after silencing of endogenous mutant p53, suggesting the specific survival effects of mutant p53. The apoptotic effect induced by mutant p53 ablation, however, is independent of p63 or p73 function.

Conclusion:

These findings provide clear evidence of a pro-survival ‘gain-of-function’ property of a subset of p53 cancer mutants in breast cancer cells.

Stability of morphine sulphate in saline under simulated patient administration conditions

OBJECTIVE

To study the stability of morphine sulphate solutions under simulated administration conditions in a patient-controlled analgesic device.

METHOD

Concentrations of 1 mg/ml and 10 mg/ml morphine sulphate in saline were monitored over 16 days under slow continuous delivery from Deltec Medication cassettes kept in the dark at a controlled temperature of 32 degrees C and a humidity between 36 and 38%. The morphine concentrations in the samples, collected at 0, 1, 2, 5, 6, 7, 9, 12, 14 and 16 days, were measured by a stability indicating high-performance liquid chromatographic method.

RESULTS

Throughout the study period, the reservoir concentrations varied within 10% of their initial values and there was no chromatographic evidence of degradation. However, the pH of both reservoirs decreased with time, but morphine is expected to be stable within the observed pH range.

CONCLUSION

This study demonstrated that the concentrating effect due to evaporation under the storage conditions described, over 16 days, was not of significance and the product was stable.

Effect of Chitosan Salts and Molecular Weight on a Nanoparticulate Carrier for Therapeutic Protein

The objective of this study was to investigate the potential of chitosan salts as a carrier in the preparation of protein-loaded nanoparticles. Glutamic and aspartic acids were used to prepare chitosan salts of 35, 100, and 800 KDa. Nanoparticles of chitosan base, chitosan glutamate, and chitosan aspartate were produced by ionotropic gelation with sodium tripolyphosphate (TPP). Bovine serum albumin (BSA) was applied as a model protein at loading concentrations ranging from 0.2 to 2 mg/mL. The size of the nanoparticles, as measured by photon correlation spectroscopy, was in the range of 195 to 3450 nm, depending on type and molecular weight of chitosan. Nanoparticles prepared with higher molecular weight chitosan showed larger sizes. The encapsulation was controlled by the competition of BSA in forming ionic cross-linking with chitosan and by the entrapment of BSA during the gelation process. Higher BSA encapsulation efficiency (EE) was obtained for nanoparticles prepared with chitosan salts compared to those prepared with the base. The higher EE was a result of a higher degree of ionization, causing more active sites to interact with BSA. In addition, a higher and faster release of BSA from the nanoparticles into pH 7.4 buffer medium was observed for nanoparticles of the chitosan salts than was observed for nanoparticles of the chitosan base. The higher and faster release was attributed to higher EE and lower entrapment of BSA within the matrix of the nanoparticle during the gelation process. The influence of molecular weight on the property of nanoparticles exhibited different effects. The difference was a result of different organic acids used to prepare nanoparticles leading to the difference in polymer conformation and viscosity of organic acid solution. Therefore, this study showed that the characteristics of chitosan nanoparticles loaded with a protein drug could be readily modulated by changing the salt form or the molecular weight of the chitosan carrier.

In vitro and in vivo evaluation of the effects of piperine on P-gp function and expression

Piperine, a major component of black pepper, is used as spice and nutrient enhancer. The purpose of the present study was to evaluate the effects of acute and prolonged piperine exposure on cellular P-gp expression and function in vitro and in vivo. Piperine at concentrations ranging from 10 to 100 microM, determined by MTT assay to be non-cytotoxic, was observed to inhibit P-gp mediated efflux transport of [(3)H]-digoxin across L-MDR1 and Caco-2 cell monolayers. The acute inhibitory effect was dependent on piperine concentration, with abolishment of [(3)H]-digoxin polarized transport attained at 50 microM of piperine. In contrast, prolonged (48 and 72 h) co-incubation of Caco-2 cell monolayers with piperine (50 and 100 microM) increased P-gp activity through an up-regulation of cellular P-gp protein and MDR1 mRNA levels. The up-regulated protein was functionally active, as demonstrated by a higher degree of [(3)H]-digoxin efflux across the cell monolayers, but the induction was readily reversed by the removal of the spice from the culture medium. Peroral administration of piperine at the dose of 112 microg/kg body weight/day to male Wistar rats for 14 consecutive days also led to increased intestinal P-gp levels. However, there was a concomitant reduction in the rodent liver P-gp although the kidney P-gp level was unaffected. Our data suggest that caution should be exercised when piperine is to be co-administered with drugs that are P-gp substrates, particularly for patients whose diet relies heavily on pepper.

Folic Acid-Conjugated Protein Cages of a Plant Virus: A Novel Delivery Platform for Doxorubicin

The protein cage of a plant virus may provide a template for monodispersed nanosized systems for drug delivery. Using the Hibiscus chlorotic ringspot virus (HCRSV) as a model plant virus, we have prepared nanosized protein cages (30 nm) capable of encapsulating the anticancer drug, doxorubicin. The technique utilized the simultaneous encapsulation of a polyprotic acid of mw 200 kDa to produce an encapsulation efficiency for doxorubicin of about 7.5%. Folic acid was conjugated onto the capsids to impart cancer-targeting capability. The resultant nanosized systems improved the uptake and cytotoxicity of doxorubicin in the ovarian cancer cells, OVCAR-3, with statistical significance. Plant virus capsids may therefore provide viable templates for targeted drug delivery in cancer chemotherapy.

Aqueous-Soluble, Non-Reversible Lipid Conjugate of Salmon Calcitonin: Synthesis, Characterization and In Vivo Activity

PURPOSE

A novel, non-reversible, aqueous-based lipidization strategy with palmitic acid as a model lipid was evaluated for conjugation with salmon calcitonin (sCT).

MATERIALS AND METHODS

A water-soluble epsilon-maleimido lysine derivative of palmitic acid was synthesized from reaction of palmitic acid N-succinimidyl ester and epsilon-maleimido lysine. The latter was generated from reaction of alpha-Boc-lysine and methylpyrrolecarboxylate, with subsequent deprotection of the Boc group. The palmitic derivative was further conjugated with sCT via a thio-ether bond to produce Mal-sCT in aqueous solution. The identity and purity of Mal-sCT was confirmed by Electrospray Ionisation Mass spectrometry (ESI-MS) and HPLC.

RESULTS

Yield of Mal-sCT was 83%. Dynamic light scattering and circular dichroism data suggested that Mal-sCT presented as a stable helical structure in aqueous solutions of varying polarity, with a propensity to aggregate at concentrations above 11 microM. Cellular uptake of Mal-sCT was twice that of sCT in the Caco-2 cell model, and the conjugate was more resistant to liver enzyme degradation. Mal-sCT exhibited comparable hypocalcemic activity to sCT when administered subcutaneously in the rat model at sCT equivalent dose of 0.114 mg/kg. Peroral Mal-sCT, however, produced variability in therapeutic outcome. While four out of six rats did not respond following intragastric gavage with Mal-sCT, two rats showed significantly suppressed plasma calcium levels (approximately 60% of baseline) for up to 10 h.

CONCLUSION

A novel non-reversible, water-soluble lipid conjugate of sCT was successfully synthesized that showed (1) different aggregation behavior and secondary structure, (2) improved enzymatic stability and cellular uptake, and (3) comparable hypocalcemic activity in vivo compared to sCT.

Impact of curcumin-induced changes in P-glycoprotein and CYP3A expression on the pharmacokinetics of peroral celiprolol and midazolam in rats

The aim of this study was to evaluate whether curcumin could modulate P-glycoprotein (P-gp) and CYP3A expression, and in turn modify the pharmacokinetic profiles of P-gp and CYP3A substrates in male Sprague-Dawley rats. Intragastric gavage of the rats with 60 mg/kg curcumin for 4 consecutive days led to a down-regulation of the intestinal P-gp level. There was a concomitant upregulation of hepatic P-gp level, but the renal P-gp level was unaffected. Curcumin also attenuated the CYP3A level in the small intestine but induced CYP3A expression in the liver and kidney. Regular curcumin consumption also caused the C(max) and area under the concentration-time curve (AUC(0-8) and total AUC) of peroral celiprolol (a P-gp substrate with negligible cytochrome P450 metabolism) at 30 mg/kg to increase, but the apparent oral clearance (CL(oral)) of the drug was reduced. Similarly, rats treated with curcumin for 4 consecutive days showed higher AUC (AUC(0-4) and total AUC) and lower CL(oral) for peroral midazolam (a CYP3A substrate that does not interact with the P-gp) at 20 mg/kg in comparison with vehicle-treated rats. In contrast, curcumin administered 30 min before the respective drug treatments did not significantly modify the pharmacokinetic parameters of the drugs. Analysis of the data suggests that the changes in the pharmacokinetic profiles of peroral celiprolol and midazolam in the rat model were contributed mainly by the curcumin-mediated down-regulation of intestinal P-gp and CYP3A protein levels, respectively.

In vitro-reassembled plant virus-like particles for loading of polyacids

The coat protein (CP) of certain plant viruses may reassemble into empty virus-like particles (VLPs) and these protein cages may serve as potential drug delivery platforms. In this paper, the production of novel VLPs from the Hibiscus chlorotic ringspot virus (HCRSV) is reported and the capacity to load foreign materials was characterized. VLPs were readily produced by destabilizing the HCRSV in 8 M urea or Tris buffer pH 8, in the absence of calcium ions, followed by removal of viral RNA by ultrahigh-speed centrifugation and the reassembly of the CP in sodium acetate buffer pH 5. The loading of foreign materials into the VLPs was dependent on electrostatic interactions. Anionic polyacids, such as polystyrenesulfonic acid and polyacrylic acid, were successfully loaded but neutrally charged dextran molecules were not. The molecular-mass threshold for the polyacid cargo was about 13 kDa, due to the poor retention of smaller molecules, which readily diffused through the holes between the S domains present on the surface of the VLPs. These holes precluded the entry of large molecules, but allowed smaller molecules to enter or exit. The polyacid-loaded VLPs had comparable size, morphology and surface-charge density to the native HCRSV, and the amount of polyacids loaded was comparable to the weight of the native genomic materials. The conditions applied to disassembly-reassembly of the virions did not change the structural conformation of the CP. HCRSV-derived VLPs may provide a promising nano-sized protein cage for delivery of anionic drug molecules.

Effects of capsaicin on P-gp function and expression in Caco-2 cells

Capsaicin is the pungent component of hot chilli, a popular spice in many populations. The aim of the present study was to evaluate the chronicity and reversibility of the modulating effect of capsaicin on both the P-gp expression and activity in the Caco-2 cell monolayers. Capsaicin at concentrations ranging from 10 to 100 microM, which were found to be non-cytotoxic towards the Caco-2 cells, were observed to inhibit P-gp mediated efflux transport of [3H]-digoxin in the cells. The acute inhibitory effect was dependent on the capsaicin concentration and duration of exposure, with abolishment of polarity of [3H]-digoxin transport attained at 50 microM of capsaicin. In contrast, longer term (48 and 72 h) co-incubation of the Caco-2 cells with capsaicin (50 and 100 microM) increased P-gp activity through an up-regulation of cellular P-gp protein and MDR1 mRNA levels. The up-regulated protein was functionally active, as demonstrated by higher degree of [3H]-digoxin efflux across the cell monolayers, but the induction was readily reversed by the removal of the spice from the culture medium. The induction of P-gp protein and mRNA levels was also influenced by capsaicin concentration and duration of exposure, with higher expression levels, in particular of the mRNA, seen at higher spice concentrations over prolonged period of incubation. Our data suggest that caution should be exercised when capsaicin is to be consumed with drugs that are P-gp substrates. In particular, the oral bioavailability of these drugs may be influenced by the P-gp status of populations that rely heavily on hot chilli in their diets.

Effects of citrus fruit juices on cytotoxicity and drug transport pathways of Caco-2 cell monolayers

The aim of this study was to correlate the taxonomy of grapefruit, pummelo, orange, lime and lemon with fruit juice-mediated cytotoxicity, modulation of epithelial permeability and P-glycoprotein (P-gp)-mediated efflux using 0-50% juice concentrations. Lime and lemon juices at 30% enhanced the absorption of [14C]-mannitol across Caco-2 cell monolayers by six- and eight-fold, respectively, but grapefruit and pummelo juices did not modulate the paracellular [14C]-mannitol transport even at 50%. Orange juice at 30% increased mannitol absorption to a comparable level as lime juice, but had minimal effects on TEER. All five juices did not modulate the passive diffusional pathway as exemplified by their negligible effects on [3H]-propranolol absorption. Grapefruit, pummelo and orange juices showed P-gp inhibitory activity by reducing rhodamine-123 (R-123) efflux and elevating R-123 cellular accumulation, but lime and lemon juices did not. Lime and lemon juices at >or=30% were cytotoxic towards Caco-2 cells. Grapefruit and pummelo juices at 10% did not affect Caco-2 cell viability, but they enhanced cell growth at concentrations of >or=30%. Orange juice increased cell viability only at lower concentrations. On the basis of these data, lime and lemon juices could be regarded as a group distinct from grapefruit and pummelo juices, while orange juice appeared to belong to a bridging group. This grouping was consistent with the categorization of the citrus fruits according to their dominant flavonoid pattern and taxonomy.

Paclitaxel-loaded PLGA nanoparticles: Potentiation of anticancer activity by surface conjugation with wheat germ agglutinin

PURPOSE

To potentiate the anticancer activity of paclitaxel-loaded PLGA nanoparticles through surface conjugation with wheat germ agglutinin (WGA).

METHODS

PLGA nanoparticles loaded with paclitaxel and isopropyl myristate (IPM) as release modifier were prepared by a solvent evaporation method. WGA was conjugated to the nanoparticle surface to give novel WIT-NP of 330+/-3 nm. In vitro cytotoxicity of WIT-NP against malignant (A549 and H1299) and normal (CCL-186) pulmonary cell lines was evaluated alongside control formulations. IC50 doses were determined by the MTT assay, while cellular apoptosis was detected by cell nuclei staining and DeadEndtrade mark Fluorometric TUNEL assay. Cell cycle arrest was confirmed by flow cytometry. Cellular uptake of 3[H]-paclitaxel from the test and control formulations was also quantified. In vivo anticancer efficacy was evaluated in the SCID mice model engrafted with the A549 tumor nodule.

RESULTS

WIT-NP had superior anti-proliferation activity against the A549 and H1299 cell lines compared with conventional paclitaxel formulations as measured by IC50 doses. This was attributed to a more efficient intracellular accumulation of paclitaxel via WGA-receptor-mediated endocytosis and IPM-facilitated intracellular paclitaxel release. WIT-NP activity was associated with paclitaxel-induced apoptosis and cell arrest in the G2/M phase. A single intratumoral injection of WIT-NP at paclitaxel dose of 10 mg/kg inhibited the growth of A549 tumor nodules without inducing significant weight loss in the SCID mice over a period of 25 days. Tumor doubling time was greater than 25 days, compared with 11 days for nodules treated with conventional paclitaxel formulation.

CONCLUSION

The formulation of WIT-NP, in which WGA is conjugated to the surface of paclitaxel and IPM-loaded PLGA nanoparticles, significantly potentiates the anticancer activity of paclitaxel.

Transfection efficiency of chitosan vectors: effect of polymer molecular weight and degree of deacetylation

Chitosans of defined molecular weight (Mw 10-213 kDa) and degree of deacetylation (DD 46-88%) were synthesized, complexed with pEGFP-C2 plasmid into nanoparticles (NP) and evaluated for cellular uptake and transfection efficiency in the A549 cell model. DNA condensation of >90% was achieved at the N/P ratio of 6, independent of the chitosan Mw and DD. However, chitosan vectors of lower Mw or DD were less efficient at retaining the DNA upon dilution, and consequentially, less capable of protecting the condensed DNA from degradation by DNase and serum components. A549 cellular uptake of the NP was also significantly reduced by decreasing the Mw or DD of the chitosan vector. These factors contributed to the low transfection efficiencies for chitosan vectors of low Mw or DD. There was good correlation between transfection efficiency, cellular uptake and zeta potential of the NP, suggesting that cellular uptake mediated by electrostatic interactions with the cell membrane preceded efficient transfection. NP produced with chitosan of Mw 213 kDa and DD of 88% showed the highest zeta potential (+23 mV), cellular uptake (4.1 microg/mg protein) and transfection efficiency (12.1%), while chitosan vector with Mw of 213 kDa and DD of 46% showed the lowest cellular uptake (0.4 microg/mg protein) and transfection efficiency (0.05%). Confocal microscopy images suggested that the chitosan-complexed DNA successfully escaped from the endo-lysosomal compartment for nuclear translocation and expression. Intracellular DNA disassembly appeared to occur at different locations depending on the retentive capacity of the chitosan vector.

Preparation and in vitro anticancer activity of wheat germ agglutinin (WGA)-conjugated PLGA nanoparticles loaded with paclitaxel and isopropyl myristate

The purpose of this study was to develop a novel lectin-conjugated isopropyl myristate (IPM)-incorporated PLGA nanoparticle system (NP) for the local delivery of paclitaxel to the lungs. Wheat germ agglutinin (WGA) was conjugated onto preformed IPM- and paclitaxel-loaded PLGA NPs by a two-step carbodiimide method following comparative uptake studies of Concanavalin A, Ricinus communis-120 and WGA on A549, H1299 and CCL-186 cells. WIT-NP with mean diameter of 331 nm and zeta potential of -4.3 mV were prepared with yield of 66% and paclitaxel encapsulation efficiency of 61%. Particle size was expanded by surface conjugation with WGA, while zeta potential was reduced by the addition of IPM and WGA. In vitro paclitaxel release profile was not affected by WGA but initial drug release was enhanced by adding IPM into the formulation. The WIT-NP showed a burst-release of about 32% of the paclitaxel load within the first 5 h followed by a slow zero-order release of another 7% of the drug load in the next 115 h. Compared with the clinical paclitaxel formulation, paclitaxel-loaded nanoparticles without IPM or WGA, or paclitaxel-loaded nanoparticles with only IPM or WGA, the WIT-NP had superior in vitro cytotoxicity against A549 and H1299 cells. IC50 for WIT-NP after 5 and 24 h incubation with A549 cells were not significantly different (15.5 and 15 microM, respectively) whereas the clinical formulation was not cytotoxic after 5 h but had IC50 of 14 microM after 24 h incubation. WIT-NP exhibited stronger cell-killing effect because of more efficient cellular uptake via WGA-receptor-mediated endocytosis and IPM-facilitated release of paclitaxel from the NPs.

Pharmacological activity of peroral chitosan-insulin nanoparticles in diabetic rats

The objective of the present study was to evaluate the effects of formulation parameters on the in vivo pharmacological activity of the chitosan-insulin nanoparticles. Chitosan-insulin nanoparticles were prepared by ionotropic gelation at pH 5.3 and 6.1 and denoted as F5.3 np and F6.1 np, respectively. F5.3 np and F6.1 np administered orally at insulin doses of 50 U/kg and/or 100 U/kg were effective at lowering the serum glucose level of streptozotocin-induced diabetic rats. The 100 U/kg-dose F5.3 np sustained the serum glucose at pre-diabetic levels for at least 11 h. In comparison, F6.1 np had a faster onset of action (2h versus 10h) but lower efficiency. The effectiveness of peroral F5.3 np and F6.1 np in lowering the serum glucose level of streptozotocin-induced diabetic rats was ascribed to the local effect of insulin in intestine. Confocal micrographs showed strong interaction between rat intestinal epithelium and chitosan nanoparticles 3h post-oral administration.

Characterization of chitosan acetate as a binder for sustained release tablets

A chitosan derivative as an acetate salt was successfully prepared by using a spray drying technique. Physicochemical characteristics and micromeritic properties of spray-dried chitosan acetate (SD-CSA) were studied as well as drug-polymer and excipient-polymer interaction. SD-CSA was spherical agglomerates with rough surface and less than 75 microm in diameter. The salt was an amorphous solid with slight to moderate hygroscopicity. The results of Fourier transform infrared (FTIR) and solid-state (13)C NMR spectroscopy demonstrated the functional groups of an acetate salt in its molecular structure. DSC and TGA thermograms of SD-CSA as well as FTIR and NMR spectrum of the salt, heated at 120 degrees C for 12 h, revealed the evidence of the conversion of chitosan acetate molecular structure to N-acetylglucosamine at higher temperature. No interaction of SD-CSA with either drugs (salicylic acid and theophylline) or selected pharmaceutical excipients were observed in the study using DSC method. As a wet granulation binder, SD-CSA gave theophylline granules with good flowability (according to the value of angle of repose, Carr's index, and Hausner ratio) and an excellent compressibility profile comparable to a pharmaceutical binder, PVP K30. In vitro release study of theophylline from the tablets containing 3% w/w SD-CSA as a binder demonstrated sustained drug release in all media. Cumulative drug released in 0.1 N HCl, pH 6.8 phosphate buffer and distilled water was nearly 100% within 6, 16 and 24 h, respectively. It was suggested that the simple incorporation of spray-dried chitosan acetate as a tablet binder could give rise to controlled drug delivery systems exhibiting sustained drug release.

Influence of dietary solvents on strength of nanofill and ormocer composites

The objective of this study was to determine the influence of dietary solvents on the shear punch strength of nanofill (Filtek Supreme [FS], 3M-ESPE) and ormocer (Admira [AM], Voco) composites. The strength of these materials was also compared to a minifill composite (Z250 [ZT], 3M-ESPE), a compomer (F2000 [FT], 3M-ESPE) and a highly viscous glass ionomer cement (Ketac Molar Quick [KM], 3M-ESPE). Thirty-two specimens (8.7 mm diameter and 1-mm thick) of each material were made, randomly divided into four groups of eight and conditioned for one week as follows-Group 1 (control): distilled water at 37 degrees C; Group 2: 0.02M citric acid at 37 degrees C; Group 3: 50% ethanol-water solution at 37 degrees C and Group 4: heptane at 37 degrees C. After conditioning, the specimens were restrained with a torque of 2.5 Nm and subjected to shear punch strength testing using a 2-mm diameter punch at a crosshead speed of 0.5 mm/minute. The shear punch strength of the specimens was computed and data subjected to ANOVA/Scheffe's tests at significance level 0.05. With the exception of AM, the strength of all materials was not significantly influenced by dietary solvents. For AM, conditioning in heptane resulted in significantly higher shear strength values. The strength of the nanofill and ormocer composites was lower than the minifill composite but higher than the compomer and highly viscous glass ionomer cement investigated.

Insulin‐Loaded Calcium Pectinate Nanoparticles: Effects of Pectin Molecular Weight and Formulation pH

Insulin-loaded calcium pectinate nanoparticles were prepared as a potential colonic delivery system by ionotropic gelation with calcium ions. The effects of pectin molecular weight (Mv) and formulation pH on the characteristics of the nanoparticles were evaluated. Commercial pectins, LM101 and LM104, with respective degrees of esterification of 36% and 28%, were depolymerized by mechanical milling to give Mv ranging from 89 to 5.6 kDa. Milled pectins did not yield nanoparticles with significantly different mean diameter and insulin association efficiency (AE) compared to nanoparticles of unmilled pectins. LM104 nanoparticles had smaller variation in mean size than the LM101 nanoparticles. Formulation pH significantly influenced the AE and stability of the nanoparticles. Increasing the pH from 2 to 3 enhanced the AE by three-fold, from 32.76% to 93.31%, at an insulin loading concentration of 80 U/mL. This increase in AE was correlated to the charge density on the pectin molecules as a function of pH. Subsequent release of associated insulin from the nanoparticles was dependent on the extent of dilution of the nanoparticle dispersion and the pH of the dissolution medium. Cross-flow filtration could be used to separate the nanoparticles from unassociated ions and molecules, without compromising the characteristics of the nanoparticles.

Uptake and Cytotoxicity of Chitosan Molecules and Nanoparticles: Effects of Molecular Weight and Degree of Deacetylation

PURPOSE

To evaluate the effects of molecular weight (Mw) and degree of deacetylation (DD) on the cellular uptake and in vitro cytotoxicity of chitosan molecules and nanoparticles.

METHODS

Chemical depolymerization and reacetylation produced chitosans of Mw 213,000 to 10,000 and DD 88-46%, respectively. Chitosan was labeled with FITC and transformed into nanoparticles by ionotropic gelation. Uptake of chitosan by confluent A549 cells was quantified by fluorometry, and in vitro cytotoxicity was evaluated by the MTT and neutral red uptakeassays.

RESULTS

Nanoparticle uptake was a saturable event for all chitosan samples, with the binding affinity and uptake capacity decreasing with decreasing polymer Mw and DD. Uptake fell by 26% when Mw was decreased from 213,000 to 10,000, and by 41% when DD was lowered from 88% to 46%; the uptake data correlated with the zeta potential of the nanoparticles. Uptake of chitosan molecules did not exhibit saturation kinetics and was less dependent on Mw and DD. Postuptake quenching with trypan blue indicated that the cell-associated chitosan nanoparticles were internalized, but not the cell-associated chitosan molecules. Chitosan molecules and nanoparticles exhibited comparable cytotoxicity, yielding similar IC50 and IC20 values when evaluated against the A549 cells. Cytotoxicity of both chitosan entities was attenuated by decreasing polymer DD but was less affected by a lowering in Mw.

CONCLUSIONS

Transforming chitosan into nanoparticles modified the mechanism of cellular uptake but did not change the cytotoxicity of the polymer toward A549 cells. Chitosan DD had a greater influence than Mw on the uptake and cytotoxicity of chitosan nanoparticles because of its effect on the zeta potential of the nanoparticles.

Mechanistic study of the uptake of wheat germ agglutinin-conjugated PLGA nanoparticles by A549 cells

The purpose of this study was to evaluate the extent and mechanism of uptake of wheat germ agglutinin-conjugated PLGA nanoparticles by A549 cells. PLGA nanoparticles of 150 nm were prepared by a solvent diffusion method and covalently conjugated to FITC-WGA (fWGA) or FITC-bovine serum albumin (fBSA) by a two-step carbodiimide method. Uptake of fWGA-PLGA and fBSA-PLGA nanoparticles by confluent A549 cells was quantified by fluorometry. A549 cellular uptake of fWGA-PLGA nanoparticles at 2 h, 37 degrees C was 5.02-fold that of fBSA-PLGA nanoparticles at a loading concentration of 2.65 mg/mL. The difference in uptake between the two types of nanoparticles was increased to 7.84-fold at a higher loading concentration of 5.3 mg/mL, but was reduced to 2.07-fold by lowering the uptake temperature to 4 degrees C. Coincubation with 5 mg/mL of unlabeled WGA negated the differential uptake of fWGA-PLGA nanoparticles at 4 degrees C, suggesting that the nanoparticles interacted with a specific WGA-binding receptor on the cell membrane. Internalization of the fWGA-PLGA nanoparticles by the A549 cells was confirmed by confocal microscopy. Filipin (1 microg/mL), a known inhibitor of caveolae, reduced the 1-h uptake of the nanoparticles by 75%. Surface modification of PLGA nanoparticles with WGA significantly enhanced its endocytosis by A549 cells by a receptor-mediated, caveola-dependent pathway.

Uptake of Chitosan and Associated Insulin in Caco-2 Cell Monolayers: A Comparison Between Chitosan Molecules and Chitosan Nanoparticles

PURPOSE

To evaluate the uptake of chitosan molecules (fCS) and nanoparticles (fNP), and their ability to mediate insulin transport in Caco-2 cell monolayers.

METHODS

Cell-associated fCS and fNP were evaluated by fluorometry, trypan blue quenching, and confocal microscopy using FITC-labeled chitosan. Chitosan-mediated transport of FITC-labeled insulin was studied in Caco-2 cell monolayers cultured on permeable inserts.

RESULTS

Caco-2 cells showed twofold higher association with fNP than fCS after 2-h incubation with 1 mg/ml samples. fNP uptake was a saturable (Km 1.04 mg/ml; Vmax 74.15 microg/mg/h), concentration- and temperature-dependent process that was inhibited by coadministered chlorpromazine. fCS uptake was temperature dependent, but was less sensitive to concentration and was inhibited by filipin. Postuptake quenching with 100 microg/ml of trypan blue suggests a significant amount of intracellular fNP, although the bulk of fCS was extracellular. Internalized fNP were located by confocal microscopy at 15 microm from the apical membrane, but there was no apparent breaching of the basal membrane. This might explain the failure of the nanoparticles to mediate significant insulin transport across the Caco-2 cell monolayer.

CONCLUSIONS

Formulation of chitosan into nanoparticles transforms its extracellular interactions with the Caco-2 cells to one of cellular internalization via clathrin-mediated endocytosis.

Ultrasonication of chitosan and chitosan nanoparticles

The objective of this study was to evaluate the effects of ultrasonication on chitosan molecules and nanoparticles. Molecular weight (M(v)) of chitosan HCl (M(v) 146 kDa and degree of deacetylation (DD) 96%) decreased linearly with increasing duration and amplitude of ultrasonication. DD and FTIR absorption were unaffected. X-ray diffraction (XRD) analysis suggested greater chain alignment in the ultrasonicated chitosan samples. Chitosan nanoparticles had mean diameter of 382 nm, polydispersity of 0.53 and zeta potential of 47 mV. Ultrasonication administered at increasing duration or amplitude decreased the mean diameter and polydispersity of the nanoparticles. Zeta potential and FTIR absorbance were unaffected, while XRD suggested a greater disarray of chain alignment in the nanoparticle matrix. Under the transmission electron microscope (TEM), freshly prepared nanoparticles were dense spherical structures which became fragmented after ultrasonication for 10 min at amplitude of 80. Untreated nanoparticle formulation turned turbid upon storage for 3 weeks at ambient conditions due to substantial swelling of the nanoparticles. Ultrasonicated nanoparticle formulation remained clear on storage. Although the particles had also swelled, they were no longer spherical, assuming instead an irregular shape with branching arms. In conclusion, high-intensity ultrasonication induced considerable damage on the chitosan nanoparticles which could affect their function as drug carriers.

Modulation of digoxin transport across Caco-2 cell monolayers by citrus fruit juices: lime, lemon, grapefruit, and pummelo

PURPOSE

To evaluate the effects of fresh lime, lemon, grapefruit, and pummelo juices on the transport of digoxin, a P-glycoprotein (P-gp) substrate, in Caco-2 cell monolayers.

METHODS

Bidirectional [3H]-digoxin fluxes across confluent Caco-2 cell monolayers were determined in 0-50% fruit juices at pH 7.4. Verapamil HCl (100 microM) served as positive control. Juice toxicity was evaluated by the 3-(4,5 dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay.

RESULTS

Apical-to-basal (A-to-B) digoxin flux was enhanced by 50% fruit juice in the order of lemon > lime > pummelo > grapefruit. The four fruit juices could be divided into two groups based on their effects on transepithelial electrical resistance (TEER), viability, and digoxin transport activity of the Caco-2 cells. Grapefruit and pummelo juices produced similar digoxin transport profiles that were characteristic of those observed with P-gp inhibitors. Both juices decreased net digoxin efflux by 1.2 U per 10% increase in juice concentration and had a propensity to increase cellular TEER at high concentrations (>30%). However, cellular TEER and viability decreased with increasing concentration of lime and lemon juices. Both juices also produced similar digoxin transport profiles, the A-to-B and B-to-A digoxin Papp increasing with increasing juice concentration above 5%. Net digoxin efflux was 30% of control value and relatively independent of juice concentration. These results paralleled the groupings of the four fruits according to their prominent flavonoid pattern and taxonomy.

CONCLUSION

The effects of lime, lemon, grapefruit, and pummelo juices on the TEER, viability, and digoxin transport activity of the Caco-2 cells appeared to be dependent on the dominant flavonoid pattern and taxonomy of the citrus fruits.

Uptake of FITC-chitosan nanoparticles by A549 cells

PURPOSE

The objective of this study was to evaluate the extent and mechanism of uptake of fluorescent chitosan nanoparticles by the A549 cells, a human cell line derived from the respiratory epithelium.

METHODS

Covalent conjugation with fluorescein-5-isothiocyanate yielded stably labeled chitosan molecules, which were successfully formulated into nanoparticles by ionotropic gelation. Uptake of fluorescein-5-isothiocyanate-chitosan nanoparticles and chitosan molecules by confluent A549 cells was quantified by fluorometry.

RESULTS

Cellular uptake of chitosan nanoparticles was concentration and temperature dependent, having Km and Vmax of 3.84 microM and 58.14 microg/mg protein/h, respectively. Uptake of chitosan nanoparticles was up to 1.8-fold higher than that of chitosan molecules alone and was not inhibited by excess unlabeled chitosan molecules. Hyperosmolarity, chlorpromazine and K+ depletion inhibited by 65, 34, and 54%, respectively, the uptake of chitosan nanoparticles at 37 degrees C, but filipin had no influence on the uptake. Confocal imaging confirmed the internalization of the chitosan nanoparticles by the A549 cells at 37 degrees C.

CONCLUSIONS

Formulation of chitosan into nanoparticles significantly improved its uptake by the A549 cells. Internalization of chitosan nanoparticles by the cells seems to occur predominantly by adsorptive endocytosis initiated by nonspecific interactions between nanoparticles and cell membranes, and was in part mediated by clathrin-mediated process.

Formulation pH modulates the interaction of insulin with chitosan nanoparticles

Previous studies on chitosan-insulin nanoparticles have reported diverse encapsulation efficiency and insulin release profiles despite similar formulation and preparation procedures. This study examined the efficiency and mechanism of association of insulin with chitosan nanoparticles in the pH range of 2.3 to 6.3. Nanoparticles of 237 to 235 nm were prepared by ionotropic gelation of chitosan with tripolyphosphate counterions. Insulin was quantified by an RP-HPLC method. The insulin association efficiency (AE) spanned a broad range from 2 to 85%, and was highly sensitive to formulation pH. Highest AE was measured at insulin loading concentrations >/= 4.28 U/mL and pH 6.1, close to the pI of native insulin and the pK(a) of chitosan. This association, attributed to physical adsorption of insulin through hydrophobic interactions with chitosan, was labile, and the associated insulin rapidly and completely released by dilution of the nanoparticles in aqueous media of pH 2 to 7.4. AE obtained at pH 5.3 was less than half that measured at pH 6.1 at corresponding insulin concentration, but the association at pH 5.3 appeared to be based on stronger interactions, because the release of insulin was pH-dependent and recovery was less than 25% even upon disintegration of the chitosan matrix. Interaction of insulin with the chitosan nanoparticles rendered the protein more susceptible to acid and enzymatic hydrolyses, the effects being more predominant in nanoparticles prepared at pH 5.3 than at pH 6.1.

Chitosan-alginate films prepared with chitosans of different molecular weights

Chitosan-alginate polyelectrolyte complex (CS-AL PEC) is water insoluble and more effective in limiting the release of encapsulated materials compared to chitosan or alginate. Coherent CS-AL PEC films have been prepared in our laboratory by casting and drying suspensions of chitosan-alginate coacervates. The objective of this study was to evaluate the properties of the CS-AL PEC films prepared with chitosans of different molecular weights. Films prepared with low-molecular-weight chitosan (Mv 1.30 x 10(5)) were twice as thin and transparent, as well as 55% less permeable to water vapor, compared to films prepared with high-molecular-weight chitosan (Mv 10.0 x 10(5)). It may be inferred that the low-molecular-weight chitosan reacted more completely with the sodium alginate (M(v) 1.04 x 10(5)) than chitosan of higher molecular weight. A threshold molecular weight may be required, because chitosans of Mv 10.0 x 10(5) and 5.33 x 10(5) yielded films with similar physical properties. The PEC films exhibited different surface properties from the parent films, and contained a higher degree of chain alignment with the possible formation of new crystal types. The PEC films exhibited good in vitro biocompatibility with mouse and human fibroblasts, suggesting that they can be further explored for biomedical applications.

Chitosan-alginate-CaCl(2) system for membrane coat application

Water-based formulations are preferred for membrane coat application because they do not require the use of noxious solvents. A novel aqueous chitosan-alginate-CaCl(2) system was evaluated as a potential formulation to produce water-insoluble membranes of biodegradable polymers. Chitosan-alginate coacervates were prepared by controlled reaction of chitosan (0.25% w/v) and sodium alginate (0.25% w/v) solutions. Coherent membranes were obtained by casting and drying the coacervates suspended in aqueous CaCl(2) solutions (0.05-0.07% w/v). Increasing the calcium content did not modify membrane thickness (25-26 microm), but reduced the water vapor transmission rate from 658 to 566 g/m(2)/day, and improved the tensile strength of the membranes from 9.33 to 17.13 MPa. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and elemental analyses of the chitosan-alginate coacervates indicated they were stable for up to 4 weeks of storage in distilled water at ambient temperature. Membranes of the stored coacervates required less calcium to attain maximum mechanical strength. They also had higher water vapor transmission rates than corresponding films prepared from fresh coacervates. On the basis of the properties of the cast film and its storage stability, the chitosan-alginate-CaCl(2) system can be considered for potential membrane coat application.

Concurrent production of chitin from shrimp shells and fungi

Crustacean shells constitute the traditional and current commercial source of chitin. Conversely, the control of fungal fermentation processes to produce quality chitin makes fungal mycelia an attractive alternative source. Therefore, the exploitation of both of these sources to produce chitin in a concurrent process should be advantageous and is reported here. Three proteolytic Aspergillus niger (strains 0576, 0307 and 0474) were selected from a screening for protease activity from among 34 zygomycete and deuteromycete strains. When fungi and shrimp shell powder were combined in a single reactor, the release of protease by the fungi facilitated the deproteinization of shrimp-shell powder and the release of hydrolyzed proteins. The hydrolyzed proteins in turn were utilized as a nitrogen source for fungal growth, leading to a lowering of the pH of the fermentation medium, thereby further enhancing the demineralization of the shrimp-shell powder. The shrimp-shell powders and fungal mycelia were separated after fermentation and extracted for chitin with 5% LiCl/DMAc solvent. Chitin isolates from the shells were found to have a protein content of less than 5%, while chitin isolates from the three fungal mycelia strains had protein content in the range of 10-15%. The relative molecular weights as estimated by GPC for all chitin samples were in the 10(5) dalton range. All samples displayed characteristic profiles for chitin in their FTIR and solid-state NMR spectra. All chitin samples evaluated with MTT and Neutral Red assays with three commercial cell lines did not display cytotoxic effects.

Preparation and characterization of chitin beads as a wound dressing precursor

Chitin was dissolved in N, N-dimethylacetamide/5% lithium chloride (DMAc/5%LiCl) to form a 0.5% chitin solution. Chitin beads were formed by dropping the 0.5% chitin solution into a nonsolvent coagulant, ethanol. The beads were left in ethanol for 24 h to permit hardening, consolidation, and removal of residual DMAc/5%LiCl solvent in order to give spherical chitin beads uniform size distribution. The ethanol-gelled chitin beads had an average diameter of 535 microm. The chitin beads were subsequently activated in 50% (w/v) NaOH solution and reacted with 1.9 M monochloroacetic acid/2-propanol solution to introduce a carboxymethylated surface layer to the chitin beads. The bilayer character of the surface-carboxymethylated chitin (SCM-chitin) beads was verified by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and confocal microscopy. The bilayered SCM-chitin beads were found to absorb up to 95 times their dry weight of water. These SCM-chitin beads have potential as a component of wound dressings.

PEC films prepared from Chitosan-Alginate coacervates

Chitosan-alginate polyelectrolyte complex (PEC) have been prepared in situ in beads and microspheres. This study examines the preparation of suitable chitosan-alginate coacervates for casting into homogeneous PEC films for potential applications in packaging, controlled release systems and wound dressings. Coacervation between chitosan and alginate was rapid, but the rate may be controlled with the addition of water miscible organic solvents. Compared with ethanol and PEG200, acetone was the more promising solvent moderator. Suspensions of fine, uniformly dispersed coacervates were produced by a dropwise addition of 0.25% w/v chitosan solution (solvent: 1: 1 v/v of 2% acetic acid and acetone) into 0.25% w/v sodium alginate solution in water under rapid agitation. The PEC films were transparent and flexible. They exhibited high permeability to water vapor, but resisted complete dissolution in 0.1 M HCI, distilled water and pH 7.4 phosphate buffer solution. Microscopic heterogeneity in the films could be reduced by immersion in aqueous media, but this was accompanied by modifications in the thickness, permeability and mechanical property of the films.

Effects of dry heat and saturated steam on the physical properties of chitosan

Heat may be employed to facilitate the processing of chitosan and to confer sterility on chitosan-based medical products. In this study, changes were analyzed of the physical properties of purified chitosan heated at 60 to 160 degrees C under specified conditions for periods ranging from 0.5 to 4 h. Two forms of heat were used for processing: dry heat generated by a convection oven and saturated steam generated by an autoclave. Dry heat at < or = 80 degrees C resulted in less rigid chains with lower glass transition temperature, improved aqueous solubility, and slightly higher [eta]. At higher temperatures, dry heat produced chromophores, which may be related to interchain crosslink formation involving the NH2 groups. The [eta] and aqueous solubility of the samples decreased with temperatures > or = 120 degrees C. The coloration of the samples intensified from yellow to brown with increasing temperatures and duration of heat exposure. Chitosan heated at 160 degrees C for > or = 2 h was insoluble in the 0.2 M acetic acid/0.1 M sodium acetate solvent. The rate and extent of the thermal reactions were increased in the presence of saturated steam; the autoclaved samples became insoluble after 2 h of heating at 115 degrees C and after 1 h at > or = 120 degrees C. On the other hand, the physical changes induced by dry heat at < or = 120 degrees C were not affected significantly by heating the chitosan samples under anoxic conditions.

Gamma irradiation of chitosan

Chitosan has potential biomedical applications that may require the final products to be sterilized before use. The gamma irradiation of purified and highly deacetylated chitosan fibers and films at sterilizing doses (up to 25 kGy) caused main chain scissions. The viscosity average molecular weight of the polymer decreased with increasing irradiation dose, the radiation yields of scission being 1.16 in air and 1.53 in anoxia. Preirradiation application of a negative pressure of 100 kPa disrupted the network structure, which may have contributed to the greater radiation yield obtained by chitosan fibers in anoxia. Radiation induced scission of the chitosan chains resulted in a lower glass transition temperature (Tg), indicative of higher segmental mobility. The Tg was below ambient at an irradiation dose of 25 kGy in air. Irradiation in air improved the tensile strength of the chitosan film, probably due to changes in chain interaction and rearrangement. Irradiation in anoxia did not affect film properties significantly, partly because the preirradiation application of negative pressure had a negligible effect on the structure of the chitosan film. Polymer network structure and the irradiation conditions are therefore important determinants of the extent of radiation induced reactions in chitosan.

Structure-activity relationships for G2 checkpoint inhibition by caffeine analogs

Caffeine inhibits the G2 checkpoint activated by DNA damage and enhances the toxicity of DNA-damaging agents towards p53-defective cancer cells. The relationship between structure and G2 checkpoint inhibition was determined for 56 caffeine analogs. Replacement of the methyl group at position 3 or 7 resulted in loss of activity, while replacement at position 1 by ethyl or propyl increased activity slightly. 8-Substituted caffeines retained activity, but were relatively insoluble. The structure-activity profile did not resemble those for other known pharmacological activities of caffeine. The active analogs also potentiated the killing of p53-defective cells by ionizing radiation, but none was as effective as caffeine.

Storage of partially deacetylated chitosan films

Chitosan has wide-ranging applications as a biomaterial, but its stability in storage is not widely known. The objective of this study was to evaluate the storage stability of films prepared from chitosan of 77% deacetylation. Both the neutralized and acetate films were evaluated, as chitosan salts offer the advantage of being soluble in water at the neutral-to-basic pH range. Aqueous solutions containing 0.5-5% acetic acid were used as solvents. The X-ray diffraction pattern, the IR spectrum, water uptake, and solubility of the films were influenced by the presence of the N-acetyl functionality, the acetate ions, and storage of the films. The anhydrous chitosan crystal in the neutralized films was unstable to storage at 4 degrees C and 28 degrees C. Its formation, as well as that of the hydrated crystal, were further hindered by the presence of even small quantities of the acetate ions. The resultant amorphous nature of the acetate films, coupled with the acidifying action of the acetic acid, led to greater water uptake and solubility compared to the neutralized films. Storage reduced the differences between the neutralized and acetate films. It also minimized the influence of the initial acetic acid content on the IR absorption and water uptake of the acetate films, exerting its leveling effects mainly within the first week of storage. Using a lower storage temperature of 4 degrees C or heating the films for 2 h at 120 degrees C prior to storage did not significantly modify the results. A pertinent factor appears to be the degree of deacetylation of the chitosan that was used to prepare the films.