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Targeting mucosal tissues in the gastrointestinal tract by particulate drug delivery systems requires a supportive platform to avoid uncontrolled dispersion. It is expected that such a platform will erode at a rapid, predetermined rate, coupled with mucoadhesive properties, all aimed at creating a critical mass of drug-loaded particles at the injured epithelium. This strategy was challenged by exploiting two types of micro-matrices (beads): calcium alginate (CaAlg) and chitosan oxalate (CtOx). The beads were loaded with different types of dyes (cationic anionic and hydrophobic) or with the BCS Class II NSAID indomethacin (Ind). Their collapse kinetics in the presence of ionic de-cross-linkers (oxalic acid in the case of CaAlg and CaCl2 in the case of CtOx) was measured in vitro (mechanical tests and dye release kinetics) and in vivo (pharmacokinetic analysis of degradation-driven cecal release of Ind in the cecum of rats). It was found that ionic de-cross-linking caused a concentration-dependent disassembly of the CaAlg and CtOx beads, leading to a burst release of the dye probes. This observation was repeated in the cecum of anesthetized rats after local concomitant administration of both types of Ind-loaded beads and ionic de-cross-linker solutions. The concomitant administration caused an enhanced absorption of similar Ind doses. It is concluded that a prototype of a partially “ smart” (non-reversible) supportive carrier, with the capability of responding to an external stimulus in a controlled manner has been demonstrated. Tailoring the de-cross-linker concentration to each polysaccharide composition would yield an optimal pulsatile effect at the desired mucosal region.

Locoregional recurrence is the most common complication after adenocarcinoma resection in the colon, despite adjuvant chemotherapy. Therapy efficacy could be improved if designed to target malignant cells by incorporating specific recognition factors in the drugs or the drug vehicles. The aim of this study was to elucidate whether the overexpression of sialic acid (SA) on colonic malignant tissues could be utilized for drug targeting by cationic polymers.Cell lines (IEC-6, SW-480 and SW-620) and colon polyps and normal adjacent tissues harvested from dimethylhydrazine (DMH) induced rats were used as in vitro and in vivo models of different metastatic stages of colon cancer. SA expression was identified by fluorescent wheat germ agglutinin (WGA), and verified by pretreatment with neuraminidase. The role of mucus in the mucosal binding experiments was explored by pretreatment with dithiothreitol (DTT). The binding of FITC labeled cationic polymers of various degrees of cationization to normal and malignant colonic cells and tissue was measured.SA was overexpressed on malignant colonic cells and tissues, and its expression correlated to the metastatic stage in vitro. The binding of the cationic copolymers to the cell lines and tissues correlated with the charge density of the polymer and with the metastatic stage of the cell line. The interaction between the malignant colonic cells and tissues with the polymers was SA dependent and increased after mucus removal.Cationic polymers could be used as a targeting tool to colonic malignant epithelium, to be implemented in drug delivery and diagnosis.

Cell lines that do not overexpress functional cyclooxygenase-2 are resistant to the normal plasma levels of celecoxib achieved following oral ingestion. Cell growth inhibition was demonstrated after 24 h exposure to 80 micromol/l celecoxib while significant death was not detected at concentrations below 120 micromol/l following 24 h exposure. This growth inhibition and death induction was identified to be independent of p53 and Hdm2 in these cells, despite wild-type p53 stabilization and Hdm2 diminution in some lines. Cell death induced by celecoxib was preceded by the generation of reactive oxygen species within 4 h of drug exposure. The precise mechanism of elicitation of reactive oxygen species in these cells remains to be elucidated, although it was found to be independent of p53 and c-Abl, while in vitro, celecoxib enhanced superoxide radical production by xanthine oxidase. Importantly, the failure of anti-oxidants to protect from death indicates that celecoxib induces death independently of reactive oxygen species and that reactive oxygen species generation may be an insufficient trigger of death in p53-deficient cells.

The purpose of this study was to develop a biodegradable drug platform composed of chitosan and guar gum and to explore the possibility of using it for local adjuvant or neoadjuvant therapy of colorectal cancer. Celecoxib (Cx), a chemopreventative drug for familial adenomatous polyposis (FAP) and under trial for reducing post surgical colorectal malignancies, was selected as a model drug for this topical system because of the contraindications that are associated with its systemic administration. Films made of chitosan (Ct) and guar gum (GG) were prepared, characterized for equilibrium swelling, mucoadhesion, in vitro and in vivo degradation and loaded with Cx. Short term dosing studies in vitro were performed in the HT-29 colon carcinoma cell line that was incubated with Cx using the MTT test to assess IC50. The impact of a single high dose was evaluated and compared with a repeating low-dose regimen. In vivo dosing experiments with Cx were performed in the perfused intestine of the anaesthetized rat. Measuring tissue LDH assessed epithelium injury. Mechanical, mucoadhesion and in vitro degradation of the polysaccharide films were dictated by manipulating the ratios of Ct and GG. The addition of rat cecal contents to the dissolution medium increased the total Cx released from those films containing high amounts of GG. MTT reduction, a measure of cell proliferation, diminished as a function of increasing drug concentration and exposure time in the HT-29 cell line studies. Local high concentrations of Cx were shown to impede the proliferation of cancer cells directly, while chemoprevention has been demonstrated with low Cx doses. Healthy cells were shown to be sensitive to high Cx doses. Maximum therapeutic efficiency in the context of minimal healthy tissue exposure would thus be predicted utilizing a local delivery system such as the proposed adhesive, biodegradable polysaccharide composites.

In December 1995, ambient radon levels exceeding 10,000 Bq/m3 were measured in a basement shelter workroom of a multilevel East Talpiot, Jerusalem, public elementary school (six grades, 600 students). The measurements were taken after cancers (breast and multiple myeloma) were diagnosed in two workers who spent their workdays in basement rooms. The school was located on a hill that geologic maps show to be rich in phosphate deposits, which are a recognized source for radon gas and its daughter products. Levels exceeding 1000,000 Bq/m3 were measured at the mouth of a pipe in the basement shelter workroom, the major point of radon entry. The school was closed and charcoal and electret ion chamber detectors were used to carry out repeated 5-day measurements in all rooms in the multilevel building over a period of several months. Radon concentrations were generally higher in rooms in the four levels of the building that were below ground level. There were some ground-level rooms in the building in which levels reached up to 1300 Bq/m3. In rooms above ground level, however, peak levels did not exceed 300 Bq/m3. Exposure control based on sealing and positive pressure ventilation was inadequate. These findings suggested that radon diffused from highly contaminated basement and ground-floor rooms to other areas of the building and that sealing off the source may have led to reaccumulation of radon beneath the building. Later, subslab venting of below-ground radon pockets to the outside air was followed by more sustained reductions in indoor radon levels to levels below 75 Bq/m3. Even so, radon accumulated in certain rooms when the building was closed. This sentinel episode called attention to the need for a national radon policy requiring threshold exposure levels for response and control. A uniform nationwide standard for school buildings below 75 Bq/m3 level was suggested after considering prudent avoidance, the controversies over risk assessment of prolonged low-level exposures in children, and the fact that exposures in most locations in the Talpiot school could be reduced below this level. Proposal of this stringent standard stimulated the search for a strategy of risk control and management based on control at the source. This strategy was more effective and probably more cost effective than one based on suppression of exposure based on sealing and ventilation. Because many Israeli areas and much of the West Bank area of the Palestinian National Authority sit on the same phosphate deposits, regional joint projects for surveillance and control may be indicated. Images Figure 1. Figure 2.

The in vitro release of physostigmine salicylate (PS) from a submicron emulsion and an aqueous solution was studied using the dialysis bag method. These formulations were then perfused to various locations along the rat small intestine (proximal, mid, and distal jejunum), and two lengths (10 and 55 cm). The disappearance of PS from the luminal compartment and its appearance in the blood compartment was monitored. In the in vitro drug release from emulsion experiments, a biphasic appearance of PS in the sink solution was observed, suggesting a possible sustained release from the emulsion. However, absorption data from perfusion studies did not correlate with this in vitro observation. No significant difference was found in absorption from emulsion versus solution in the mid jejunum where PS absorption was maximal. The difference between the two liquid formulations was observed only in those intestinal segments where the absorption was relatively low [absorption rate values of 4.6 +/- 0.86 and 9.98 +/- 2.04 (log%/min) x 10(-3) in the proximal and distal parts of the small intestine, respectively, as compared with 14.0 +/- 1.2-14.8 +/- 1.1 (log%/min) x 10(-3) in the mid jejunum]. In the distal part of the rat small intestine, PS was absorbed significantly better from solution than from the submicron emulsion. Cholinesterase activity in blood samples collected after intestinal perfusion with emulsion or solution revealed lower enzyme activity following emulsion administration.

The aim of the present study was to evaluate the toxicity of biodegradable hydrogels in the rat with a future aim of utilizing this hydrogel as a vehicle for brachytherapy delivery in cancer patients. Two types of chitosan hydrogels: fast degrading and slow degrading; were prepared and surgically implanted in rats. The adjacent tissue response to the gels after subcutaneous and intraperitoneal implantation was examined histologically and found to be identical to typical foreign body response and was milder than the response to absorbable surgical sutures (Vicril). Neither tissue damage nor gel fragments could be detected in distant organs (brain, heart, lungs, liver, spleen, kidney, and sternal bone marrow) after implantation of the hydrogels. The degradation mechanism of the gels was studied in vivo, and it was deduced that an oxidative process degraded the chitosan. Loading the hydrogels with a radioisotope (131I-norcholesterol) caused a severe tissue response and necrosis in adjacent tissues only at a distance of several microns. It is concluded that crosslinked chitosan implants could serve as alternative, biocompatible, and safe biodegradable devices for radioisotope delivery in brachytherapy for cancer.

Brachytherapy has many potential roles in cancer therapy. However, major constraints are associated with placement and removal procedures of the brachytherapy machinery. An attractive approach would be the use of a biodegradable implant loaded with a radioisotope, thus enabling targeted radiotherapy, while reducing the need for surgical procedures for the removal of brachytherapy hardware. In this study, crosslinked chitosan (Ct) hydrogels were prepared and loaded with 131I-norcholesterol (131I–NC). The radioactive hydrogels (131I–NC–Ct) were implanted adjacent to 4T1 cell-induced tumors in two different xenograft mice models either as primary therapy or surgical adjuvant therapy of breast cancer. Non-treated mice and mice implanted with naive (non-radioactive) hydrogels served as control groups. In the primary therapy model, the progression rate of the tumor was delayed by two weeks compared with the non-treated and the naive-implant control animals, resulting in a one-week extension in the survival of the treated animals. In the adjuvant therapy model, for the treatment of minimal residual disease, 131I–NC–Ct implants were able to prevent 69% of tumor recurrence, and to prevent metastatic spread resulting in long-term survival, compared with 0% long-term survival of the non-treated and the naive control groups. Imaging of the hydrogel's in vivo elimination revealed a first order process with a half-life of 14 days. The degradation was caused by oxidation of the Ct as was assessed by in vitro H&E stain. Biodegradable radioactive implants are suggested as a novel platform for the delivery of brachytherapy. This radiotherapy regimen may prevent locoregional recurrence and metastatic spread after tumor resection.