Injectable candidate sealants for fetal membrane repair: bonding and toxicity in vitro

OBJECTIVE

This study was undertaken to test injectable surgical sealants that are biocompatible with fetal membranes and that are to be used eventually for the closure of iatrogenic membrane defects.

STUDY DESIGN

Dermabond (Ethicon Inc, Norderstedt, Germany), Histoacryl (B. Braun GmbH, Tuttlingen, Germany), and Tissucol (Baxter AG, Volketwil, Switzerland) fibrin glue, and 3 types of in situ forming poly(ethylene glycol)-based polymer hydrogels were tested for acute toxicity on direct contact with fetal membranes for 24 hours. For the determination of elution toxicity, extracts of sealants were incubated on amnion cell cultures for 72 hours. Bonding and toxicity was assessed through morphologic and/or biochemical analysis.

RESULTS

Extracts of all adhesives were nontoxic for cultured cells. However, only Tissucol and 1 type of poly(ethylene glycol)-based hydrogel, which is a mussel-mimetic tissue adhesive, showed efficient, nondisruptive, nontoxic bonding to fetal membranes. Mussel-mimetic tissue adhesive that was applied over membrane defects that were created with a 3.5-mm trocar accomplished leak-proof closure that withstood membrane stretch in an in vitro model.

CONCLUSION

A synthetic hydrogel-type tissue adhesive that merits further evaluation in vivo emerged as a potential sealing modality for iatrogenic membrane defects.

Acute lymphoblastic leukemia in a patient with chronic cyanoacrylate exposure

Environmental agents have long been thought to be linked to the development of malignancies. Due to the difficulty in identifying and verifying exposures to such agents, only a few chemical compounds are clearly linked to malignancies. We report here the case of a 36-year-old man with pre-B cell acute lymphoblastic leukemia. This patient was using industrial strength glue to reattach a chipped tooth for approximately 1 year, and such use was associated with chronic exposure of his oral mucosa to this glue. This case raises the possibility that chronic exposure to cyanoacrylates, the adhesive agents in industrial strength glue, may be associated with the development of acute lymphoblastic leukemia in humans.

Body distribution and in situ evading of phagocytic uptake by macrophages of long-circulating poly (ethylene glycol) cyanoacrylate-co-n-hexadecyl cyanoacrylate nanoparticles

AIM

To investigate the body distribution in mice of [14C]-labeled poly methoxyethyleneglycol cyanoacrylate-co-n-hexadecyl cyanoacrylate (PEG-PHDCA) nanoparticles and in situ evading of phagocytic uptake by mouse peritoneal macrophages.

METHODS

PEG-PHDCA copolymers were synthesized by condensation of methoxypolyethylene glycol cyanoacetate with [14C]-hexadecyl-cyanoacetate. [14C]-nanoparticles were prepared using the nanoprecipitation/solvent diffusion method, while fluorescent nanoparticles were prepared by incorporating rhodamine B. In situ phagocytic uptake was evaluated by flow cytometry. Body distribution in mice was evaluated by determining radioactivity in tissues using a scintillation method.

RESULTS

Phagocytic uptake by macrophages can be efficiently evaded by fluorescent PEG-PHDCA nanoparticles. After 48 h, 31% of the radioactivity of the stealth [14C]-PEG-PHDCA nanoparticles after iv injection was still found in blood, whereas non-stealth PHDCA nanoparticles were cleaned up from the bloodstream in a short time. The distribution of stealth PEG-PHDCA nanoparticles and non-stealth PHDCA nanoparticals in mice was poor in lung, kidney, and brain, and a little higher in hearts. Lymphatic accumulation was unusually high for both stealth and non-stealth nanoparticles, typical of lymphatic capture. The accumulation of stealth PEG-PHDCA nanoparticles in the spleen was 1.7 times as much as that of non-stealth PHDCA (P< 0.01). But the accumulation of stealth PEG-PHDCA nanoparticles in the liver was 0.8 times as much as that of non-stealth PHDCA (P< 0.05).

CONCLUSION

PEGylation leads to long-circulation of nanoparticles in the bloodstream, and splenotropic accumulation opens up the potential for further development of spleen-targeted drug delivery.

Differential Stripping: Determination of the Amount of Topically Applied Substances Penetrated into the Hair Follicles

The determination of penetration pathways of topically applied substances into the skin is the subject of several investigations. Recently, follicular penetration has become a major focus of interest. To date, a direct, non-invasive quantification of the amount of topically applied substance penetrated into the follicles had not been possible. The development of such a method was the aim of this study. Therefore, the advantages of both stripping techniques, tape stripping and cyanoacrylate skin surface biopsy, were combined and evaluated. Tape stripping was used to remove the part of the stratum corneum that contained the topically applied dye. Subsequently, the follicular contents were ripped off by cyanoacrylate skin surface biopsy. The combined method termed "differential stripping" was evaluated in vitro and in vivo, and the amount of topically applied fluorescent dye penetrated into the hair follicles was quantified after different penetration times. After 30 min, 5% of the recovered concentration of sodium fluorescein was found in the follicular infundibula, where it was still detectable after 48 h. Altogether, the results of this investigation revealed that differential stripping is a new method that can be used to study the penetration of topically applied substances into the follicular infundibula non-invasively and selectively.

A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles

Poly(MePEG2000cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems.

Oral and subcutaneous absorption of insulin poly(isobutylcyanoacrylate) nanoparticles

Dispersions of insulin poly(isobutylcyanoacrylate) nanoparticles were obtained by anionic in situ polymerization using aqueous pluronic acid solution. Results showed a decrease in particle size diameter by increasing the pluronic acid concentration. Nanoparticles prepared in the presence of 2.5% pluronic acid resulted in particles of 85 nm average diameter and 59% intra-particular insulin load without the use of the oily core [Damge, C., Michel, M., Aprahamian, M., Couveur, P., 1988. New approach for oral administration with polycyanoacrylate nanocapsules as drug carrier. Diabetes 37, 246-251]. In vivo testing was performed on streptozocin induced diabetic rats. The subcutaneous injection of insulin nanoparticles was able to prolong its duration of hypoglycemic effect from 6 to 72 h. Effective oral absorption of the entrapped insulin was significantly better (p<0.01) when compared with non-encapsulated insulin or the control experiments.

Absorption of ethyl 2-cyanoacrylate tissue adhesive

The aim of this study was to investigate absorption of ethyl 2-cyanoacrylate glue when used as a tissue adhesive. Ethyl 2-cyanoacrylate was applied subcutaneously to four rats; its presence in blood and urine was investigated by using High Pressure Liquid Chromatography. Blood samples were drawn at baseline and after 2, 4, 6, 24, 48, 54, 78, 96 hours following application. Urine samples were obtained at baseline and after 4, 24, 48, 72, 96 hours. Administration of ethyl 2-cyanoacrylate resulted in its absorption of unchanged ethyl 2-cyanoacrylate and unknown metabolites, in plasma and urine.

Incorporation of biodegradable nanoparticles into human airway epithelium cells-in vitro study of the suitability as a vehicle for drug or gene delivery in pulmonary diseases

PURPOSE

Nanoparticles are able to enhance drug or DNA stability for purposes of optimised deposition to targeted tissues. Surface modifications can mediate drug targeting. The suitability of nanoparticles synthesised out of porcine gelatin, human serum albumin, and polyalkylcyanoacrylate as drug and gene carriers for pulmonary application was investigated in vitro on primary airway epithelium cells and the cell line 16HBE14o-.

METHODS

The uptake of nanoparticles into these cells was examined by confocal laser scan microscopy (CLSM) and flow cytometry (FACS). Further the cytotoxicity of nanoparticles was evaluated by an LDH-release-test and the inflammatory potential of the nanoparticles was assessed by measuring IL-8 release.

RESULTS

CLSM and FACS experiments showed that the nanoparticles were incorporated into bronchial epithelial cells provoking little or no cytotoxicity and no inflammation as measured by IL-8 release.

CONCLUSIONS

Based on their low cytotoxicity and the missing inflammatory potential in combination with an efficient uptake in human bronchial epithelial cells, protein-based nanoparticles are suitable drug and gene carriers for pulmonary application.

Drug delivery to resistant tumors: the potential of poly(alkyl cyanoacrylate) nanoparticles

Simultaneous cellular resistance to multiple lipophilic drugs represents a major problem in cancer chemotherapy. This drug resistance may appear clinically either as a lack of tumor size reduction or as the occurrence of clinical relapse after an initial positive response to antitumor treatment. The resistance mechanism can have different origins either directly linked to specific mechanisms developed by the tumor tissue or connected to the more general problem of distribution of a drug towards its targeted tissue. The purpose of this paper is to summarize the results of the use of poly(alkyl cyanoacrylate) nanoparticles to overcome multidrug resistance (MDR) phenomena at both the cellular and the non-cellular level.

A computationally derived structural model of doxorubicin interacting with oligomeric polyalkylcyanoacrylate in nanoparticles

We report a molecular simulation study of doxorubicin interacting within a frame of n-butyl polycyanoacrylate, one of the most commonly encountered polymers in the production of nanoparticles. Emphasis is put on the tetrameric, hexameric and octameric oligomers (PACA's). Log P was calculated for all interacting species. Molecular dynamics along with energy minimization processes (molecular mechanics MM2, semi-empirical quantum mechanics PM3) were employed to probe the conformational behavior of doxorubicin and polyalkylcyanoacrylate both as isolated species and interacting with each other. A docked structure of protonated doxorubicin with two octamers of n-butyl polycyanoacrylate is described. Among the main stability factors of the assembly was the charge-dipole interaction representing a stabilizing contribution of -33 kcal/mol. The mechanism of aggregation and desegregation (doxorubicin release) can be summarized as follows: oligomeric PACA's are lipophilic entities that scavenge amphiphilic doxorubicin already during the polymerization process by extraction of the protonated species from the aqueous environment to the increasingly lipophilic phase of the growing PACA's. The establishment of hydrogen bonds between the ammonium N-H function and the cyano groups is noteworthy. The cohesion in PACA nanoparticle comes therefore from a blend of dipole-charge interaction, H bonds, and hydrophobic forces,

Poly(ethylene glycol)-coated hexadecylcyanoacrylate nanospheres display a combined effect for brain tumor targeting

The aim of the present study was to evaluate the tumor accumulation of radiolabeled long-circulating poly(ethylene glycol) (PEG)-coated hexadecylcyanoacrylate nanospheres and non-PEG-coated hexadecylcyanoacrylate nanospheres (used as control), after intravenous injection in Fischer rats bearing intracerebrally well established 9L gliosarcoma. Both types of nanospheres showed an accumulation with a retention effect in the 9L tumor. However, long-circulating nanospheres concentrated 3.1 times higher in the gliosarcoma, compared with non-PEG-coated nanospheres. The tumor-to-brain ratio of pegylated nanospheres was found to be 11, which was in accordance with the ratios reported for other carriers tested for brain tumor targeting such as long-circulating liposomes or labels for magnetic resonance imaging. In addition, a 4- to 8-fold higher accumulation of the PEG-coated carriers was observed in normal brain regions, when compared with control nanospheres. Using a simplified pharmacokinetic model, two different mechanisms were proposed to explain this higher concentration of PEG-coated nanospheres in a tumoral brain. 1) in the 9L tumor, the preferential accumulation of pegylated nanospheres was attributable to their slower plasma clearance, relative to control nanospheres. Diffusion/convection was the proposed mechanism for extravasation of the nanospheres in the 9L interstitium, across the altered blood-brain barrier. 2) In addition, PEG-coated nanospheres displayed an affinity with the brain endothelial cells (normal brain region), which may not be considered as the result of a simple diffusion/convection process. The exact underlying mechanism of such affinity deserves further investigation, since it was observed to be as important as specific interactions described for immunoliposomes with the blood-brain barrier.

Effects of formulation variables on characteristics of poly (ethylcyanoacrylate) nanocapsules prepared from w/o microemulsions

The effect of several formulation variables on some of the physico-chemical characteristics of poly (ethyl cyanoacrylate) (PECA) nanocapsules prepared by the interfacial polymerisation of biocompatible water-in-oil microemulsions was investigated. In all cases, yields were high (>90%) and the polydispersity in size of nanocapsules was narrow. The molecular weight of the nanocapsules formed was influenced by the pH of the aqueous component of the microemulsion, increasing with increasing pH. The size of the nanocapsules formed (ranging from around 130 to 180 nm) was a function of the ratio of the mass of monomer used to the water weight fraction of the microemulsion, increasing as this ratio was increased. This is due to the formation of a thicker polymer wall resulting from the increased mass of monomer available per unit interfacial area as this ratio is increased. The rate of release of insulin from nanocapsules was also influenced by this ratio, in agreement with its effect on wall thickness. This study demonstrates that many pharmaceutically relevant physico-chemical properties of poly (alkyl cyanoacrylate) (PACA) nanocapsules prepared by interfacial polymerisation of microemulsions can readily be manipulated by changing either the pH of the aqueous component, the water weight fraction of the microemulsion or the mass of monomer used for polymerisation.

PEGylated polycyanoacrylate nanoparticles as vector for drug delivery in prion diseases

PEGylated polymeric nanoparticles are hereby presented as a potential efficient drug carrier for the delivery of active therapeutic molecules in prion experimental diseases. Based on their blood long-circulating characteristics, these PEGylated particles made by the amphiphilic copolymer poly [methoxy poly(ethylene glycol) cyanoacrylate-co-hexadecyl cyanoacrylate] (PEG-PHDCA), showed comparatively conventional non-PEGylated nanoparticles, a higher uptake by the spleen and the brain which are both the target tissues of PrPres accumulation in scrapie infected animals.

Targeting of 3'-azido 3'-deoxythymidine (AZT)-loaded poly(isohexylcyanoacrylate) nanospheres to the gastrointestinal mucosa and associated lymphoid tissues

PURPOSE

The aim of the studv was to evaluate the capacity of poly(isohexylcyanoacrylate) nanospheres to concentrate 3'-azido 3'-deoxythymidine (AZT) in the intestinal epithelium and associated immunocompetent cells, which are known to be one of the major reservoirs of the human immunodeficiency virus (HIV).

METHODS

The tissue concentration of 3H-radiolabeled AZT in the gastrointestinal (GI) tract was obtained 30 and 9() minutes after intragastric administration to rats at a dose of 0.25 mg AZT/100 g of body weight. The distribution along the intestine was determined. AZT concentrations in the lymph were obtained by lymphatic duct cannulation.

RESULTS

Unlike the solution. nanoparticles did concentrate AZT very cfficiently in the intestinal mucosa, as well as in the Peyer's patches, and could simultaneously control the release of free AZT. Concentration in Peyer's patches was 4 times higher for nanoparticles, compared with the control solution. The tissue concentration was 30-45 microM, which was much higher than the reported IC50 of AZT (0.06-1.36 microM) and was regularly distributed along the gastrointestinal tract.

CONCLUSIONS

Nanoparticles have been shown to be efficient in concentrating AZT in the intestinal epithelium and gut-associated lymphoid tissues, supporting the view that these particles may represent a promising carrier to treat specifically the GI reservoir of HIV.

Lymphatic targeting with nanoparticulate system

Much effort has been made to achieve lymphatic targeting of drugs using colloidal carriers. This paper reviews the recent progress in the development of biodegradable nanoparticulate systems, including nanospheres, emulsions, and liposomes. The major purpose of lymphatic targeting is to provide an effective anticancer chemotherapy to prevent the metastasis of tumor cells by accumulating the drug in the regional lymph node via subcutaneous administration. The objectives of lymph targeting also involve the localization of diagnostic agents to the regional lymph node to visualize the lymphatic vessels before surgery, and the improvement of peroral bioavailability of macromolecular drugs, like polypeptides or proteins, which are known to be selectively taken up from the Peyer's patch in the intestine. Nanocapsules, which are ultrafine oily droplet-coated polymeric substances, are probably one of the most promising candidates of colloidal carriers. Surface engineering by the interfacial deposition method can provide a suitable size distribution and necessary surface characteristics to the nanocapsules. Our recent in vivo study proved that polyisobutylcyanoacrylate nanocapsules showed enhanced accumulation of drug in the lymph node, compared with other carriers such as emulsions and liposomes.

Ileal uptake of polyalkylcyanoacrylate nanocapsules in the rat

The ileal uptake of polyalkylcyanoacrylate nanocapsules (less than 300 nm in diameter) has been investigated in the rat. Iodised oil (Lipiodol) was used as the tracer for X-ray microprobe analysis in scanning electron microscopy. Lipiodol nanocapsules, or an emulsion of Lipiodol, were administered in the lumen of an isolated ileal loop of rat. Lipiodol nanocapsules improved the absorption of the tracer as indicated by increased concentrations of iodine in the mesenteric blood (+27%, P < 0-01, compared with Lipiodol emulsion). Intestinal biopsies were taken at different time points and the samples underwent cryofixation and freeze-drying. The nanocapsules were characterized by their strong iodine emission, and electron microscopy of the biopsy samples revealed nanocapsules in the intraluminal mucus of the non-follicular epithelium, then in the intercellular spaces between enterocytes, and finally the nanocapsules were found within intravillus capillaries. However, nanocapsules were most abundant in the Peyer's patches, where the intestinal epithelium had been crossed by way of the specialized epithelial cells, designated membranous cells, or M cells, and their adjacent absorptive cells. These observations were confirmed quantitatively by measuring iodine concentrations in the various tissue compartments. Ten minutes after the intraluminal administration of Lipiodol nanocapsules, the emission of iodine peaked in the mucus (+77%, P < 0.01), in M cells (+366%, P <0.001), in enterocytes adjacent to M cells (+70%, P < 0.05) and in lymph vessels (+59%, P < 0.05). Polyalkylcyanoacrylate nanocapsules were able to pass through the ileal mucosa of the rat via a paracellular pathway in the non-follicular epithelium, and most predominantly, via M cells and adjacent enterocytes in Peyer's patches.

Transmucosal delivery systems for calcitonin: a review

The commercial availability of peptides and proteins and their advantages as therapeutic agents have been the basis for tremendous efforts in designing delivery systems for such agents. The protection of these agents from biological fluids and physiological interactions is crucial for the treatment efficacy. One such agent is salmon calcitonin, a 32 amino-acid polypeptide hormone used in the treatment of bone diseases such as Paget's disease, hypercalcemia and osteoporosis. Researchers have studied different routes to deliver salmon calcitonin more effectively, including nasal, oral, vaginal and rectal delivery. These systems are designed to protect the polypeptide from the biological barriers that each delivery route imposes. Oil-based and polymer-based delivery systems are discussed.

Stealth PEGylated polycyanoacrylate nanoparticles for intravenous administration and splenic targeting

The aim of the present work was to investigate the biodistribution characteristics of PEG-coated polycyanoacrylate nanoparticles prepared by the nanoprecipitation/solvent diffusion method using the previously synthesized poly(MePEGcyanoacrylate-hexadecylcyanoacrylate) copolymer. It was observed that [14C]-radiolabeled PEGylated nanoparticles remained for a longer time in the blood circulation after intravenous administration to mice, compared to the non-PEGylated poly(hexadecylcyanoacrylate) (PHDCA) nanoparticles. Furthermore, hepatic accumulation was dramatically reduced, whereas a highly increased spleen uptake was shown. The PEGylation degree of the polymer seemed not to affect the in vivo behavior of the nanoparticles, whereas previously obtained in vitro data have shown a modification of plasma protein adsorption depending on the density of PEG at the surface of the particles. Moreover, the study of the in vitro cytotoxicity of the nanoparticles revealed that the PEGylation of the cyanoacrylate polymer reduced its toxicity. These results open up interesting perspectives for the targeting of drugs to other tissues than the liver.

Stereoselective uptake of an organic anion across the renal basolateral membrane in isolated perfused rat kidney

To clarify which process in renal secretion is responsible for the stereoselective renal secretion of organic anions, the renal handling of enantiomers of 5-monomethylsulfamoyl-6,7-dichloro-2, 3-dihydrobenzofuran-2-carboxylic acid (MBCA) was studied by the multiple-indicator dilution method, using isolated perfused rat kidney. After bolus injection of (R)-(+)-[14C]MBCA or (S)-(-)-[14C]MBCA into the renal artery, the outflow patterns for the perfusate and the urinary excretion rate profiles were estimated by statistical moment analysis. AUC values and mean transit times in kidney for the MBCA enantiomers indicated that (R)-(+)-MBCA was excreted much more extensively in urine and that it had a higher affinity for renal tissue than did (S)-(-)-MBCA. A significantly larger intrinsic clearance of secretion for (R)-(+)-MBCA attested to the R-(+)-preferential renal secretion. The uptake rate constant across the basolateral membrane, the ratio of the uptake rate constant to the free fraction in the perfusate, and the intracellular distribution volume were significantly larger for (R)-(+)-MBCA than for (S)-(-)-MBCA, indicating that uptake across the basolateral membrane and intracellular distribution were R-(+)-preferential. However, the mean time across renal epithelial cells for secreted molecules, the single-pass mean residence time in renal epithelial cells, and the rate constant for secretion across the brush-border membrane were not significantly different between enantiomers. The simultaneous presence of (R)-(+)-MBCA decreased the intrinsic clearance of secretion, the ratio of the uptake rate constant to the free fraction in the perfusate, and the intracellular distribution volume for (S)-(-)-[14C]MBCA, although the secretion rate constant, the mean time across renal epithelial cells for secreted molecules, and the single-pass mean residence time in renal epithelial cells were not influenced by (R)-(+)-MBCA, confirming that uptake across the basolateral membrane and intracellular distribution were stereoselective processes.

Poly(alkyl cyanoacrylate) nanospheres for oral administration of insulin

Poly(alkyl cyanoacrylate) nanocapsules have been successfully used for oral administration of insulin in diabetic rats. This work reports a suitable formulation for insulin-loaded nanospheres composed of full polymeric structures formed by polymerization of isobutyl cyanoacrylate (IBCA) in an acidic medium, insulin (15 U/mL) being added to the polymerization medium 60 min after the onset of polymerization. These nanospheres (MW 364) displayed a mean size of 145 nm and an association rate of 1 U of insulin/mg of polymer. They protected insulin from the degradation by proteolytic enzymes in vitro, especially when they were dispersed in an oily medium (Miglyol 812) containing surfactive agents (Poloxamer 188 and deoxycholic acid). When dispersed in the same medium, insulin-loaded nanospheres (100 U/kg of body weight), administered perorally in streptozotocin-induced diabetic rats, provoked a 50% decrease of fasted glycemia from the second hour up to 10-13 days. This effect was shorter (2 days) or absent when nanospheres were dispersed in water with surfactive agents or not. Using 14C-labeled nanospheres loaded with [125I]insulin, it was found that nanospheres increased the uptake of [125I]insulin or its metabolites in the gastrointestinal tract, blood, and liver while the excretion was delayed when compared to [125I]insulin nonassociated to nanospheres; in addition, 14C- and 125I-radioactivities disappeared progressively as a function of time, parallel to the biological effect. Thus insulin-loaded nanospheres can be considered as a convenient delivery system for oral insulin at the prerequisite that they were dispersed in an oily phase containing surfactants.

3-Methoxybutylcyanoacrylate: evaluation of biocompatibility and bioresorption

The biocompatibility and bioresorption of 3-methoxybutylcyanoacrylate (MBCA) was evaluated in vivo using female Wistar albino rats. MBCA was found to elicit slight to moderate tissue reaction similar to isobutylcyanoacrylate (iBCA) which has been sold commercially as a surgical adhesive (Bucrylate, Ethicon). MBCA was judged less reactive to tissue than ethylcyanoacrylate (ECA). The MBCA implants in rat gluteal muscles also resorbed within approx. 16 wk while iBCA implants remained essentially unchanged at 36 wk in vivo. In vitro resorption in phosphate buffer (pH 7.2) at 37 degrees C showed the same trend. The MBCA performed similarly to iBCA as a haemostat on excised rat livers and as an adhesive on rat skin incisions and had comparable adhesive bond strength.

Jejunal absorption, pharmacological activity, and pharmacokinetic evaluation of indomethacin-loaded poly(d,l-lactide) and poly(isobutyl-cyanoacrylate) nanocapsules in rats

The jejunal absorption of indomethacin nanocapsules was studied using an in vivo infusion technique. Jejunal absorption of indomethacin from the nanocapsules was slightly delayed as compared to a commercial indomethacin solution. The plasma and jejunal mucosa indomethacin concentrations were similar in both cases. However, the nanocapsules protected the rat jejunum from the ulcerating effect of indomethacin, probably by avoiding direct contact of the free drug with the surface of the mucosa. The pharmacokinetic profile of indomethacin nanocapsule formulations was compared to a solution of free drug following oral administration of 5 mg/kg in rats; no difference in the mean concentration-time profiles of the drug was observed. Blood levels of thromboxane showed a sustained biological activity, over a period of 24 hr, of indomethacin-loaded nanocapsules, relative to the drug in solution, following oral administration.

Dissolution of isobutyl 2-cyanoacrylate on long-term follow-up

Eight patients with arteriovenous malformations (AVMs) in the basal ganglionic and deep parietooccipital regions and one patient with an AVM in the shoulder region showed resorption of the isobutyl 2-cyanoacrylate cast and recanalization of the arteries after delayed follow-up angiography. All the AVMs were large, had multiple arterial pedicles, and revealed significant obliteration of the AVM immediately after embolotherapy. Although a 50-75% obliteration was achieved immediately after embolization, follow-up angiography 6-20 months later revealed almost the original status. The residual bucrylate cast was disproportionately small compared with the recanalized malformation in seven patients, while in two patients there was no evidence of bucrylate on plain films. Degradation of bucrylate probably is due to the lysosomal activity of the endothelial cells. The results from our nine patients with some degree of resorption of isobutyl 2-cyanoacrylate and six with recanalized AVMs 6-20 months after embolization suggest that operable AVMs should be excised soon after embolotherapy and inoperable AVMs should be embolized as completely as possible.

Distribution of polyhexylcyanoacrylate nanoparticles in nude mice over extended times and after repeated injection

Carbon-14-labeled polyhexylcyanoacrylate nanoparticles, with diameters between 200 and 300 nm, were injected intravenously into nude mice. The distribution in liver, spleen, lung, heart, kidney, GI tract, gonads, brain, muscle, and serum was investigated by liquid scintillation counting. After a single injection, the radiolabel was cleared slowly with 45% remaining after 28 d and 8% remaining after 140 d. After repeated injection with an interval of 28 d (twice or thrice), relatively higher proportions of the dose were found in the spleen and lung as compared with those in other organs. No histological alterations were observed in the liver, spleen, or lung.

Toxicity and association of polycyanoacrylate nanoparticles with hepatocytes

The degradation of polybutylcyanoacrylate (PBC) and polyhexylcyanoacrylate (PHC) nanoparticles, together with their association with and toxicity towards isolated hepatocytes, were determined. Nanoparticles were not taken up by rat hepatocytes at a significant level. The LD50S of PBC and PHC nanoparticles towards hepatocytes were 0.4 mg/2 x 10(6) cells and greater than 1 mg/2 x 10(6) cells respectively. This hepatocyte toxicity cannot be attributed solely to the formaldehyde formed during degradation.