A bioorthogonal system reveals antitumour immune function of pyroptosis.

Bioorthogonal chemistry capable of operating in live animals is needed to investigate biological processes such as cell death and immunity. Recent studies have identified a gasdermin family of pore-forming proteins that executes inflammasome-dependent and -independent pyroptosis1-5. Pyroptosis is proinflammatory, but its effect on antitumour immunity is unknown. Here we establish a bioorthogonal chemical system, in which a cancer-imaging probe phenylalanine trifluoroborate (Phe-BF3) that can enter cells desilylates and 'cleaves' a designed linker that contains a silyl ether. This system enabled the controlled release of a drug from an antibody-drug conjugate in mice. When combined with nanoparticle-mediated delivery, desilylation catalysed by Phe-BF3 could release a client protein-including an active gasdermin-from a nanoparticle conjugate, selectively into tumour cells in mice. We applied this bioorthogonal system to gasdermin, which revealed that pyroptosis of less than 15% of tumour cells was sufficient to clear the entire 4T1 mammary tumour graft. The tumour regression was absent in immune-deficient mice or upon T cell depletion, and was correlated with augmented antitumour immune responses. The injection of a reduced, ineffective dose of nanoparticle-conjugated gasdermin along with Phe-BF3 sensitized 4T1 tumours to anti-PD1 therapy. Our bioorthogonal system based on Phe-BF3 desilylation is therefore a powerful tool for chemical biology; our application of this system suggests that pyroptosis-induced inflammation triggers robust antitumour immunity and can synergize with checkpoint blockade.

A Novel, Nonpeptidic, Orally Active Bivalent Inhibitor of Human ß-Tryptase.

ß-Tryptase is released from mast cells upon degranulation in response to allergic and inflammatory stimuli. Human tryptase is a homotetrameric serine protease with 4 identical active sites directed toward a central pore. These active sites present an optimized scenario for the rational design of bivalent inhibitors, which bridge 2 adjacent active sites. Using (3-[1-acylpiperidin-4-yl]phenyl)methanamine as the pharmacophoric core and a disiloxane linker to span 2 active sites we have successfully produced a novel bivalent tryptase inhibitor, compound 1a, with a comparable profile to previously described inhibitors. Pharmacological properties of compound 1a were studied in a range of in vitro enzymic and cellular screening assays, and in vivo xenograft models. This non-peptide inhibitor of tryptase demonstrated superior activity (IC50 at 100 pmol/L tryptase = 1.82 nmol/L) compared to monomeric modes of inhibition. X-ray crystallography validated the dimeric mechanism of inhibition, and 1a demonstrated good oral bioavailability and efficacy in HMC-1 xenograft models. Furthermore, compound 1a demonstrated extremely slow off rates and high selectivity against-related proteases. This highly potent, orally bioavailable and selective inhibitor of human tryptase will be an invaluable tool in future studies to explore the therapeutic potential of attenuating the activity of this elusive target.

MUC1 aptamer-conjugated mesoporous silica nanoparticles effectively target breast cancer cells.

In the present study, we developed aptamer (Apt) conjugated mesoporous silica nanoparticles (MSNs) for specific delivery of epirubicin (EPI) to breast cancer cells. MSNs were synthesized and functionalized with 3-mercaptopropyltrimethoxysilane (3-MPTMS), followed by MUC1 aptamer conjugation through disulfide bonds. The nanoparticles were analyzed by transmission electron microscopy (TEM), particle size analyzer, zeta potential, elemental analysis (CHNS), aptamer conjugation efficiency, drug loading efficiency, and drug release profile. Cell uptake and in vitro cytotoxicity of different formulations were performed. The results of MSNs characterization confirmed spherical nanoparticles with thiol functional groups. Particle size of obtained nanoparticles was 163 nm in deionized water. After conjugation of MUC1 aptamer and EPI loading (MSN-MUC1-EPI), particle size increased to 258 nm. The aptamer conjugation to MSNs with disulfide bonds were confirmed using gel retardation assay. Cellular uptake studies revealed better cell uptake of MSN-MUC1-EPI compared to MSN-EPI. Moreover, cytotoxicity study results in MCF7 cell lines showed improved cytotoxicity of MSN-MUC1-EPI in comparison with MSN-EPI or EPI at the same concentration of drug. These results exhibited that MSN-MUC1-EPI has the potential for targeted drug delivery into MUC1 positive breast cancer cells to improve drug efficacy and alleviate side effects.

Effect of Several HIV Antigens Simultaneously Loaded with G2-NN16 Carbosilane Dendrimer in the Cell Uptake and Functionality of Human Dendritic Cells.

Dendrimers are highly branched, star-shaped, and nanosized polymers that have been proposed as new carriers for specific HIV-1 peptides. Dendritic cells (DCs) are the most-potent antigen-presenting cells that play a major role in the development of cell-mediated immunotherapy due to the generation and regulation of adaptive immune responses against HIV-1. This article reports on the associated behavior of two or three HIV-derived peptides simultaneously (p24/gp160 or p24/gp160/NEF) with cationic carbosilane dendrimer G2-NN16. We have found that (i) immature DCs (iDCs) and mature (mDCs) did not capture efficiently HIV peptides regarding the uptake level when cells were treated with G2-NN16-peptide complex alone; (ii) the ability of DCs to migrate was not depending on the peptides presence; and (iii) with the use of molecular dynamic simulation, a mixture of peptides decreased the cell uptake of the other peptides (in particular, NEF hinders the binding of more peptides and is especially obstructing of the binding of gp160 to G2-NN16). The results suggest that G2-NN16 cannot be considered as an alternative carrier for delivering two or more HIV-derived peptides to DCs.

Novel Water-Soluble Mucoadhesive Carbosilane Dendrimers for Ocular Administration.

The purpose of this research was to determine the potential use of water-soluble anionic and cationic carbosilane dendrimers (generations 1-3) as mucoadhesive polymers in eyedrop formulations. Cationic carbosilane dendrimers decorated with ammonium -NH3(+) groups were prepared by hydrosylilation of Boc-protected allylamine and followed by deprotection with HCl. Anionic carbosilane dendrimers with terminal carboxylate groups were also employed in this study. In vitro and in vivo tolerance studies were performed in human ocular epithelial cell lines and rabbit eyes respectively. The interaction of dendrimers with transmembrane ocular mucins was evaluated with a surface biosensor. As proof of concept, the hypotensive effect of a carbosilane dendrimer eyedrop formulation containing acetazolamide (ACZ), a poorly water-soluble drug with limited ocular penetration, was tested after instillation in normotensive rabbits. The methodology used to synthesize cationic dendrimers avoids the difficulty of obtaining neutral -NH2 dendrimers that require harsher reaction conditions and also present high aggregation tendency. Tolerance studies demonstrated that both prototypes of water-soluble anionic and cationic carbosilane dendrimers were well tolerated in a range of concentrations between 5 and 10 µM. Permanent interactions between cationic carbosilane dendrimers and ocular mucins were observed using biosensor assays, predominantly for the generation-three (G3) dendrimer. An eyedrop formulation containing G3 cationic carbosilane dendrimers (5 µM) and ACZ (0.07%) (289.4 mOsm; 5.6 pH; 41.7 mN/m) induced a rapid (onset time 1 h) and extended (up to 7 h) hypotensive effect, and led to a significant increment in the efficacy determined by AUC0(8h) and maximal intraocular pressure reduction. This work takes advantage of the high-affinity interaction between cationic carbosilane dendrimers and ocular transmembrane mucins, as well as the tensioactive behavior observed for these polymers. Our results indicate that low amounts of cationic carbosilane dendrimers are well tolerated and able to improve the hypotensive effect of an acetazolamide solution. Our results suggest that carbosilane dendrimers can be used in a safe range of concentrations to enhance the bioavailability of drugs topically administered in the eye.

A pH-responsive asymmetric lipid vesicle as drug carrier.

In order to increase the loading efficiency of drug carriers, here we demonstrated a microfluidic method to fabricate an asymmetric vesicle, which contains trichloro(1H,1H,2H,2H-perfluoroocty-l)silane (TPS) inner leaflet and lipid outer leaflet. The asymmetric vesicle was characterised by fluorescence microscopy and Fourier transform infra-red spectrum. In vitro cytotoxicity of the vesicles carrying 5-fluorouacil (5-FU) has also been studied.

Fluoride Varnishes--Is There a Correlation Between Fluoride Release and Deposition on Enamel?

PURPOSE: Fluoride uptake of enamel after application of fluoride varnishes was compared with fluoride release into artificial saliva. The hypothesis was that fluoride uptake is higher for products exhibiting faster fluoride release. MATERIALS AND METHODS: Fluoride varnishes, i.e. Fluor Protector S, Duraphat, MI Varnish, Clinpro White Varnish, Profluorid Varnish and Enamel Pro Varnish were applied on bovine enamel specimens. Subsequently, specimens were incubated in artificial saliva. After removal of the varnishes, surface bound fluoride was extracted with potassium hydroxide and measured with an ion-selective electrode. Structurally bound fluoride was etched from the same specimens with perchloric acid. Fluoride release of varnish films into artificial saliva was measured for comparison. RESULTS: After 4 h in artificial saliva, the highest total enamel fluoride uptake of 47.9 µg F·cm-² was found with Fluor Protector S, followed by Enamel Pro Varnish with 22.1 µg F·cm-². The other products ranged between 12-16 µg F·cm-². This was several times higher than the negative control. Fluoride uptake did not correlate with release into artificial saliva. During the first 4 h, Duraphat released the lowest and MI Varnish the highest amount of fluoride with 7.7 and 249 µg F·cm-², respectively. The fluoride uptake of these two products was not statistically different. CONCLUSION: Enamel fluoride uptake cannot be predicted from the fluoride release rate of a product. Hence, based on the results of this study, fluoride release into artificial saliva is no measure for the efficacy of a fluoride varnish.

Silylation improves the photodynamic activity of tetraphenylporphyrin derivatives in vitro and in vivo.

The effects of silyl and hydrophilic groups on the photodynamic properties of tetraphenylporphyrin (TPP) derivatives have been studied in vitro and in vivo. Silylation led to an improvement in the quantum yield of singlet oxygen sensitization for both sulfo and carboxy derivatives, although the silylation did not affect other photophysical properties. Silylation also improved the cellular uptake efficiency for both sulfo and carboxy derivatives, enhancing the in vitro photodynamic activity of the photosensitizer in U251 human glioma cells. The carboxy derivative (SiTPPC4 ) was found to show higher cellular uptake efficiency and in vitro photodynamic activity than the corresponding sulfo derivative (SiTPPS4 ), which indicates that the carboxy group is a more promising hydrophilic group than the sulfo group in the silylated porphyrin. SiTPPC4 was found to show high selective accumulation efficiency in tumors, although almost no tumor selectivity was observed for the nonsilylated porphyrin. The concentration of SiTPPC4 in tumors was 13 times higher than that in muscle 12 h after drug administration. We also studied tumor response after treatment and found that silylation enhanced in vivo photodynamic activity significantly. SiTPPC4 shows higher photodynamic activity than NPe6 with white light irradiation.

Self-Activating Therapeutic Nanoparticle: A Targeted Tumor Therapy Using Reactive Oxygen Species Self-Generation and Switch-on Drug Release.

One of the recent advances in nanotechnology within the medical field is the development of a nanoformulation of anticancer drugs or photosensitizers. Cancer cell-specific drug delivery and upregulation of the endogenous level of reactive oxygen species (ROS) are important in precision anticancer treatment. Within our article, we report a new therapeutic nanoformulation of cancer cell targeting using endogenous ROS self-generation without an external initiator and a switch-on drug release (ROS-induced cascade nanoparticle degradation and anticancer drug generation). We found a substantial cellular ROS generation by treating an isothiocyanate-containing chemical and functionalizing it onto the surface of porous silicon nanoparticles (pSiNPs) that are biodegradable and ROS-responsive nanocarriers. Simultaneously, we loaded an ROS-responsive prodrug (JS-11) that could be converted to the original anticancer drug, SN-38, and conducted further surface functionalization with a cancer-targeting peptide, CGKRK. We demonstrated the feasibility as a cancer-targeting and self-activating therapeutic nanoparticle in a pancreatic cancer xenograft mouse model, and it showed a superior therapeutic efficacy through ROS-induced therapy and drug-induced cell death. The work presented is a new concept of a nanotherapeutic and provides a more feasible clinical translational pathway.

A pH-responsive dissociable mesoporous silica-based nanoplatform enabling efficient dual-drug co-delivery and rapid clearance for cancer therapy.

The balance between tumor accumulation and renal clearance has severely limited the efficacy of mesoporous silica-based drug nanocarriers in cancer therapy. Herein, a pH-responsive dissociable mesoporous silica-based nanoplatform with efficient dual-drug co-delivery, tumor accumulation and rapid clearance for cancer therapy is achieved by adjusting the wetting of the mesoporous silica surface. At pH 7.4, the synthesized spiropyran- and fluorinated silane-modified ultrasmall mesoporous silica nanoparticles (SP-FS-USMSN) self-assemble to form larger nanoclusters (denoted as SP-FS-USMSN cluster) via hydrophobic interactions, which can effectively co-deliver anticancer drugs, doxorubicin hydrochloride (Dox) and curcumin (Cur), based on the mesopores within SP-FS-USMSN and the voids among the stacked SP-FS-USMSN. At pH 4.5-5.5, the conformational conversion of spiropyran from a "closed" state to an "open" state causes the wetting of the SP-FS-USMSN surface, leading to the dissociation of the SP-FS-USMSN cluster for drug release and renal clearance. The in vitro and in vivo studies demonstrate that the Cur and Dox co-loaded SP-FS-USMSN cluster (Cur-Dox/SP-FS-USMSN cluster) possesses great combined cytotoxicity, and can accumulate into tumor tissue by its large size-favored EPR effect and potently suppress tumor growth in HepG2-xenografted mice. This research demonstrates that the SP-FS-USMSN cluster may be a promising drug delivery system for cancer therapy and lays the foundation for practical mesoporous silica-based nanomedicine designs in the future.

Amino-decorated mesoporous silica nanoparticles for controlled sofosbuvir delivery.

The present study describes synthesis of amino-decorated mesoporous silica nanoparticles (MSNs) for sustained delivery and enhanced bioavailability of sofosbuvir. Sofosbuvir is active against hepatitis C virus and pharmaceutically classified as class III drug according to biopharmaceutics classification system (BCS). MSNs were synthesized using modified sol-gel method and the surface was decorated with amino functionalization. Drug loaded MSNs were also grafted with polyvinyl alcohol in order to compare it with the amino-decorated MSNs for sustained drug release. The prepared MSNs were extensively characterized and the optimized formulation was toxicologically and pharmacokinetically evaluated. The functionalized MSNs of 196 nm size entrapped 29.13% sofosbuvir in the pores, which was also confirmed by the decrease in surface area, pore volume and pore size. The drug-loaded amino-decorated MSNs revealed an improved thermal stability as confirmed by thermal analysis. Amino-decorated MSNs exhibited Fickian diffusion controlled sofosbuvir release as compared with non-functionalized and PVA grafted MSNs. Amino-decorated MSNs were deemed safe to use in Sprague-Dawley rats after 14-days exposure as confirmed by the toxicological studies. More interestingly, we achieved a 2-fold higher bioavailability of sofosbuvir in Sprague-Dawley rats in comparison with sofosbuvir alone, and the Tmax was delayed 3-times indicating a sustained release of sofosbuvir.

Quantitative Correlation of Nanotopography with Cell Spreading via Focal Adhesions Using Adipose-Derived Stem Cells.

Nanotopography mimicking extracellular environments reportedly impact cell morphological changes; however, elucidating this relationship has been challenging. To control cellular responses using nanostructures, in this study, the quantitative relationship between nanotopography and cell spreading mediated by focal adhesions (FAs) is demonstrated using adipose-derived stem cells (ASCs). The spreading of ASCs and area of FAs are analyzed for the distribution of filamentous actin and vinculin, respectively, using fluorescent images. FAs require a specific area for adhesion (herein defined as effective contact area [ECA]) to maintain cell attachment on nanopillar arrays. An ECA is the area of FAs supported by nanopillars, multiplying the area fraction (AF) of their top surface. Regarding the spreading of cells, the mean area of ASCs linearly decreases as the mean area of FAs increases. Because the area of FAs is inversely correlated to the AF of the nanopillar arrays, the spreading of cells can be quantitatively correlated with nanotopography. The results provide a conceptual framework for controlling cell behaviors to design artificial substrates for tissue-engineering applications.

Specific targeting of tumor angiogenesis by RGD-conjugated ultrasmall superparamagnetic iron oxide particles using a clinical 1.5-T magnetic resonance scanner.

Angiogenesis is essential for the development of malignant tumors and provides important targets for tumor diagnosis and therapy. To noninvasively assess the angiogenic profile of tumors, novel alpha(v)beta(3) integrin-targeted ultrasmall superparamagnetic iron oxide particles (USPIOs) were designed and their specific uptake by endothelial cells was evaluated in vitro and in vivo. USPIOs were coated with 3-aminopropyltrimethoxysilane (APTMS) and conjugated with Arg-Gly-Asp (RGD) peptides. Accumulation in human umbilical vein endothelial cells (HUVECs) was evaluated using Prussian blue staining, transmission electron microscopy, magnetic resonance (MR) imaging, and inductively coupled plasma mass spectrometry. Uptake of RGD-USPIO by HUVECs was significantly increased when compared with unlabeled USPIO and could be competitively inhibited by addition of unbound RGD. The ability of the RGD-USPIO to noninvasively distinguish tumors with high (HaCaT-ras-A-5RT3) and lower (A431) area fractions of alpha(v)beta(3) integrin-positive vessels was evaluated using a 1.5-T MR scanner. Indeed, after RGD-USPIO injection, there was a more pronounced decrease in T(2) relaxation times in HaCaT-ras-A-5RT3 tumors than in A431 tumors. Furthermore, T(2)*-weighted images clearly identified the heterogeneous arrangement of vessels with alpha(v)beta(3) integrins in HaCaT-ras-A-5RT3 tumors by an irregular signal intensity decrease. In contrast, in A431 tumors with predominantly small and uniformly distributed vessels, the signal intensity decreased more homogeneously. In summary, RGD-coupled, APTMS-coated USPIOs efficiently label alpha(v)beta(3) integrins expressed on endothelial cells. Furthermore, these molecular MR imaging probes are capable of distinguishing tumors differing in the degree of alpha(v)beta(3) integrin expression and in their angiogenesis profile even when using a clinical 1.5-T MR scanner.

Photodynamic therapy of ocular melanoma with bis silicon 2,3-naphthalocyanine in a rabbit model.

PURPOSE: To investigate bis (tri-n-hexylsiloxy) silicon 2,3-naphthalocyanine (SINc; 0.5 mg/kg) for photodynamic therapy of an experimental ocular melanoma in pigmented rabbits. METHODS: SINc was dissolved in canola oil by heating, emulsified with Tween 80, and administered by ear vein. Pharmacokinetics were studied in frozen tumor sections by fluorescence microscopy using a charge coupled device, camera-based, low-light detection system with digital image processing at 1 and 24 hours. A Ti:sapphire laser and a microlens were used to deliver the light (770 nm; 40 mW/cm2; 20 J/cm2). A control rabbit received light without SINc. RESULTS: Localization studies of SINc showed intravascular distribution shifting to a tumor stromal and perivascular distribution 24 hours after treatment. Tissue thermal damage after irradiation was minimal in the control. Exudative retinal detachments were not observed. Tumor destruction was observed, with sharp demarcation to a depth of 3.5 mm. CONCLUSIONS: Tumor light penetration was good at 770 nm, and thermal effects from the exciting light alone were minimal. Photodynamic therapy with SINc resulted in localized tumor destruction reflecting the light beam path without damage to adjacent tissue or intraocular complications.

In vitro and in vivo antimicrobial activity of covalently coupled quaternary ammonium silane coatings on silicone rubber.

Biomaterial-centered infection is a dreaded complication associated with the use of biomedical implants. In this paper, the antimicrobial activity of silicone rubber with a covalently coupled 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride (QAS) coating was studied in vitro and in vivo. Gram-positive Staphylococcus aureus ATCC 12600, Staphylococcus epidermidis HBH, 102, and Gram-negative Esherichia coli O2K2 and Pseudomonas aeruginos AK1 were seeded on silicone rubber with and without QAS-coating, in the absence or presence of adsorbed human plasma proteins. The viability of the adherent bacteria was determined using a live/dead fluorescent stain and a confocal laser scanning microscope. The coating reduced the viability of adherent staphylococci from 90% to 0%), and of Gram-negative bacteria from 90% to 25% while the presencc of adsorbed plasma proteins had little influence. The biomaterials were also subcutaneously implanted in rats for 3 or 7 days, while pre- or postoperatively seeded with S. aureus ATCC 12600. Preoperative seeding resulted in infection of 7 out of 8 silicone rubber implants against 1 out of 8 QAS-coated silicone rubber implants. Postoperative seeding resulted in similar infection incidences on both implant types, but the numbers of adhering bacteria were 70% lower on QAS-coated silicone rubber. In conclusion, QAS-coated silicone rubber shows antimicrobial properties against adhering bacteria, both in vitro and in vivo.

Protective effect of topically applied fluoride in relation to fluoride sensitivity of mutans streptococci.

The aim of the present in vitro experiments was to determine whether the protection of enamel by topically applied fluoride against demineralization by bacterial acids would depend on the fluoride sensitivity of the bacteria. Glucose-agarose gel suspensions of fluoride-sensitive and fluoride-resistant mutans streptococci were placed on bovine enamel specimens with different amounts of fluoride. One group of specimens was untreated, a second group had been pretreated with a F-lacquer, and a third group had been pretreated with the F-lacquer and rinsed subsequently with a KOH-solution, to remove deposited CaF2. After 22-hour incubations at 37 degrees C, the amounts of calcium and lactate and the pH of the agarose gels were determined. This procedure was repeated on three consecutive days. Two parent S. mutans strains, one parent S. sobrinus strain, and five fluoride-resistant derivatives were tested. Both pretreatments gave a significant protection to the enamel specimens. For the S. mutans strains, the degree of protection did not depend on the fluoride sensitivity of the strains. For the S. sobrinus strains, the results suggested a reduced protection against demineralization by the fluoride-resistant derivatives. Only from the second group of enamel specimens was enough fluoride released for inhibition of bacterial metabolism. Presumably, it was released by the dissolution of CaF2. It is concluded that a possible adaptation of mutans streptococci in dental plaque to frequent exposures to fluoride will not necessarily decrease the caries-preventive effects caused by topically applied fluoride agents.

Photodynamic therapy of B16 pigmented melanoma with liposome-delivered Si(IV)-naphthalocyanine.

The possibility of extending photodynamic therapy to the treatment of highly pigmented neoplastic lesions was tested by using Si(IV)-naphthalocyanine (SiNc) as a tumor-localizing agent. Si(IV)-naphthalocyanine displays intense absorbance at 776 nm (epsilon = 5 x 10(5) M-1 cm-1), where melanin absorption becomes weaker. As an experimental model we selected B16 pigmented melanoma subcutaneously transplanted to C57BL mice. Upon injection of 0.5 or 1 mg kg-1 of liposome-incorporated SiNc, maximal accumulation of the photosensitizer in the tumor was observed at 24 h with recoveries of 0.35 and 0.57 microgram g-1, respectively. However, the tumor targeting by SiNc shows essentially no selectivity, since the photosensitizer concentrations in the skin (peritumoral tissue) were very similar to those found in the tumor at all postinjection times examined by us. Irradiation of SiNc-loaded melanoma with 776 nm light from a diode laser at 24 h postinjection induces tumor necrosis and delay of tumor growth. The effect appears to be of purely photochemical nature at dose rates up to 260 mW cm-2; at higher dose rates, thermal effects are likely to become important.

Dimethylsilane polyamines: cytostatic compounds with potentials as anticancer drugs. II. Uptake and potential cytotoxic mechanisms.

Dimethylsilane tetramines are structural analogues of spermine with a (CH3)2 Si-group incorporated into the central carbon chain. They have potential as anticancer drugs. Their cytotoxic effect was considered to rely mainly on their polyamine antagonist property. In order to obtain new ideas about cellular mechanisms, which are potential targets of the dimethylsilane polyamines, the effects of these compounds on some basic cell functions, such as protein and DNA synthesis, and calmodulin antagonism were studied. In addition, their mode of accumulation in cells was investigated. It became evident that the intracellular accumulation of dimethylsilane polyamines is almost exclusively achieved via the polyamine transport system. However, the exchange of a part of the intracellular natural polyamines against dimethylsilane polyamines has only a small effect on polyamine uptake. Binding to the endoplasmic reticulum and inhibition of protein synthesis are presumably important for the cytotoxic action of bis(11-amino-4,8-diazaundecyl)dimethylsilane, a hexamine, but seem of no importance for the tetramines. Calmodulin antagonism, however, is likely to contribute to their cytotoxic effect.

Metabolism of [(14)C]flusilazole in the goat.

[Phenyl(U)-(14)C] and [triazole(3)-(14)C]flusilazole ([(bis 4-fluorophenyl)]methyl(1H-1,2,4-triazole-1-ylmethyl)silane; I) were extensively metabolized when fed to lactating goats (Capra hircus). The primary metabolites identified in goat tissues and milk were bis(4-fluorophenyl)(methyl)silanol (II) and 1H-1,2,4-triazole (III). Concentrations of total radiolabeled residues in the milk ranged from 0.09 to 0.74 microg/mL. Concentrations of radiolabeled residues found in tissues when the [(14)C] label was in the phenyl or triazole position, respectively, were 13.5 and 3.54 microg/g (liver), 8.74 and 0.75 microg/g (kidney), 0.41 and 0.52 microg/g (leg muscle), and 4.07 and 0.94 microg/g (back fat). Urine contained an additional major metabolite identified as [bis(4-fluorophenyl)](methyl)silylmethanol (IV) and its glucuronic acid conjugate (V). With either labeled form of flusilazole, the majority of the recovered radiolabel was excreted in urine or feces.

Characterization of drug release and diffusion mechanism through hydroxyethylmethacrylate/methacrylic acid pH-sensitive hydrogel.

Hydroxyethylmethacrylate/methacrylic acid copolymer cross-linked with ethylenglycol dimethacrylate was prepared by a bulk free radical polymerization method. The permeability studies of this pH-sensitive hydrogel to drugs with different water solubilities showed a water-content dependent diffusion or pore mechanism for ephedrine HCl (water-soluble model drug), whereas, a partition or solute-diffusion mechanism for indomethacin (a water-insoluble drug) was seen. Data analysis of release tests, according to the swelling interface number and Peppas equation for ephedrine HCl in pH 7.4, showed a biexponential model kinetic, whereas in pH 1.2 a swelling-controlled mechanism was seen. Indomethacin was released by an anomalous or non-Fickian release kinetics.