Tumor-penetrating iRGD facilitates penetration of poly(floxuridine-ketal)-based nanomedicine for enhanced pancreatic cancer therapy.

Efficient intratumoral penetration is essential for nanomedicine to eradicate pancreatic tumors. Although nanomedicine can enter the perivascular space of pancreatic tumors, their access to distal tumor cells, aloof from the vessels, remains a formidable challenge. Here, we synthesized an acid-activatable macromolecular prodrug of floxuridine (FUDR)-poly(FUDR-ketal), engineered a micellar nanomedicine of FUDR, and intravenously co-administered the nanomedicine with the tumor-penetrating peptide iRGD for enhanced treatment of pancreatic tumor. A FUDR-derived mono-isopropenyl ether was synthesized and underwent self-addition polymerization to afford the hydrophobic poly(FUDR-ketal), which was subsequently co-assembled with amphiphilic DSPE-mPEG into the micellar nanomedicine with size of 12 nm and drug content of 56.8 wt% using nanoprecipitation technique. The acetone-based ketal-linked poly(FUDR-ketal) was triggered by acid to release FUDR to inhibit cell proliferation. In an orthotopic pancreatic tumor model derived from KPC (KrasLSL-G12D/+; Trp53LSL-R172H/+; Pdx1-Cre) cells that overexpress neuropilin-1 (NRP-1) receptor, iRGD improved penetration of FUDR nanomedicine into tumor parenchyma and potentiated the therapeutic efficacy. Our nanoplatform, along with iRGD, thus appears to be promising for efficient penetration and activation of acid-responsive nanomedicines for enhanced pancreatic cancer therapy.

Aptamers Entirely Built from Therapeutic Nucleoside Analogues for Targeted Cancer Therapy.

Owing to the specific and high binding affinity of aptamers to their targets, aptamer-drug conjugates (ApDCs) have emerged as a promising drug delivery system for targeted cancer therapy. However, in a conventional ApDC, the aptamer segment usually just serves as a targeting moiety, and only a limited number of drug molecules are sequentially conjugated to the oligonucleotide, giving a relatively low drug loading capacity. To address this challenge, herein we employ four clinically approved nucleoside analogues, including clofarabine (Clo), ara-guanosine (AraG), gemcitabine (Ge), and floxuridine (FdU), to replace all natural nucleosides in aptamer sequences, generating a series of whole drug-constituted DNA-like oligomers that are termed drugtamers. Similar to their parent aptamers, the obtained drugtamers maintain the targeting capability and can specifically bind to the target receptors overexpressed on the cancer cell surface. With 100% drug loading ratio, active targeting capability, and enzyme-mediated release of active therapeutics, our drugtamers can strongly induce the apoptosis of cancer cells and inhibit the tumor progression, which enables a new potential for a better targeted cancer therapy.

Evaluation of Floxuridine Oligonucleotide Conjugates Carrying Potential Enhancers of Cellular Uptake.

Conjugation of small molecules such as lipids or receptor ligands to anti-cancer drugs has been used to improve their pharmacological properties. In this work, we studied the biological effects of several small-molecule enhancers into a short oligonucleotide made of five floxuridine units. Specifically, we studied adding cholesterol, palmitic acid, polyethyleneglycol (PEG 1000), folic acid and triantennary N-acetylgalactosamine (GalNAc) as potential enhancers of cellular uptake. As expected, all these molecules increased the internalization efficiency with different degrees depending on the cell line. The conjugates showed antiproliferative activity due to their metabolic activation by nuclease degradation generating floxuridine monophosphate. The cytotoxicity and apoptosis assays showed an increase in the anti-cancer activity of the conjugates related to the floxuridine oligomer, but this effect did not correlate with the internalization results. Palmitic and folic acid conjugates provide the highest antiproliferative activity without having the highest internalization results. On the contrary, cholesterol oligomers that were the best-internalized oligomers had poor antiproliferative activity, even worse than the unmodified floxuridine oligomer. Especially relevant is the effect induced by palmitic and folic acid derivatives generating the most active drugs. These results are of special interest for delivering other therapeutic oligonucleotides.

Dietary serine-microbiota interaction enhances chemotherapeutic toxicity without altering drug conversion.

The gut microbiota metabolizes drugs and alters their efficacy and toxicity. Diet alters drugs, the metabolism of the microbiota, and the host. However, whether diet-triggered metabolic changes in the microbiota can alter drug responses in the host has been largely unexplored. Here we show that dietary thymidine and serine enhance 5-fluoro 2'deoxyuridine (FUdR) toxicity in C. elegans through different microbial mechanisms. Thymidine promotes microbial conversion of the prodrug FUdR into toxic 5-fluorouridine-5'-monophosphate (FUMP), leading to enhanced host death associated with mitochondrial RNA and DNA depletion, and lethal activation of autophagy. By contrast, serine does not alter FUdR metabolism. Instead, serine alters E. coli's 1C-metabolism, reduces the provision of nucleotides to the host, and exacerbates DNA toxicity and host death without mitochondrial RNA or DNA depletion; moreover, autophagy promotes survival in this condition. This work implies that diet-microbe interactions can alter the host response to drugs without altering the drug or the host.

Comparative pharmacokinetic study of PEGylated gemcitabine and gemcitabine in rats by LC-MS/MS coupled with pre-column derivatization and MSALL technique.

Gemcitabine is a small molecular antitumor compound used to treat many types of solid tumors. The clinical application of gemcitabine is limited by its short biological half-life, rapid metabolism and poor tumor tissue targeting. The covalent attachment of polyethylene glycol to gemcitabine is a promising technique to overcome these limitations. After PEGylation, PEGylated gemcitabine could be metabolized into gemcitabine and its metabolites in vivo. Due to the scale effect of PEGylated gemcitabine, the DMPK process of the original drug is greatly changed. Therefore, understanding the pharmacokinetic behavior of PEGylated gemcitabine, gemcitabine and the metabolite dFdU in vivo is really important to clarify the antitumoral activity of these compounds. It would also guide the development of other PEGylated drugs. Due to the complex structure and diverse physiochemical property of PEG, direct quantification analysis of PEGylated gemcitabine presented many challenges in terms of assay sensitivity, selectivity, and robustness. In this article, a data-independent acquisition method, MSALL-based approach using electrospray ionization (ESI) coupled quadrupole time of flight mass spectrometry (MS), was utilized for the determination of PEGylated gemcitabine in rat plasma. The technique consists of a Q1 mass window through all the precursor ions, fragmenting and recording all product ions. PEGylated gemcitabine underwent dissociation in collision cell to generate a series of PEG related ions at m/z 89.0604, 133.0868, 177.1129 of 2, 3, 4 repeating ethylene oxide subunits and PEGylated gemcitabine related ions at m/z 112.0514. PEGylated gemcitabine was detected by the high resolution extracted ions based on the specific compound. For gemcitabine and dFdU, the study used derivatization of these high polarity compounds with dansyl chloride to improve their chromatographic retention. This paper describes comparative pharmacokinetic study of PEGylated gemcitabine and gemcitabine in rats by LC-MS/MS coupled with pre-column derivatization and MSALL technique. The results show that PEGylation could reduce the drug clearance of the conjugated compounds and increase the drug plasma half-life. After administration of PEGylated gemcitabine, the exposure of the free gemcitabine in vivo is lower than administration of gemcitabine, which means that PEGylated gemcitabine possesses lower toxicity compared with gemcitabine.

Pharmacokinetics of Capecitabine and Four Metabolites in a Heterogeneous Population of Cancer Patients: A Comprehensive Analysis.

Capecitabine is an oral prodrug of the anticancer drug 5-fluorouracil (5-FU). The primary aim of this study was to develop a pharmacokinetic model for capecitabine and its metabolites, 5'-deoxy-5-fluorocytidine (dFCR), 5'-deoxy-5-fluorouridine (dFUR), 5-FU, and fluoro-ß-alanine (FBAL) using data from a heterogeneous population of cancer patients (n = 237) who participated in seven clinical studies. A four-transit model adequately described capecitabine absorption. Capecitabine, dFCR, and FBAL pharmacokinetics were well described by two-compartment models, and dFUR and 5-FU were subject to flip-flop pharmacokinetics. Partial and total gastrectomy were associated with a significantly faster capecitabine absorption resulting in higher capecitabine and metabolite peak concentrations. Patients who were heterozygous polymorphic for a genetic mutation encoding dihydropyrimidine dehydrogenase, the DPYD*2A mutation, demonstrated a 21.5% (relative standard error 11.2%) reduction in 5-FU elimination. This comprehensive population model gives an extensive overview of capecitabine and metabolite pharmacokinetics in a large and heterogeneous population of cancer patients.

Rabeprazole intake does not affect systemic exposure to capecitabine and its metabolites, 5'-deoxy-5-fluorocytidine, 5'-deoxy-5-fluorouridine, and 5-fluorouracil.

PURPOSE: Several retrospective studies have shown that the antitumor efficacy of capecitabine-containing chemotherapy decreases when co-administered with a proton pump inhibitor (PPI). Although a reduction in capecitabine absorption by PPIs was proposed as the underlying mechanism, the effects of PPIs on capecitabine pharmacokinetics remain unclear. We prospectively examined the effects of rabeprazole on the pharmacokinetics of capecitabine and its metabolites. METHODS: We enrolled patients administered adjuvant capecitabine plus oxaliplatin (CapeOX) for postoperative colorectal cancer (CRC) patients and metastatic CRC patients receiving CapeOX with/without bevacizumab. Patients receiving a PPI before registration were allocated to the rabeprazole group, and the PPI was changed to rabeprazole (20 mg/day) at least 1 week before the initiation of capecitabine treatment. On day 1, oral capecitabine (1000 mg/m2) was administered 1 h after rabeprazole intake. Oxaliplatin (and bevacizumab) administration on day 1 was shifted to day 2 for pharmacokinetic analysis of the first capecitabine dose. Plasma concentrations of capecitabine, 5'-deoxy-5-fluorocytidine, 5'-deoxy-5-fluorouridine, and 5-fluorouracil were analyzed by high-performance liquid chromatography. Effects of rabeprazole on inhibition of cell proliferation by each capecitabine metabolite were examined with colon cancer cells (COLO205 and HCT116). RESULTS: Five and 9 patients enrolled between September 2017 and July 2018 were allocated to rabeprazole and control groups, respectively. No significant effects of rabeprazole on area under the plasma concentration-time curve divided by capecitabine dose for capecitabine and its three metabolites were observed. Rabeprazole did not affect the proliferation inhibition of colon cancer cells by the respective capecitabine metabolites. CONCLUSION: Rabeprazole does not affect capecitabine pharmacokinetics.

Evaluation of 5-[18F]fluoro-2'-deoxycytidine as a tumor imaging agent: A comparison of [18F]FdUrd, [18F]FLT and [18F]FDG.

One of the hallmarks of cancer is increased cell proliferation. Measurements of cell proliferation by estimation of DNA synthesis with several radiolabeled nucleosides have been tested to assess tumor growth. Deoxycytidine can be phosphorylated by deoxycytidine kinase (dCK) and is incorporated into DNA. This study evaluated a radiofluorinated deoxycytidine analog, 5-[18F]fluoro-2'-deoxycytidine ([18F]FdCyd), as a proliferation probe and compared it with 5-[18F]fluoro-2'-deoxyuridine ([18F]FdUrd), 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT), and [18F]fluorodeoxyglucose ([18F]FDG) in a tumor-bearing mouse model. [18F]FdCyd was synthesized from two precursors by direct electrophilic substitution. The serum stability and partition coefficient of [18F]FdCyd were evaluated in vitro. Positron emission topography (PET) imaging of Lewis lung carcinoma (LLC)-bearing mice with [18F]FdCyd, [18F]FdUrd, [18F]FLT, and [18F]FDG were evaluated. [18F]FdCyd was stable in mouse serum and normal saline for up to 4 h. With all radiotracers except [18F]FLT, PET can clearly delineate the tumor lesion. [18F]FdCyd and [18F]FdUrd showed high accumulation in the liver and kidney. The SUV and tumor-to-muscle (T/M) ratios derived from PET imaging of the radiotracers were [18F]FDG > [18F]FdCyd > [18F]FdUrd > [18F]FLT. Selective retention in tumors with a favorable tumor/muscle ratio makes [18F]FdCyd a protential candidate for further investigation as a proliferation imaging agent.

Gemcitabine and metabolite pharmacokinetics in advanced NSCLC patients after bronchial artery infusion and intravenous infusion.

PURPOSE: We investigated the safety, pharmacokinetics, and efficacy of gemcitabine administered via bronchial artery infusion (BAI) and IV infusion in advanced NSCLC patients. METHODS: Patients were eligible if they had received at least two prior cytotoxic chemotherapy regimens. Gemcitabine was administered via BAI as 600 mg/m2 on day one of cycle one, followed by IV as 1000 mg/m2 on day eight of cycle one, and IV on days one and eight of all subsequent cycles. Pharmacokinetics for gemcitabine and dFdU metabolite in plasma, and dFdCTP active metabolite in peripheral blood mononuclear cells (PBMC) were evaluated. Intensive pharmacokinetic sampling was performed after BAI and IV infusions during cycle one. RESULTS: Three male patients (age range 59-68 years) were evaluated. All patients responded with stable disease or better. One PR was observed after cycle three, and the remaining had SD. Cmax (mean ± SD) following BAI for gemcitabine, dFdCTP, and dFdU were 7.71 ± 0.13, 66.5 ± 40.6, and 38 ± 6.27 µM and following IV infusion, 17 ± 2.36, 50.8 ± 3.61, and 83.2 ± 12.3 µM, respectively. The AUCinf (mean ± SD) following BAI for gemcitabine, dFdCTP, and dFdU were 6.89 ± 1.2, 791.1 ± 551.2, and 829.9 ± 217.8 µM h and following IV infusion, 12.5 ± 3.13, 584 ± 86.6, and 1394.64 ± 682.2 µM h, respectively. The AUC and Cmax of dFdCTP after BAI were higher than IV. The median OS was 6.27 months. No grade 3 or 4 toxicity was observed. The most common side effects were all grade ≤ 2 involving nausea, vomiting, rigor, thrombocytopenia, and anemia. CONCLUSIONS: Systemic exposure to dFdCTP was higher after BAI than IV in two out of three patients.

Selective depletion of metastatic stem cells as therapy for human colorectal cancer.

Selective elimination of metastatic stem cells (MetSCs) promises to block metastatic dissemination. Colorectal cancer (CRC) cells overexpressing CXCR4 display trafficking functions and metastasis-initiating capacity. We assessed the antimetastatic activity of a nanoconjugate (T22-GFP-H6-FdU) that selectively delivers Floxuridine to CXCR4+ cells. In contrast to free oligo-FdU, intravenous T22-GFP-H6-FdU selectively accumulates and internalizes in CXCR4+ cancer cells, triggering DNA damage and apoptosis, which leads to their selective elimination and to reduced tumor re-initiation capacity. Repeated T22-GFP-H6-FdU administration in cell line and patient-derived CRC models blocks intravasation and completely prevents metastases development in 38-83% of mice, while showing CXCR4 expression-dependent and site-dependent reduction in foci number and size in liver, peritoneal, or lung metastases in the rest of mice, compared to free oligo-FdU. T22-GFP-H6-FdU induces also higher regression of established metastases than free oligo-FdU, with negligible distribution or toxicity in normal tissues. This targeted drug delivery approach yields potent antimetastatic effect, through selective depletion of metastatic CXCR4+ cancer cells, and validates metastatic stem cells (MetSCs) as targets for clinical therapy.

Floxuridine Homomeric Oligonucleotides "Hitchhike" with Albumin In†Situ for Cancer Chemotherapy.

Automated attachment of chemotherapeutic drugs to oligonucleotides through phosphoramidite chemistry and DNA synthesis has emerged as a powerful technology in constructing structure-defined and payload-tunable oligonucleotide-drug conjugates. In practice, however, in vivo delivery of these oligonucleotides remains a challenge. Inspired by the systemic transport of hydrophobic payloads by serum albumin in nature, we report the development of a lipid-conjugated floxuridine homomeric oligonucleotide (LFU20) that "hitchhikes" with endogenous serum albumin for cancer chemotherapy. Upon intravenous injection, LFU20 immediately inserts into the hydrophobic cave of albumin to form an LFU20/albumin complex, which accumulates in the tumor by the enhanced permeability and retention (EPR) effect and internalizes into the lysosomes of cancer cells. After degradation, cytotoxic floxuridine monophosphate is released to inhibit cell proliferation.

Pharmacokinetic analysis of metronomic capecitabine in refractory metastatic colorectal cancer patients.

The aim of the present study was to assess the pharmacokinetics (PK) of metronomic capecitabine and its metabolites in a population of refractory metastatic colorectal cancer (mCRC) patients. Thirty-four patients (M/F, 22/12) with a diagnosis of mCRC received capecitabine 800 mg p.o. twice a day and cyclophosphamide 50 mg/day p.o. Blood samples were collected at baseline, 15 min, 30 min, 1 h, 1.5 h, 2 h, 3 h and 5 h at day 1 after capecitabine administration. Plasma concentrations of capecitabine and its metabolites were measured by high performance liquid chromatography and the main PK parameters were calculated. Maximum plasma concentrations (Cmax) of capecitabine (11.51 ± 9.73 µg/ml) occurred at 0.5 h, whereas the Cmax of 5'-deoxy-5-fluorocytidine (5'-DFCR; 2.45 ± 2.93 µg/ml), 5'-deoxy-5-fluorouridine (5'-DFUR; 6.43 ± 8.2 µg/ml), and 5-fluorouracil (5-FU; 0.24 ± 0.16 µg/ml) were found at 1 h, 1.5 h and 1 h, respectively. Capecitabine, 5'-DFCR, 5'-DFUR and 5-FU AUCs at day 1 were 21.30 ± 10.78, 5.2 ± 4.6, 19.59 ± 3.83 and 0.66 ± 0.77 hxµg/ml, respectively. In conclusion, low doses of capecitabine were rapidly absorbed and extensively metabolized, achieving measurable plasma concentrations in a heavily pretreated population of patients.

Simultaneous determination of gemcitabine prodrug, gemcitabine and its major metabolite 2', 2'-difluorodeoxyuridine in rat plasma by UFLC-MS/MS.

To improve bioavailability and provide resistance to deamination, an array of gemcitabine (dFdC) prodrugs carrying the acyl modifications has been successful in the optimization of pharmacokinetic properties of dFdC, but the reports about 4-N-carbobenzoxy-dFdC (Cbz-dFdC), a dFdC prodrug bearing alkyloxycarbonyl modification, are relatively rare. Notably, in vivo enzymatic hydrolysis was an absolutely essential factor for the activation of these prodrugs, which is correlated with the anti-tumor activity. Therefore, detailed metabolism studies of Cbz-dFdC should be carried out for a more authentic pharmacodynamic evaluation. In order to detect the pharmacokinetic characteristics of Cbz-dFdC, a selective, sensitive and accurate method for the simultaneous determination of Cbz-dFdC, along with dFdC and its major metabolite dFdU in rat plasma was developed and validated using UFLC-MS/MS techniques. Column was at 40 °C for separation using an eluent with acetonitrile and 0.1% formic acid, 1 mM ammonium formate at a flow rate of 0.2 mL/min. Detection was performed using ESI source in positive ion selected reaction monitoring mode by monitoring the following ion transitions m/z 398.1 → 202.2 (Cbz-dFdC), m/z 264.1 → 112.0 (dFdC), m/z 265.3 → 113.2 (dFdU) and m/z 246.1 → 112.0 (IS). Analytes were extracted by simple precipitation with acetonitrile containing internal standards followed by liquid-liquid extraction with ethyl acetate. The calibration curves of Cbz-dFdC, dFdC and dFdU were linear in the concentration range of 2 to 500 ng/mL, 2 to 500 ng/mL and 40 to 10,000 ng/mL, respectively. The assay ranges selected for the three analytes were appropriate and minimized the need for reanalysis. All the validation data, such as intra- and inter-day precision, accuracy, selectivity and stability, were within the required limits. In conclusion, the sensitive analytical assay was selective and accurate for the determination of rat plasma concentrations of Cbz-dFdC, dFdC and dFdU from a single LC-MS/MS analysis and well-suited to support pharmacokinetic studies.

DNA Trojan Horses: Self-Assembled Floxuridine-Containing DNA Polyhedra for Cancer Therapy.

Based on their structural similarity to natural nucleobases, nucleoside analogue therapeutics were integrated into DNA strands through conventional solid-phase synthesis. By elaborately designing their sequences, floxuridine-integrated DNA strands were synthesized and self-assembled into well-defined DNA polyhedra with definite drug-loading ratios as well as tunable size and morphology. As a novel drug delivery system, these drug-containing DNA polyhedra could ideally mimic the Trojan Horse to deliver chemotherapeutics into tumor cells and fight against cancer. Both in vitro and in vivo results demonstrate that the DNA Trojan horse with buckyball architecture exhibits superior anticancer capability over the free drug and other formulations. With precise control over the drug-loading ratio and structure of the nanocarriers, the DNA Trojan horse may play an important role in anticancer treatment and exhibit great potential in translational nanomedicine.

Synergistic Combination Chemotherapy of Camptothecin and Floxuridine through Self-Assembly of Amphiphilic Drug-Drug Conjugate.

Combination chemotherapy has been widely applied in cancer treatment; however, the cocktail administration of combination chemotherapy could cause the nonuniform biodistribution of anticancer agents, thus impairing the therapeutic efficacy. In the present study, to address this concern, we proposed a novel strategy of preparing self-assembled nanoparticles from amphiphilic drug-drug conjugate for synergistic combination chemotherapy. The conjugate was synthesized by two-step esterification of hydrophobic camptothecin (CPT) and hydrophilic floxuridine (FUDR) through a linker compound. Because of its amphiphilic nature, the CPT-FUDR conjugate self-assembled into stable nanoparticles which could simultaneously release fixed dosage of the two drugs in cancer cells. In vitro studies demonstrated synergistic anticancer efficacy of the CPT-FUDR nanoparticles including improved cell apoptosis, varied cell cycle arrest, as well as effective inhibition of cancer cell proliferation.

Simultaneous determination of capecitabine and its three nucleoside metabolites in human plasma by high performance liquid chromatography-tandem mass spectrometry.

Capecitabine (Cape) is a prodrug that is metabolized into 5'-deoxy-5-fluorocytidine (DFCR), 5'-deoxy-5-fluorouridine (DFUR), and 5-fluorouracil (5-FU) after oral administration. A liquid chromatography-tandem mass spectrometry method for the simultaneous determination of capecitabine and its three metabolites in human plasma was developed and validated. The ex vivo conversion of DFCR to DFUR in human blood was investigated and an appropriate blood sample handling condition was recommended. Capecitabine and its metabolites were extracted from 100 µL of plasma by protein precipitation. Adequate chromatographic retention and efficient separation were achieved on an Atlantis dC18 column under gradient elution. Interferences from endogenous matrix and the naturally occurring heavy isotopic species were avoided. Detection was performed in electrospray ionization mode using a polarity-switching strategy. The method was linear in the range of 10.0-5000 ng/mL for Cape, DFCR, and DFUR, and 2.00-200 ng/mL for 5-FU. The LLOQ was established at 10.0 ng/mL for Cape, DFCR, and DFUR, and 2.00 ng/mL for 5-FU. The inter- and intra-day precisions were less than 13.5%, 11.1%, 9.7%, and 11.4%, and the accuracy was in the range of -13.2% to 1.6%, -2.4% to 2.5%, -7.1% to 8.2%, and -2.0% to 3.8% for Cape, DFCR, DFUR, and 5-FU, respectively. The matrix effect was negligible under the current conditions. The mean extraction recoveries were within 105-115%, 92.6-101%, 94.0-100%, and 85.1-99.9% for Cape, DFCR, DFUR, and 5-FU, respectively. Stability testing showed that the four analytes remained stable under all relevant analytical conditions. This method has been applied to a clinical bioequivalence study.

Degradation of Resin Composites in a Simulated Deep Cavity

The aim of this study was to analyze the sorption and solubility of a nanofilled (Filtek Z350) and a midifilled (Filtek P60) resin composite in oral environment-like substances, in a simulated deep cavity. A cylindrical cavity prepared in a bovine incisor root was incrementally filled with resin composites. The obtained resin composite cylinders were cut perpendicularly to the axis to obtain 1-mm-thick discs that were divided into fifteen groups (n=5) according to depth (1, 2, 3, 4 and 5 mm) and immersion media (distilled water - DW, artificial saliva - AS and lactic acid - LA). The sorption and solubility were calculated based on ISO 4049:2000. Additionally, the degree of conversion (DC%) was calculated by FT-IR spectroscopy. Data were analyzed using multifactor analysis of variance (MANOVA) followed by Tukey's HSD post-hoc test and linear regression analysis (a=0.05). The DC% was higher for the midifilled resin composite and was negatively influenced by cavity depth (p<0.05). The nanofilled resin composite presented higher sorption and solubility than did the midifilled (p<0.05). The immersion media influenced the sorption and the solubility as follows: LA>AS>DW, (p<0.05). Both phenomena were influenced by cavity depth, with the sorption and solubility increasing from 1 to 5 mm (p<0.05). The degradation of resin composite restorations may be greater in the deepest regions of class II restorations when the composite is exposed to organic acids present in the oral biofilm (lactic acid).

O objetivo deste estudo foi analisar a absorção e a solubilidade de uma resina composta nanopartículada (Filtek Z350) e de uma híbrida (Filtek P60) em substâncias simuladoras do ambiente oral em um modelo de cavidade profunda. Uma cavidade cilíndrica, construída em uma raiz de um incisivo bovino, foi preenchida incrementalmente com as resinas compostas. Os cilindros obtidos foram seccionados perpendicularmente ao eixo para obtenção de discos com 1 mm de espessura, que foram divididos em 15 grupos (n=5) de acordo com a profundidade (1, 2, 3, 4 e 5 mm) e o meio de imersão (água destilada - AD, saliva artificial - SA e ácido lático - AL). A absorção e a solubilidade foram calculadas com base na norma ISO 4049:2000(E). Adicionalmente, o grau de conversão (GC%) foi calculado através de espectroscopia FT-IR. Os dados obtidos foram analisados usando análise de variância multifatorial, teste de Tukey HSD e análise de regressão linear (a=0,05). A resina composta híbrida apresentou o maior grau de conversão, sendo este influenciado pela profundidade da cavidade (p<0,05). A resina composta nanopartículada apresentou maiores valores de absorção e solubilidade (p<0,05). O meio de imersão influenciou a absorção e a solubilidade: AL>SA>AD (p<0,05). Ambos os fenômenos foram influenciados pela profundidade da cavidade, com os valores aumentando de 1 para 5 mm (p<0,05). A degradação de restaurações de resinas compostas pode ser maior em regiões profundas de restaurações classe II e quando o material é exposto à ácidos orgânicos produzidos pelo biofilme oral (ácido lático).

Recolonization of Mutans Streptococci after Application of Chlorhexidine Gel

Streptococcus mutans is specifically suppressed by intensive treatment with chlorhexidine gel, but the time for recolonization and the effect on other oral bacteria are not totally clear. In this study, recolonization of mutans streptococci was evaluated in nine healthy adult volunteers, who were highly colonized with this microorganism. Stimulated saliva was collected before (baseline) and at 1, 7, 14, 21 and 28 days after application of 1% chlorhexidine gel on volunteers' teeth for two consecutive days. On each day, the gel was applied using disposable trays for 3 x 5 min with intervals of 5 min between each application. Saliva was plated on blood agar to determine total microorganisms (TM); on mitis salivarius agar to determine total streptococci (TS) and on mitis salivarius agar plus bacitracin to determine mutans streptococci (MS). Chlorhexidine was capable of reducing the counts of MS and the proportion of MS with regard to total microorganisms (%MS/TM) (p<0.05), but these values did not differ statistically from baseline (p>0.05) after 14 days for MS and 21 days for %MS/TM. The counts of TM and TS and the proportion of MS to total streptococci did not differ statistically from baseline (p>0.05) after chlorhexidine treatment. The results suggest that the effect of chlorhexidine gel treatment on suppression of mutans streptococci is limited to less than a month in highly colonized individuals.

Streptococcus mutans é especificamente suprimido pelo tratamento intensivo com clorexidina em gel, mas o tempo de recolonização e o efeito em outras bactérias orais não está totalmente claro. Nesse estudo, a recolonização de estreptococos do grupo mutans foi avaliado em nove voluntários adultos saudáveis, os quais eram altamente colonizados por esse microrganismo. Saliva estimulada foi coletada antes (baseline) e 1, 7, 14, 21 e 28 dias após a aplicação de clorexidina em gel a 1% nos dentes dos voluntários por dois dias consecutivos. Em cada dia, o gel foi aplicado utilizando moldeiras descartáveis por 3 x 5 min com intervalos de 5 min entre cada aplicação. A saliva foi inoculada em ágar sangue para determinação dos microrganismos totais (MT); em mitis salivarius ágar para determinação dos estreptococos totais (ET) e em meio mitis salivarius com bacitracina para determinar a contagem de estreptococos do grupo mutans (EGM). O tratamento com clorexidina foi capaz de reduzir as contagens de EGM e a proporção de EGM em relação aos microrganismos totais (%EGM/MT) (p<0,05), mas esses valores não diferiram estatisticamente do baseline (p>0,05) após 14 dias para EGM e 21 dias para %EGM/MT. As contagens de MT e ET e a proporção de EGM em relação a estreptococos totais não difereriram estatisticamente do baseline (p>0,05) após o tratamento com clorexidina. Os resultados sugerem que o efeito do tratamento com clorexidina em gel na supressão de estreptococos do grupo mutans é limitado a menos de um mês em indivíduos altamente colonizados. .

Comportamentos e práticas sexuais de homens que fazem sexo com homens / Sexual behaviors and practices of men who have sex with men / Conductas y prácticas sexuales de los hombres que tienen sexo con hombres

Objetivou-se identificar comportamentos e práticas sexuais de homens que fazem sexo com homens no contexto da vulnerabilidade ao HIV/AIDS. Estudo transversal, exploratório descritivo. Foi realizado em um local de sociabilidade gay de Fortaleza, no Estado do Ceará, entre novembro de 2010 e março de 2011, por meio de entrevista com 189 homens que fazem sexo com homens. Encontrou-se uma amostra composta, majoritariamente, por jovens, solteiros e com alto nível educacional. A história sexual demonstrou o início precoce da vida sexual, com prevalência elevada de relação sexual com parceira do sexo oposto. Houve alta frequência de testagem para o HIV. As práticas sexuais revelaram prevalência superior da realização de sexo oral e anal, bem como altos níveis de proteção no sexo anal, apesar de baixa no sexo oral. Constatou-se uma maior incorporação das práticas de prevenção em relação ao panorama nacional do início da epidemia.

The objective was to identify behaviors and sexual practices of men who have sexual relations with other men in the context of vulnerability to HIV/AIDS. This was a cross-sectional, exploratory and descriptive study. It was carried out in a gay sociability place in Fortaleza, Ceará, Brazil, between November 2010 and March 2011, through interviews with 189 men who have sex with men. The ethical aspects were respected. We found a sample consisting mostly by young, single, and highly educated men. The sexual history demonstrated the early onset of sexual activity, with a high prevalence of sexual intercourse with a partner of the opposite sex. There was also a high prevalence of HIV testing. Sexual practices revealed high prevalence of performing oral and anal sex, as well as high levels of protection in anal sex, despite the low protection in oral sex. A greater incorporation of prevention practices was found compared to the national scene in the beginning of the disease outbreak.

El objetivo fue identificar los comportamientos y las prácticas sexuales de los hombres que tienen sexo con hombres en el contexto de la vulnerabilidad al VIH/SIDA. Fue un estudio transversal, descriptivo y exploratorio. Se celebró en una sociabilidad local gay de Fortaleza, Ceará, Brasil, entre noviembre de 2010 y marzo de 2011, a través de entrevistas con 189 hombres que tienen sexo con hombres. Se encontró una muestra compuesta en su mayoría por jóvenes, solteros y con alto nivel de educación. La historia sexual demostró el inicio temprano de la actividad sexual, la alta prevalencia de relaciones sexuales con una pareja del sexo opuesto. Hubo alta prevalencia de la prueba del VIH. Las prácticas sexuales revelaron una alta prevalencia de realizar sexo oral y anal, así como altos niveles de protección en el sexo anal, a pesar de la baja protección en el sexo oral. Se encontró una mayor incorporación de las prácticas de prevención en relación con la escena nacional en el inicio de la epidemia.

História da saúde da criança: conquistas, políticas e perspectivas / History of the child's health: conquers, policies and perspectives / Historia de la salud del niño: conquistas, políticas y perspectivas

Objetivou-se descrever e refletir sobre os aspectos relacionados à história social e às políticas públicas de assistência à saúde da criança no Brasil. Realizou-se breve contextualização histórica sobre as transformações no ser criança no Brasil e no mundo, apresentando-se as perspectivas referentes às políticas públicas de saúde da criança no âmbito nacional. Observou-se que a evolução histórica da participação da criança na sociedade encontra-se atrelada às mudanças nas políticas públicas de assistência, traduzida em queda da mortalidade infantil, aliada a desafios como a redução da morbimortalidade por agravos perinatais e causas evitáveis. Os avanços e conquistas na saúde da criança encontram-se em um movimento de mudança paradigmática para um modelo de construção de redes e da integralidade do cuidado. Esse contexto aponta a necessidade de formação de recursos humanos para esta área, tendo em vista à promoção e prevenção em saúde, assim como uma melhor qualidade de vida dessa população.

The aim of this study was describing and reflecting about the aspects related to the social history and public policies for the children's health assistance in Brazil. A brief historical contextualization was realized concerning changes on the way the society views the child in Brazil and around the world, also perspectives considering public policies for the children's health in the national context were presented. It was possible to identify that the historical evolution of the child participation in the society is linked to the changes in the assistance public policies, which were demonstrated in the child death decrease and associated to challenges, like the morbimortality reduction caused by perinatal injuries and avoidable causes. The advances and conquers in the child's health are evolved in a paradigmatic change movement into a model of a net formation and a comprehensiveness care. This context requires the human resources preparation for such area, based on the health promotion and prevention, as well as a better quality of life of the population.

El objetivo del estudio fue describir y reflexionar acerca de los aspectos relacionados con la historia social y las políticas públicas de asistencia de salud de niños en Brasil. Una breve contextualización acerca de las transformaciones en el modo de ser niño en Brasil y en el mundo, así como las perspectivas relacionadas a las políticas públicas de salud del niño en el contexto nacional. La evolución histórica de la participación del niño en la sociedad encuentra-se vinculada a las modificaciones de las políticas públicas de asistencia, que se mira en la reducción de la mortalidad infantil, acercada de desafíos como la reducción de la morbimortalidad por injurias perinatales y causas evitables. Los avanzos y conquistas na salud del niño se encuentran en uno movimiento de modificacion paradigmática para un modelo de construcción de redes y de la integralidad del cuidado. En este contexto se observa la necesidad de formación de recursos personales para esta área, con base en la promoción y prevención en salud y una mejor cualidad de vida de esa población.