Adhesión a dentina parte I: características del sustrato y sistemas adhesivos / Dentin bonding part I: substrate characteristics and bonding systems

La Odontología Restauradora contemporánea no puede concebirse sin la adhesión de los materiales restauradores a las estructuras dentarias. En mu-chos procedimientos restauradores, no sólo el esmal-te sino también la dentina se encuentra involucrada, por lo tanto, la adhesión a esta última juega un rol cla-ve en el éxito clínico. No obstante, todavía supone un gran desafío lograr una adhesión estable y predeci-ble en el tiempo. El propósito del presente artículo es analizar las características principales de la dentina como sustrato adhesivo y describir los sistemas ad-hesivos actuales y sus mecanismos de acción (AU)

Contemporary Restorative Dentistry cannot be conceived without the adhesion of restorative materials to dental structures. In many restorative procedures not only the enamel, but also the dentin is involved, therefore dentin bonding plays a key role in their success. However, it is still a great challenge to achieve stable and predictable dentin bonding over time. The aim of this article is to analyze the main characteristics of dentin as an adhesive substrate and to describe current adhesive systems and their bonding mechanisms (AU)

Nanotechnology for Topical Drug Delivery to the Anterior Segment of the Eye.

Topical drug delivery is one of the most challenging aspects of eye therapy. Eye drops are the most prevalent drug form, especially for widely distributed anterior segment eye diseases (cataracts, glaucoma, dry eye syndrome, inflammatory diseases, etc.), because they are convenient and easy to apply by patients. However, conventional drug formulations are usually characterized by short retention time in the tear film, insufficient contact with epithelium, fast elimination, and difficulties in overcoming ocular tissue barriers. Not more than 5% of the total drug dose administered in eye drops reaches the interior ocular tissues. To overcome the ocular drug delivery barriers and improve drug bioavailability, various conventional and novel drug delivery systems have been developed. Among these, nanosize carriers are the most attractive. The review is focused on the different drug carriers, such as synthetic and natural polymers, as well as inorganic carriers, with special attention to nanoparticles and nanomicelles. Studies in vitro and in vivo have demonstrated that new formulations could help to improve the bioavailability of the drugs, provide sustained drug release, enhance and prolong their therapeutic action. Promising results were obtained with drug-loaded nanoparticles included in in situ gel.

Global Substance Registration System: consistent scientific descriptions for substances related to health.

The US Food and Drug Administration (FDA) and the National Center for Advancing Translational Sciences (NCATS) have collaborated to publish rigorous scientific descriptions of substances relevant to regulated products. The FDA has adopted the global ISO 11238 data standard for the identification of substances in medicinal products and has populated a database to organize the agency's regulatory submissions and marketed products data. NCATS has worked with FDA to develop the Global Substance Registration System (GSRS) and produce a non-proprietary version of the database for public benefit. In 2019, more than half of all new drugs in clinical development were proteins, nucleic acid therapeutics, polymer products, structurally diverse natural products or cellular therapies. While multiple databases of small molecule chemical structures are available, this resource is unique in its application of regulatory standards for the identification of medicinal substances and its robust support for other substances in addition to small molecules. This public, manually curated dataset provides unique ingredient identifiers (UNIIs) and detailed descriptions for over 100 000 substances that are particularly relevant to medicine and translational research. The dataset can be accessed and queried at https://gsrs.ncats.nih.gov/app/substances.

Actuation Properties of Paper Actuators Fabricated Using PEDOT/PSS Electrode Films.

The development of actuators for power sources is essential for the efficient manipulation of fluids in microfluidics systems. In this work, a capacitor-type three-layer paper actuator was fabricated by sandwiching a polyelectrolyte layer between two films of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS). The paper actuator exhibited stable large electromechanical deformations in bilateral symmetry under alternating square-wave electric field. The actuation properties were examined in a function of voltage (±0.5, ±1, ±1.5, ±2, and ±2.5 V) and frequency (1, 0.5, 0.2, and 0.05 Hz). In addition, the PEDOT/PSS electrode films with different thicknesses were prepared, and the effects of actuator thickness on actuation properties were examined. As a result, it was found that the actuator displacement increased considerably with reducing actuator thickness. In addition, the actuator with a thickness of 48 µm demonstrated a maximum displacement of 5.8 mm at a voltage of 1.5 V and a frequency of 0.05 Hz. The proposed actuator can be potentially used in the development of power sources for micropumps and check valves of microfluidic devices.

Use of Deep Eutectic Solvents in Polymer Chemistry-A Review.

This review deals with two overlapping issues, namely polymer chemistry and deep eutectic solvents (DESs). With regard to polymers, specific aspects of synthetic polymers, polymerization processes producing such polymers, and natural cellulose-based nanopolymers are evaluated. As for DESs, their compliance with green chemistry requirements, their basic properties and involvement in polymer chemistry are discussed. In addition to reviewing the state-of-the-art for selected kinds of polymers, the paper reveals further possibilities in the employment of DESs in polymer chemistry. As an example, the significance of DES polarity and polymer polarity to control polymerization processes, modify polymer properties, and synthesize polymers with a specific structure and behavior, is emphasized.

Principles of Structural Design of Conjugated Polymers Showing Excellent Charge Transport toward Thermoelectrics and Bioelectronics Applications.

Conjugated polymers, especially their second generation with a donor-acceptor alternating structure, have promising properties. These are suitable for two emerging fields, thermoelectrics and bioelectronics, if appropriate structural designs are implemented. This review aims to give a perspective for the potential and challenges of novel conjugated polymers in such applications. In particular, the aspects of synthetic design and the consequences of modifications of the chemical structure on the charge transport in selected second-generation conjugated polymers are reviewed. By understanding the effects of structural motifs on the overall material properties, polymers can be specifically tailored for the respective application. The basics of charge transport measurements are briefly summarized, as the charge transport plays an important role for thermoelectrics as well as for bioelectronics. In particular, the correlation between the reported charge carrier mobility values and the structural design of the polymers is reviewed. Examples of the application of second-generation conducting polymers in thermoelectrics and bioelectronics are shown to demonstrate the current state of research. Finally, the prospect of a purposeful design of new materials for these two emerging fields is discussed.

Identification Performance of Different Types of Handheld Near-Infrared (NIR) Spectrometers for the Recycling of Polymer Commodities.

For sustainable utilization of raw materials and environmental protection, the recycling of the most common polymers-polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS)-is an extremely important issue. In the present communication, the discrimination performance of the above polymer commodities based on their near-infrared (NIR) spectra measured with four real handheld (<200 g) spectrometers based on different monochromator principles were investigated. From a total of 43 polymer samples, the diffuse reflection spectra were measured with the handheld instruments. After the original spectra were pretreated by second derivative and standard normal variate (SNV), principal component analysis (PCA) was applied and unknown samples were tested by soft independent modeling of class analogies (SIMCA). The results show that the five polymer commodities cluster in the score plots of their first three principal components (PCs) and, furthermore, samples in calibration and test sets can be correctly identified by SICMA. Thus, it was concluded that on the basis of the NIR spectra measured with the handheld spectrometers the SIMCA analysis provides a suitable analytical tool for the correct assignment of the type of polymer. Because the mean distance between clusters in the score plot reflects the discrimination capability for each polymer pair the variation of this parameter for the spectra measured with the different handheld spectrometers was used to rank the identification performance of the five polymer commodities.

Flow-batch analysis of clenbuterol based on analyte extraction on molecularly imprinted polymers coupled to an in-system chromogenic reaction. Application to human urine and milk substitute samples.

A fully automated spectrophotometric method based on flow-batch analysis has been developed for the determination of clenbuterol including an on-line solid phase extraction using a molecularly imprinted polymer (MIP) as the sorbent. The molecularly imprinted solid phase extraction (MISPE) procedure allowed analyte extraction from complex matrices at low concentration levels and with high selectivity towards the analyte. The MISPE procedure was performed using a commercial MIP cartridge that was introduced into a guard column holder and integrated in the analyzer system. Optimized parameters included the volume of the sample, the type and volume of the conditioning and washing solutions, and the type and volume of the eluent. Quantification of clenbuterol was carried out by spectrophotometry after in-system post-elution analyte derivatization based on azo-coupling using N- (1-Naphthyl) ethylenediamine as the coupling agent to yield a red-colored compound with maximum absorbance at 500nm. Both the chromogenic reaction and spectrophotometric detection were performed in a lab-made flow-batch mixing chamber that replaced the cuvette holder of the spectrophotometer. The calibration curve was linear in the 0.075-0.500mgL-1 range with a correlation coefficient of 0.998. The precision of the proposed method was evaluated in terms of the relative standard deviation obtaining 1.1% and 3.0% for intra-day precision and inter-day precision, respectively. The detection limit was 0.021mgL-1 and the sample throughput for the entire process was 3.4h-1. The proposed method was applied for the determination of CLB in human urine and milk substitute samples obtaining recoveries values within a range of 94.0-100.0%.

A comprehensive review on polyelectrolyte complexes.

Global research on polyelectrolytes at a fundamental and applied level is intensifying because the advantages of sustainability are being accepted in academia and industrial research settings. During recent decades, polyelectrolytes became one of the most attractive subjects of scientific research owing to their great potential in the areas of advanced technologies. Polyelectrolytes are a type of polymer that have multitudinous ionizable functional groups. Ionized polyelectrolytes in solution can form a complex with oppositely charged polyelectrolytes - a polyelectrolyte complex (PEC). The present article provides a comprehensive review on PECs and their classification, theory and characterization, as well as a critical analysis of the current research.

Composition analysis of fractions of extracellular polymeric substances from an activated sludge culture and identification of dominant forces affecting microbial aggregation.

Extracellular polymeric substances (EPS) appear to play a critical role in the formation of bioaggregates, such as sludge flocs, in activated sludge processes. Here, we systematically investigated the composition and chemical structure of various EPS fractions excreted from an activated sludge culture using multi-analysis techniques to examine the ability of the sludge to aggregate. Chemical analysis was used with a three-dimensional excitation emission matrix and Fourier transform infrared spectroscopy, applying inter-particle forces theory. The combined findings revealed that hydrophobic groups, especially protein-related N-H, were present in a greater proportion in tightly bound EPS (TB-EPS). This result, which explained the specificity of TB-EPS in the chemical structure, was consistent with data indicating that TB-EPS contained a large amount of protein-like substances (86.7 mg/g of mixed liquor volatile suspended solids, 39.7% of the total EPS). Subsequently, a novel experimental procedure was developed to pinpoint key inter-particle forces in sludge aggregation. The result revealed that hydrogen bonds are the predominant triggers that promote sludge aggregation. This comprehensive analysis indicated that hydrophobic proteins in TB-EPS are responsible for the critical role played by hydrogen bonds in sludge formation. Our findings highlight the need to elucidate the mechanisms of TB-EPS-mediated flocculation in future efforts.

Uncertainty in the Life Cycle Greenhouse Gas Emissions from U.S. Production of Three Biobased Polymer Families.

Interest in biobased products has been motivated, in part, by the claim that these products have lower life cycle greenhouse gas (GHG) emissions than their fossil counterparts. This study investigates GHG emissions from U.S. production of three important biobased polymer families: polylactic acid (PLA), polyhydroxybutyrate (PHB) and bioethylene-based plastics. The model incorporates uncertainty into the life cycle emission estimates using Monte Carlo simulation. Results present a range of scenarios for feedstock choice (corn or switchgrass), treatment of coproducts, data sources, end of life assumptions, and displaced fossil polymer. Switchgrass pathways generally have lower emissions than corn pathways, and can even generate negative cradle-to-gate emissions if unfermented residues are used to coproduce energy. PHB (from either feedstock) is unlikely to have lower emissions than fossil polymers once end of life emissions are included. PLA generally has the lowest emissions when compared to high emission fossil polymers, such as polystyrene (mean GHG savings up to 1.4 kg CO2e/kg corn PLA and 2.9 kg CO2e/kg switchgrass PLA). In contrast, bioethylene is likely to achieve the greater emission reduction for ethylene intensive polymers, like polyethylene (mean GHG savings up to 0.60 kg CO2e/kg corn polyethylene and 3.4 kg CO2e/kg switchgrass polyethylene).

Mucoadhesive polymeric platform for drug delivery; a comprehensive review.

Mucoadhesion can be defined as adhesion in biological setting. Process of mucoadhesion takes place in 3 stages- the first stage being that of wetting or swelling of mucoadhesive polymer. Second stage involves interpenetration of the chains of mucoadhesive polymer and the third stage involves formation of chemical bonds between entangled chains. Several polymer related factors like molecular weight, chain length, degree of cross-linking, hydration, functional groups, charge, polymer concentration and several environmental and physiological factors like contact time, mucin turnover rate and mucus viscosity affect the degree of mucoadhesion. Formulation scientists have structured and engineered several mucoadhesive polymers for their usefulness in enhancement of bioavailability, controlled and targeted drug delivery. Mucoadhesive polymers can be classified as non-specific first generation polymers and novel second generation polymers based on the mechanism of mucoadhesion. Mucoadhesive drug delivery systems have been applied to buccal cavity, oesophagus, gastrointestinal tract, eye, nasal cavity, vagina and rectal cavity. Several in vitro/ex vivo and in vivo evaluation techniques have evolved for the evaluation of mucoadhesive strength of these polymers. This review provides historical perspective on mucoadhesive polymers and an understanding of the phenomenon of mucoadhesion, factors affecting mucoadhesion, types of mucoadhesive polymers, their practical applications and the various evaluation techniques for determination of mucoadhesive strength.

Underwater self-cleaning scaly fabric membrane for oily water separation.

Oily wastewater is always a threat to biological and human safety, and it is a worldwide challenge to solve the problem of disposing of it. The development of interface science brings hope of solving this serious problem, however. Inspired by the capacity for capturing water of natural fabrics and by the underwater superoleophobic self-cleaning property of fish scales, a strategy is proposed to design and fabricate micro/nanoscale hierarchical-structured fabric membranes with superhydrophilicity and underwater superoleophobicity, by coating scaly titanium oxide nanostructures onto fabric microstructures, which can separate oil/water mixtures efficiently. The microstructures of the fabrics are beneficial for achieving high water-holding capacity of the membranes. More importantly, the special scaly titanium oxide nanostructures are critical for achieving the desired superwetting property toward water of the membranes, which means that air bubbles cannot exist on them in water and there is ultralow underwater-oil adhesion. The cooperative effects of the microscale and nanoscale structures result in the formation of a stable oil/water/solid triphase interface with a robust underwater superoleophobic self-cleaning property. Furthermore, the fabrics are common, commercially cheap, and environmentally friendly materials with flexible but robust mechanical properties, which make the fabric membranes a good candidate for oil/water separation even under strong water flow. This work would also be helpful for developing new underwater superoleophobic self-cleaning materials and related devices.

Classification of stimuli-responsive polymers as anticancer drug delivery systems.

Although several anticancer drugs have been introduced as chemotherapeutic agents, the effective treatment of cancer remains a challenge. Major limitations in the application of anticancer drugs include their nonspecificity, wide biodistribution, short half-life, low concentration in tumor tissue and systemic toxicity. Drug delivery to the tumor site has become feasible in recent years, and recent advances in the development of new drug delivery systems for controlled drug release in tumor tissues with reduced side effects show great promise. In this field, the use of biodegradable polymers as drug carriers has attracted the most attention. However, drug release is still difficult to control even when a polymeric drug carrier is used. The design of pharmaceutical polymers that respond to external stimuli (known as stimuli-responsive polymers) such as temperature, pH, electric or magnetic field, enzymes, ultrasound waves, etc. appears to be a successful approach. In these systems, drug release is triggered by different stimuli. The purpose of this review is to summarize different types of polymeric drug carriers and stimuli, in addition to the combination use of stimuli in order to achieve a better controlled drug release, and it discusses their potential strengths and applications. A survey of the recent literature on various stimuli-responsive drug delivery systems is also provided and perspectives on possible future developments in controlled drug release at tumor site have been discussed.

An efficient approach for preprocessing data from a large-scale chemical sensor array.

In this paper, an artificial olfactory system (Electronic Nose) that mimics the biological olfactory system is introduced. The device consists of a Large-Scale Chemical Sensor Array (16; 384 sensors, made of 24 different kinds of conducting polymer materials)that supplies data to software modules, which perform advanced data processing. In particular, the paper concentrates on the software components consisting, at first, of a crucial step that normalizes the heterogeneous sensor data and reduces their inherent noise. Cleaned data are then supplied as input to a data reduction procedure that extracts the most informative and discriminant directions in order to get an efficient representation in a lower dimensional space where it is possible to more easily find a robust mapping between the observed outputs and the characteristics of the odors in input to the device. Experimental qualitative proofs of the validity of the procedure are given by analyzing data acquired for two different pure analytes and their binary mixtures. Moreover, a classification task is performed in order to explore the possibility of automatically recognizing pure compounds and to predict binary mixture concentrations.

A new classification paradigm of extracellular polymeric substances (EPS) in activated sludge: separation and characterization of exopolymers between floc level and microcolony level.

Extracellular polymeric substances (EPS) play a crucial role in the formation of activated sludge flocs. However, until now, the EPS are rather classified by the method used for extraction than by a theoretical consideration of their function and composition. In this paper, a new classification paradigm of EPS was proposed, which offered a novel approach to identify the role of EPS in the formation of activated sludge flocs. The current study gave an exploration to distinguish the EPS in the floc level (extra-microcolony polymers, EMPS) and in the microcolony level (extra-cellular polymers, ECPS). It was found that cation exchange resin treatment is efficient to disintegrate the flocs for EMPS extraction, however, inefficient to disaggregate the microcolonies for ECPS harvesting. A two-steps extraction strategy (cation exchange resin treatment followed by ultrasonication-high speed centrifugation treatment) was suggested to separate these two types of EPS in activated sludge flocs and the physicochemical characteristics of EMPS and ECPS were compared. The protein/polysaccharide ratio of ECPS was higher than that of EMPS and the molecular weight of proteins in EMPS and ECPS were found to be different. The ECPS contained higher molecular weight proteins and more hydrophobic substances than the EMPS contained. The result of excitation-emission matrix fluorescence spectroscopy analysis also showed that the EMPS and the ECPS have different fluorescent expressions and the components of EMPS were more diverse than that of ECPS. All results reported herein demonstrated that two different types of exopolymers exist in the activated sludge flocs and the inter-particle forces for aggregation of activated sludge flocs are not identical between the floc level and the microcolony level. It suggested that cation bridging interactions are more crucial in floc level flocculation, while the entanglement and hydrophobic interactions are more important in microcolony level cohesion.

[Influence of polymer type on the physical properties and the release study of papaverine hydrochloride from tablets]. / Wplyw rodzaju polimeru na wlasciwosci fizyczne i proces uwalniania chlorowodorku papaweryny z tabletek.

BACKGROUND: Polymers are widely used in drug manufacturing. Researchers studied their impact on the bioavailability of active substances or on physical properties of tablets for many years. OBJECTIVES: To study the influence of polymer excipients, such as microcrystalline cellulose (Avicel PH 101, Avicel PH 102), croscarmellose sodium, crospovidone or polyvinylpyrrolidone, on the release profile of papaverine hydrochloride from tablets and on the physical properties of tablets. MATERIAL AND METHODS: Six series of uncoated tablets were prepared by indirect method, with previous wet granulation. Tablets contained papaverine hydrochloride and various excipients. The physical properties of the prepared granules, tablets and the release profile of papaverine hydrochloride from tablets were examined. The content of papaverine hydrochloride from the release study were determined spectrophotometrically. RESULTS: All tablets met the pharmacopoeia requirements during following tests: the disintegration time of tablets, uncoated tablets resistance to abrasion, the weight uniformity and dose formulations, their dimensions, the resistance to crushing of tablets and the drug substance content in the tablet. In four cases more than 80% of papaverine was released up to 2 min, in one formula it was up to 5 min, and in last one up to 10 min. CONCLUSIONS: Tablets containing crospovidone disintegrated faster than tablets with croscarmellose sodium. Adding gelatinized starch to the tablet composition increased the disintegration time, hardness and delayed the release of papaverine. During the wet granulation process, granules containing polyvinylpyrrolidone were characterized by a suitable flow properties and slightly prolonged disintegration time. Tablets containing Avicel PH 102 compared to tablets with Avicel PH 101 had less weight loss during the test of mechanical resistance, improved hardness and faster release profile of papaverine from tablets.

Roll-to-roll cohesive, coated, flexible, high-efficiency polymer light-emitting diodes utilizing ITO-free polymer anodes.

This paper reports solution-processed, high-efficiency polymer light-emitting diodes fabricated by a new type of roll-to-roll coating method under ambient air conditions. A noble roll-to-roll cohesive coating system utilizes only natural gravity and the surface tension of the solution to flow out from the capillary to the surface of the substrate. Because this mechanism uses a minimally cohesive solution, the roll-to-roll cohesive coating can effectively realize an ultra-thin film thickness for the electron injection layer. In addition, the roll-to-roll cohesive coating enables the fabrication of a thicker polymer anode film more than 250 nm at one time by modification of the surface energy and without wasting the solution. It is observed that the standard sheet resistance deviation of the polymer anode is only 2.32 Ω/□ over 50 000 bending cycles. The standard sheet resistance deviation of the polymer anode in the different bending angles (0 to 180°) is 0.313 Ω/□, but the case of the ITO-PET is 104.93 Ω/□. The average surface roughness of the polymer anode measured by atomic force microscopy is only 1.06 nm. Because the surface of the polymer anode has a better quality, the leakage current of the polymer light-emitting diodes (PLEDs) using the polymer anode is much lower than that using the ITO-PET substrate. The luminous power efficiency of the two devices is 4.13 lm/W for the polymer anode and 3.21 lm/W for the ITO-PET. Consequently, the PLEDs made by using the polymer anode exhibited 28% enhanced performance because the polymer anode represents not only a higher transparency than the ITO-PET in the wavelength of 560 nm but also greatly reduced roughness. The optimized the maximum current efficiency and power efficiency of the device show around 6.1 cd/A and 5.1 lm/W, respectively, which is comparable to the case of using the ITO-glass.

Species of phosphorus in the extracellular polymeric substances of EBPR sludge.

In this study, the species of extracellular phosphorus and their transformation during extracellular polymeric substances (EPS) extraction were explored by using (31)P nuclear magnetic resonance spectroscopy. Results show that the extraction methods had a substantial influence on the phosphorus species in the extracted EPS. Cation exchange resin method was more appropriate for extracting EPS from the enhanced biological phosphorus removal (EBPR) sludge. Orthophosphate, pyrophosphate and polyphosphate were the main species of phosphorus found to be present in the EPS, which together accounted for about 6.6-10.5% of the total phosphorus in the EBPR sludge. The high percentage of extracellular phosphorus and their diverse species might reveal a new insight into the characteristics of the phosphorus in EPS in EBPR system.

Synthesis and MALDI-ToF characterization of dendronized poly(ethylene glycol)s

Well-defined hybrids of linear poly(ethylene glycol)s (PEGs) and dendritic polyesters were prepared via the dendronization of the alcohol end groups of the mono and difunctional linear PEGs. Though useful for rudimentary product characterization, GPC and NMR could not verify the overall structural purity of these linear-dendritic hybrids. On the other hand, the detailed data provided by MALDI-ToF mass spectrometry enabled confirmation of the high structural purity of the dendronized PEGs at each step of the dendronization procedure. The well-defined number of functionalities on these dendronized PEGs, renders them particularly useful for research in the biomedical sphere where functionality and purity are of the utmost importance. The MALDI-ToF mass spectrometric approach described herein represents a valuable technique for detailed monitoring of these dendronization reactions, as well as a variety of other polymer end group modifications.

Híbridos bem definidos de poli(etilenoglicol) lineares (PEGs) e poliésteres dendriméricos foram preparados via "dendronização" de álcool e grupos de PEGs lineares mono e bifuncionais. Embora úteis para a caracterização rudimentar de produtos, Cromatografia por Permeação em Gel e RMN podem não demonstrar a pureza estrutural global desses híbridos lineares dendríticos. Por outro lado, informações detalhadas provenientes de espectrometria de massas MALDI-ToF permitiram a confirmação de elevada pureza estrutural de PEGs "dendronizados" em cada passo do processo de "dendronização". O número de funcionalidades bem definidas destes PEGs "dendronizados", torna-os particularmente úteis para pesquisa na área biomédica, na qual funcionalidade e pureza são de grande importância. A abordagem de espectrometria de massas MALDI-ToF descrita aqui representa uma técnica valiosa para o monitoramento detalhado destas reações de "dendronização", bem como diversas modificações de outros polímeros e grupos.