Drug Permeability - Best Practices for Biopharmaceutics Classification System (BCS)-Based Biowaivers: A workshop Summary Report.

The workshop "Drug Permeability - Best Practices for Biopharmaceutics Classification System (BCS) Based Biowaivers" was held virtually on December 6, 2021, organized by the University of Maryland Center of Excellence in Regulatory Science and Innovation (M-CERSI), and the Food and Drug Administration (FDA). The workshop focused on the industrial, academic, and regulatory experiences in generating and evaluating permeability data, with the aim to further facilitate implementation of the BCS and efficient development of high-quality drug products globally. As the first international permeability workshop since the BCS based biowaivers was finalized as the ICH M9 guideline, the workshop included lectures, panel discussions, and breakout sessions. Lecture and panel discussion topics covered case studies at IND, NDA, and ANDA stages, typical deficiencies relating to permeability assessment supporting BCS biowaiver, types of evidence that are available to demonstrate high permeability, method suitability of a permeability assay, impact of excipients, importance of global acceptance of permeability methods, opportunities to expand the use of biowaivers (e.g. non-Caco-2 cell lines, totality-of-evidence approach to demonstrate high permeability) and future of permeability testing. Breakout sessions focused on 1) in vitro and in silico intestinal permeability methods; 2) potential excipient effects on permeability and; 3) use of label and literature data to designate permeability class.

Production, partial characterization, and use of a red biochrome produced by Serratia sakuensis subsp. nov strain KRED for dyeing natural fibers.

We have described a novel red biochrome, 514 Da in size, produced by solid-state cultivation of a bacterial isolate obtained from garden soil. The growth requirements of the isolate, the chemical characteristics of the biochrome produced, and the application of the biochrome in dying of silk, wool, and cotton fabrics have been studied. The biochrome obtained after 52 h of incubation and having a λ (max) of 535 nm was used for dyeing the fabrics. We found that silk, wool, and cotton fabrics dyed with this new natural red compound have high color strength values and dye uptake along with good color fastness as well as antibacterial activity.

Implications of obesity for drug therapy: limitations and challenges.

Obesity has become a worldwide challenge with significant health and socioeconomic implications. One of the major implications is its impact on drug therapy. In order to gain a better understanding of this impact, we surveyed the regulatory guidances, the newly approved molecular entity drug products, and drug product labels in the Physician's Desk Reference. This review summarizes the findings of the survey along with the existing knowledge on pharmacokinetic and pharmacodynamic changes associated with obesity.

Computer simulated screening of dentin bonding primer monomers through analysis of their chemical functions and their spatial 3D alignment.

Binding interactions between dentin bonding primer monomers and dentinal collagen were studied by an analysis of their chemical functions and their spatial 3D alignment. A trial set of 12 monomers used as primers in dentin adhesives was characterized to assess them for binding to a complementary target. HipHop utility in the Catalyst software from Accelrys was used for the study. Ten hypotheses were generated by HipHop procedures involving (a) conformational generation using a poling technique to promote conformational variation, (b) extraction of functions to remodel ligands as function-based structures, and (c) identification of common patterns of functional alignment displayed by low energy conformations. The hypotheses, designated as pharmacaphores, were also scored and ranked. Analysis of pharmacaphore models through mapping of ligands revealed important differences between ligands. Top-ranked poses from direct docking simulations using type 1 collagen target were mapped in a rigid manner to the highest ranked pharmacophore model. The visual match observed in mapping and associated fit values suggest a strong correspondence between direct and indirect docking simulations. The results elegantly demonstrate that an indirect approach used to identify pharmacaphore models from adhesive ligands without a target may be a simple and viable approach to assess their intermolecular interactions with an intended target. Inexpensive indirect/direct virtual screening of hydrophilic monomer candidates may be a practical way to assess their initial promise for dentin primer use well before additional experimental evaluation of their priming/bonding efficacy. This is also of value in the search/design of new compounds for priming dentin.

A bone-like precoating strategy for implants: collagen immobilization and mineralization on pure titanium implant surface.

Many surface modification strategies are currently of interest in improving integration of implants to bone. An in vitro precoating of a bone-like mineralized layer of immobilized collagen on the implant surface is a potentially valuable approach to improve host acceptance of the implant. The goal of this investigation was to develop a method to precoat in vitro a bone-like mineralized collagen layer on a pure titanium dental implant surface. The study was conducted on acid-etched and nonetched surfaces of screw implants. Initially, a procedure was standardized to self-assemble collagen from a collagen solution. In subsequent experiments, the implant was also placed inside the solution, and after 3 days, collagen was found to be coated on the implant surface. Mineralization of the collagen gel as well as collagen coating on the implant was carried out by calcium phosphate precipitation from a mineralizing solution of calcium chloride containing polyvinyl phosphonic acid and polyaspartic acid, which served as polyanionic additives to help disperse the precipitation and template mineral nucleation. The implant was kept in the mineralizing solution and maintained for 2 weeks in an incubator at 37 degrees C with a phosphate vapor phase generated from a vial containing dihydrogen ammonium phosphate in the incubator. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis confirmed the coated layer to be a biomimetic bone-like mineralized type 1 collagen. Initial studies using osteoblast-like cells indicated cellular attachment on the modified surface. The method appears to be a promising way to generate in vitro a bone-like layer on the implant surface.

Microleakage and Resin-to-Dentin Interface Morphology of Pre-Etching versus Self-Etching Adhesive Systems.

The purpose of this study was to compare the microleakage and tissue-adhesive interface morphology from Class V restorations using different systems of dentin adhesives. Class V cavities were prepared on buccal surfaces of 27 extracted caries-free molars and premolars. Teeth were randomly assigned to one of three groups: (1) Prime & Bond NT, a 5(th) generation system using an initial step of total etch followed by a second step of application of a self bonding primer (2) Clearfil SE Bond, a 5(th) generation adhesive system employing two separate steps of self-etch priming and subsequent bonding (3) One-up Bond F, a 6(th) generation one step self-etching, self-priming and self-bonding adhesive. Microleakage and interface morphology of teeth restored with these adhesives and a composite resin were evaluated. Kruskal-Wallis Test (p = 0.05) was used to analyze the results. SEM analysis was used to relate interface morphology to microleakage. The mean and (SD) values of microleakage were: Prime and Bond NT: 0.15 (0.33), Clearfil SE Bond: 0.06 (0.17) and One-up Bond F: 2.96 (0.63). The mean microleakage for One-up Bond was significantly higher than for the other groups (p<0.05). Protruding tags in dentin channels were observed in Prime and Bond and Clearfil systems, but not in One-up Bond. The single step adhesive system, although more convenient for the clinician, uses a low viscosity formulation difficult to keep in place on cavity walls. It also tends to be too aggressive and hydrophilic to create an impermeable hybridized tissue-adhesive interfacial layer resistant to microleakage. Two-step adhesive systems, on the other hand, were retained on all segments of the cavosurface during application, and formed a hybridized interfacial layer resistant to microleakage.

Computational analysis of adhesion of primer ligands to dentinal collagen: effect of spacer groups in ligand and amino Acid residue sequence differences in collagen.

This study sought to assess by computer modeling the interactions between dentinal collagen and primer monomer ligands used to promote bonding of restorations to tooth. Modeling was carried out both by direct and indirect methods to probe interaction mechanisms. Ligands studied in this investigation conformed chemically to methacrylate phosphates of alkane diol, with changes in the number of methylene spacer groups. Increase in number of methylene groups in the series introduces increasing levels of ligand conformational freedom. An automatic docking program was used to analyze the effect of these changes on primer-collagen interactions in direct (target-based) modeling. The effect of limited modifications of amino acid residue sequences in structural variants of type 1 dentinal collagen was also assessed in this approach. The indirect (ligand-based) modeling used a pharmacaphore search to mimic primer binding to type 1 collagen using a common functional alignment algorithm. Docking energy, and the non-bonded and electrostatic contributions to it, showed statistically highly significant differences (p<0.0001) with ligand conformational freedom. But the effect of collagen composition differences was, although statistically significant (p<0.05), relatively small. Both target-based direct docking and ligand-based indirect modeling visualizations showed that conformations tended to align in a 3-D geometric pattern in bound states, and that the conformational flexibility of the ligands played a critical role in alignment. The results suggest that incorporation of spacer groups in primer monomers may modify dentin bonding to improve overall adhesion under optimum conditions.

Flexural creep deformation and recovery in dental composites.

OBJECTIVES: Three different popular composite resin systems for dental restorative applications are microfilled, minifilled and midifilled types in which deformation under stress and recovery after stress removal may be strongly influenced by filler parameters and resin formulation. The purpose of this in vitro study was to evaluate these differences in selected composite resins. MATERIALS: Three composites, Clearfil (midifill), Charisma (minifill) and Durafill (microfill), were evaluated. Elastic, viscoelastic and viscous deformation of the composites under a constant stress and the subsequent recovery on removal of stress were measured. Dynamical mechanical properties of these materials were also characterized. RESULTS: The mean values (and SD) of elastic, viscoelastic and viscous components of overall deformation (mm), respectively, under a constant stress of 45(5)KPa were as follows: Clearfil, 0.17(0.03), 0.06(0.02), 0.03(0.05); Charisma, 0.34(0.1), 0.09(0.04), 0.14(0.03); Durafill, 0.68(0.06), 0.14(0.03), 0.23(0.03) The results show that there are significant differences (P<0.0001) between the different composite resins in the elastic, viscoelastic and viscous segments of deformation. The microfilled system deformed significantly more than the minifilled, and the minifilled system more than the midifilled. Storage modulus values evaluated by dynamic mechanical analysis were also significantly different (P<0.0001). The observed differences were readily explained by the differences in the type and volume fraction of the filler content in the composites. CONCLUSIONS: Differences in time dependent deformation and recovery as well as dynamic mechanical properties of dental composites were strongly influenced by filler parameter differences. The clinical performance of restorations may be strongly influenced by the observed differences.

Transport and metabolism of the tea flavonoid (-)-epicatechin by the human intestinal cell line Caco-2.

PURPOSE: Tea flavonoids, including (-)-epicatechin (EC), have been suggested to have chemopreventive properties in cancer. However, there is limited knowledge of the oral bioavailability of these dietary compounds. The purpose of this study was to gain a better understanding of the absorption of EC. METHODS: The intestinal epithelial membrane transport of EC was examined using the monolayer of the human Caco-2 cell line grown in Transwells, a common model of intestinal absorption. EC and its metabolites were measured by high performance liquid chromatography with diode array detection. RESULTS: EC showed no apical to basolateral absorption at concentrations ranging from 5 to 50 microM. In contrast, EC demonstrated basolateral to apical efflux with a Papp value of 0.67 +/- 0.05 x l0(-6) cm/sec, i.e., slightly higher than for mannitol, 0.50 +/- 0.30 x 10(-6) cm/ sec, a paracellular transport marker. There was a 50% reduction in the efflux of EC in the presence of 50 microM MK-571, a competitive inhibitor of the MRP2 transporter expressed in the apical membrane of Caco-2 cells. Most important. the presence of 50 microM MK-571 resulted in clearly measurable apical to basolateral absorption of EC with a Papp of 0.31 +/- 0.06 x 10(-6) cm/sec. Two polar metabolites, M1 and M2, were formed from EC, both of which appeared exclusively on the apical side. MK-571 (50 microM) dramatically inhibited the transport for both of these metabolites. Incubations with inorganic 35SO4(2-) and hydrolysis by aryl sulfatase strongly suggested that these metabolites were sulfate conjugates. CONCLUSIONS: These results suggest an important role for the multispecific organic anion transporter MRP2 in the bioavailability of EC and possibly other tea flavonoids.

Microleakage of compomer class V restorations: effect of load cycling, thermal cycling, and cavity shape differences.

STATEMENT OF PROBLEM: Microleakage is an important problem with direct filling restorations and an understanding of the factors that contribute to it is of critical importance. PURPOSE: This study investigated the effect of thermal and occlusal load cycling, and limited cavity preparation on microleakage of compomer Class V restorations in vitro. MATERIAL AND METHODS: Class V cavities were randomly prepared on the buccal and lingual surfaces of 32 recently extracted molars and premolars and restored with Dyract compomer restorative system as per the manufacturer's directions. Teeth were randomly assigned to 1 of 4 treatment groups with 8 teeth in each group: (I) thermocycling only; (II) load cycling only; (III) both thermocycling and load cycling; and (IV) no treatment. All teeth were then immersed in 2% basic fuchsin solution for 24 hours. Dye penetration was measured linearly using color photographic prints. ANOVA, comparisons between means, and correlation were used to analyze the results. RESULTS: Thermocycling and cavity preparation had a significant effect on microleakage, but load cycling did not. Occlusal margins leaked more than the gingival margins. CONCLUSION: Class V restorations demonstrated increased microleakage under the conditions of thermal cycling and nonretentive cavity design. More microleakage occurred at occlusal margins than at gingival margins. The effect of load cycling is complicated by considerations of the types of stresses applied and the restorative material response to such stresses.

Measurement of submucosal forces transmitted to dental implants.

Early loading of dental implants after placement is believed to be a major cause for premature implant failure. If a transitional denture or partial denture is used during the healing period, occlusal forces may be transmitted to the submerged implant, leading to poorly differentiated growth of bone cells and/or potential inhibition of osseointegration at the bone-implant interface. The objective of this study was to develop an experimental model to measure the force transmission and to characterize the effect of selected loading conditions and relief methods on the forces transmitted to the implant. The loading conditions studied included unilateral and bilateral loading of the prosthesis. Forces were measured at two different relief conditions (relief with and without soft liner) and were compared against a control with no relief. The results show that fabrication of the prosthesis with a proper relief at the implant-denture junction can eliminate the submucosal force transmission to the implant on loading the denture both under unilateral and bilateral loading conditions. When a soft liner is used at the relief site, the transmitted force is small, but a finite value is reproducibly recorded. With no relief, the submucosal force transmission is high and may adversely affect the healing process or osseointegration. The experimental model is valuable in measuring and understanding the submucosal forces that are transmitted to the implant by loading the transitional prosthesis, and such measurement may assist in the proper design of the prosthesis for improved clinical durability and for other uses.

Color stability of dental composites as a function of shade.

STATEMENT OF PROBLEM: The selection of shade of composites for restorative applications may have a significant effect on color degradation through environmental exposure. PURPOSE: This study characterized the color changes in composites as a function of shade through environmental effects such as ultraviolet light exposure. MATERIAL AND METHODS: Five shades of two composites were subjected to ultraviolet light exposure at 37 degrees C for 24 hours after initial storage for 24 hours in distilled water at 37 degrees C. The lightness and chromaticity values of color were measured both before and after ultraviolet light exposure with a Minolta Chromameter. The total color change as well as changes in the lightness and chromaticity values were measured in the CIE L*a*b* scale and analyzed to monitor color degradation, if any. RESULTS: Color degradation was a significant function of shade and occurred primarily as an increase in yellowness. Color changes increased with the lightness of the shade in both composite systems. CONCLUSION: The lighter shades of composites were likely to be subject to higher color degradation through environmental effects of ultraviolet light exposure.

Development and evaluation of a new 3-D digitization and computer graphic system to study the anatomic tissue and restoration surfaces.

It is necessary to visualize and reconstruct tissue anatomic surfaces accurately for a variety of oral rehabilitation applications such as surface wear characterization and automated fabrication of dental restorations, accuracy of reproduction of impression and die materials, etc. In this investigation, a 3-D digitization and computer-graphic system was developed for surface characterization. The hardware consists of a profiler assembly for digitization in an MTS biomechanical test system with an artificial mouth, an IBM PS/2 computer model 70 for data processing and a Hewlett-Packard laser printer for hardcopy outputs. The software used includes a commercially available Surfer 3-D graphics package, a public domain data-fitting alignment software and an inhouse Pascal program for intercommunication plus some other limited tasks. Surfaces were digitized before and after rotation by angular displacement, the digital data were interpolated by Surfer to provide a data grid and the surfaces were computer graphically reconstructed: Misaligned surfaces were aligned by the data-fitting alignment software under different choices of parameters. The effect of different interpolation parameters (e.g. grid size, method of interpolation) and extent of rotation on the alignment accuracy was determined. The results indicate that improved alignment accuracy results from optimization of interpolation parameters and minimization of the initial misorientation between the digitized surfaces. The method provides important advantages for surface reconstruction and visualization, such as overlay of sequentially generated surfaces and accurate alignment of pairs of surfaces with small misalignment.

Thermoanalytical characterization of visible light cure dental composites.

Selected commercial and experimental composites and resin systems have been evaluated by thermal analysis techniques of Differential Scanning Calorimetry, Thermogravimetric Analysis and Thermomechanical Analysis. Important thermal data such as heat of cure, coefficient of thermal expansion, dimensional changes over selected temperature ranges, filler weight percent, onset temperature of decomposition, etc. have been determined. Heat of cure, thermal expansion coefficient and dimensional changes appear to follow an inverse linear regression fit with filler fraction in the composite. Thermal expansion changes and exothermic reactions with temperature indicate secondary cure during postcure heating. The thermally-induced decomposition occurs in multiple stages indicating presence of different structural species in the resin matrix.

Tarnish of dental alloys by oral microorganisms.

Five dental alloys, on exposure to blood and chocolate media with and without inoculated microorganisms, showed varying degrees of tarnish. The results indicated a composition-dependent tarnish behavior of alloys in microorganism-inoculated media, indicating a potential role for the oral microorganisms in inducing clinically observed tarnish of dental alloys. Actinomyces viscosus and periodontal pocket specimens show a similarity in their activity to induce tarnish in base metal-containing dental alloys.

Direct post and core pattern made with light-curing composite resin.

An unfilled Bis-GMA composite resin can be used advantageously for making an accurate cast post and core pattern. The technique is faster and easier than normal pattern fabrication methods using an unfilled acrylic resin, wax, or a combination of the two.

Computer-controlled differential scanning calorimetry of dental composites.

In this paper, computer-controlled differential scanning calorimetry has been used to evaluate the heat liberated and the temperature rise associated with the light cure of selected dental composites. In addition, the effect of postcure heating and increased ambient temperature of light cure are examined in terms of potential secondary cure. The results indicate significant differences between the mean heats of cure of different composites, primarily reflecting the filler fraction variations of the composites. In addition, increased cure activity appears to result from both postcure heating as well as thermal activation due to higher ambient temperature of light cure. The results are analyzed and attributed to variations in resin phase composition and resin content per unit weight of composite as well as thermally induced enhancement of cure.

Interactive effects of etching and pre-oxidation on porcelain adherence to non-precious alloys: a guided planar shear test study.

Interactive effects of etching and pre-oxidation on porcelain adherence to non-precious alloys were studied by a guided planar shear bond test under non-cantilever conditions. The results indicated that electrolytic etching decreases bond strength, but that oxidation of etched surfaces restores the bond strength level. The results are explained by a hypothesis that depletion of critical elemental species occurs during etching. Potential replenishment of the lost elements during subsequent oxidation, although not confirmed, may assist in improving bond strength.

Evaluation of the ability of glass-ionomer cement to bond to glass-ionomer cement.

This study investigated the cohesive bond strengths of glass-ionomer cement at three setting and etching intervals and compared these bonds to the shear strength of the material itself. Bonded cylinders were created and then sheared using the Instron Universal Testing Machine. Analysis of bond values of glass ionomer added to glass ionomer indicate bond variability and low cohesive bond strength of the material. Bond values of unbonded glass-ionomer material indicate that the material itself is stronger than bonds established between bonded samples.

Demineralization and ion binding action of polycarboxylate cement liquid on human dental enamel.

The demineralization and ion binding effects on dental tissues due to poly(acrylic) acid attack under different dilution conditions of the latter are studied by scanning electron microscope (SEM) and infrared (IR) spectroscopy. The results indicate that in addition to the general demineralization effects such as preferential prism core attack, prism periphery attack, and protruding prism rods, competing ion binding effects also occur. Using optimum dilution conditions, the microstructural effects of demineralization and ion binding are shown and the effects are related to IR spectral observations.