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PubMed2003

Influence of micelle solubilization by tocopheryl polyethylene glycol succinate (TPGS) on solubility enhancement and percutaneous penetration of estradiol.

The effect of micellar solubilization on the enhancement of the solubility and percutaneous penetration of estradiol by the surface-active agent, tocopheryl polyethylene glycol succinate (TPGS) was characterized in this study. Results show that the solubility of estradiol was improved in the presence of TPGS through micellar solubilization. The critical micelle concentration (CMC) of TPGS increased with increasing ethanol concentration in the medium. With the flux corrected to the saturated level (J(corrected)) of the free form of estradiol, an increase in the alcohol content of the medium resulted in an increase in J(corrected) for all levels of TPGS examined. For the same level of alcohol content, an increase in the TPGS concentration mostly led to a small extent of decrease in J(corrected). However, the extent of decrease was more obvious in media containing more than 60% alcohol. We also confirmed that only an insignificant amount of TPGS was transported across the skin (below the detection limit of 2 microg/ml). Permeabilities (P(eff)), which describe the overall effects (DK/H) on the stratum corneum (SC), decreased with increasing TPGS concentration for media containing 0, 40, 60, and 80% alcohol, whereas they increased then decreased with increasing TPGS concentration for media containing 10 and 20% alcohol. The enhancement ratios based on P(eff) assuming that the medium contained 0% TPGS and alcohol as unity did not increase accordingly with increases in TPGS concentration at the same level as alcohol. Likewise, the enhancement ratios for the same level of TPGS increased with low alcohol content, but then decreased with increasing alcohol content. We concluded that micellar solubilization by TPGS was able to improve the solubility of estradiol, but it only had an insignificant influence on the skin. Interfacial coverage of TPGS with increasing TPGS concentration and hindrance of the partitioning of estradiol by the increasing alcohol content might play a role in influencing the permeability of estradiol.

Administration, Cutaneous↗
PubMed1988

Equilibrium and dynamic bilayer structural properties of unsaturated acyl chain phosphatidylcholine-cholesterol-rhodopsin recombinant vesicles and rod outer segment disk membranes as determined from higher order analysis of fluorescence anisotropy decay.

Limited-frequency phase-modulation fluorometry of diphenylhexatriene (DPH) and trimethylammonium-diphenylhexatriene (TMA-DPH) was used to characterize the equilibrium and dynamic lipid structural properties of (1) reconstituted egg phosphatidylcholine (egg PC)-rhodopsin vesicles varying in rhodopsin content from 0 to approximately 1 mol %, (2) reconstituted PC-cholesterol-rhodopsin vesicles containing approximately 1 mol % rhodopsin and 0, approximately 15, or approximately 30 mol % cholesterol with egg PC, DOPC (di-18:1-PC), or PAPC (16:0,20:4-PC) as the phospholipid constituent, and (3) native bovine rod outer segment disk membranes. Experiments were conducted at 37, 25, 15, and 5 degrees C. Fluorescence lifetime analysis was performed by fitting the data to a constrained, discrete, biexponential model. Rotational depolarization properties were considered by a model requiring a single rotational diffusion coefficient and capable of producing orthogonal, bimodal orientational distributions for DPH and unimodal distributions for TMA-DPH [Straume, M., & Litman, B. J. (1987) Biochemistry 26, 5113-5120]. Unbleached rhodopsin reduced mean fluorophore lifetimes in proportion to the amount of protein present in PC vesicles as a result of probe-to-retinal energy transfer by (1) redistributing the relative lifetime contributions in favor of the short lifetime population and (2) reducing the lifetimes of each derived population. Lifetimes were increased by cholesterol and by reduction of the temperature, but the relative proportions of derived short- and long-lifetime populations were not affected. TMA-DPH lifetimes were more sensitive (in a relative manner) than were those of DPH. These observations are interpreted in terms of cholesterol and reduced temperature each inhibiting water penetrability into these bilayers, with a greater effect occurring in the headgroup and interfacial regions (probed by TMA-DPH) than in the hydrophobic bilayer interior (probed by DPH). Diunsaturated DOPC-rhodopsin recombinants were more resistant to temperature-dependent lifetime changes than were mixed-chain egg PC or PAPC vesicles. This suggests less favorable interaction of rhodopsin with diunsaturated PCs than with mixed-chain PCs. Lifetimes in disk membranes exhibited this same temperature dependence although DPH in disks had lifetimes longer than those seen in recombinant vesicles. TMA-DPH lifetimes in disks were more similar to those observed in cholesterol-containing recombinants. It would therefore appear that the large proportion of small, charged (at pH 7) phosphatidylethanolamine and phosphatidylserine headgroups present in disks reduces water penetrability into the d

Animals↗
PubMed2005

Activation, inhibition, and destabilization of Thermomyces lanuginosus lipase by detergents.

Lipases catalyze the hydrolysis of triglycerides and are activated at the water-lipid interface. Thus, their interaction with amphiphiles such as detergents is relevant for an understanding of their enzymatic mechanism. In this study, we have characterized the effect of nonionic, anionic, cationic, and zwitterionic detergents on the enzymatic activity and thermal stability of Thermomyces lanuginosus lipase (TlL). For all detergents, low concentrations enhance the activity of TlL toward p-nitrophenyl butyrate by more than an order of magnitude; at higher detergent concentrations, the activity declines, leveling off close to the value measured in the absence of detergent. Surprisingly, these phenomena mainly involve monomeric detergent, as activation and inhibition occur well below the cmc for the nonionic and zwitterionic detergents. For anionic and cationic detergents, activation straddles the monomer-micelle transition. The data can be fitted to a three state interaction model, comprising free TlL in the absence of detergent, an activated complex with TlL at low detergent concentrations, and an enzyme-inhibiting complex at higher concentrations. For detergents with the same headgroup, there is an excellent correspondence between carbon chain length and ability to activate and inhibit TlL. However, the headgroup and number of chains also modulate these effects, dividing the detergents overall into three broad groups with rising activation and inhibition ability, namely, anionic and cationic detergents, nonionic and single-chain zwitterionic detergents, and double-chain zwitterionic detergents. As expected, only anionic and cationic detergents lead to a significant decrease in lipase thermal stability. Since nonionic detergents activate TlL without destabilizing the protein, activation/inhibition and destabilization must be independent processes. We conclude that lipase-detergent interactions occur at many independent levels and are governed by a combination of general and structurally specific interactions. Furthermore, activation of TlL by detergents apparently does not involve the classical interfacial activation phenomenon as monomeric detergent molecules are in most cases responsible for the observed increase in activity.

Anions↗
PubMed1991

Kinetic characterization of phospholipase A2 modified by manoalogue.

Manoalogue, a synthetic analogue of the sea sponge-derived manoalide, has been previously shown to partially inactivate the phospholipase A2 from cobra venom (Reynolds, L. J., Morgan, B. P., Hite, E. D., Mihelich, E. D., & Dennis, E. A. (1988) J. Am. Chem. Soc. 110, 5172) by reacting with enzyme lysine residues. In the present study, the inactivation of the phospholipases A2 from pig pancreas, bee venom, and cobra (Naja naja naja) venom by manoalogue was studied in detail. Manoalogue-treated enzymes were examined in the scooting mode on vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphomethanol. Here the native enzymes bound irreversibly to the vesicles and hydrolyzed all of the phospholipids in the outer monolayer without leaving the surface of the interface. All three manoalogue-treated enzymes showed reduced catalytic turnover for substrate hydrolysis in the scooting mode, and the modified enzymes did not hop from one vesicle to another. Thus, inactivation by manoalogue is not due to the decrease in the fraction of enzyme bound to the substrate interface. This result was also confirmed by fluorescence studies that directly monitored the binding of phospholipase A2 to vesicles. A chemically modified form of the pig pancreatic phospholipase A2 in which all of the lysine epsilon-amino groups have been amidinated was not inactivated by manoalogue, indicating that the modification of lysine residues and not the amino-terminus is required for the inactivation. Several studies indicated that the manoalogue-modified enzymes contain a functional active site. For example, studies that monitored the protection by ligands of the active site from attack by a alkylating agent showed that manoalogue-modified pig phospholipase A2 was capable of binding calcium, a substrate analogue, lipolysis products, and a competitive inhibitor. Furthermore, relative to native enzymes, manoalogue-modified enzymes retained significantly higher catalytic activities when acting on water-soluble substrates than when acting on vesicles in the scooting mode. Intact manoalogue had no affinity for the catalytic site on the enzyme as it did not inhibit the enzyme in the scooting mode and it did not protect the active site from alkylation. Pig pancreatic phospholipase A2 bound to micelles of 2-hexadecyl-sn-glycero-3-phosphocholine was resistant to inactivation by manoalogue, suggesting that the modification of lysine residues on the interfacial recognition surface of the enzyme was required for inactivation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Overestimating hybrid layer quality in polished adhesive/dentin interfaces.

The most popular techniques for determining the quality of the hybrid layer (HL) have relied on morphologic characterization of the polished adhesive/dentin (a/d) interfaces before and after acid-bleach chemical treatment. Using these techniques, the existence of smooth, acid-resistant layers has been consistently reported for most adhesive systems. The purpose of this study was to determine whether popular specimen preparation techniques that include polishing and acid-bleach treatment modify the a/d interface, mask the complexity of the HL, and lead to inaccurate assessment of the quality of the HL. To understand the impact of specimen preparation techniques on the morphology of the resin-dentin interface, polished and unpolished specimens from the same tooth were closely compared after different acid-bleach chemical treatment procedures. Two one-bottle adhesives, that is, 3M Single Bond and Pulpdent UNO, exhibiting distinct differences in hydrophilic/hydrophobic composition, were used in this investigation. Using specimens from the same tooth, the effect of chemical treatments on the morphology of the resin-dentin interdiffusion zone and the differences in the morphology of polished and unpolished specimens after these same treatments were studied with scanning electron microscopy. It was shown that conventional specimen preparation techniques that include polishing and acid-bleach treatment can adversely affect and even obscure the structural detail of the a/d interface in specimens that possess a porous HL. The results indicated that the Pulpdent UNO/dentin interface had better quality than the 3M Single Bond/dentin interface. The difference in the quality of HL can be attributed to factors such as compositional differences that impact the adhesive interaction with water, that is present within the substrate during wet bonding. The inability of the conventional acid-bleach procedure to reveal the differences in the scanning electron microscopy interfacial morphology was overcome in this investigation by using a multistep technique.

Acid Etching, Dental↗
PubMed2005

A mechanical interpretation of pressure chamber measurements--what does the strength of the squeeze tell us?

Argument still continues about what properties of a plant organ the pressure chamber measures. A mechanical (as opposed to a thermodynamic) analysis is made of the system squeezed by the pressurized gas, the non-gaseous part of the leaf. The boundary of the system is defined so that it remains at constant mass, and constant density is assumed, during the squeeze. This is equivalent to assuming constant volume. On those assumptions, it is shown that the liquid is brought to the cut surface by a change of shape of the system. Generic mechanical principles are then used to deduce a priori, a quantitative interpretation of the balance pressure. The formal mechanical interpretation involves two variables, the interfacial tension and the change in surface area, which cannot currently be measured. Instead of these, we used two related variables which can be measured, the mass fraction of water in the leaf (Q) and the maximum mass fraction of water at full saturation (Qx) to deduce an approximate mechanical interpretation. When Q is close to Qx, we deduced that the balance pressure (Pb) required for the shape change should be approximately proportional to the reduction in mass in changing from Qx to Q, a variable called the relative water loss (RWL). The constant of proportionality (kappa) is a basic characteristic of the type of leaf used, and the final relation, Pb=kappa (RWL) is called Relation A. We then deduce that the constant kappa should be an approximately linear function of Qx. The linear function is defined by limiting values, so that when Qx is 1, kappa is predicted to be 0 bar, and at the other extreme, when Qx is 0, kappa is predicted to be in the range 500-1000 bar. This is called Relation B. Experiments with 32 leaves from 10 species are used to test the mechanical interpretation. The results showed that Relation A was a reasonable approximation for most of the tested leaves. The data for 10 species, were used to estimate Relation B, confirming that as Qx approached 1, kappa did approach 0 bar as predicted, and that as Qx approached 0, kappa approached approximately 750 bar, consistent with the a priori prediction of 500-1000 bar. The relations were also successfully tested using independent published data. An estimate of Qx is shown to be of considerable practical value in (a) converting Pb to water status and vice versa; (b) characterizing leaf morphology and composition; and (c) rationalizing quantitatively the functional classes of xerophytes, mesophytes and hygrophytes. The assumption of constant density inside the outer boundary of the non-gaseous material cannot be guaranteed, and when this is violated, our (or any other) interpretation of Pb is unreliable. Investigation of the conditions under which this assumption is invalid should be a high priority.

Biomechanical Phenomena↗
PubMed1998

Structural and morphological characterization of ultralente insulin crystals by atomic force microscopy: evidence of hydrophobically driven assembly.

Although x-ray crystal structures exist for many forms of insulin, the hormone involved in glucose metabolism and used in the treatment of diabetes, x-ray structural characterization of therapeutically important long-acting crystalline ultralente insulin forms has been elusive because of small crystal size and poor diffraction characteristics. We describe tapping-mode atomic force microscopy (TMAFM) studies, performed directly in crystallization liquor, of ultralente crystals prepared from bovine, human, and porcine insulins. Lattice images obtained from direct imaging of crystal planes are consistent with R3 space group symmetry for each insulin type, but the morphology of the human and porcine crystals observed by AFM differs substantially from that of the bovine insulin crystals. Human and porcine ultralente crystals exhibited large, molecularly flat (001) faces consisting of hexagonal arrays of close packed hexamers. In contrast, bovine ultralente crystals predominantly exhibited faces with cylindrical features assignable to close-packed stacks of insulin hexamers laying in-plane, consistent with the packing motif of the (010) and (011) planes. This behavior is attributed to a twofold increase in the hydrophobic character of the upper and lower surfaces of the donut-shaped insulin hexamer in bovine insulin compared to its human and porcine counterparts that results from minor sequence differences between these insulins. The increased hydrophobicity of these surfaces can promote hexamer-hexamer stacking in precrystalline aggregates or enhance attachment of single hexamers along the c axis at the crystal surface during crystal growth. Both events lead to enhanced growth of ¿hk0¿ planes instead of (001). The insulin hexamers on the (010) and (110) faces are exposed "edge-on" to the aqueous medium, such that solvent access to the center of the hexamer and to solvent channels is reduced compared to the (001) surface, consistent with the slower dissolution and reputed unique basal activity of bovine ultralente insulin. These observations demonstrate that subtle variations in amino acid sequence can dramatically affect the interfacial structure of crystalline proteins.

Animals↗
PubMed1996

Specific phospholipid association with apolipoprotein A-I stimulates cholesterol efflux from human fibroblasts. Studies with reconstituted sonicated lipoproteins.

To understand how the lipid composition of high density lipoprotein mediates the efflux of cellular cholesterol, we have characterized the effects of variations in the lipid composition of well defined model sonicated apolipoprotein A-I (apoA-I)-containing lipoprotein (LpA-I) particle on cholesterol efflux from cultured human skin fibroblasts. LpA-I particles with varying content of phosphatidylcholine (POPC), phosphatidylinositol, sphingomyelin, cholesterol ester, and triolein were prepared by co-sonication. Association of as little as 5 mol of phosphatidylcholine with apoA-I is sufficient to transform lipid-free apoA-I into a distinct lipoprotein-like particle that is a significantly better acceptor of cellular cholesterol. Increasing the ratio of POPC/apoA-I from 5/1 to 35.5/1 in the sonicated LpA-I is associated with a significant increase in the release of cellular cholesterol. At low POPC/apoA-I ratios, native gradient gel electrophoresis of the LpA-I shows these lipoproteins to be small complexes (around 5-6 nm), with only 1 molecule of apoA-I (Lp1A-I). At a POPC/apoA-I ratio above 11/1, LpA-I form well defined complexes that contain 2 molecules of apoA-I (Lp2A-I) and range in size from 7.6 to 7.7 nm. Inclusion of sphingomyelin into an Lp1A-I further stimulates cholesterol efflux significantly. In contrast, inclusion of either sphingomyelin or phosphatidylinositol into a sonicated Lp2A-I has no effect on cholesterol efflux. Incorporation of cholesterol ester and/or triolein into an Lp2A-I particle is associated with a small reduction in cholesterol efflux to these lipoproteins. Therefore, cholesterol efflux from human fibroblasts is directly proportional to the amount and type of phospholipid in a sonicated LpA-I particle. Changes in the conformation and charge of apoA-I that result from changes in the lipid composition of a sonicated LpA-I particle appear to directly affect the ability of the lipoprotein to bind and retain cholesterol molecules. These data therefore suggest that the adsorption/desorption of cholesterol molecules to/from a sonicated LpA-I complex may be less sensitive to interfacial lipid-lipid interactions, but may depend on a conformation-dependent ability of apoA-I to bind cholesterol.

Apolipoprotein A-I↗
PubMed1992

Peptide hormone-membrane interactions: the aggregational and conformational state of lipo-gastrin derivatives and their receptor binding affinity.

The (2RS)-1,2-dipalmitoyl-3-mercaptoglycerol/-, (2RS)-1,2-dimyristoyl-3-mercaptoglycerol/-, and (2RS)-1-myristoyl-2-palmitoyl-3-mercaptoglycerol/maleoyl-bet a-alanyl- [Nle15]-human-gastrin-(2-17) adducts were prepared as lipo-gastrin derivatives of explicitly primary amphiphilic properties. As representative of this class of lipo-gastrins, the dimyristoyl derivative has been thoroughly characterized in its aggregational state since, among the three compounds, theoretically it should exhibit the lowest degree of lipid character. It aggregates in aqueous solution to form monodispersed unilamellar spherical vesicles with dislocation of the peptide moiety at the bilayer surface in predominantly unordered structure. The liposomes are remarkably stable toward solubilization with trifluoroethanol and toward vesicle to micelle transition with neutral and negatively charged surfactants even above their critical micellar concentrations. Asymmetric fusion with the detergent micelles induces polydispersion of the liposomes in terms of shape and size without affecting in significant manner the mode of display of the gastrin portions at the bilayer surface. Only the positively charged hexadecyltrimethylammonium hydroxide provokes the collapse of the vesicles into mixed micelles with concomitant altered dislocation of the gastrin-peptide in the new aggregational state. Despite the lipid properties of the gastrin derivatives, i.e., formation of liposomes, they retain remarkable receptor affinities (IC50 = 1.5 x 10(-9) M for myristoyl-palmitoyl-gastrin, IC50 = 2.0 x 10(-9) M for di-myristoyl-gastrin and IC50 = 3.1 x 10(-9) M for di-palmitoyl-gastrin vs IC50 = 2.8 x 10(-10) M for Nle15-gastrin). Since the displacement of radiolabeled Nle15-gastrin from rat pancreatic acinar cell line membrane preparations by both the parent gastrin hormone and the three lipo-gastrins occurs in parallel manner, the data support a mechanism of receptor occupancy via accumulation of the gastrins at the membrane surface and their two-dimensional diffusion to the target receptor. Thereby the differentiated decrease of affinity in function of fatty acid chain length has to be attributed to the energetically more or less favored transfer of the monomers from the donor vesicles to the acceptor membranes. Moreover, according to this model migration of the lipo-gastrins with their interdigitating di-fatty-acyl moieties should be delayed, again in lipid structure-dependent manner, in comparison to the parent gastrin molecule, which is free to float in the membrane interfacial phase.

Amino Acid Sequence↗
PubMed1983

Quasi-elastic light-scattering studies of aqueous biliary lipid systems. Cholesterol solubilization and precipitation in model bile solutions.

We have employed quasi-elastic light-scattering methods to characterize micellar aggregates and microprecipitates formed in aqueous solutions containing sodium taurocholate (TC), egg lecithin (L), and cholesterol (Ch). Particle size and polydispersity were studied as functions of Ch mole fraction (XCh = 0-15%), L/TC molar ratio (0-1.6), temperature (5-85 degrees C), and total lipid concentration (3 and 10 g/dL in 0.15 M NaCl). For XCh values below the established solubilization limits (XChmax) [Carey, M. C., & Small, D. M. (1978) J. Clin. Invest. 61, 998], added Ch has little influence on the size of simple TC micelles (type 1 systems), on the coexistence of simple and mixed TC-L micelles (type 2 systems), or on the growth of "mixed disc" TC-L micelles (type 3 systems). For supersaturated systems (XCh/XChmax greater than 1), 10 g/dL type 1 systems (L/TC = 0) exist as metastable micellar solutions even at XCh/XChmax = 5.3. Metastability is decreased in type 2 systems (0 less than L/TC less than 0.6), and "labile" microprecipitation occurs when XCh/XChmax exceeds approximately 1.6. In 10 g/dL mixtures, the microprecipitates initially range in size from 500 to 20000 A and later coalesce to form a buoyant macroscopic precipitate phase. In 3 g/dL mixtures, the microprecipitates are smaller (200-400 A) and remain as a stable, noncoalesced microdispersion. Transmission electron microscopy of the microprecipitates formed at both concentrations indicates a globular noncrystalline structure, and lipid analysis reveals the presence of cholesterol and lecithin in a molar ratio (Ch/L) of approximately 2/1, suggesting that the microprecipitates represent a metastable cholesterol-rich liquid-crystalline phase. In supersaturated type 3 systems (0.6 less than L/TC less than 2.0), the precipitate phase is a lecithin-rich liquid-crystalline phase which likewise coalesces in a 10 g/dL system but forms stable vesicle (liposomal) structures (600-800 A radius) in 3 g/dL systems. In conjunction with these experimental data, we present a quantitative thermodynamic analysis of Ch solubilization in model bile systems from which rigorous deductions of the free energy and enthalpy change for solubilization of cholesterol monohydrate in type 1 and type 2 systems are obtained. In addition, we employ homogeneous nucleation theory to analyze the origin of the metastable/labile limit in supersaturated systems and to deduce the interfacial tension between microprecipitates and solution. On the basis of these experimental data and theoretical analyses, we offer new hypotheses on the structure and physiology of bile and the pathogenesis of Ch gallstones. In particular, it is suggested that the "stable" microprecipitates observed in 3 g/dL type 2 systems may provide a secondary vehicle (in addition to micelles) for cholesterol transport in supersaturated hepatic bile.

Bile↗
PubMed2006

Polymorph farming of acetaminophen and sulfathiazole on a chip.

PURPOSE: The aim of this paper is to understand at a given temperature (1) the role of template films, the droplet volume of a saturated sulfathiazole aqueous solution and the solvent on polymorph screening of sulfathiazole on a silicon wafer, and (2) the effect of template films on the acetaminophen crystal face at the template-crystal interface. MATERIALS AND METHODS: Template Effect: Spun cast template films of non-annealed chitosan and annealed chitosan at 140 degrees C on silicon wafers were prepared. A 0.01-cm(3) saturated sulfathiazole aqueous solution droplets were deposited on both kinds of chitosan film. Sulfathiazole crystals were produced on those films by evaporation at 25 degrees C. Volume Effect: Different droplet volumes of a saturated sulfathiazole aqueous solution ranging from 0.01 to 0.14 to 2.7 cm(3) were deposited on non-annealed chitosan films. Sulfathiazole crystals were generated on those films by evaporation at 25 degrees C. Solvent Effect: 0.01 cm(3) saturated sulfathiazole methanol solution droplets were deposited on non-annealed chitosan films and sulfathiazole crystals were formed on those films by evaporation at 25 degrees C. The formation pathways of different sulfathiazole crystal polymorphs of the above mentioned effects were analyzed and verified by systematic studies. Template-crystal Interfacial Study: Millimeter-sized acetaminophen crystals were successfully grown on non-annealed chlorosulfonated poly(ethylene) (PE-Chl) and chitosan template films by cooling the saturated acetaminophen aqueous solution from 50 to 25 degrees C in which those template films were immersed. The bonding energies for specific carbons collected by electron spectroscopy for chemical analysis (ESCA) at the acetaminophen crystal surface, together with the molecular interactions between acetaminophen and PE-Chl and between acetaminophen and chitosan in separately prepared solid dispersion film samples detected by Fourier transformed infrared (FTIR) spectroscopy, proved to be useful for identifying the crystal face of acetaminophen essential for its specific intermolecular interactions at the template-crystal interface. RESULTS: Thermodynamically metastable sulfathiazole Form I crystals were reproducibly obtained on the non-annealed chitosan films whereas the stable sulfathiazole Form III crystals were repeatedly formed on the annealed chitosan films. Droplet volumes and solvents were also found responsible for the polymorphic outcome of sulfathiazole in the kinetically driven area of two overlapping metastable zones from two competing polymorphs of Form I and Form III. Thermodynamically stable sulfathiazole Form III crystals were formed on the non-annealed chitosan films instead when the droplet volumes of a saturated sulfathiazole aqueous solution were increased from 0.01 to 0.14 cm(3) and 2.7 cm(3). When the solvent was changed from water to methanol, the thermodynamically stable sulfathiazole Form III crystals were again observed on the non-annealed chitosan films even from the 0.01 cm(3) saturated sulfathiazole methanol solution droplets. CONCLUSIONS: Template surfaces were thought to provide specific functional groups to either change the energy barrier for the nuclei formation of the thermodynamically metastable Form I or alter the droplet contact angle and the droplet surface area which was related to the droplet evaporation time. The evaporation time determines the amount of time available for the polymorphic transformation from Form I to Form III. Apparently, droplet volumes could also determine the amount of time needed to reach supersaturation and the amount of time available for a polymorphic transformation from Form I to Form III. In addition, the molecular conformation and viscosity of solvents such as methanol might alter the original nucleation kinetics in water and lead to a more rapid polymorphic transformation from Form I to Form III. Template films of PE-Chl and chitosan were found to be critical for determining the face of a millimeter-sized acetaminophen crystal at the template-crystal interface. The idea of performing polymorph screening on the template film deposited on a chip has opened up a new doorway to examine the roles of: (1) various kinds of drug carrier in the form of a template film, (2) the droplet volume of a saturated solution, and (3) the type of solvent used, in polymorphic control. Growing millimeter-sized crystals directly on the chip of template has also provided a convenient technology enabling platform for examining the crystal-template interface by solid-state characterization techniques such as ESCA.

Acetaminophen↗