Presence Of Hydroxypropyl Methylcellulose Research Articles

Designing self-nanoemulsifying delivery systems to enhance bioaccessibility of hydrophobic bioactives (nobiletin): Influence of hydroxypropyl methylcellulose and thermal processing

Emulsion-based delivery systems are widely utilized for encapsulation of hydrophobic bioactive compounds. However, they must be carefully designed to retain and stabilize the encapsulated components during storage, and to release them after ingestion. In the present work, the influence of hydroxypropyl methylcellulose (HPMC) addition and heat treatment on the retention and release of a model hydrophobic nutraceutical (nobiletin) in nanoemulsions prepared by self-emulsification was investigated. Physical stability was assessed by measuring nobiletin retention, crystal morphology, and droplet size during storage. Further, the bioaccessibility of nobiletin was evaluated using a simulated gastrointestinal model. The results indicated that the presence of HPMC in the aqueous phase improved the retention of nobiletin in the nanoemulsions, without promoting any physical instability. The saturation concentration of nobiletin in the nanoemulsions increased from 4.5 to 6.0 mg/mL in the presence of HPMC. Heating the nanoemulsions promoted rapid droplet coalescence above a critical temperature. The combination of HPMC addition and heat treatment increased the retention time of nobiletin in nanoemulsions. Neither HPMC addition nor heat treatment affected the bioaccessibility (around 85%) of nobiletin when it was fully dissolved in the nanoemulsions. However, when nobiletin was not fully dissolved in the nanoemulsions, HPMC addition (from 52 to 59% without heat treatment) and heat treatment (from 52% to 82% without HPMC and from 59% to 84% with HPMC) increased the bioaccessibility. These findings are useful for the rational design and fabrication of nanoemulsion-based delivery systems with high loading efficiency and good release characteristics.

In vitro and in vivo performance of supersaturable self-nanoemulsifying system of trans-resveratrol

To develop an optimized supersaturable self-nanoemulsifying drug delivery system (S-SNEDDS) in order to improve the oral bioavailability of trans-resveratrol (t-RVT), together with surmounting poor aqueous solubility, enterohepatic recirculation and controlling drug precipitation, by employing a precipitation inhibitor (PPI) that is, hydroxypropyl methylcellulose (HPMC). The long-term stability of a previously reported formulation optimized long chain triglycerides (OPT LCT-SNEDDS), consisting of Lauroglycol FCC and Transcutol P, indicated rapid precipitation of trans-resveratrol. Following incorporation of the selected PPI, the precipitates were differentiated using the X-ray diffraction (XRD) technique. An in vitro supersaturation test was carried out for the S-SNEDDS formulation. The S-SNEDDS formulation was appraised for pharmacokinetic and in situ perfusion studies. In vitro dilution of the S-SNEDDS formulation resulted in the formation of a nanoemulsion, followed by a slow precipitation of t-RVT in the S-SNEDDS formulation vis-à-vis SNEDDS formulated with OPT-LCT, where it undergoes rapid precipitation, yielding a low t-RVT concentration. The pharmacokinetic study indicated that the AUC0-8h of the S-SNEDDS formulation increased by nearly 1.33-fold in the presence of HPMC vis-à-vis the OPT LCT-SNEDDS, at a drug dose of 20 mg/kg. The in situ perfusion parameters, viz., fraction absorbed and effective permeability, demonstrated significant improvement in the rate and extent of absorption from the S-SNEDDS formulation. This case demonstrates that the supersaturatable approach is effective in delivering and in improving the oral bioavailability of t-RVT.

Caffeic acid loading wound dressing: physicochemical and biological characterization.

Caffeic acid has been described as active against bacteria commonly isolated from wound infections. However, its low stability and poor solubility reduce caffeic acid applicability as a pharmaceutical product. These parameters can be enhanced by complexation with cyclodextrin. The main goal of the present work was to incorporate caffeic acid on cyclodextrin-based hydrogels capable of controlled delivery, in order to be used as antibacterial wound dressing. Cyclodextrin-based hydrogels were prepared by direct crosslinking of β-cyclodextrin or hydroxypropyl-β-cyclodextrin with 1,4-butanediol diglycidyl ether in the presence of hydroxypropyl methylcellulose. The hydrogels obtained combine good physicochemical properties (viscoelasticity, superabsorbency and high ability to retain and deliver caffeic acid) with the preservation of caffeic acid' antibacterial activity and effect on fibroblasts, with gel-β-cyclodextrin the most suited. The hydrogels obtained could be useful as caffeic acid delivery-system devices for the treatment of wound infections.

HPMC layered tablets modified with chitosan and xanthan as matrices for controlled‐release fertilizers

ABSTRACTPolymeric matrices based on hydroxypropyl methylcellulose (HPMC) with xanthan (X) or chitosan (Q) and using KNO3 as a model fertilizer were prepared as three‐layered tablets and assayed as controlled release fertilizers (CRFs). The dynamic swelling behavior was analyzed in order to interpret the water uptake mechanism, which in general proved to be non‐Fickian. The presence of HPMC allows a substantially constant rate of fertilizer release. The release mechanism of KNO3 was analyzed and can be described as non‐Fickian diffusion, with release exponents ranging from 0.85 to 1.01, suggesting polymer relaxation as the major process controlling fertilizer release. Durability in soil indicates the blend Q‐HPMC as the more long‐lasting matrix of those tested, remaining at least 34 weeks. Both blends improve HPMC properties for agronomical applications, with X‐HPMC increasing the swelling rate and Q‐HPMC extending the permanence in the soil. Therefore, layered X‐HPMC and Q‐HPMC matrices can be proposed as suitable materials for the development of CRFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40839.

Microwave-assisted synthesis of anisotropic gold nanocrystals in polymer matrix and their catalytic activities

We report a facile and fast one-pot microwave (MW) synthesis of gold nanotriangle, nanobranches and nanorod. Gold salt is reduced to gold nanoparticles by ethylene glycol/polyethylene glycol in the presence of hydroxypropyl methyl cellulose. Morphology of the nanocrystals can be tailored by varying the amount of capping agents, reducing agent and the MW irradiation time. Synthesised nanoparticles are characterised by ultraviolet–visible (UV–Vis), transmission electron microscopic and X-ray diffraction spectroscopy study. The key requirement for producing the gold triangle and gold nanorod of higher aspect ratio is the adequate MW heating time. The photocatalytic activity of gold nanocrystals is investigated by monitoring the photochemical reduction of 2,4,6-trinitrophenol (TNP) in the presence of excess NaBH4. The reaction is first order with respect to the concentration of TNP. It has been observed that the catalytic efficiency of rod-like gold nanocrystals is higher than the other gold nanocrystals.

Effects of particle size, food, and capsule shell composition on the oral bioavailability of dabrafenib, a BRAF inhibitor, in patients with BRAF mutation-positive tumors

Dabrafenib is a small-molecule inhibitor of BRAF kinase activity that is currently being developed for the treatment of BRAF V600 mutation-positive melanoma. This clinical, open-label, two-cohort (n = 14 per cohort), randomized study was designed to evaluate the effect of drug substance particle size, and food on the plasma pharmacokinetics of a single oral dose of dabrafenib in patients with BRAF V600 mutation-positive solid tumors. In addition, an exploratory cross-cohort comparison of the relative bioavailability of single-dose dabrafenib administered in gelatin and hydroxypropyl methylcellulose (HPMC) capsules was performed. Higher bioavailability was noted with nonmicronized drug substance (larger particle size), under fasting conditions, and with HPMC capsules. Initial dissolution results at pH 1.2 showed higher dissolution of gelatin relative to HPMC capsules inconsistent with clinical data. Subsequent in vitro dissolution studies were conducted in fasted-state simulated gastric fluid over a 24-h period and showed that HPMC capsules reached a higher percentage of dabrafenib dissolved than gelatin capsules. The presence of HPMC is believed to inhibit precipitation of dabrafenib as the freebase, thereby maintaining a supersaturated solution over an extended period of time. Dabrafenib has been administered in pivotal clinical studies on an empty stomach using micronized drug substance in HPMC capsules. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:3100–3109, 2013

Inhibition of Crystal Nucleation and Growth by Water-Soluble Polymers and its Impact on the Supersaturation Profiles of Amorphous Drugs

The impact of water-soluble polymers on drug supersaturation behavior was investigated to elucidate the role of water-soluble polymers in enhancing the supersaturation levels of amorphous pharmaceuticals. Hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP), and Eudragit L-100 (Eudragit) were used as representative polymers, and griseofulvin and danazol were used as model drugs. Supersaturation profiles of amorphous drugs were measured in biorelevant dissolution tests. Crystal growth rate was measured from the decrease in dissolved drug concentration in the presence of seed crystals. Nucleation kinetics was evaluated by measuring the induction time for nucleation. All experiments were performed in the presence and absence of polymers. The degree of supersaturation of the amorphous model drugs increased with an increase in the inhibitory efficiency of polymers against crystal nucleation and growth (HPMC > PVP > Eudragit). In the presence of HPMC, the addition of seed crystals diminished the supersaturation ratio dramatically for griseofulvin and moderately for danazol. The results demonstrated that the polymers contributed to drug supersaturation by inhibiting both nucleation and growth. The effect of the polymers was drug dependent. The detailed characterization of polymers would allow selection of appropriate crystallization inhibitors and a planned quality control strategy for the development of supersaturable formulations.

Competitive adsorption behavior of β-lactoglobulin, α-lactalbumin, bovin serum albumin in presence of hydroxypropylmethylcellulose. Influence of pH

The interfacial properties at the air–water (A/W) of each individual whey proteins (β-lactoglobulin, β-lg; α-lactalbumin, α-la; bovin serum albumin, BSA), and their mixtures with a surface-active polysaccharide, hydroxypropylmethylcellulose (HPMC) were studied at pH 3 or 6. The interfacial films were studied by measurement surface pressure (π) isotherms and dynamics of adsorption. At equilibrium proteins surface activity was affected by pH only at low concentrations (below 1·10−2 % wt/wt), due to their pH-dependent conformational changes. HPMC resulted less surface active at pH 3 (below 1·10−4 % wt/wt concentration) that at pH 6. On kinetic studies (π–t), the behavior of β-lg, HPMC and BSA did not change with pH but α-la presented a higher surface activity at pH 3 than 6, even on saturating bulk concentrations. Mixtures of β-lg or BSA with HPMC showed a behavior in between that of single components revealing a net competence for the interface but the mixture α-la and HPMC at pH 6 showed an enhance adsorption. Rheological studies (surface dilatational elastic, Ed, over time) presented the major differences for pHs evaluated. The α-la formed extremely viscoelastic films at pH 6.0, while at pH 3 has the lowest Ed value. β-lg and HPMC films were more viscoelastic at pH 6, being Ed protein film higher. Finally, BSA presented the lowest viscoelastic films without differences between both pHs. For mixtures: i) at pH 6 β-lg/HPMC mixture Ed was dominated by HPMC; at pH 3.0, Ed begins dominated by HPMC, reaching an intermediate value; ii) α-la/HPMC mixture formed more viscoelastic films at pH 6.0 with an intermediate Ed value, while at pH 3.0 the Ed is dominated by protein; iii) BSA/HPMC mixture presented a similar trend in Ed behavior at both pHs.

Synthesis of HPMC stabilized nickel nanoparticles and investigation of their magnetic and catalytic properties

Nickel nanoparticles synthesized from NiCl2·6H2O by hydrazine hydrate in mixed solvent of ethanol and water in the presence of hydroxypropylmethylcellulose (HPMC) as protective and stabilizing agents. The morphology and sizes of synthesized Ni nanoparticles were studied by field-emission-scanning-electron microscopy (FESEM). Structural properties of nanoparticles were examined by X-ray diffraction (XRD). The polymer stabilized Ni nanoparticles were characterized by Fourier-transform infrared (FTIR) spectroscopy. The magnetic measurement showed that the resultant Ni nanoparticles were ferromagnetic. Also, the saturation magnetization (MS), remanent magnetization (MR) and coercivity (MR) were observed to increase with decreasing temperature. The results of magnetic characterization showed that the magnetic properties of the HPMC stabilized Ni nanoparticles are quite different from those of the bared Ni nanoparticles. All the observed magnetic properties essentially reflected the very typical nanoparticle type nature. Consequently, the resulting Ni nanoparticles were found to be highly active and recyclable catalyst for Suzuki coupling reactions.

Modulated dissolution rate from the inclusion complex of antichagasic benznidazole and cyclodextrin using hydrophilic polymer

Benznidazole (BNZ) is the primary chemotherapeutic agent for treating Chagas’ disease; however, its poor water solubility and irregular oral absorption lead to the treatment failure in the chronic phase. The aim of this work was to investigate the utility of the polymer hydroxypropyl methylcellulose (HPMC) in controlling the release of BNZ from solid inclusion complexes with cyclodextrin to overcome the problem of its bioavailability. Preliminary studies of solubility were conducted in solution using selected β-cyclodextrin derivatives according to an experimental mixture design. The best cyclodextrin composition was used to produce solid-state systems by kneading in the presence or absence of HPMC. The formulations were characterized by different physico-chemical techniques, including the dissolution rate. Hydroxypropyl-β-cyclodextrin (HPβCD) produced the greatest improvement in drug solubility and was selected for the development of solid systems. Assays confirmed the production of true inclusion complexes between BNZ and HPβCD. The dissolution rate of the BNZ-HPβCD system was markedly increased, while the presence of HPMC retarded drug release. An optimal formulation obtained by the combination of kneading systems developed in appropriate ratios could be a promising drug delivery system with a prolonged therapeutic effect coupled with more balanced bioavailability. The produced systems present interesting perspectives for Chagas’ therapy.

Enhanced oral bioavailability of silybin by a supersaturatable self-emulsifying drug delivery system (S-SEDDS)

A high payload supersaturatable self-emulsifying drug delivery system (S-SEDDS) was explored to improve the oral bioavailability of silybin, a poorly water-soluble drug candidate, employing hydroxypropyl methylcellulose (HPMC) as a precipitation inhibitor. The S-SEDDS formulation consisted of silybin, Labrafac CC, Cremophor RH40, Labrasol, and 5% HPMC. The pseudo-ternary phase diagrams were constructed to identify the self-emulsifying regions. The droplet size characterization study demonstrated that the mean droplet size of the optimized S-SEDDS formulation was smaller than the conventional SEDDS formulation upon dilution with 0.1M HCl, largely because of the presence of the HPMC. In vitro dilution of the S-SEDDS formulation resulted in formation of a microemulsion, followed by a slow precipitation of silybin, while the conventional SEDDS formulation undergoes rapid precipitation, yielding a low silybin solution concentration. The results showed that the presence of HPMC effectively sustained the supersaturated state by retarding the precipitation kinetics. The in vivo study indicated that the area under the concentration–time curve (AUC0→12h) of the silybin-S-SEDDS increased by nearly 3-fold more than those of the conventional SEDDS without the presence of HPMC at a drug dose of 533mg/kg. This case demonstrates that supersaturatable formulations are an effective delivery approach to improve the oral bioavailability of poorly soluble drugs.

Solution-phase synthesis of silver nanodiscs in HPMC-matrix and simulation of UV–vis extinction spectra using DDA based method

Present investigation demonstrates a very simple seed-mediated route, using hydroxypropyl methyl cellulose (HPMC) as stabilizing agent, for the synthesis of silver nanodiscs in aqueous solution. Central to the concept of seed-mediated growth of nanoparticles is that small nanoparticle seeds serve as nucleation centres to grow nanoparticles to a desired size and shape. It is found that the additional citrate ions in the growth solution play the pivotal role in controlling the size of silver nanodiscs. Similar to the polymers in the solution, citrate ions could be likewise dynamically adsorbed on the growing silver nanoparticles and promote the two-dimensional (2D) growth of nanoparticles. Morphological, structural, and spectral changes associated with the seed-mediated growth of the nanoparticles in the presence of HPMC are characterized using UV–vis and TEM spectroscopic studies. Metal nanoparticles have received increasing attention for their peculiar capability to control local surface plasmon resonance (LSPR) when interacting with incident light waves. Extensive simulation study of the UV–vis extinction spectra of our synthesized silver nanodiscs has been carried out using discrete dipole approximation (DDA) methodology.

Differences in crystallization rate of nitrendipine enantiomers in amorphous solid dispersions with HPMC and HPMCP

To clarify the contribution of drug–polymer interaction to the physical stability of amorphous solid dispersions, we studied the crystallization rates of nitrendipine (NTR) enantiomers with identical physicochemical properties in the presence of hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP) and polyvinylpyrrolidone (PVP). The overall crystallization rate at 60 °C and the nucleation rate at 50–70 °C of (+)-NTR were lower than those of (−)-NTR in the presence of 10–20% HPMC or HPMCP. In contrast, similar crystallization profiles were observed for the NTR enantiomers in solid dispersions containing PVP. The similar glass transition temperatures for solid dispersions of (−)-NTR and (+)-NTR suggested that the molecular mobility of the amorphous matrix did not differ between the enantiomers. These results indicate that the interaction between the NTR enantiomers and HPMC or HPMCP is stereoselective, and that differences in the stereoselective interaction create differences in physical stability between (−)-NTR and (+)-NTR at 50–70 °C. However, no difference in physical stability between the enantiomers was obvious at 40 °C. Loss of the difference in physical stability between the NTR enantiomers suggests that the stereoselective interaction between NTR and the polymers may not contribute significantly to the physical stabilization of amorphous NTR at 40 °C.

DDA-Based Simulation of UV–vis Extinction Spectra of Ag Nanorods Synthesized Through Seed-Mediated Growth Process

Present investigation demonstrates a very simple seed-mediated route for the synthesis of silver nanorods in aqueous solution. Central to the concept of seed-mediated growth of nanoparticles is that small nanoparticle seeds serve as nucleation centres to grow nanoparticles to a desired size and shape. Hydroxypropyl methyl cellulose (HPMC) has been used as soft template for one-dimensional growth of silver particles. Morphological, structural and spectral changes that are associated with the seed-mediated growth of the nanoparticles in presence of HPMC are characterized using UV–vis and HR-TEM spectroscopic study. Simulation of UV–vis extinction spectra of our synthesized silver nanorods has been carried out using discrete dipole approximation methodology. The broad red-shifted longitudinal extinction band of green-coloured silver sol has been explained, due to the presence of silver nanorods of different aspect ratios.

Analysis of nucleation kinetics of poorly water-soluble drugs in presence of ultrasound and hydroxypropyl methyl cellulose during antisolvent precipitation

In this paper, nucleation kinetics of four poorly water-soluble drugs namely, itraconazole (ITZ), griseofulvin (GF), ibuprofen (IBP) and sulfamethoxazole (SFMZ) when precipitated by liquid antisolvent precipitation using water as antisolvent is examined in order to identify thermodynamic and kinetic process parameters as well as material properties that affect nucleation rate and hence, the particle size. The nucleation rates have been estimated for precipitation with and without ultrasound and hydroxypropyl methyl cellulose (HPMC). It is found that the nucleation rates increase significantly in presence of ultrasound and HPMC. Analysis of nucleation kinetics indicates that an increase in diffusivity due to ultrasound and a decrease in solid–liquid interfacial surface tension due to HPMC result in higher nucleation rates. Analysis also shows that reduction in interfacial surface tension due to HPMC is higher for a drug with lowest aqueous solubility (such as ITZ) as compared to drugs with higher aqueous solubility. It is also observed that it is easy to precipitate submicron particles of a drug with lowest aqueous solubility (such as ITZ) compared to drug molecules (such as SFMZ) with higher aqueous solubility in presence of HPMC.

Rheological and interfacial properties of Pickering emulsions prepared by fumed silica suspensions pre-adsorbed poly(N-isopropylacrylamide)

Pickering emulsions were prepared by mixing silicone oil with fumed silica suspensions pre-adsorbed poly(N-isopropylacrylamide) (PNIPAM) in the continuous water phase as a function of added amount of two PNIPAM samples. Characteristics of the resulting oil dispersed in water (O/W) Pickering emulsions were determined by the measurements of volume factions of emulsified silicone oil, adsorbed amounts of the silica suspensions pre-adsorbed PNIPAM, oil droplet size, and some rheological responses, such as hysteresis loop, stress–strain sweep curve, and dynamic viscoelastic moduli. They were compared with those of the silicone oil emulsions prepared by the fumed silica suspensions pre-adsorbed hydroxypropyl methyl cellulose (HPMC). The adsorbed amounts of the silica suspensions pre-adsorbed polymer were increased with an increase in the added amount of polymer, irrespective of the polymer. This led to (1) an increase in the volume fraction of emulsified silicone oil, (2) a decrease in the size of oil droplets, (3) an increase in the difference between the up and down curves at lower shear rates for the negative hysteresis loops, and (4) an increase in the storage moduli ( G′) for the solid-like viscoelastic responses. However, the volume fraction of the emulsified oil in the emulsified phase for the emulsions in the presence of PNIPAM increased with an increase in the adsorbed amount of the silica suspension, whereas the opposite was obtained in the presence of HPMC. This was attributed to the stronger hydrophobic interactions and they caused (1) the larger difference of the hysteresis loops and (2) the larger magnitude of G′ value for the former emulsion than those for the latter one at the higher added amounts of polymers.

Combined effect of hydroxypropyl methylcellulose and hydroxypropyl-β-cyclodextrin on physicochemical and dissolution properties of celecoxib

Investigation on the influence of hydroxypropyl methylcellulose (HPMC) on solubility and dissolution properties of celecoxib/hydroxypropyl-β-cyclodextrin system was carried out, with the ultimate goal of enhancing the drug bioavailability. 1H-NMR and 13C-NMR spectroscopy were first performed to elucidate the type of interactions between celecoxib (CEL) and hydroxypropyl-β-cyclodextrin (HP-β-CD). Then, solubility studies in the absence and in the presence of HPMC were carried out in aqueous solution. After heating in autoclave of CEL/HP-β-CD/HPMC suspensions a synergistic increasing effect on the aqueous solubility of CEL was observed. In fact, the presence of both HP-β-CD (0.05 M) and HPMC (0.25% w/v) gave rise to a 330-fold CEL solubility increase, whereas the cyclodextrin alone provided a 34-fold increase. Gibbs free energy values calculated from phase solubility data were all negative, indicating the spontaneous nature of CEL solubilization, and they decreased in the presence of HPMC, demonstrating that the solubilization conditions became more favorable. CEL/HP-β-CD and CEL/HP-β-CD/HPMC solid systems (physical mixtures and coevaporated products) were characterized by differential scanning calorimetry and infrared spectroscopy. Results suggested that the coevaporation method yields a high degree of amorphous entities and indicated the formation of a CEL/HP-β-CD complex in the coevaporated products. The positive effect of HPMC is particularly evident when looking at the CEL dissolution rate from the binary and ternary solid systems. Specifically, the percent of CEL dissolved after 10 min. resulted 84.21% for ternary coevaporated product and 50.18% for binary coevaporated product with respect to 13.10% for the drug alone.

Soy protein–polysaccharides interactions at the air–water interface

This work studies the interfacial behavior of mixed soy protein (SP) + polysaccharide (PS) systems to gain knowledge on the interactions between these biopolymers at the air–water interface under dynamic conditions at neutral pH where a limited incompatibility between macromolecules can occur. The PSs used were: hydroxypropylmethylcellulose (HPMC) as surface-active PS; lambda carrageenan ( λ C ) and locust bean (LB) gum as non-surface-active PSs. Protein and PS concentration in the mixed systems were 2% and 0.25%, respectively. The dynamic surface pressure and rheological properties of films were evaluated with a drop tensiometer at 20 ∘ C , pH 7 and ionic strength 0.05 M. The presence of HPMC and λ C greatly increased the surface pressure, surface dilatational elasticity and relative viscoelasticity on the basis of different mechanisms. HPMC competed for the interface with SP, but due to its unusual strong surface activity it could dominate the surface pressure and improve film viscoelasticity. The modification of surface pressure and rheological properties of adsorbed SP films in the presence of λ C necessarily suggests the participation of λ C + contaminants at the interface. Pure λ C could influence the interface by a complexation mechanism, or indirectly by a depletion mechanism in the vicinity of the interface. In addition surface-active contaminant of λ C if strongly bound to the PS could bring some PS molecules at the interface. LB little affected the surface pressure and rheological properties of SP films even if surface-active contaminants were present in the commercial preparation. Differences in the interaction of λ C and LB gum with the protein should be mainly ascribed to different degrees of incompatibility and to the fact that LB is not charged.

Stable carbamazepine colloidal systems using the cosolvent technique

The aim of this paper was to prepare stable carbamazepine nanosuspensions containing 10 mg/ml drug concentration by screening different polymers. Stable formulations were created by the cosolvent technique with polyethylene glycol (PEG-300) and water as the cosolvents. Rapid growth of long needle shaped CBZ crystals was observed in the absence of polymer. The presence of hydroxypropyl methylcellulose (HPMC) or methylcellulose (MC) inhibited crystal growth and the mean particle sizes were in the range 10–20 nm. Simultaneous presence of HPMC and polyvinylpyrrolidon (PVP PF17) polymers in CBZ suspensions enhanced the overall stability of the formulations. The additional stability improvement was attributed to the interaction between the polymers by the formation of hydrogen bonds. Suspension stability was evaluated over 5 months where the particle size remained constant. FT-Raman studies showed the existence of form I within the stable CBZ suspensions.

Interaction of hydroxypropylmethylcellulose with gluten proteins: Small deformation properties during thermal treatment

The possible interaction between hydroxypropylmethylcellulose (HPMC) and gluten proteins has been investigated in order to understand the effect of the HPMC in bakery products. Dynamic oscillatory studies at small deformations indicated that the presence of varying concentrations of HPMC induces a softening effect (decrease in G′ and G″) in the gluten dough. During heating of HMPC–gluten mixtures, HPMC gelation only became evident when a minimum amount of HPMC was present (HPMC/gluten ratio was 0.075), conferring some strength to the gluten dough at 85 °C. The presence of HPMC did not modify the viscoelastic behaviour of gluten dough during cooling, however, at 25 °C, increased G′ and G″ were observed with HPMC. Gluten proteins increased their solubility in sodium dodecyl sulphate in the presence of HPMC, which besides the viscoelastic results, suggests that HPMC could interfere with the protein association and its further aggregation during heating, likely occupying the space of the proteins in the gluten network. Therefore, separate from interactions of starch and HPMC, the HPMC effect on bakery products could be partially due to the functional replacement of the gluten proteins in the gluten network. This effect is intensified after HPMC gelation, and also modifies the protein self-association during baking.