Drug-polymer Mixtures Research Articles

Polymeric additives to sustain the dissolution enhancement of niclosamide nanocrystals formed via freeze drying

Nanocrystal formation is an effective method to increase the dissolution of drug compounds with limited solubilities. Niclosamide is a sparingly soluble compound, and it also tends to become an even less soluble monohydrate upon contact with dissolution media. We utilized freeze drying to successfully generate niclosamide nanocrystals, which displayed rapid initial dissolution but also suffered from the expedited formation of the monohydrate. Therefore, we explored some pharmaceutically acceptable polymers to overcome the unfavorable anhydrate-to-monohydrate transformation. Poly(vinylpyrrolidone-co-vinyl acetate) (Mw 45000–70000) effectively retarded the monohydrate formation in a concentration-dependent manner, and 3–5% in the drug-polymer mixture was enough to sustain the enhanced initial dissolution of niclosamide nanocrystals. The area under the dissolution curve tripled due to the combined effect of the nanocrystal formation and the monohydrate inhibition. This study demonstrates an example of the one-pot freeze-drying process to form an optimized drug-additive mixture to realize the full potential of drug nanocrystals.

A Pioneer Review on Intermolecular Hydrogen Bonding in Drug-Polymer Mixtures: Implication of a Stable Delivery System

Intermolecular hydrogen bonding plays a pivotal role in the stability and efficacy of drug-polymer mixtures, which are essential components in modern drug delivery systems. The knowledge of prominent interactions might provide a means to optimize the physiochemical stability of the developed targeted system. Hence, this review explores the fundamental principles of hydrogen bonding in drug-polymer interactions which can significantly influence the solubility, stability and release profiles of pharmaceutical formulations. The review provides an in-depth examination of the types of functional groups that participate in hydrogen bonding, the characterization techniques employed to study these interactions and the implications of hydrogen bonding on drug delivery. Case studies of successful drug-polymer systems stabilized by hydrogen bonding are presented, highlighting the practical applications and challenges associated with these formulations. Furthermore, the review discusses the future perspectives in this field, including the design of novel polymers and the integration of computational modeling to predict hydrogen bonding behavior. By understanding and leveraging hydrogen bonding, researchers can optimize drug delivery systems, ensuring enhanced bioavailability, controlled release and improved patient outcomes. This review aims to serve as a comprehensive resource for pharmaceutical scientists and formulators, offering insights into the strategic use of hydrogen bonding to develop more effective and stable drug delivery systems.

Measuring and Modeling of Melt Viscosity for Drug Polymer Mixtures.

Melt viscosity is an essential property in pharmaceutical processes such as mixing, extrusion, fused deposition modeling, and melt coating. Measuring and modeling of the melt viscosity for drug/polymer mixtures is essential for optimization of the manufacturing process. In this work, the melt viscosity of nine formulations containing the drug substances acetaminophen, itraconazole, and griseofulvin, as well as the pharmaceutical polymers Eudragit EPO, Soluplus, and Plasdone S-630, were analyzed with a rotational and oscillatory rheometer. The shear rate, temperature, and drug fraction were varied systematically to investigate their influence on viscosity. The results for the pure polymers showed typical shear-thinning behavior and are fundamental for modeling with the Carreau and Arrhenius approaches. The investigations of the viscosity of the drug/polymer mixtures resulted in a plasticizing or a filler effect, depending on the type of drug and the phase behavior. A drug shift factor was proposed to model the change in viscosity as a function of the drug fraction. On this basis, a universal model to describe the melt viscosity of drug/polymer mixtures was developed, considering shear rate, temperature, and drug fraction.

Challenges, current status and emerging strategies in the development of rapidly dissolving FDM 3D-printed tablets: An overview and commentary.

Since the approval of a 3D-printed tablet by the FDA in 2015 for marketing, there has been a great interest in 3D printing in the pharmaceutical field for the development of personalized and on-demand medications. Among various 3D printing methods explored for the development of oral solid dosage form like tablet, the fused deposition modeling (FDM) 3D-printing, where the drug-polymer mixtures are first converted into filaments by hot melt extrusion (HME) and then the filaments are printed into tablets using 3D printers by applying computer-aided design principles, has emerged as the most attractive option. However, no FDM 3D-printed tablets have yet been marketed as the technology faces many challenges, such as limited availability of pharmaceutical-grade polymers that can be printed into tablets, low drug-polymer miscibility, the need for high temperature for HME and 3D-printing, and slow drug release rates from tablets. These challenges are discussed in this article with a special focus on drug release rates since FDM 3D-printing usually leads to the preparation of slow-release tablets while the rapid release from dosage forms is often desired for optimal therapeutic outcomes of new drug candidates. Pros and cons of various strategies for the development of rapidly dissolving FDM 3D-printed tablets reported in the literature are reviewed. Finally, two case studies on emerging strategies for the development of rapidly dissolving FDM 3D-printed tablets are presented, where one outlines a systematic approach for formulating rapidly dissolving tablets, and the other describes a novel strategy to increase dissolution rates of drugs from FDM 3D-printed tablets, which at the same time can also increase drug-polymer miscibility and printability of tablets and lower processing temperatures. Thus, this overview and commentary discusses various issues involving the formulation of rapidly dissolving FDM 3D-printed tablets and provides guidance for the development of commercially viable products.

Ammonio Methacrylate Copolymer (Type B)-Diltiazem Interactions in Solid Dispersions and Microsponge Drug-Delivery Systems.

This paper presents a complex analytical study on the distribution, solubility, amorphization, and compatibility of diltiazem within the composition of Eudragit RS 100-based particles of microspongeous type. For this purpose, a methodology combining attenuated total reflectance Fourier transform infrared (ATR-FTIR) absorption spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX), and in vitro dissolution study is proposed. The correct interpretation of the FTIR and drug-dissolution results was guaranteed by the implementation of two contrasting reference models: physical drug–polymer mixtures and casting-obtained, molecularly dispersed drug–polymer composites (solid dispersions). The spectral behavior of the drug–polymer composites in the carbonyl frequency (νCO) region was used as a quality marker for the degree of their interaction/mutual solubility. A spectral-pattern similarity between the microsponge particles and the solid dispersions indicated the molecular-type dispersion of the former. The comparative drug-desorption study and the qualitative observations over the DSC and SEM-EDX results confirmed the successful synthesis of a homogeneous coamorphous microsponge-type formulation with excellent drug-loading capacity and “controlled” dissolution profile. Among them, the drug-delivery particles with 25% diltiazem content (M-25) were recognized as the most promising, with the highest population of drug molecules in the polymer bulk and the most suitable desorption profile. Furthermore, an economical and effective analytical algorithm was developed for the comprehensive physicochemical characterization of complex delivery systems of this kind.

Rheological Investigation of Hydroxypropyl Cellulose-Based Filaments for Material Extrusion 3D Printing.

The rheological properties of drug–polymer mixtures have a significant influence on their processability when using transformative techniques, such as hot-melt-extrusion and material-extrusion 3D printing; however, there has been limited data on printable systems. This study investigated the rheological properties of 17 formulations of successful printed tablets for both immediate and controlled release. Hydroxypropyl cellulose was used in various ratios to obtain printable filaments in combination with various drugs (indomethacin or theophylline), polymers and disintegrants. The complex viscosity, shear thinning behavior and viscoelastic properties were affected by the drug load, polymer composite, disintegrant type, temperature and shear rate applied. Larger windows of processing viscosity were revealed. The viscosity of the printable blends could be as low as the range 10–1000 Pa·s at 100 rad/s angular frequency. All formulations showed shear thinning behavior with a broad slope of complex viscosity from −0.28 to −0.74. The addition of 30–60% drug or disintegrant tended to have greater viscosity values. While microcrystalline cellulose was found to be an alternative additive to lower the storage and loss modulus among disintegrants. This rheological data could be useful for the preformulation and further development of material-extrusion 3D-printing medicines.

The Effect of Process Variables and Binder Concentration on Tabletability of Metformin Hydrochloride and Acetaminophen Granules Produced by Twin Screw Melt Granulation with Different Polymeric Binders.

In twin screw melt granulation, granules are produced by passing mixtures of drug substances and polymeric binders through twin screw extruder such that temperatures are maintained below melting point of drugs but above glass transition of polymers used, whereby the polymers coat surfaces of drug particles and cause their agglomeration into granules. Since various formulation factors, such as binder type and concentration, and processing variables like extrusion temperature, screw configuration, and screw speed, can influence the granulation process, the present investigation was undertaken to study their effects on tabletability of granules produced. Three different types of polymeric binders, Klucel® EXF (hydroxypropyl cellulose), Eudragit® EPO (polyacrylate binder), and Soluplus® (polyvinyl caprolactam-co-vinyl acetate-ethylene glycol graft polymer), were used at 2, 5, and 10% concentrations. Metformin hydrochloride (HCl) (mp: 222°C) and acetaminophen (mp: 169°C) were used as model drugs, and drug-polymer mixtures with metformin HCl were extruded at 180, 160, and 130°C, while those with acetaminophen were extruded at 130 and 110°C. Other process variables included screw configurations: low, medium, and high shear for metformin HCl, and low and mediumshear for acetaminophen; feed rates: 20 and 60 g/min; and screw speed of 100 and 300 RPM. Formulation and process variables had significant impact on tabletability. The target tensile strength of ≥2 MPa could be obtained with all polymers and at all processing temperatures when metformin HCl was granulated at 180°C and acetaminophen at 130°C. At other temperatures, the target tensile strength could be achieved at certain specific sets of processing conditions.

Crystallised chitosan + Vitamin-E Coated Drug-Eluting Stents to Prevent Restenosis and Stent Associated Infections

Drug-Eluting Stents (DES) was developed to reduce re-endothelialisation and thrombosis. Chitosan due to its biocompatible and biodegradable property, it is used in drug delivery and wound healing applications. Chitosan-Vitamin E (alpha-tocopherol) coated stents were prepared by seeding and crystallisation process. Drug release profile, anti-bacterial activity and biocompatibility were analysed. FESEM analysis of the coated stent evidenced the homogenous coating of the drug-polymer mixture does not provide any surface space on the stent for the bacterial adhesion. Maximum bacterial reduction percentage was observed for biofilm-producing Staphylococcus aureus (96.6±1.04%). Escherichia coli and Pseudomonas aeruginosa showed bacterial reduction percentage of 93.3±2.51% and 93.6±2.08% respectively. Release profiles of crystalline chitosan from the coated stents indicated that the rate of chitosan release was sustained and constant with the release time. Chitosan coated stent samples showed significant biocompatibility indicated by the cell viability percentage of 96.6±1.04% when compared with the control samples (99.1±0.76%). To conclude, the drug-releasing phenomenon aided by the vitamin was correlated with its ability to prevent the formation of restenosis in atherosclerosis cases.

Characterizing Drug-Polymer Interactions in Aqueous Solution with Analytical Ultracentrifugation.

We present a new approach for characterizing drug-polymer interactions in aqueous media, using sedimentation velocity analytical ultracentrifugation (AUC). We investigated the potential interaction of ketoconazole (KTZ), a poorly water-soluble drug, with polyacrylic acid (PAA) and a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus) in aqueous buffers. The effect of the polymer on the sedimentation coefficient of the drug was the observable metric. The drug alone, when subjected to AUC, exhibited a very narrow sedimentation peak at 0.2 Svedberg (S), in agreement with the expectation for a monomeric drug with a molar mass < 1000 Dalton. Conversely, the neat polymers showed broad profiles with higher sedimentation coefficients, reflecting their larger more heterogeneous size distributions. The sedimentation profiles of the drug-polymer mixtures were expectedly different from the profile of the neat drug. With KTZ-Soluplus, a complete shift to faster sedimentation times (indicative of an interaction) was observed, while with KTZ-PAA, a split peak indicated the existence of the drug in both free and interacting states. The sedimentation profile of carbamazepine, a second model drug, in the presence of hydroxypropyl methyl cellulose acetate succinate (HPMCAS, another polymer) revealed multiple "populations" of drug-polymer species, very similar to the sedimentation profile of neat HPMCAS. The interactions probed by AUC were compared with the results from isothermal titration calorimetry. In vitro dissolution tests performed on amorphous solid dispersions prepared with the same drug-polymer pairs suggested that the interactions may play a role in prolonging drug supersaturation. The results show the possibility of characterizing drug-polymer interactions in aqueous solution with high hydrodynamic resolution, addressing a major challenge frequently encountered in the mechanistic investigations of the dissolution behavior of amorphous solid dispersions.

Enhancement of the Physical and Chemical Stability of Amorphous Drug–Polymer Mixtures via Cryogenic Comilling

Amorphous dispersions of the Biclotymol antiseptic are obtained in polyvinylpyrrolidone (PVP), for different drug loadings, by comilling at temperatures below the glass transition of both components. Characterization of the dispersions by scanning differential calorimetry and temperature-dependent broadband dielectric spectroscopy shows them to be homogeneous amorphous molecular mixtures. A single glass transition with pronounced enthalpy recovery peak is observed, indicative of the formation of a homogeneous glass state characterized by substantial aging. The polymer has a considerable antiplasticizing effect on the drug, increasing its glass transition temperature (Tg) to well above room temperature. The Tg of the mixture increases linearly with the macromolecular mass fraction. Three (macro)molecular relaxations are identified in the isothermal dielectric spectra of the mixtures. The slowest process corresponds to the cooperative (α relaxation) dynamics of the polymer chains and drug molecules simultan...

A study to identify the contribution of Soluplus® component homopolymers to the solubilization of nifedipine and sulfamethoxazole using the melting point depression method

PurposeExploit the Flory-Huggins Theory and its interaction parameter to measure the contribution of each of the homopolymers of the graft copolymer Soluplus® to the solubilization of sulfamethoxazole (SMX) and nifedipine (NIF). MethodsThe melting point depression for each crystalline drug in the presence of Soluplus® and each of its component homopolymers, namely poly(N-vinyl caprolactam) (PVCL), poly(vinylacetate) (PVAc), and poly(ethyleneglycol) (PEG), was measured at various drug levels using differential scanning calorimetry. Glass transition temperatures were calculated across the entire range for drug-polymer mixtures for comparison to the Gordon-Taylor prediction. The intersection of the melting point depression curve with the mixture glass transition curve provides an estimate of the solubility of the drug in the polymer. The solubility of these crystalline drugs in each homopolymer was calculated and a solubility in Soluplus® was estimated based on the homopolymer contributions. ResultsPEG 6000 exhibited a negative interaction parameter with SMX and NIF, indicating a relatively strong drug-polymer interaction. For PVAc, a small positive interaction parameter indicated a relatively weak drug-polymer interaction. The approach was not suitable for assessing the drug-PVCL interaction. However, other approaches could be taken to estimate the solubility of the drug in a polymer, including extrapolating the enthalpy of melting as a function of the volume fraction of the polymer to zero enthalpy to determine the maximum concentration miscible with the polymer and equating a parameter across the ideal solubility equation and the Flory-Huggins equation. ConclusionThe Flory-Huggins Theory allowed identification of the contribution of two of the homopolymers to the solubilization of NIF and SMX by Soluplus®, namely PEG and PVAc. PVAc and PVCL each demonstrated a weak interaction with each drug. However, PEG 6000 would substantially contribute to the drug solubilization due to its marked affinity for each drug.

PREPARATION AND EVALUATION OF DROTAVERINE HCL ORAL DISINTEGRATING TABLETS USING SOLID MIXTURE TECHNIQUE

Objective: The objective of this study is to formulate orally disintegrating taste masked tablets of drotaverine HCl using solid mixture technique.Methods: Taste masked drug-polymer solid mixtures of drotaverine HCl were prepared by using hydroxypropyl methylcellulose (HPMC) 3 cps and rxcipient® FM1000/calcium silicate (rxcipient) as carriers employing kneading method using varying drug-polymer ratios of 1:1, 1:5, 1:7.5, and 1:9. Prepared drug-polymer mixtures evaluated for taste masking, and the ratio of drug-polymer is optimized. The granules and tablets prepared with optimized drug-polymer ratio were evaluated for pre- and post-compression parameters, in vitro dissolution studies, Fourier-transformation infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD) studies.Results: The drug:polymer ratios 1:7.5 with rxcipient and 1:9 with HPMC were optimized based on taste evaluation. The pre-compression results showed that all the formulae have good flow properties. The post-compression evaluations showed that all the formulae met the specifications of orally disintegrating tablets. From all the prepared taste masked drotaverine HCl tablets, R10 formulation consisting of 4% croscarmellose sodium and H9 formulation consisting of 3% croscarmellose sodium, 3% sodium starch glycolate, and 2% microcrystalline cellulose shown more than 99% drug release in 60 min, and both the formulations showed better taste masking and were meting oral disintegrating tablet (ODT) parameters. The optimized formulation was characterized by FTIR, DSC, and XRD studies and found no incompatibility.Conclusion: The results demonstrated that the prepared drotaverine HCl ODT showed better taste masking and meeting the parameters of ODT formulations R10 and H9. The present solid mixture technique can be effectively used for taste masking.

Differential scanning calorimetry isothermal hold times can impact interpretations of drug-polymer dispersability in amorphous solid dispersions

Differential scanning calorimetry (DSC) is a commonly employed analytical technique for the analysis and characterization of amorphous solid dispersions. However, steps typical of standard temperature programs can alter the material in situ. Data for two active pharmaceutical ingredients are detailed, wherein isothermal hold times, traditionally employed to remove thermal history and/or residual solvent, were observed to impact the observed dispersability of the compounds in polyvinylpyrrolidone vinyl-acetate copolymer (PVPva). Re-crystallized tolbutamide was observed to re-dissolve in PVPva, while terfenadine was observed to crystallize during the isothermal hold period. Exposing co-solidified drug-polymer mixtures to temperature changes and experimental hold times can potentially confound correct categorization of dispersability, particularly when DSC is used as the lone characterization technique. This work illustrates the importance of using a combination of techniques to improve the certainty of conclusions made with respect to the true, initial physical state of a co-solidified mixture.

Rheological analysis of itraconazole-polymer mixtures to determine optimal melt extrusion temperature for development of amorphous solid dispersion

The objective of this investigation was to develop a systematic method for the determination of optimal processing temperatures of drug-polymer mixtures for the development of amorphous solid dispersion (ASD) by melt extrusion. Since melt extrusion is performed at high temperature, it is essential that the processing temperature should be as low as possible to minimize degradation of drug and polymer, and yet the temperature should be high enough that the drug-polymer mixture attains certain viscosity that is extrudable and the drug dissolves in the molten polymer. By using itraconazole (ITZ) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft co-polymer (Soluplus®, BASF) as, respectively, the model drug and the polymeric carrier, melt viscosities of drug-polymer mixtures with 5, 10, 20 and 30% ITZ were studied as functions of temperature and angular frequency. All these concentrations were below the miscibility limit as it was shown separately by film casting that ITZ was miscible with the polymer up to 40%. Since the angular frequency of a rheometer may not be high enough to simulate the shear rate within an extruder, torque analysis as a function of temperature during melt extrusion of selected drug-polymer mixtures was also conducted. The presence of dissolved ITZ had a plasticizing effect on the polymer used, and an intersection point around 150–155°C was observed, above which viscosities of drug-polymer mixtures were lower than that of polymer itself. Drug-polymer mixtures with 5 to 30% ITZ were extrudable at 150°C, and torque analysis showed that the mixture with 20% ITZ can be extruded even at 145°C. These temperatures were 17 to 22°C below the melting point of ITZ (167°C). ITZ dissolved due to the drug-polymer miscibility, the viscosity attained, and the shear rate generated. It was confirmed by PXRD and DSC that the extrudates were amorphous. Viscosity and miscibility of drug-polymer mixtures during melt extrusion were identified as critical factors in determining optimal processing temperature.

Rheological Characterization of Molten Polymer-Drug Dispersions as a Predictive Tool for Pharmaceutical Hot-Melt Extrusion Processability.

The aim of this study was to investigate (i) the influence of drug solid-state (crystalline or dissolved in the polymer matrix) on the melt viscosity and (ii) the influence of the drug concentration, temperature and shear rate on polymer crystallization using rheological tests. Poly (ethylene oxide) (PEO) (100.000g/mol) and physical mixtures (PM) containing 10-20-30-40% (w/w) ketoprofen or 10% (w/w) theophylline in PEO were rheologically characterized. Rheological tests were performed (frequency and temperature sweeps in oscillatory shear as well as shear-induced crystallization experiments) to obtain a thorough understanding of the flow behaviour and crystallization of PEO-drug dispersions. Theophylline did not dissolve in PEO as the complex viscosity (η*) of the drug-polymer mixture increased as compared to that of neat PEO. In contrast, ketoprofen dissolved in PEO and acted as a plasticizer, decreasing η*. Acting as a nucleating agent, theophylline induced the crystallization of PEO upon cooling from the melt. On the other hand, ketoprofen inhibited crystallization upon cooling. Moreover, higher concentrations of ketoprofen in the drug-polymer mixture increasingly inhibited polymer crystallization. However, shear-induced crystallization was observed for all tested mixtures containing ketoprofen. The obtained rheological results are relevant for understanding and predicting HME processability (e.g., barrel temperature selection) and downstream processing such as injection moulding (e.g., mold temperature selection).

The flow properties and presence of crystals in drug-polymer mixtures: Rheological investigation combined with light microscopy

The presence of solid matter in polymer melts affects the rheological properties of a drug-polymer mixture, and thus the processability of these mixtures in melt-based processes. The particle morphological changes related to dissolution and crystal growth in the mixtures of paracetamol and ibuprofen with polyethylene oxide and methacrylate copolymer (Eudragit® E PO) were observed by polarized microscopy simultaneously while measuring their rheological properties within temperature ranges relevant for melt processes, such as hot melt extrusion and fused deposition modeling 3D printing. The dissolution of solid crystalline matter into the molten polymer and its effects on the rheological parameters showed that the plasticization effect of the drug was highly dependent on the temperature range, and at a temperature high enough, plasticization induced by the small-molecule drugs could enhance the flowability even at very high drug loads. Therefore, even supersaturated mixtures can be plasticized efficiently, enabling their melt processing, such as hot melt extrusion or 3D printing. The combination of rheometry and polarized light microscopy proved to be very useful for studying the link between morphological changes in the drug-polymer and the flow behavior of the drug-polymer mixtures at different temperature ranges and deformation modes.

Controlling the Release of Indomethacin from Glass Solutions Layered with a Rate Controlling Membrane Using Fluid-Bed Processing. Part 1: Surface and Cross-Sectional Chemical Analysis.

Fluid bed coating has been shown to be a suitable manufacturing technique to formulate poorly soluble drugs in glass solutions. Layering inert carriers with a drug-polymer mixture enables these beads to be immediately filled into capsules, thus avoiding additional, potentially destabilizing, downstream processing. In this study, fluid bed coating is proposed for the production of controlled release dosage forms of glass solutions by applying a second, rate controlling membrane on top of the glass solution. Adding a second coating layer adds to the physical and chemical complexity of the drug delivery system, so a thorough understanding of the physical structure and phase behavior of the different coating layers is needed. This study aimed to investigate the surface and cross-sectional characteristics (employing scanning electron microscopy (SEM) and time of flight secondary ion mass spectrometry (ToF-SIMS)) of an indomethacin-polyvinylpyrrolidone (PVP) glass solution, top-coated with a release rate controlling membrane consisting of either ethyl cellulose or Eudragit RL. The implications of the addition of a pore former (PVP) and the coating medium (ethanol or water) were also considered. In addition, polymer miscibility and the phase analysis of the underlying glass solution were investigated. Significant differences in surface and cross-sectional topography of the different rate controlling membranes or the way they are applied (solution vs dispersion) were observed. These observations can be linked to the polymer miscibility differences. The presence of PVP was observed in all rate controlling membranes, even if it is not part of the coating solution. This could be attributed to residual powder presence in the coating chamber. The distribution of PVP among the sample surfaces depends on the concentration and the rate controlling polymer used. Differences can again be linked to polymer miscibility. Finally, it was shown that the underlying glass solution layer remains amorphous after coating of the rate controlling membrane, whether formed from an ethanol solution or an aqueous dispersion.

A minitablet formulation made from electrospun nanofibers

The purpose of this study was to evaluate electrospun drug loaded nanofibers as a new matrix for minitablets. Prednisone, a poorly water-soluble drug, was loaded into povidone (polyvinylpyrrolidone, PVP) nanofibers using the process of electrospinning. The drug-loaded nanofiber mat was compressed into minitablets with a 2mm diameter and a height of 2.63±0.04mm. SEM analysis of the minitablet identified a nano-web structure with a nanofiber diameter in the range of 400–500nm. The minitablets met the requirements of the US Pharmacopeia with respect to content uniformity and friability. DSC and XRPD analysis of the minitablet indicated that the drug-polymer mixture was a one-phase amorphous system. XRPD analysis of the drug loaded nanofiber mat after 10-months of storage at ambient temperature showed no evidence of recrystallization of the drug. Solubility and dissolution properties of the drug formulated into a nanofiber mat and minitablet were evaluated. These results show that electrospun nanofibers may provide a useful matrix for the further development of minitablets.

Investigation of Drug-Polymer Compatibility Using Chemometric-Assisted UV-Spectrophotometry.

A simple chemometric-assisted UV-spectrophotometric method was used to study the compatibility of clindamycin hydrochloride (HC1) with two commonly used natural controlled-release polymers, alginate (Ag) and chitosan (Ch). Standard mixtures containing 1:1, 1:2, and 1:0.5 w/w drug–polymer ratios were prepared and UV scanned. A calibration model was developed with partial least square (PLS) regression analysis for each polymer separately. Then, test mixtures containing 1:1 w/w drug–polymer ratios with different sets of drug concentrations were prepared. These were UV scanned initially and after three and seven days of storage at 25 °C. Using the calibration model, the drug recovery percent was estimated and a decrease in concentration of 10% or more from initial concentration was considered to indicate instability. PLS models with PC3 (for Ag) and PC2 (for Ch) showed a good correlation between actual and found values with root mean square error of cross validation (RMSECV) of 0.00284 and 0.01228, and calibration coefficient (R2) values of 0.996 and 0.942, respectively. The average drug recovery percent after three and seven days was 98.1 ± 2.9 and 95.4 ± 4.0 (for Ag), and 97.3 ± 2.1 and 91.4 ± 3.8 (for Ch), which suggests more drug compatibility with an Ag than a Ch polymer. Conventional techniques including DSC, XRD, FTIR, and in vitro minimum inhibitory concentration (MIC) for (1:1) drug–polymer mixtures were also performed to confirm clindamycin compatibility with Ag and Ch polymers.

RETRACTED ARTICLE: Study of the Transformations of Micro/Nano-crystalline Acetaminophen Polymorphs in Drug-Polymer Binary Mixtures

This study elucidates the physical properties of sono-crystallised micro/nano-sized acetaminophen/paracetamol (PMOL) and monitors its possible transformation from polymorphic form I (monoclinic) to form II (orthorhombic). Hydrophilic Plasdone® S630 copovidone (S630), N-vinyl-2-pyrrolidone and vinyl acetate copolymer, and methacrylate-based cationic copolymer, Eudragit® EPO (EPO), were used as polymeric carriers to prepare drug/polymer binary mixtures. Commercially available PMOL was crystallised under ultra sound sonication to produce micro/nano-sized (0.2–10 microns) crystals in monoclinic form. Homogeneous binary blends of drug-polymer mixtures at various drug concentrations were obtained via a thorough mixing. The analysis conducted via the single X-ray crystallography determined the detailed structure of the crystallised PMOL in its monoclinic form. The solid state and the morphology analyses of the PMOL in the binary blends evaluated via differential scanning calorimetry (DSC), modulated temperature DSC (MTDSC), scanning electron microscopy (SEM) and hot stage microscopy (HSM) revealed the crystalline existence of the drug within the amorphous polymeric matrices. The application of temperature controlled X-ray diffraction (VTXRPD) to study the polymorphism of PMOL showed that the most stable form I (monoclinic) was altered to its less stable form II (orthorhombic) at high temperature (>112°C) in the binary blends regardless of the drug amount. Thus, VTXRD was used as a useful tool to monitor polymorphic transformations of crystalline drug (e.g. PMOL) to assess their thermal stability in terms of pharmaceutical product development and research.