Ultrahigh nanostructured drug payloads from degradable mesoporous silicon aerocrystals

Porous silicon has found increased attention as a drug delivery system due to its unique features such as high drug payloads, surface area and biodegradation. In this study supercritical fluid (SCF) assisted drying of ultrahigh porosity (>90%) silicon particles and flakes was shown to result in much higher mesopore volumes (~4.66 cm³/g) and surface areas (~680 m²/g) than with air-drying. The loading and physical state of the model drug (S)-(+)-Ibuprofen in SCF dried matrices was quantified and assessed using thermogravimetric analysis, differential scanning calorimetry, UV-Vis spectrophotometry, gravimetric analysis, gas adsorption and electron microscopy. Internal drug payloads of up to 72% were achieved which was substantially higher than values published for both conventionally dried porous silicon (17-51%) and other mesoporous materials (7-45%). In-vitro degradability kinetics of SCF-dried matrices in simulated media was also found to be faster than air-dried controls. The in-vitro release studies provided improved but sustained drug dissolution at both pH 2.0 and pH 7.4.

Engineering and manufacturing of pharmaceutical co-crystals: a review of solvent-free manufacturing technologies

Design and synthesis of pharmaceutical cocrystals have received great interest in recent years. Cocrystallization of drug substances offers a tremendous opportunity for the development of new drug products with superior physical and pharmacological properties such as solubility, stability, hydroscopicity, dissolution rates and bioavailability. It is now possible to engineer and develop cocrystals via 'green chemistry' and environmentally friendly approaches such as solid-state synthesis in the absence of organic solvents. In addition, significant efforts have been directed towards computational screening, cocrystal manufacturing in a continuous manner and real-time monitoring for quality purposes by using various analytical tools. Pharmaceutical cocrystals are not fully exploited yet and there is a lot of ground to cover before they can be successfully utilized as medical products.

One-step continuous extrusion process for the manufacturing of solid dispersions

The purpose of this study was to evaluate the performance of synthetic magnesium aluminometasilicate (MAS) as a novel inorganic carrier in hot melt extrusion (HME) processing of indomethacin (IND) for the development of solid dispersions. A continuous extrusion process at various IND/excipient blend ratios (20%, 30% and 40%) was performed using a twin-screw extruder. Physicochemical characterization carried out by SEM, DSC, and XRPD demonstrated the presence of IND in amorphous nature within the porous network of the inorganic material for all extruded formulations. Further, AFM and FTIR studies revealed a single-phase amorphous system and intermolecular H-bonding formation. The IND/MAS extrudates showed enhanced INM dissolution rates within 100% been released within 1h. Stability studies under accelerated conditions (40°C, RH 75%) showed that MAS retained the physical stability of the amorphous solid dispersions even at high drug loadings for 12 months.

Studies of intermolecular interactions in solid dispersions using advanced surface chemical analysis

The aim of this study is to utilise an advanced surface chemical analysis based on X-ray photoelectron spectroscopy (XPS) to determine and characterise drug/polymer interactions in solid dispersions manufactured via hot melt extrusion (HME).

Correction: Studies of intermolecular interactions in solid dispersions using advanced surface chemical analysis

Correction for ‘Studies of intermolecular interactions in solid dispersions using advanced surface chemical analysis’ by M. Maniruzzaman et al., RSC Adv., 2015, 5, 74212–74219.

Continuous cocrystallisation of carbamazepine and trans-cinnamic acid via melt extrusion processing

High quality carbamazepine–trans–cinnamic acid cocrystals were produced by hot melt extrusion. The extruded cocrystals showed improved dissolution rates. In-line NIR showed that cocrystals were formed gradually along the mixing zones of the extruder.

Diclofenac sodium sustained release hot melt extruded lipid matrices

Sustained release diclofenac sodium (Df-Na) solid lipid matrices with Compritol® 888 ATO were developed in this study. The drug/lipid powders were processed via cold and hot melt extrusion at various drug loadings. The influence of the processing temperatures, drug loading and the addition of excipients on the obtained dissolution rates was investigated. The physicochemical characterization of the extruded batches showed the existence of crystalline drug in the extrudates with a small amount being solubilized in the lipid matrix. The drug content and uniformity on the tablet surface were also investigated by using energy dispersive X-ray microanalysis. The dissolution rates were found to depend on the actual Df-Na loading and the nature of the added excipients, while the effect of the processing temperatures was negligible. The dissolution mechanism of all extruded formulations followed Peppas-Korsemeyer law, based on the estimated determination coefficients and the dissolution constant rates, indicating drug diffusion from the lipid matrices.

Synthesis of mesoporous silica nanoparticles and drug loading of poorly water soluble drug cyclosporin A

Mesoporous silica nanoparticles (MSNs) are introduced as chemically and thermally stable nanomaterials with well-defined and controllable morphology and porosity. It is shown that these particles possess external and internal surfaces that can be selectively functionalized with multiple organic and inorganic groups. Silica nano-particles were synthesized by chemical methods from tetraethylorthosilicate (TEOS), methanol (CH3OH) and deionised water in the presence of sodium hydroxide as catalyst at 80°C temperature. The nature and morphology of particles was investigated by scanning electron microscopy (SEM), N2 adsorption/desorption method using BET instrument and X-ray diffraction (XRD). Silica nanoparticles are applicable to a wide range of therapeutic entities from small molecule to peptides and proteins including hydrophobic and hydrophilic entities. Drug loading does not require chemical modification of the molecule; there are no changes in the drug structure or activity after loading and subsequent release of the drug. Thus, well suited to solve formulation problems associated with hydrophobic drugs such as peptide and protein drugs like cyclosporine A. Silica nanoparticles improved the solubility of poorly water soluble drugs and enhanced the absorption and bioavailability of these compounds.

A polarographic methodology for continuous non-destructive monitoring of drug release from liposomes

A simple methodology based on the differential pulse polarography (DPP) was developed for non-destructive monitoring of drug release from liposomes. The methodology was also capable of determining not only the released material that remained free in the liposomal suspension but also the amount of the drug which was eventually adsorbed on the vesicles surface after its release from the liposomes. Based on this methodology the release kinetics of encapsulated chlorothiazide in 5 mg ml(-1) DRV liposomes was studied at 37 degrees C at pH 7.4. The results were compared to those obtained by centrifuging the DRV sample and measuring the free drug in the supernatant solution with UV-spectroscopy. Approximately 70% of the initially encapsulated drug were released within 24 h of which ca. 46% were subsequently adsorbed on vesicles' surface.

Enhanced dissolution of Oxcarbazepine microcrystals using a static mixer process

The purpose of this study was to form micronized powders of Oxcarbazepine (OXC), a poorly water-soluble drug, using a static mixer technique to enhance the dissolution rate. Controlled precipitation was achieved injecting the organic OXC solution rapidly into an aqueous methylcellulose (MC) protective solution by means of a static mixer thus providing turbulent and homogeneous mixing. Furthermore, a factorial design was implemented for data analysis. The physicochemical properties of the freeze-dried dispersions were evaluated by differential scanning calorimetry (DSC), infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Drug microcrystals showed a narrow size distribution with approximately 2 microm mean particle size and high drug loading. DSC and FTIR studies revealed that the drug remained in crystalline state and no drug-polymer interaction occurred. The dissolution studies showed enhanced dissolution of OXC microcrystals compared to the pure drug. The static mixer technique was proved capable for micro-sized polymeric particles. This is an inexpensive, less time consuming and fully scalable process for development of poorly soluble drugs.

Stable carbamazepine colloidal systems using the cosolvent technique

The aim of this paper was to prepare stable carbamazepine nanosuspensions containing 10mg/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.

Nano- and micro-particulate formulations of poorly water-soluble drugs by using a novel optimized technique

A novel technique for the production of nano- and micro-particulate formulations of poorly water-soluble drugs has been developed. This technique involves the use of static mixer elements to provide fast precipitation by continuous turbulent mixing of two liquid flows, an aqueous phase and an organic phase, respectively. The objective of this study was to develop the mixer technique by investigating the influence of the element number on the particle size of the resulting dispersions. Four model active pharmaceutical ingredients (APIs) with a variety of polymers, lipids or surfactants underwent intensive mixing and the final suspensions showed a narrow size distribution. Parameters such as the flow rate and the temperature of the precipitated organic-aqueous phases were also significant in the reduction of particle size. Further development of the mixing technique led to reproducible and stable formulations with minimal excipient amounts. These formulations were spray- or freeze-dried to improve stability.