Supercritical carbon dioxide assisted complexation of benznidazole: γ-cyclodextrin for improved dissolution

Drug-excipient compatibility studies in formulation development: A case study with benznidazole and monoglycerides

Monoglycerides (MGs) such as glycerol monolaurate (GML) and glycerol monostearate (GMS) have been used as excipients in oral formulations because of their emulsifying effect as well as their ability to inhibit the precipitation and intestinal efflux of drugs. Excipient-drug compatibility studies, however, have been underexplored. In this study, benznidazole (BNZ) was selected as a drug model due to the difficulty in improving its solubility and because of the potential impact on public health (it is the only drug currently used to treat Chagas disease). The effect of different processing conditions (maceration, ball milling, and melting) on the physical-chemistry properties of BNZ/MGs mixtures was investigated to guide the rational development of new solid formulations. GML was more effective in improving the solubility of BNZ, which could be due to its more malleable structure, less hydrophobic nature, and greater interaction with BNZ. The formation of hydrogen bonds between the imidazole group of BNZ and the polar region of GML was confirmed by spectroscopy analyses (IR, 1H NMR). The higher the monoglyceride content in the mixture, the higher the BNZ solubility. Regardless of the method of processing the mixture, the drug was found to be crystalline. Polarized light microscopy analysis showed the presence of spherulites. Overall, these findings suggest that preparation methods of BNZ:MGs formulations that involve thermal or/and mechanical treatment have a low impact on the solid properties of the material, and this allows for the production of formulations with reproducible performance.

Synergistic chemo-/photothermal therapy based on supercritical technology-assisted chitosan-indocyanine green/luteolin nanocomposites for wound healing

Despite the success, it is highly challenging to battle against pathogenic biofilms-based chronic bacterial infections by conventional antibiotic therapy. Herein, we report a near-infrared (NIR)/acid-induced nanoplatform based on chitosan (CS)-coated indocyanine green (ICG, photosensitizer)/luteolin (LUT, a natural quorum sensing inhibitor) nanocomposites (ICG/LUT-CS) as antibacterial and antibiofilm agents for skin wound healing. Initially, the ICG/LUT nanoplatforms are prepared by the supercritical antisolvent technology and coated with the CS layer. The obtained ICG/LUT-CS with ultra-high encapsulation efficiency exhibited more favorable photothermal conversion effects and improved NIR laser/acid dual-induced drug release behavior than individual modalities, achieving exceptional bacteria-killing and biofilm elimination effects. Moreover, the ICG/LUT-CS realized the synergetic effects of chemotherapy and photothermal therapy outcomes for wound healing. Together, our findings provided an appealing strategy for the rapid preparation and future translational application of ICG/LUT-CS as an ideal agent for fighting against biofilm infections.

Leishmaniasis and Chagas disease: Is there hope in nanotechnology to fight neglected tropical diseases?

Nanotechnology is revolutionizing many sectors of science, from food preservation to healthcare to energy applications. Since 1995, when the first nanomedicines started being commercialized, drug developers have relied on nanotechnology to improve the pharmacokinetic properties of bioactive molecules. The development of advanced nanomaterials has greatly enhanced drug discovery through improved pharmacotherapeutic effects and reduction of toxicity and side effects. Therefore, highly toxic treatments such as cancer chemotherapy, have benefited from nanotechnology. Considering the toxicity of the few therapeutic options to treat neglected tropical diseases, such as leishmaniasis and Chagas disease, nanotechnology has also been explored as a potential innovation to treat these diseases. However, despite the significant research progress over the years, the benefits of nanotechnology for both diseases are still limited to preliminary animal studies, raising the question about the clinical utility of nanomedicines in this field. From this perspective, this review aims to discuss recent nanotechnological developments, the advantages of nanoformulations over current leishmanicidal and trypanocidal drugs, limitations of nano-based drugs, and research gaps that still must be filled to make these novel drug delivery systems a reality for leishmaniasis and Chagas disease treatment.

Characterization of excipients to improve pharmaceutical properties of sirolimus in the supercritical anti-solvent fluidized process

Enhanced drug release and bioavailability of poorly soluble active pharmaceutical ingredient (API) can be achieved via a fluidized bed coating integrated with supercritical anti-solvent (SAS-FB) - a process of precipitating drug particles onto carrier granules. However, in the absence of excipients, SAS-FB often results in crystalline of the API on the surface of carriers, limiting the improvement of pharmaceutical properties. Co-processing with excipients is considered an effective approach to improve drug release in the SAS-FB process. Our study used sirolimus, an immune suppressive agent, as the model API to characterize excipients for their effect on pharmaceutical properties in the SAS-FB process. We show that co-precipitation of excipients and sirolumus impacts on carrier specific surface area and drug yield. Among the tested excipients, formulation containing polyvinylpyrrolidone K30 achieved the highest drug yield. Importantly, compared with Rapamune® tablet, our optimized formulation displayed a superior in vivo oral bioavailability by 3.05-fold in Sprague-Dawley rats and 3.99-fold in beagle dogs. A series of characterization of the processed API was performed to understand the mechanism by which excipients contributed to drug dissolution properties. Our study provides a useful guidance for the use of excipients in the SAS-FB technology to improve pharmaceutical properties of sirolimus and other poorly soluble drugs.

Engineering mesoporous silica nanoparticles towards oral delivery of vancomycin

Vancomycin (Van) is a key antibiotic of choice for the treatment of systemic methicillin resistant Staphylococcus aureus (MRSA) infections. However, due to its poor membrane permeability, it is administered parenterally, adding to the cost and effort of treatment. The poor oral bioavailability of Van is mainly due to its physico-chemical properties that limit its paracellular and transcellular transport across gastrointestinal (GI) epithelium. Herein we report the development of silica nanoparticles (SNPs)-based formulations that are able to enhance the epithelial permeability of Van. We synthesized SNPs of different pore sizes (2 nm and 9 nm) and modified their surface charge and polarity by attaching different functional groups (-NH₂, -PO₃, and -CH₃). Van was loaded within these SNPs at a loading capacity in the range of ca. 18-29 wt%. The Van-loaded SNPs exhibited a controlled release behaviour when compared to un-encapsulated Van which showed rapid release due to its hydrophilic nature. Among Van-loaded SNPs, SNPs with large pores showed a prolonged release compared to SNPs with small pores while SNPs functionalised with -CH₃ groups exhibited a slowest release among the functionalised SNPs. Importantly, Van-loaded SNPs, especially the large pore SNPs with negative charge, enhanced the permeability of Van across an epithelial cell monolayer (Caco-2 cell model) by up to 6-fold, with P_app values up to 1.716 × 10^-5 cm s^-1 (vs. 0.304 × 10^-5 cm s^-1 for un-encapsulated Van) after 3 h. The enhancement was dependent on both the type of SNPs and their surface functionalisation. The permeation enhancing effect of SNPs was due to its ability to transiently open the tight junctions measured by decrease in transepithelial resistance (TEER) which was reversible after 3 h. All in all, our data highlights the potential of SNPs (especially SNPs with large pores) for oral delivery of Van or other antimicrobial peptides.

Effect of the Carrier on the Coprecipitation of Curcumin through Supercritical-Assisted Atomization

In this paper, composite systems containing curcumin (CUR) were prepared through supercritical-assisted atomization (SAA), using different carriers. Curcumin is particularly interesting in the pharmaceutical and nutraceutical fields for its antioxidant, antitumoral, and anti-inflammatory properties. However, its therapeutic effect on human health is restricted by its poor water solubility and low dissolution rate, limiting its absorption after its oral administration. To increase the dissolution rate and then the bioavailability of the active compound, CUR was coprecipitated with polymeric, i.e., polyvinylpyrrolidone (PVP) and dextran (DXT), and not polymeric, i.e., hydroxypropyl-β-cyclodextrin (HP-β-CD), carriers. The effects of some operating parameters, namely the concentration of solutes in solution and the active compound/carrier ratio, on the morphology and the particle size distribution of the powders were investigated. Submicrometric particles were produced with all the carriers. Under the best operating conditions, the mean diameters ± standard deviation were equal to 0.69 ± 0.20 μm, 0.40 ± 0.13 μm, and 0.81 ± 0.25 μm for PVP/CUR, DXT/CUR, and HP-β-CD/CUR, respectively. CUR dissolution rates from coprecipitated particles were significantly increased in the case of all the carriers. Therefore, the results are exciting from a pharmaceutical and nutraceutical point of view, to produce supplements containing curcumin, but assuring a high dissolution rate and bioavailability and, consequently, a more effective therapeutic effect.

Preparation of Solid Dispersions of Simvastatin and Soluplus Using a Single-Step Organic Solvent-Free Supercritical Fluid Process for the Drug Solubility and Dissolution Rate Enhancement

The study was designed to investigate the feasibility of supercritical carbon dioxide (scCO₂) processing for the preparation of simvastatin (SIM) solid dispersions (SDs) in Soluplus^® (SOL) at temperatures below polymer’s glass transition. The SIM content in the SDs experimental design was kept at 10, 20 and 30% to study the effect of the drug–polymer ratio on the successful preparation of SDs. The SIM–SOL formulations, physical mixtures (PMs) and SDs were evaluated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and dissolution studies. The scCO₂ processing conditions and drug–polymer ratio were found to influence the physicochemical properties of the drug in formulated SDs. SIM is a highly crystalline drug; however, physicochemical characterisation carried out by SEM, DSC, and XRD demonstrated the presence of SIM in amorphous nature within the SDs. The SIM–SOL SDs showed enhanced drug dissolution rates, with 100% being released within 45 min. Moreover, the drug dissolution from SDs was faster and higher in comparison to PMs. In conclusion, this study shows that SIM–SOL dispersions can be successfully prepared using a solvent-free supercritical fluid process to enhance dissolution rate of the drug.

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.

Supercritical Carbon Dioxide as a Green Alternative to Achieve Drug Complexation with Cyclodextrins

Cyclodextrins are widely used in pharmaceutics to enhance the bioavailability of many drugs. Conventional drug/cyclodextrin complexation techniques suffer from many drawbacks, such as a high residual content of toxic solvents in the formulations, the degradation of heat labile drugs and the difficulty in controlling the size and morphology of the product particles. These can be overcome by supercritical fluid technology thanks to the outstanding properties of supercritical CO₂ (scCO₂) such as its mild critical point, its tunable solvent power, and the absence of solvent residue after depressurization. In this work the use of scCO₂ as an unconventional medium to achieve the complexation with native and substituted cyclodextrins of over 50 drugs, which belong to different classes, are reviewed. This can be achieved with different approaches such as the “supercritical solvent impregnation” and “particle-formation” techniques. The different techniques are discussed to point out how they affect the complexation mechanism and efficiency, the physical state of the drug as well as the particle size distribution and morphology, which finally condition the release kinetics and drug bioavailability. When applicable, the results obtained for the same drug with various cyclodextrins, or different complexation techniques are compared with those obtained with conventional approaches.