Impact of Membranes on In Vitro Release Assessment: a Case Study Using Dexamethasone.

In vitro release studies are commonly used to assess the product performance of topical dosage forms. In such studies, the mass transport of drugs through synthetic membranes into a receiving chamber filled with a release medium is measured. The release medium is also passed through filtration membranes prior to chromatographic analysis. There are no official guidelines directing membrane selection for in vitro release studies or for filtration. Considering the diversity in membrane materials and their physical properties, the aim of this study was to investigate membrane-drug binding and the effect of various membranes on the release performance of a model drug dexamethasone (DEX) using USP dissolution apparatus IV. Seven membranes of different pore sizes (0.45 and 1.2 µm) and materials (cellulose acetate, polyethersulfone, and nylon) were assessed. Two different methods, syringe filter and 24-h incubation, were used for the determination of membrane-drug binding effects at low drug concentrations and saturated concentration conditions. Cellulose acetate and nylon membranes showed significant drug binding after 24-h incubations at both drug concentrations. DEX diffusion through membranes was significantly slowed down in all the tested membranes when compared with DEX solution without membranes. The extent of the retardation varied due to the differences in membrane structures. In conclusion, materials and sources of membranes affected drug dissolution profiles and the results showed membrane-drug binding effects. Proper selection of membranes with low drug binding ability and low diffusion resistance is essential to ensure appropriate and reproducible in vitro release assessments and filtration studies. Graphical Abstract.

Liquisolid Pellets and Liqui-Pellets Are Not Different.

Our research group has pioneered the development of liquisolid pellets as a new drug delivery system targeting at the improvement of the dissolution rates of poorly water-soluble drugs, combining the technological and biopharmaceutical advantages of both multiparticulate and liquisolid systems. Recently, Lam and collaborators claimed the invention of "liqui-pellets" as "the emerging next-generation oral dosage form which stems from liquisolid concept in combination with pelletization technology". However, the concept of liqui-pellet is not novel. As we demonstrate in this commentary, liqui-pellets are the same type of preparation as our previously and extensively reported liquisolid pellets. Liquisolid pellets have been disclosed in a patent application and public peer-reviewed articles covering the concept, preparation and challenges associated with these systems. There are no technical differences that justify excluding our previous reports as the first reports on liquisolid pellets or liqui-pellets. This commentary highlights the similarities between liquisolid pellets and liqui-pellets, focusing on the anteriority of liquisolid pellets as disclosed by our group.

Liquisolid pellets: A pharmaceutical technology strategy to improve the dissolution rate of ritonavir.

Liquisolid pellets (LPs) prepared by extrusion-spheronization are promising delivery systems to improve the dissolution rate of poorly water-soluble drugs. However, developing LPs for high dose drugs (e.g. antiretroviral ritonavir, RTV) is a major challenge due to technical and quality constraints. In this study, formulations LP1 and LP2 were obtained (RTV 100 mg/unit dose) using microcrystalline cellulose (carrier), Kollidon® CL-SF (coating and disintegrating material) and high load (30%, w/w) of Kolliphor® EL or PEG 400 (non-volatile solvent). LP1 and LP2 had narrow size distribution, good morphological properties, and excellent flowability. The partial conversion of RTV polymorph I to the less soluble form II occurred during the preparation of the liquid medications. LP1 (containing Kolliphor® EL) achieved 82.64 ±â€¯2.17% of drug dissolved in 30 min (Q30min), compared with 53.14 ±â€¯0.6% and 42.42 ±â€¯2.09% for LP2 (containing PEG 400) and Norvir® tablets, respectively. Also, LP1 promoted 1.9-fold/1.7-fold and 8.19-fold/8.29-fold increases in Q30min/DE60min (dissolution efficiency) as compared to neat RTV polymorphs I and II, respectively.

Impact of Porous Excipients on the Manufacturability and Product Performance of Solid Self-Emulsifying Drug Delivery Systems.

FDA-approved self-emulsifying medicines rely on liquid-based formulations, which can exhibit limited stability and short shelf-lives. Solid self-emulsifying drug delivery systems (SEDDS) can improve such issues, but there is still a great need for identifying suitable porous carriers to convert liquid SEDDS into solids without impairing their mechanical properties, functionality, and industrial feasibility. The impact of SEDDS adsorption on tableting is also poorly understood. Therefore, solid SEDDS were prepared by adsorbing liquid SEDDS onto ten commercially available porous excipients. Products were assessed with respect to mechanical behavior, tabletability, and product performance. Adsorbing SEDDS onto porous excipients led to satisfactory stability, with the exception of Zeopharm® 600 due to its high alkalinity, and Neusilin® US2/UFL2, which caused quercetin to crystallize out of the liquid concentrate. SEDDS adsorption reduced the elastic recovery of most excipients, making tableting achievable using Aeroperl® 300 and Aerosil® 200/300. The impact of SEDDS on elastic recovery provides additional understanding on solid SEDDS manufacture process. Acceptable tablets were made via direct compression but with slow disintegration. Addition of a superdisintegrant (crospovidone 5% w/w) ensured tablet manufacturing without impairment of product performance. Solid SEDDS displayed several technical advantages over their liquid counterparts, but attention must be given to the properties of the porous excipient chosen. Drug-excipient interactions play a significant role in drug degradation and crystallization in solid SEDDS. Improved mechanical behavior upon adsorption led to well-composed tablets that performed satisfactorily in vitro upon addition of a superdisintegrant. This study provides an insight on excipient-oriented rational development of solid SEDDS.

Sublingual indocyanine green films for non-invasive swallowing assessment and inflammation detection through NIR/SWIR optical imaging.

Indocyanine green (ICG) is the most commonly used FDA-approved agent for clinical optical imaging, administered through injections only, due to its poor membrane permeability. Although ICG has vast potential for non-invasive non-radioactive imaging in patients, the clinical applications are limited by the invasive administration and short half-life in blood circulation. To expand the clinical value of ICG, non-toxic chitosan-based ICG-loaded films were designed for sublingual administration for near-infrared (NIR) and short-wave infrared (SWIR) optical imaging. Two film formulations were developed with different ICG release rates. Mold-casted self-emulsifying films rapidly released ICG (80% in 4 h) in the form of nanosized droplets, which were mostly swallowed and produced significant contrast of upper digestive tract to enable in vivo swallowing evaluations using NIR/SWIR imaging. Regular films released ICG slowly (80% in 25 h), allowing for steady absorption of ICG to systemic circulation. Inflammation in mouse feet was detected within 30 min after sublingual administration with a 1.43-fold fluorescence increase within 1 h at the inflammation sites, comparable to a 1.76-fold increase through intravenous injection. Administering ICG using sublingual films displayed notable potential for non-invasive diagnosis and monitoring of inflammatory conditions and swallowing disorders, addressing a current need for alternatives to ICG parenteral administration.

Toward Long-Term Accurate and Continuous Monitoring of Nitrate in Wastewater Using Poly(tetrafluoroethylene) (PTFE)-Solid-State Ion-Selective Electrodes (S-ISEs).

Long-term accurate and continuous monitoring of nitrate (NO3-) concentration in wastewater and groundwater is critical for determining treatment efficiency and tracking contaminant transport. Current nitrate monitoring technologies, including colorimetric, chromatographic, biometric, and electrochemical sensors, are not feasible for continuous monitoring. This study addressed this challenge by modifying NO3- solid-state ion-selective electrodes (S-ISEs) with poly(tetrafluoroethylene) (PTFE, (C2F4)n). The PTFE-loaded S-ISE membrane polymer matrix reduces water layer formation between the membrane and electrode/solid contact, while paradoxically, the even more hydrophobic PTFE-loaded S-ISE membrane prevents bacterial attachment despite the opposite approach of hydrophilic modifications in other antifouling sensor designs. Specifically, an optimal ratio of 5% PTFE in the S-ISE polymer matrix was determined by a series of characterization tests in real wastewater. Five percent of PTFE alleviated biofouling to the sensor surface by enhancing the negative charge (-4.5 to -45.8 mV) and lowering surface roughness (Ra: 0.56 ± 0.02 nm). It simultaneously mitigated water layer formation between the membrane and electrode by increasing hydrophobicity (contact angle: 104°) and membrane adhesion and thus minimized the reading (mV) drift in the baseline sensitivity ("data drifting"). Long-term accuracy and durability of 5% PTFE-loaded NO3- S-ISEs were well demonstrated in real wastewater over 20 days, an improvement over commercial sensor longevity.

Redox Potential and ROS-Mediated Nanomedicines for Improving Cancer Therapy.

SIGNIFICANCE: The overabundance of reactive oxygen species (ROS) and antioxidants in cancer cells represents a challenge for therapeutic intervention, while also providing an opportunity for the development of new strategies to improve clinical therapeutic outcomes. Recent Advances: Nanotechnology has advanced tremendously in recent decades and now offers many potential opportunities to leverage altered redox status to improve conventional therapies. Highly tunable nanoparticle delivery systems have shown great promise for improving the following: (i) chemotherapy via selective redox-sensitive drug release in tumor cells and limited systemic toxicity; (ii) photodynamic therapy via enhancing photoactivation and/or ROS production; and (iii) radiation therapy via enhancing ROS production. Great progress has also been made regarding novel nanoparticle-mediated therapies to enhance tumor cell death via ROS generation and angiogenic inhibition. CRITICAL ISSUES: Current anticancer therapies are limited by systemic side effects and resistance. The inherent heterogeneity and hypoxic status of solid tumors impose significant barriers for even the most rationally designed nanoparticle systems. In addition, few comprehensive biodistribution and toxicity evaluations exist, and clinical efficacy remains to be established. The practicality of many nanoparticle systems is compromised by variable in vivo responses and scale-up difficulties due to complicated chemistry and prohibitive manufacturing costs. FUTURE DIRECTIONS: As nanoparticle design continues to advance, improved therapeutic efficacy will likely follow. Actively targeted systems may improve distribution specificity but more positive clinical demonstrations are needed. Further investigation into systemic and intracellular distribution as well as toxicity will improve understanding of how these nanoparticle systems can be applied to improve existing therapies.

Overcoming hypoxia-induced chemoresistance to cisplatin through tumor oxygenation monitored by optical imaging.

Perfluorocarbon nanoparticles have been reported to deliver oxygen to tumors and reduce hypoxia-induced radioresistance, however few studies have been carried out to study its role in reducing hypoxia-induced chemoresistance. The oxygenation effect also varies dramatically between different perfluorocarbon formulations and protocols, and there have been no efficient tools to monitor dynamic changes of tumor oxygenation non-invasively. Our goal was to promote tumor oxygenation using perfluorooctyl bromide (PFOB) nanoemulsion and to assess its role in sensitizing tumors to cisplatin treatment. A novel optical imaging protocol was also created to monitor the dynamic changes of tumor oxygenation in real-time. Methods: PFOB nanoemulsion with high oxygen-carrying capacity was prepared and administered to tumor-bearing mice intravenously. Tumor oxygenation was monitored using optical imaging with a hypoxia probe injected intratumorally, thus the oxygenation dynamics and best oxygenation protocol were determined. Various treatment groups were studied, and the tumor growth was monitored to evaluate the role of oxygenation in sensitizing tumors to cisplatin treatment. Results: PFOB nanoemulsion with and without pre-oxygenation along with carbogen breathing resulted in much better tumor oxygenation compared to carbogen breathing alone, while PFOB with air breathing did not show significant increase in tumor oxygenation. Pre-oxygenated PFOB with carbogen breathing produced the most effective oxygenation as early as 5 min post administration. In vitro and in vivo data showed preoxygenated PFOB nanoemulsion with carbogen breathing could increase cisplatin-mediated apoptosis of cancer cells and inhibited tumor growth at a low dose of cisplatin (1 mg/kg) treatment. Furthermore, the treatment did not induce nephrotoxicity. Conclusions: Preoxygenated PFOB nanoemulsion with carbogen breathing can effectively increase tumor oxygenation, which has a great potential to prevent/overcome hypoxia-induced chemotherapy resistance. In addition, optical imaging with intratumoral injection of the hypoxia probe was an efficient tool to monitor tumor oxygenation dynamics during PFOB administration, providing better understanding on oxygenation effects under different protocols.

Genetically Engineered Bacterial Outer Membrane Vesicles with Expressed Nanoluciferase Reporter for in Vivo Bioluminescence Kinetic Modeling through Noninvasive Imaging.

Outer membrane vesicles (OMVs) produced by Gram-negative bacteria play significant roles in the biomedical field as they can be facilely functionalized using genetic engineering tools and thus often serve as a versatile multifunctional nanoparticles for a variety of applications. In this study, we investigated the multifaceted bioluminescence kinetics of a NanoLuc luciferase-expressed outer membrane vesicle produced by E. coli. This multifunctional OMV emits strong blue luminescence at 460 nm after mixing with the substrate furimazine, which potentially can be used for bioluminescence-based optical imaging. Characterization of the vesicles was performed via dynamic light scattering and nanoparticle tracking analysis. A murine animal model was used to observe the in vivo behavior of the bioluminescence produced by outer membrane vesicles through post subcutaneous administration. The bioluminescence signal was tracked by noninvasive in vivo optical imaging, while in vitro cytotoxicity and ex vivo tissue histopathology were studied to demonstrate the biocompatibility of the engineered OMVs. A theoretical model was also developed to simulate the relevant enzyme-substrate reaction kinetics along with absorption of the in vivo system. The interplay of the reaction and absorption is in good agreement with the experimental results. The study shows a great potential of the genetically engineered vesicles as an interesting class of functional nanomaterials for imaging-related biomedical applications.

Association of PLGA Microspheres to Carrier Pellets by Fluid Bed Coating: A Novel Approach towards Improving the Flowability of Microparticles.

Micro- and nanoparticles have been vastly studied due to their biopharmaceutical advantages. However, these particles generally display very weak packing and poor mechanical properties. Hereby, a new methodology is proposed to associate poorly flowing particles to macrostructures targeting the improvement of flowability and redispersibility of the particles. Cecropia glaziovii-loaded PLGA microspheres (4.59 ± 0.04 µm) were associated with carrier pellets by film coating in a top-spray fluid bed equipment. Optimal conditions were determined employing a IV-Optimal factorial design and RGB image analysis as 1% (w/v) Kollicoat® Protect as coating polymer (2:1 weight ratio of coating suspension to carrier pellets), containing 5 mg/mL microspheres (loading of 28.07 ± 1.01 mg/g). The method led to an improvement of the overall flowability. No relevant molecular interactions between PLGA microspheres and polymers were found. Microspheres detached rapidly from the surface of the pellets, without agglomeration, when exposed to hydrodynamic forces. In vitro release profiles, prior to and after fluid bed coating, showed no relevant changes in drug release rate and extent. The methodology developed is suitable for further applications when an improvement on the flow properties and redispersibility of the product is desired. We showed an easy-to-implement methodology that can be executed without significant increase in costs.

Carnauba wax as a promising excipient in melt granulation targeting the preparation of mini-tablets for sustained release of highly soluble drugs.

Mini-tablets are a new tendency in solid dosage form design for overcoming therapeutic obstacles such as impaired swallowing and polypharmacy therapy. Among their advantages, these systems offer therapeutic benefits such as dose flexibility and combined drug release patterns. The use of lipids in the formulation has also drawn considerable interest as means to modify the drug release from the dosage form. Therefore, this paper aimed at developing sustained release mini-tablets containing the highly soluble drugs captopril and metformin hydrochloride. Carnauba wax was used as a lipid component in melt granulation, targeting the improvement of the drugs poor flowability and tabletability, as well as to sustain the drug release profiles in association with other excipients. To assist sustaining the drug release, Ethocel™ (EC) and Kollicoat® SR 30D associated with Opadry® II were employed as matrix-forming and reservoir-forming materials, respectively. The neat drugs, granules and the bulk formulations were evaluated for their angle of repose, compressibility index, Hausner ratio and tabletability. Mini-tablets were evaluated for their weight variation, hardness, friability, drug content and in-vitro drug release. The results indicated that melt granulation with carnauba wax improved the flow and the tabletability of the drugs, allowing the preparation of mini-tablets with adequate tensile strength under reduced compaction pressures. All mini-tablet formulations showed acceptable hardness (within the range of 1.16 to 3.93Kp) and friability (<0.1%). The melt-granulated captopril in matrix systems containing 50% EC (45P, 100P or 100FP) and the melt-granulated metformin hydrochloride in reservoir systems coated with Kollicoat® SR 30D and Opadry® II (80:20 with 10% weight gain or 70:30 with 20% weight gain) exhibited release profiles adequate to sustained release formulations, for over 450min. Therefore, carnauba wax proved to be a promising excipient in melt granulation targeting the preparation of mini-tablets for sustained release of soluble drugs.