Supersaturated silica-lipid hybrids (super-SLH): An improved solid-state lipid-based oral drug delivery system with enhanced drug loading

Influence of polymer and surfactant-based precipitation inhibitors on supersaturation-driven absorption of Ibrutinib from high-dose lipid-based formulations

There is a growing pharmaceutical interest in supersaturated lipid-based formulations (Super-LbF) as an innovative strategy to enhance drug loading capacities while simultaneously reducing pill burden. This approach involves increasing the drug concentration above its equilibrium solubility in a lipid solution, achieved through temperature-induced supersaturation or the dissolution of lipophilic ionic salts. However, the physical instability and potential drug precipitation upon the dispersion of LbF remain critical. The focus of this work was to assess the impact of polymer and surfactant as precipitation inhibitors (PIs) in Super-LbF and investigate whether PIs can effectively address the aforementioned challenges. Ibrutinib (Ibr) was selected as a model drug due to its limited solubility and dissolution characteristics. The optimized formulations were characterized with a focus on dispersibility, lipolysis-permeation, and physical stability during storage. The inclusion of PIs in Super-LbF significantly enhanced physical stability by increasing viscosity and reducing the degree of supersaturation through elevated equilibrium solubility. During the dispersion and digestion study, varying levels of transient supersaturation were observed for both Super-LbF and PI-loaded Super-LbF. A noteworthy 2.5 to 3-fold increase in the solubilization ratio was observed for PI-loaded Super-LbF in comparison to Super-LbF without PI. This increase indicates a significant rise in transient drug supersaturation through kinetic and thermodynamic precipitation inhibition mechanisms. Moreover, lipolysis-permeation studies revealed increased flux values with enhanced solubilization, except in the case of Pluronic® F68, which exhibited a reduced free drug concentration near the Permeapad® barrier. Further, the in vivo absorption study confirmed that prolonged supersaturation, facilitated by PIs, contributed to enhancement in drug exposure in rats. PI-loaded Super-LbFs demonstrated a significant improvement (5.1 to 8.9-fold) in the absorption profile compared to Super-LbF without PI (p < 0.001). The study results indicate that incorporating PIs into Super-LbF enhances physical stability and maintains transient drug supersaturation under digestive conditions. Overall, this formulation approach shows promise for expanding the application of LbF to enable the successful oral delivery of high-dose regimen drugs.

Thermally-Induced Supersaturation Approach for Optimizing Drug Loading and Biopharmaceutical Properties of Supersaturated Lipid-Based Formulations: Case Studies with Ibrutinib and Enzalutamide

Lipid-based formulations (LbFs) have demonstrated success in pharmaceutical applications; however, challenges persist in dissolving entire doses of the drug into defined liquid volumes. In this study, the temperature-induced supersaturation method was employed in LbF to address drug loading and pill burden issues. Supersaturated LbFs (super-LbF) were prepared using the temperature-induced supersaturation method, where the drug load is above its equilibrium solubility. Further, the influence of the drug's physicochemical and thermal characteristics on drug loading and their relevance with an apparent degree of supersaturation (aDS) was studied using two model drugs, ibrutinib and enzalutamide. All the prepared LbFs were evaluated in terms of physical stability, dispersion, and solubilization capacity, as well as pharmacokinetic assessments. Drug re-crystallization was observed in the lipid solution on long-term storage at higher aDS values of 2-2.5. Furthermore, high-throughput lipolysis studies demonstrated a significant decrease in drug concentration across all LbFs (regardless of drug loading) due to a decline in the formulation solvation capacity and subsequent generation of in-situ supersaturation. Further, the in vivo results demonstrated comparable pharmacokinetic parameters between conventional LbF and super-LbF. The short duration of the thermodynamic metastable state limits the potential absorption benefits. However, super-LbFs of Ibr and Enz showed superior profiles, with 1.7-fold and 5.2-fold increased drug exposure compared to their respective crystalline suspensions. In summary, this study emphasizes the potential of temperature-induced supersaturation in LbF for enhancing drug loading and highlights the intricate interplay between drug properties, formulation characteristics, and in vivo performance.

Functionalized calcium carbonate (FCC) as a novel carrier to solidify supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS)

Functionalized calcium carbonate (FCC), a novel pharmaceutical excipient, has shown promising properties in the field of oral drug delivery. The current study aimed at evaluating the feasibility of FCC as a carrier for the solidification of self-nanoemulsifying drug delivery systems (SNEDDS) containing the poorly water-soluble model drug carvedilol (CRV). Conventional, subsaturated SNEDDS (80 %-SNEDDSliquid) and supersaturated SNEDDS (200 %-SNEDDSliquid) were loaded onto FCC via physical adsorption at three ratios; 2.5:1, 3.0:1 and 3.5:1 (w/w) of FCC:SNEDDSliquid, respectively, generating free-flowing powders (SNEDDSFCC) with drug loading ranging from 0.8 % to 2.6 % (w/w) CRV. The emulsification of SNEDDSFCC in a USP II dissolution setup (in purified water) was characterized using dynamic light scattering, resulting in similar droplet sizes and PDIs as observed for their liquid counterparts. The morphology and physical state of the obtained SNEDDSFCC were characterized using scanning electron microscopy and differential scanning calorimetry. The physical stability and drug release upon dispersion were assessed as a function of storage time. The 200 %-SNEDDSliquid were physically stable for 6 days, however, solidification using FCC stabilized the supersaturated concentrations of CRV for a test period of up to 10 weeks (solidification ratios 3.0:1 and 3.5:1 (FCC:SNEDDSliquid)). SNEDDSFCC achieved an improved rate and extent of drug release upon dispersion compared to the crystalline CRV in tap water (pH 7.5), however, to a lesser extent than their liquid counterparts. After 8 weeks of storage (25 °C at dry conditions), FCC was still able to rapidly release the SNEDDSliquid and demonstrated the same rate and extent of drug release as freshly prepared samples. The solidification of 200 %-SNEDDSliquid in presence of FCC greatly improved the drug loading and showed an enhanced drug release profile compared to the conventional systems. In conclusion, FCC showed potential as a carrier for solidification of SNEDDS and for the development of novel supersaturated solid SNEDDS for the oral delivery of poorly water-soluble drugs.

Battle of the milky way: Lymphatic targeted drug delivery for pathogen eradication

Many viruses, bacteria, and parasites rely on the lymphatic system for survival, replication, and dissemination. While conventional anti-infectives can combat infection-causing agents in the bloodstream, they do not reach the lymphatic system to eradicate the pathogens harboured there. This can result in ineffective drug exposure and reduce treatment effectiveness. By developing effective lymphatic delivery strategies for antiviral, antibacterial, and antiparasitic drugs, their systemic pharmacokinetics may be improved, as would their ability to reach their target pathogens within the lymphatics, thereby improving clinical outcomes in a variety of acute and chronic infections with lymphatic involvement (e.g., acquired immunodeficiency syndrome, tuberculosis, and filariasis). Here, we discuss approaches to targeting anti-infective drugs to the intestinal and dermal lymphatics, aiming to eliminate pathogen reservoirs and interfere with their survival and reproduction inside the lymphatic system. These include optimized lipophilic prodrugs and drug delivery systems that promote lymphatic transport after oral and dermal drug intake. For intestinal lymphatic delivery via the chylomicron pathway, molecules should have logP values >5 and long-chain triglyceride solubilities >50 mg/g, and for dermal lymphatic delivery via interstitial lymphatic drainage, nanoparticle formulations with particle size between 10 and 100 nm are generally preferred. Insight from this review may promote new and improved therapeutic solutions for pathogen eradication and combating infective diseases, as lymphatic system involvement in pathogen dissemination and drug resistance has been neglected compared to other pathways leading to treatment failure.

Lipid based formulations as supersaturating oral delivery systems: From current to future industrial applications

Lipid-based formulations, in particular supersaturated lipid-based formulations, are important delivery approaches when formulating challenging compounds, as especially low water-soluble compounds profit from delivery in a pre-dissolved state. In this article, the classification of lipid-based formulation is described, followed by a detailed discussion of different supersaturated lipid-based formulations and the recent advances reported in the literature. The supersaturated lipid-based formulations discussed include both the in situ forming supersaturated systems as well as the thermally induced supersaturated lipid-based formulations. The in situ forming drug supersaturation by lipid-based formulations has been widely employed and numerous clinically available products are on the market. There are some scientific gaps in the field, but in general there is a good understanding of the mechanisms driving the success of these systems. For thermally induced supersaturation, the technology is not yet fully understood and developed, hence more research is required in this field to explore the formulations beyond preclinical studies and initial clinical trials.

Bioengineered "Molecular Glue"-Mediated Tumor-Specific Cascade Nanoreactors with Self-Destruction Ability for Enhanced Precise Starvation/Chemosynergistic Tumor Therapy

The ordered and directed functionalization of targeting elements on the surface of nanomaterials for precise tumor therapy remains a challenge. To address the above problem, herein, we adopted a materials-based synthetic biotechnology strategy to fabricate a bioengineered fusion protein of materials-binding peptides and targeting elements, which can serve as a "molecular glue" to achieve a directional and organized assembly of targeting biological macromolecules on the surface of nanocarriers. The hypoxia microenvironment of solid tumors inspired the rapid development of starvation/chemosynergistic therapy; however, the unsatisfied spatiotemporal specific performance hindered its further development in precise tumor therapy. As a proof of concept, a bioengineered fusion protein containing a dendritic mesoporous silicon (DMSN)-binding peptide, and a tumor-targeted and acidity-decomposable ferritin heavy chain 1 (FTH1), was constructed by fusion expression and further assembled on the surface of DMSN companying with the insertion of hypoxia-activated prodrug tirapazamine (TPZ) and glucose oxidase (GOX) to establish a nanoreactor for precise starvation/chemosynergistic tumor therapy. In this context, the as-prepared therapeutic nanoreactors revealed obvious tumor-specific accumulation and an endocytosis effect. Next, the acidic tumor microenvironment triggered the structural collapse of FTH1 and the subsequent release of GOX and TPZ, in which GOX-mediated catalysis cut off the nutrition supply to realize starvation therapy based on the consumption of endogenous glucose and further provided an exacerbated hypoxia environment for TPZ in situ activation to initiate tumor chemotherapy. More significantly, the presence of "molecular glue" elevated the tumor-targeting capacity of nanoreactors and further enhanced the starvation/chemosynergistic therapeutic effect remarkably, suggesting that such a strategy provided a solution for the functionality of nanomaterials and facilitated the design of novel targeting nanomedicines. Overall, this study highlights materials-binding peptides as a new type of "molecular glue" and opens new avenues for designing and exploring active biological materials for biological functions and applications.

Supersaturating lipid-based solid dispersion of atazanavir provides enhanced solubilization and supersaturation in the digestive aqueous phase

Understanding and controlling the drug solubilization in digestive environment is of great importance in the design of lipid based solid dispersion (LBSD) for oral delivery of poorly aqueous soluble drugs. In the current study we determined the extent of drug solubilization and supersaturation of supersaturating lipid based solid dispersion which is governed by formulation variables like drug payload, lipid composition, solid carrier properties and lipid to solid carrier ratio. Initially, the impact of lipid chain length and drug payload on drug solubilization in lipid preconcentrate and dispersibility were evaluated to design liquid LbF of the model antiretroviral drug, atazanavir. The temperature induced supersaturation method enhanced the drug payload in medium chain triglyceride formulation at 60 °C. Further, the selected liquid supersaturated LbF was transformed into solid state LbF by employing different solid carriers including silica (Neusilin® US2 and Aerosil® 200), clay (Montmorillonite and Bentonite) and polymer (HPMC-AS and Kollidon® CL-M). The fabricated LBSDs were evaluated for solid state characterization to identify the physical nature of drug. In vitro digestion studies were conducted using pH-stat lipolysis method to assess the supersaturation propensity in aqueous digestive phase. Results revealed that LBSDs with silica and polymer carriers showed maximum drug solubilization throughout experiment compared to liquid LbF. The ionic interaction between drug-clay particles significantly reduced the ATZ partitioning from clay based LBSDs. LBSDs with dual purpose solid carrier like HPMC-AS and Neusilin® US2 offers the potential to improve drug solubilization of ATZ for physiologically relevant time. Lastly, we conclude that evaluation of formulation variables is crucial to achieve optimal performance of supersaturating LBSD.

The Influence of Blonanserin Supersaturation in Liquid and Silica Stabilised Self-Nanoemulsifying Drug Delivery Systems on In Vitro Solubilisation

Reformulating poorly water-soluble drugs as supersaturated lipid-based formulations achieves higher drug loading and potentially improves solubilisation and bioavailability. However, for the weak base blonanserin, silica solidified supersaturated lipid-based formulations have demonstrated reduced in vitro solubilisation compared to their liquid-state counterparts. Therefore, this study aimed to understand the influence of supersaturated drug load on blonanserin solubilisation from liquid and silica solidified supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) during in vitro lipolysis. Stable liquid super-SNEDDS with varying drug loads (90-300% of the equilibrium solubility) were solidified by imbibition into porous silica microparticles (1:1 lipid: silica ratio). In vitro lipolysis revealed greater blonanserin solubilisation from liquid super-SNEDDS compared to solid at equivalent drug saturation levels, owing to strong silica-BLON/lipid interactions, evidenced by a significant decrease in blonanserin solubilisation upon addition of silica to a digesting liquid super-SNEDDS. An increase in solid super-SNEDDS drug loading led to increased solubilisation, owing to the increased drug:silica and drug:lipid ratios. Solidifying SNEDDS with silica enables the fabrication of powdered formulations with higher blonanserin loading and greater stability than liquid super-SNEDDS, however at the expense of drug solubilisation. These competing parameters need careful consideration in designing optimal super-SNEDDS for pre-clinical and clinical application.

Fundamental Aspects of Lipid-Based Excipients in Lipid-Based Product Development

Poor aqueous solubility of drugs is still a foremost challenge in pharmaceutical product development. The use of lipids in designing formulations provides an opportunity to enhance the aqueous solubility and consequently bioavailability of drugs. Pre-dissolution of drugs in lipids, surfactants, or mixtures of lipid excipients and surfactants eliminate the dissolution/dissolving step, which is likely to be the rate-limiting factor for oral absorption of poorly water-soluble drugs. In this review, we exhaustively summarize the lipids excipients in relation to their classification, absorption mechanisms, and lipid-based product development. Methodologies utilized for the preparation of solid and semi-solid lipid formulations, applications, phase behaviour, and regulatory perspective of lipid excipients are discussed.

Enhancement of drug penetration rate by enriching skin hydration: a novel amalgamation of microemulsion and supersaturation

Background:

The evolving need and facilitation of topical formulations have risen in the present era. Topical industries are continually striving to satisfy patients with newer and innovative products. However, dry skin is the critical factor contributing to drug penetration into the skin.

Objective:

The current research aimed to develop cost-effective and commercially feasible industrial scale microemulsion of wheat germ oil to enrich skin hydration, enhancing the drug permeation rate.

Methods:

The Pseudo-ternary phase diagram was constructed for screening of microemulsion components. Wheat germ oil containing O/W microemulsion was prepared and evaluated for physicochemical parameters, thermodynamic stability study, globule size determination, enhancement of skin hydration, and skin permeation rate by ex vivo study.

Results:

The wheat germ oil containing microemulsion was prepared by incorporating tween 20 [surfactant] and ethanol [co-surfactant]. All physicochemical parameters were in the ideal range. Following the thermodynamic stability study, the TEM study showed globule size of optimized microemulsions in the range of 69.64 nm to 84.42 nm. The skin moisture tester showed a high hydration level for more than eight hours. An Ex vivo study revealed higher drug flux [Jss] of Pomegranate peel Extract [17.99 μg/cm2/h] with an enhancement ratio of 1.69.

Conclusion:

The topical formulation application has become challenging for researchers due to the skin's dryness and lower water content. However, the developed WGO microemulsion aids more penetration and is helpful to achieve higher drug flux. In addition, it is a cost-effective, easy to prepare, and patient-friendly drug delivery system.

Role of Silica Intrawall Microporosity on Abiraterone Acetate Solubilization and In Vivo Oral Absorption

SBA-15 mesoporous silica (MPS) has been widely used in oral drug delivery; however, it has not been utilized for solidifying lipid-based formulations, and the impact of their characteristic intrawall microporosity remains largely unexplored. Here, we derive the impact of the MPS microporosity on the in vitro solubilization and in vivo oral pharmacokinetics of the prostate cancer drug abiraterone acetate (AbA) when coencapsulated along with medium chain lipids into the pores. AbA in lipid (at 80% equilibrium solubility) was imbibed within a range of MPS particles (with comparable morphology and mesoporous structure but contrasting microporosity ranging from 0-247 m²/g), and their solid-state properties were characterized. Drug solubilization studies during in vitro lipolysis revealed that microporosity was the key factor in facilitating AbA solubilization by increasing the surface area available for drug-lipid diffusion. Interestingly, microporosity hindered hydrolysis of AbA to its active metabolite, abiraterone (Ab), under simulated intestinal conditions. This unique relationship between microporosity and AbA/Ab aqueous solubilization behavior was hypothesized to have significant implications on the subsequent bioavailability of the active metabolite. In vivo oral pharmacokinetics studies in male Sprague-Dawley rats revealed that MPS with moderate microporosity attained the highest relative bioavailability, while poor in vitro-in vivo correlations (IVIVC) existed between in vitro drug solubilization during lipolysis and in vivo AUC. Despite this, a reasonable IVIVC was established between the in vitro solubilization and in vivo C_max, providing evidence for an association between silica microporosity and oral drug absorption.

Formation of Self-Assembled Liquid Crystalline Nanoparticles and Absorption Enhancement of Ω-3s by Phospholipids and Oleic Acids

This study aimed to optimize and evaluate self-assembled liquid crystalline nanoparticles (SALCs) prepared from phospholipids and oleic acid for enhancing the absorption of Ω-3s. We explored the structure and optimal formulation of SALCs, which are composed of Ω-3 ethyl ester (Ω-3 EE), phospholipids, and oleic acid, using a ternary diagram and evaluated the improvement in Ω-3 dissolution, permeation, and oral bioavailability. The in vitro dissolution and pharmacokinetics of Ω-3 SALCs were compared with those of Omacor soft capsules (as the reference). The shape of the liquid crystal was determined according to the composition of phospholipids, oleic acids, and Ω-3s and was found to be in cubic, lamellar, and hexagonal forms. The dissolution rates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) obtained from Ω-3 SALCs were 1.7 to 2.3-fold higher than those of the Omacor soft capsules. Furthermore, a pharmacokinetic study in male beagle dogs revealed that Ω-3 SALCs increased the oral bioavailability of Ω-3 EE by 2.5-fold for EPA and 3.1-fold for DHA compared with the reference. We found an optimal formulation that spontaneously forms liquid crystal-based nanoparticles, improving the bioavailability of EPA and DHA, not found in the existing literature. Our findings offer insight into the impact of nanoparticle phase on the oral delivery of oil-soluble drugs and provide a novel Ω-3 EE formulation that improves the bioavailability of EPA and DHA.

The Influence of Solidification on the in vitro Solubilisation of Blonanserin Loaded Supersaturated Lipid-Based Oral Formulations

Supersaturated silica-lipid hybrids have previously demonstrated improved in vitro solubilisation and in vivo oral bioavailability of poorly water-soluble drugs, however were only fabricated using a single lipid (LFCS type I formulations) and were not compared to their liquid precursors. This study investigated the influence of lipid formulation classification (type I vs. type II vs. type IIIA/SNEDDS) and physical state (liquid LBF vs. solidified with silica) on the in vitro solubilisation of the poorly soluble, weak base, anti-psychotic drug, blonanserin (BLON), from a supersaturated lipid-based formulation (LBF). Stable liquid supersaturated LBF were fabricated using BLON (loaded at 150% of its equilibrium solubility), and solidified through encapsulation within porous silica microparticles at a 1:1 ratio. Their physicochemical properties and in vitro solubilisation during lipolysis were compared. Supersaturated BLON was encapsulated in the non-crystalline form. All supersaturated LBF improved the solubilisation of pure BLON during lipolysis regardless of their lipid formulation type or their physical state (1.7- to 13.4-fold). SNEDDS achieved greater solubilisation than the type II formulations (1.4- to 1.7-fold). Furthermore, the liquid precursors achieved greater solubilisation than the silica solidified formulations (4.5- to 5.7-fold). Additionally, in an attempt to increase BLON solubilisation, a spray-dried SNEDDS and dual-loaded solidified super-SNEDDS solidified with silica pre-loaded with BLON was developed, however did not significantly improve solubilisation. Liquid SNEDDS were identified as the optimal oral supersaturated LBF strategy for BLON based on in vitro lipolysis studies. Solidification of LBF using silica is a viable strategy for improving stability, however for drugs such as BLON, solidification may impede in vitro release and solubilisation.

Nanoporous Silica Entrapped Lipid-Drug Complexes for the Solubilization and Absorption Enhancement of Poorly Soluble Drugs

This study aims to examine the contribution of nanoporous silica entrapped lipid-drug complexes (NSCs) in improving the solubility and bioavailability of dutasteride (DUT). An NSC was loaded with DUT (dissolved in lipids) and dispersed at a nanoscale level using an entrapment technique. NSC microemulsion formation was confirmed using a ternary phase diagram, while the presence of DUT and lipid entrapment in NSC was confirmed using scanning electron microscopy. Differential scanning calorimetry and X-ray diffraction revealed the amorphous properties of NSC. The prepared all NSC had excellent flowability and enhanced DUT solubility but showed no significant difference in drug content homogeneity. An increase in the lipid content of NSC led to an increase in the DUT solubility. Further the NSC were formulated as tablets using D-α tocopheryl polyethylene glycol 1000 succinate, glyceryl caprylate/caprate, and Neusilin^®. The NSC tablets showed a high dissolution rate of 99.6% at 30 min. Furthermore, NSC stored for 4 weeks at 60 °C was stable during dissolution testing. Pharmacokinetic studies performed in beagle dogs revealed enhanced DUT bioavailability when administered as NSC tablets. NSC can be used as a platform to develop methods to overcome the technical and commercial limitations of lipid-based preparations of poorly soluble drugs.

Porous Nanostructure, Lipid Composition, and Degree of Drug Supersaturation Modulate In Vitro Fenofibrate Solubilization in Silica-Lipid Hybrids

The unique nanostructured matrix obtained by silica-lipid hybrids (SLHs) is well known to improve the dissolution, absorption, and bioavailability of poorly water-soluble drugs (PWSDs). The aim of this study was to investigate the impact of: (i) drug load: 3–22.7% w/w, (ii) lipid type: medium-chain triglyceride (Captex 300) and mono and diester of caprylic acid (Capmul PG8), and (iii) silica nanostructure: spray dried fumed silica (FS) and mesoporous silica (MPS), on the in vitro dissolution, solubilization, and solid-state stability of the model drug fenofibrate (FEN). Greater FEN crystallinity was detected at higher drug loads and within the MPS formulations. Furthermore, an increased rate and extent of dissolution was achieved by FS formulations when compared to crystalline FEN (5–10-fold), a commercial product; APO-fenofibrate (2.4–4-fold) and corresponding MPS formulations (2–4-fold). Precipitation of FEN during in vitro lipolysis restricted data interpretation, however a synergistic effect between MPS and Captex 300 in enhancing FEN aqueous solubilization was attained. It was concluded that a balance between in vitro performance and drug loading is key, and the optimum drug load was determined to be between 7–16% w/w, which corresponds to (200–400% equilibrium solubility in lipid S_eq). This study provides valuable insight into the impact of key characteristics of SLHs, in constructing optimized solid-state lipid-based formulations for the oral delivery of PWSDs.

The effect of drug ionization on lipid-based formulations for the oral delivery of anti-psychotics

Lipid-based formulations (LBFs) are well-known to improve the oral bioavailability of poorly water-soluble drugs (PWSDs) by presenting the drug to the gastrointestinal environment in a molecularly dispersed state, thus avoiding the rate-limiting dissolution step. Risperidone and lurasidone are antipsychotics drugs which experience erratic and variable absorption, leading to a low oral bioavailability. The aim of this research was to develop and investigate the performance of risperidone and lurasidone when formulated as an emulsion and silica-lipid hybrid (SLH). Lurasidone and risperidone were dissolved in Capmul® MCM at 100% and 80% their equilibrium solubility, respectively, prior to forming a sub-micron emulsion. SLH microparticles were fabricated by spray-drying a silica stabilised sub-micron emulsion to form a solid powder. The performances of the formulations were evaluated in simulated intestinal media under digesting conditions, where the emulsion and SLH provided a 17-fold and 23-fold increase in LUR solubilisation, respectively. However, the performance of RIS was reduced by 2.2-fold when encapsulated within SLH compared to pure drug. Owing to its pKa, RIS adsorbed to the silica and thus, dissolution was significantly hindered. The results reveal that LBFs may not overcome the challenges of all PWSDs and physiochemical properties must be carefully considered when predicting drug performance.

Development and characterisation of ibuprofen-loaded nanoemulsion with enhanced oral bioavailability

Lipophilic compounds constitute a majority of therapeutics in the pipeline of drug discovery. Despite possessing enhanced efficacy and permeability, some of these drugs suffer poor solubility necessitating the need of a suitable drug delivery system. Nanoemulsion is a drug delivery system that provides enhanced solubility for poorly soluble drugs in an attempt to improve the oral bioavailability. The purpose of this study is to develop a nanoemulsion system using ibuprofen as a model drug in order to investigate the potential of this colloidal system to enhance the absorption of poorly water-soluble drugs. Ibuprofen loaded-nanoemulsion with different drug concentrations (1.5, 3 and 6% w/w) were formulated from olive oil, sucrose ester L-1695 and glycerol using D-phase emulsification technique. A pseudoternary phase diagram was utilised to identify the optimal excipient composition to formulate the nanoemulsion system. In vitro diffusion chamber studies using rodent intestinal linings highlighted improved absorption profile when ibuprofen was delivered as nanoemulsion in comparison to microemulsions and drug-in-oil systems. This was further corroborated by in vivo studies using rat model that highlighted a two-fold increase in ibuprofen absorption when the drug was administered as a nanoemulsion relative to drug-in-oil system. On the other hand, when ibuprofen was administered as microemulsions, only a 1.5-fold increase in absorption was observed relative to drug-in-oil system. Thus, this study highlights the potential of using nanoemulsion as a drug delivery system to enhance the oral bioavailability of hydrophobic drugs.

Enhancement of abiraterone acetate oral bioavailability by supersaturated-silica lipid hybrids

Abiraterone acetate (AbA) has an oral bioavailability of <10% due to its poor water solubility. Here we investigate the performance of silica-lipid hybrids (SLH) and supersaturated SLH (super-SLH) in improving oral bioavailability of AbA. Specifically, we investigate the influence of lipid type and AbA saturation level of the equilibrium solubility in the lipid (S_eq), and explore in vitro-in vivo correlation (IVIVC). An oral pharmacokinetic study was conducted in fasted Sprague-Dawley rats. Suspensions of the formulations were administered via oral gavage at an AbA dose of 25 mg/kg. Plasma samples were collected and analyzed for drug content. SLH with a saturation level of 90% S_eq enhanced the oral bioavailability of unformulated AbA by 31-fold, and super-SLH with saturation levels of 150, 200 and 250% S_eq, enhanced the bioavailability by 11, 10 and 7-fold, respectively. In comparison with the commercial product Zytiga, SLH (90% S_eq) increased the oral bioavailability 1.43-fold whereas super-SLH showed no improvement. A reasonable IVIVC existed between the performance of unformulated AbA, SLH and super-SLH, in the in vitro lipolysis and in vivo oral pharmacokinetic studies. SLH and super-SLH significantly enhanced the oral bioavailability of AbA. Additionally, supersaturation of SLH improved drug loading but did not correlate with enhanced AbA bioavailability.

Enhancing the oral bioavailability of simvastatin with silica-lipid hybrid particles: The effect of supersaturation and silica geometry

Silica-lipid hybrid (SLH) microparticles are a solidified lipid-based drug delivery system under investigation for their aptitude to enhance the oral bioavailability of poorly water-soluble drugs. The cholesterol-lowering agent, simvastatin (SIM), is poorly water-soluble and undergoes extensive first pass metabolism, resulting in a low oral bioavailability of approximately 5%. Hence, the current pre-clinical studies investigated the application of SLH technology to SIM with a supersaturation approach, aiming to enhance bioavailability and drug loading capacity. Additionally, the effect of silica was explored by evaluating the performance of SLH fabricated with silica of different particle geometries. SLH microparticles with supersaturated SIM loading levels ranging from 100% to 400% above the equilibrium solubility were successfully fabricated using either Aerosil® 300 or Syloid® 244 silica. All SLH formulations existed as white free-flowing powders, consisting of spherical porous microparticles for Aerosil® 300, and aggregated irregular microparticles for Syloid® 244. During in vitro dissolution in pH 7.0 media, the SLH formulations performed up to 4.4-fold greater than pure SIM powder. Furthermore, in vivo oral pharmacokinetics in male Sprague-Dawley rats revealed that the SLH formulations enhanced the oral bioavailability of SIM up to 6.1-fold and 2.9-fold, in comparison to pure SIM powder and a commercially available formulation (Simvastatin Sandoz®), respectively. The greatest in vivo performance enhancement was observed for the SLH formulation manufactured with Syloid® 244 silica with a supersaturation level of 200%. SLH technology demonstrated to be a successful formulation strategy to significantly improve the oral bioavailability of SIM in rodents and therefore, has a strong potential to also improve the oral bioavailability of SIM in humans.

Supersaturated-Silica Lipid Hybrids Improve in Vitro Solubilization of Abiraterone Acetate

PURPOSE

Abiraterone acetate (AbA) is a poorly water-soluble drug with an oral bioavailability of <10% and a significant pharmaceutical food effect. We aimed to develop a more efficient oral solid-state lipid-based formulation for AbA using a supersaturated silica-lipid hybrid (super-SLH) approach to achieve high drug loading, improve in vitro solubilization and mitigate the food effect, while gaining a mechanistic insight into how super-SLH are digested and release drug.

METHODS

The influence of super-SLH saturation level and lipid type on the physicochemical properties and in vitro solubilization during lipolysis of the formulations was investigated and compared to the commercial product, Zytiga.

RESULTS

Super-SLH achieved significantly greater levels of AbA solubilization compared to Zytiga. Solubilization was influenced by the AbA saturation level, which determined the solid state of AbA and the relative amount of lipid, and the lipid utilized, which determined its degree of digestion and the affinity of the lipid and digestion products to the silica. A fine balance existed between achieving high drug loads using supersaturation and improving performance using the lipid-based formulation approach. The non-supersaturated SLH prepared with Capmul PG8 mitigated the 3-fold in vitro food effect.

CONCLUSION

SLH and super-SLH improve in vitro solubilization of AbA, remove the food effect and demonstrate potential to improve oral bioavailability in vivo. Graphical Abstract Abiraterone acetate was formulated as silica-lipid hybrids and demonstrated enhanced in vitro solubilization in comparison to pure abiraterone acetate and commercial product, Zytiga.

Oral formulation strategies to improve the bioavailability and mitigate the food effect of abiraterone acetate

Abiraterone acetate, marketed as Zytiga®, is an antiandrogen medication used in the treatment of prostate cancer. Abiraterone acetate is a BCS Class IV compound associated with several oral delivery challenges. Its low solubility and high lipophilicity lead to poor oral bioavailability (<10%) and a dramatic positive food effect (5-10-fold). Hence, a large dose of abiraterone acetate (1000 mg per day) is prescribed to patients who must fast for at least 1 h before and 2 h after administration. The recent expiry of Zytiga®s' patent has led to the emergence of publications describing improved oral formulation strategies for abiraterone acetate. This review aims to discuss the characteristics of abiraterone acetate that lead to its unfavorable oral delivery, examine the oral formulation strategies that have been applied, and to describe potential alternative oral formulation strategies that have been used for other BCS Class IV drugs, to determine the most valuable strategies to develop novel and improved alternatives to the current commercial product. Specific emphasis of this review is placed on enabling oral formulation strategies that can improve solubilization and bioavailability, reduce the clinical dose and remove the pharmaceutical food effect to ultimately provide prostate cancer patients with a more efficient formulation with greater patient compliance.

A pre-formulation strategy for the liposome encapsulation of new thioctic acid conjugates for enhanced chemical stability and use as an efficient drug carrier for MPO-mediated atherosclerotic CVD treatment

Lipoyl-apocynin and lipoyl-sesamol are bio-active conjugates of thioctic acid, synthesized using a benign chemical approachviathe combination of thioctic acid and the powerful bio-phytonutrients, apocynin and sesamol, respectively.

Supersaturated Silica-Lipid Hybrid Oral Drug Delivery Systems: Balancing Drug Loading and In Vivo Performance

Supersaturated silica-lipid hybrid (super-SLH) drug carriers are a recent strategy to improve the drug loading of oral solid lipid based formulations, however they are yet to be studied in vivo. This study investigated the in vivo pharmacokinetics (PK) of super-SLH containing ibuprofen (IBU), as a model Biopharmaceutics Classification Scheme (BCS) class II drug, analyzing the influence of supersaturated drug loading on oral bioavailability and assessing in vitro-in vivo correlation (IVIVC). In addition, super-SLH was directly compared with spray-dried SLH and Nurofen to explore its potential advantages over the well-established and commercial formulations. Fasted male Sprague-Dawley rats were administered formulation suspensions (10 mg/kg IBU) via oral gavage, and blood samples were acquired and plasma was analyzed for IBU concentrations over 24 hours. In vivo, super-SLH with drug loads of 9.5 (99.5% saturated) and 19.3% w/w (227% saturated) achieved bioavailabilities equal to spray-dried SLH and 2.2-fold greater than Nurofen. This effect diminished for super-SLH with a drug load of 29.1% w/w (389% saturated), which exhibited a bioavailability of less than Nurofen due to its greater extent of supersaturation and larger content of crystalline IBU. The super-SLH containing 19.3% w/w IBU provided the greatest PK performance, achieving the same degree of bioavailability enhancement as spray-dried SLH and requiring 63% less formulation. A significant positive IVIVC was observed between the performances of the formulations. These findings indicate the potential of super-SLH as an improved oral solid lipid based formulation strategy for enhancing oral bioavailability of other BCS class II drugs.

A Comparative Study of the Use of Mesoporous Carbon and Mesoporous Silica as Drug Carriers for Oral Delivery of the Water-Insoluble Drug Carvedilol

Mesoporous carriers have been extensively applied to improve the dissolution velocity and bioavailability of insoluble drugs. The goal of this work was to compare the drug-loading efficiency (LE) and drug-dissolution properties of mesoporous silica nanoparticles (MSN) and mesoporous carbon nanoparticles (MCN) as drug vectors oral delivery of water-insoluble drugs. For this purpose, MSN and MCN with similar particle size, surface area, and mesoporous diameter were prepared to precisely evaluate the effects of different textures on the drug-loading and dissolution behavior of insoluble drugs. Carvedilol (CAR), a Bio-pharmaceutic Classification System (BCS) class II drug, was loaded in the MSN and MCN by the solvent adsorption method and solvent evaporation method with different carrier–drug ratios. The carboxylated MCN (MCN–COOH) had a higher LE for CAR than MSN for both the two loading methods due to the strong adsorption effect and π–π stacking force with CAR. In vitro drug dissolution study showed that both MSN and MCN-COOH could improve the dissolution rate of CAR compared with the micronized CAR. In comparison to MSN, MCN-COOH displayed a slightly slower dissolution profile, which may be ascribed to the strong interaction between MCN-COOH and CAR. Observation of cell cytotoxicity and gastrointestinal mucosa irritation demonstrated the good biocompatibility of both MSN and MCN–COOH. The present study encourages further research of different carriers to determine their potential application in oral administration.

An update on polymer-lipid hybrid systems for improving oral drug delivery

INTRODUCTION

A promising approach that has recently emerged to overcome the complex biobarriers and interrelated challenges associated with oral drug absorption is to combine the benefits of polymeric and lipid-based nanocarriers within one hybrid system. This multifaceted formulation strategy has given rise to a plethora of polymer-lipid hybrid (PLH) systems with varying nanostructures and biological activities, all of which have demonstrated the ability to improve the biopharmaceutical performance of a wide range of challenging therapeutics.

AREAS COVERED

The multitude of polymers that can be combined with lipids to exert a synergistic effect for oral drug delivery have been identified, reviewed and critically evaluated. Specific focus is attributed to preclinical studies performed within the past 5 years that have elucidated the role and mechanism of the polymer phase in altering the oral absorption of encapsulated therapeutics.

EXPERT OPINION

The potential of PLH systems has been clearly identified; however, improved understanding of the structure-activity relationship between PLH systems and oral absorption is fundamental for translating this promising delivery approach into a clinically relevant formulation. Advancing research within this field to identify optimal polymer, lipid combinations and engineering conditions for specific therapeutics are therefore encouraged.

Solidification to improve the biopharmaceutical performance of SEDDS: Opportunities and challenges

Self-emulsifying drug delivery systems (SEDDS) offer potential for overcoming the inherent slow dissolution and poor oral absorption of hydrophobic drugs by retaining them in a solubilised state during gastrointestinal transit. However, the promising biopharmaceutical benefits of liquid lipid formulations has not translated into widespread commercial success, due to their susceptibility to long term storage and in vivo precipitation issues. One strategy that has emerged to overcome such limitations, is to combine the solubilisation and dissolution enhancing properties of lipids with the stabilising effects of solid carrier materials. The development of intelligent hybrid drug formulations has presented new opportunities to harness the potential of emulsified lipids in optimising oral bioavailability for lipophilic therapeutics. Specific emphasis of this review is placed on the impact of solidification approaches and excipients on the biopharmaceutical performance of self-emulsifying lipids, with findings highlighting the key design considerations that should be implemented when developing hybrid lipid-based formulations.

Investigation of the blends of chitosan and tragacanth as potential drug carriers for the delivery of ibuprofen in the intestine

This study provides a new potential hydrogel for the intestinal delivery of ibuprofen.

Engineering intelligent particle-lipid composites that control lipase-mediated digestion

Nanostructured particle-lipid composites have emerged as state-of-the-art carrier systems for poorly water-soluble bioactive molecules due to their ability to control and enhance the lipase-mediated hydrolysis of encapsulated triglycerides, leading to a subsequent improvement in the solubilisation and absorption of encapsulated species. The first generation of particle-lipid composites (i.e. silica-lipid hybrid (SLH) microparticles) were designed and fabricated by spray drying a silica nanoparticle-stabilised Pickering emulsion, to create a novel three-dimensional architecture, whereby lipid droplets were encapsulated within a porous matrix support. The development of SLH microparticles has acted as a solid foundation for the synthesis of several next generation particle-lipid composites, including polymer-lipid hybrid (PLH) and clay-lipid hybrid systems (CLH), which present lipase with unique lipid microenvironments for optimised lipolysis. This review details the methods utilised to engineer lipid hybrid particles and the strategic investigations that have been performed to determine the influence of key material characteristics on digestion enzyme activity. In doing so, this provides insight into manipulating the mechanism of lipase action through the intelligent design of lipid-based biomaterials for their use in drug delivery formulations and novel functional foods.

Montmorillonite and Laponite Clay Materials for the Solidification of Lipid-Based Formulations for the Basic Drug Blonanserin: In Vitro and in Vivo Investigations

Solid-state lipid-based formulations offer great potential for the improved oral delivery of poorly water-soluble drugs. This study investigates the use of the high-surface-area clay materials, montmorillonite and laponite, as solid carriers for lipid-based formulations. The unique cation-exchange properties of clay platelets were exploited to preload the ionizable hydrophobic compound, blonanserin, prior to encapsulating a drug-loaded lipid solution. Thus, solid-state lipid-based formulations with dual-loading capabilities were developed and studied. These formulations were compared with simple clay-based lipid formulations, where blonanserin was loaded in the lipid phase only. The drug release behavior of all clay-based formulations was assessed during in vitro dissolution studies under simulated gastric conditions and in vitro fasting intestinal lipolysis studies. Montmorillonite- and laponite-based lipid formulations significantly reduced blonanserin solubilization relative to a control lipid solution and silica-lipid hybrid particles, owing to incomplete drug release from the clay cation-exchange sites. This phenomenon was replicated during in vivo pharmacokinetic studies, whereby the bioavailability of simple clay-based lipid formulations was decreased relative to controls. Importantly, the solid-state dual-loaded montmorillonite-based lipid formulation provided an optimal pharmacokinetic performance, achieving the same degree of bioavailability enhancement as the control lipid solution. These findings indicate the potential of solid-state dual-loaded clay-based lipid formulations for increasing drug loading levels and enhancing the oral absorption of poorly soluble weak base compounds.