Liposomal 5-Fluorouracil Polymer Complexes Facilitate Tumor-Specific Delivery: Pharmaco-Distribution Kinetics Using Microdialysis

Liposomes are widely used as carriers for anticancer drugs due to their ability to prolong the retention of encapsulated drugs in blood plasma while directing their distribution increasingly into tumor tissue. We report on the development of stealth liposomal formulations for the common chemotherapy drug 5-fluorouracil, where pharmacokinetic studies were undertaken using a microdialysis probe to specifically quantify drug accumulation in tumor, which was contrasted to drug exposure to healthy tissue. Greater accumulation of the drug into the tumor than into healthy subcutaneous tissue was observed for neutral and cationic liposomal 5-fluorouracil polymer complexes in comparison to the conventional delivery by an injected solution. Increased drug accumulation in tumor also correlated to reduced tumor growth. This research has generated new mechanistic insight into liposomal-specific delivery to tumors with potential to improve the efficacy and reduce the toxicity of chemotherapy.

Mimicking the Gastrointestinal Mucus Barrier: Laboratory-Based Approaches to Facilitate an Enhanced Understanding of Mucus Permeation

The gastrointestinal mucus layer plays a significant role in maintaining gut homeostasis and health, offering protective capacities against the absorption of harmful pathogens as well as commensal gut bacteria and buffering stomach acid to protect the underlying epithelium. Despite this, the mucus barrier is often overlooked during preclinical pharmaceutical development and may pose a significant absorption barrier to high molecular weight or lipophilic drug species. The complex chemical and physical nature of the dynamic mucus layer has proven problematic to reliably replicate in a laboratory setting, leading to the development of multiple mucus models with varying complexity and predictive capacity. This, coupled with the wide range of analysis methods available, has led to a plethora of possible approaches to quantifying mucus permeation; however, the field remains significantly under-represented in biomedical research. For this reason, the development of a concise collation of the available approaches to mucus permeation is essential. In this review, we explore widely utilized mucus mimics ranging in complexity from simple mucin solutions to native mucus preparations for their predictive capacity in mucus permeation analysis. Furthermore, we highlight the diverse range of laboratory-based models available for the analysis of mucus interaction and permeability with a specific focus on in vitro, ex vivo, and in situ models. Finally, we highlight the predictive capacity of these models in correlation with in vivo pharmacokinetic data. This review provides a comprehensive and critical overview of the available technologies to analyze mucus permeation, facilitating the efficient selection of appropriate tools for further advancement in oral drug delivery.

Harnessing the potential of nanostructured formulations to mimic the food effect of lurasidone

Lurasidone is an important antipsychotic drug indicated for the treatment of schizophrenia and bipolar disorder, with an oral bioavailability of 9-19% owing to its poor aqueous solubility. Additionally, lurasidone exhibits a 2-fold positive food effect, such that patients must administer their medication with a meal, leading to significant non-compliance. The aim of this research was to evaluate the in vitro and in vivo performance of lurasidone when engineered as nanostructured systems. Specifically, a nanosuspension, nano-emulsion and silica-lipid hybrid (SLH) microparticles were formulated and the influence of composition and nanostructure on the mechanism of solubilisation was compared. Formulations were shown to enhance fasted state solubilisation levels in vitro by up to 5.9-fold, compared to pure drug. Fed- and fasted-state solubilisation profiles revealed that in contrast to the nanosuspension and nano-emulsion, lurasidone SLH mitigated the positive pharmaceutical effect of lurasidone. In vivo pharmacokinetic evaluations revealed that the nanosuspension, nano-emulsion and SLH enhanced the bioavailability of lurasidone by 3-fold, 2.4-fold and 8.8-fold, respectively, compared to pure drug after oral administration. For lurasidone, the combination of lipid-based nanostructure and porous silica nanostructure (SLH) led to optimal fasted state bioavailability which can ultimately result in enhanced treatment efficacy, easier dosing regimens and improved patient outcomes.

Diffusion of Lipid Nanovesicles Bound to a Lipid Membrane Is Associated with the Partial-Slip Boundary Condition

During diffusion of nanoparticles bound to a cellular membrane by ligand-receptor pairs, the distance to the laterally mobile interface is sufficiently short for their motion to depend not only on the membrane-mediated diffusivity of the tethers but also in a not yet fully understood manner on nanoparticle size and interfacial hydrodynamics. By quantifying diffusivity, velocity, and size of individual membrane-bound liposomes subjected to a hydrodynamic shear flow, we have successfully separated the diffusivity contributions from particle size and number of tethers. The obtained diffusion-size relations for synthetic and extracellular lipid vesicles are not well-described by the conventional no-slip boundary condition, suggesting partial slip as well as a significant diffusivity dependence on the distance to the lipid bilayer. These insights, extending the understanding of diffusion of biological nanoparticles at lipid bilayers, are of relevance for processes such as cellular uptake of viruses and lipid nanoparticles or labeling of cell-membrane-residing molecules.

Bioinspired drug delivery strategies for repurposing conventional antibiotics against intracellular infections

Bacteria have developed a wealth of strategies to avoid and resist the action of antibiotics, one of which involves pathogens invading and forming reservoirs within host cells. Due to the poor cell membrane permeability, stability and retention of conventional antibiotics, this renders current treatments largely ineffective, since achieving a therapeutically relevant antibiotic concentration at the site of intracellular infection is not possible. To overcome such challenges, current antibiotics are 'repurposed' via reformulation using micro- or nano-carrier systems that effectively encapsulate and deliver therapeutics across cellular membranes of infected cells. Bioinspired materials that imitate the uptake of biological particulates and release antibiotics in response to natural stimuli are recently explored to improve the targeting and specificity of this 'nanoantibiotic' approach. In this review, the mechanisms of internalization and survival of intracellular bacteria are elucidated, effectively accentuating the current treatment challenges for intracellular infections and the implications for repurposing conventional antibiotics. Key case studies of nanoantibiotics that have drawn inspiration from natural biological particles and cellular uptake pathways to effectively eradicate intracellular pathogens are detailed, clearly highlighting the rational for harnessing bioinspired drug delivery strategies.

Absence of SARS-CoV-2 in the air and on the surfaces within the school environment

To the best of our knowledge to date there are no scientific studies specifically investigating whether the SARS-CoV-2 virus is present in the air or on the various surfaces in the school environment. The aim of this study was to determine if SARS-CoV-2 is present on various high touch surfaces and in the air across the elementary, middle and high schools in the Chester County of Pennsylvania, USA. One hundred and fifty surface swab samples and 45 air samples were analysed for the presence of the virus. All the samples tested were negative for the presence of SARS-CoV-2. The results indicate that the spread of the virus through contact and through air in the school buildings across the USA is highly unlikely.

Investigation of Self-Emulsifying Drug-Delivery System Interaction with a Biomimetic Membrane under Conditions Relevant to the Small Intestine

Self-emulsifying drug-delivery systems (SEDDS) have been extensively shown to increase oral absorption of solvation-limited compounds. However, there has been little clinical and commercial use of these formulations, in large part because the demonstrated advantages of SEDDS have been outweighed by our inability to precisely predict drug absorption from SEDDS using current in vitro assays. To overcome this limitation and increase the biological relevancy of in vitro assays, an absorption function can be incorporated using biomimetic membranes. However, the effects that SEDDS have on the integrity of a biomimetic membrane are not known. In this study, a quartz crystal microbalance with dissipation monitoring and total internal reflection fluorescence microscopy were employed as complementary methods to in vitro lipolysis-permeation assays to characterize the interaction of various actively digested SEDDS with a liquescent artificial membrane comprising lecithin in dodecane (LiDo). Observations from surface analysis showed that interactions between the digesting SEDDS and LiDo membrane coincided with inflection points in the digestion profiles. Importantly, no indications of membrane damage could be observed, which was supported by flux profiles of the lipophilic model drug felodipine (FEL) and impermeable marker Lucifer yellow on the basal side of the membrane. There was a correlation between the digestion kinetics of the SEDDS and the flux of FEL, but no clear correlation between solubilization and absorption profiles. Membrane interactions were dependent on the composition of lipids within each SEDDS, with the more digestible lipids leading to more pronounced interactions, but in all cases, the integrity of the membrane was maintained. These insights demonstrate that LiDo membranes are compatible with in vitro lipolysis assays for improving predictions of drug absorption from lipid-based formulations.

TIRF Microscopy-Based Monitoring of Drug Permeation Across a Lipid Membrane Supported on Mesoporous Silica

There is an urgent demand for analytic approaches that enable precise and representative quantification of the transport of biologically active compounds across cellular membranes. In this study, we established a new means to monitor membrane permeation kinetics, using total internal reflection fluorescence microscopy confined to a ≈500 nm thick mesoporous silica substrate, positioned underneath a planar supported cell membrane mimic. This way, we demonstrate spatiotemporally resolved membrane permeation kinetics of a small-molecule model drug, felodipine, while simultaneously controlling the integrity of, and monitoring the drug binding to, the cell membrane mimic. By contrasting the permeation behaviour of pure felodipine with felodipine coupled to the permeability enhancer caprylate (C8), we provide evidence for C8-facilitated transport across lipid membranes, thus validating the potential for this approach to successfully quantify carrier system-induced changes to cellular membrane permeation.

Surgical Outcome Following Early Decompressive Hemicraniectomy in Patients of Severe Traumatic Brain Injury: A Retrospective Study

Introduction: Traumatic Brain Injury (TBI) has become an epidemic and remains the leading cause of death and disability in people of 2nd to 4th decade. Road Traffic Accidents (RTA) are responsible for the majority of cases. Primary brain injury sustained on impact and secondary brain injury that develops in following hours and days contribute together to overall injury and decides ultimate outcome. The goal of management in any TBI patient aims to prevent secondary brain injury. Understanding the importance of Intracranial Pressure (ICP) is key to minimise secondary injury. Decompressive hemicraniectomy is a novel technique of reducing ICP in patients of severe brain injury. It’s judicious and timely performance not only saves life but also prevents the dreaded consequences of raised ICP. Aim: To evaluate the role of early decompressive hemicraniectomy in improving the survival rate among patients of severe TBI and analysing the important factors (glasgow coma scale, airway status, timing of surgery) affecting the surgical outcome. Materials and Methods: It was a retrospective study conducted at the Department of Neurosurgery, Veer Surendra Sai Institute of Medical Sciences and Research, Burla, Odisha, India between September 2016 to March 2020. Case records of 60 patients of TBI who had undergone unilateral Decompressive Craniectomy (DECRA) were analysed. The decision for decompressive hemicraniectomy was purely based upon Glasgow Coma Scale GCS) and Computed Topography (CT) findings. The presence of an evacuable mass lesion, diffuse oedema and obliteration of basal cistern in CT was considered to be the most important criteria for the early decompressive procedure. Patients were assessed until their discharge from ward. Statistical analysis was performed by statistical package for science version 12. Results: A total of 60 patients with severe TBI, who underwent DECRA were analysed. Road Traffic Accident (RTA) was the predominant mechanism of injury. All had presence of a surgically evacuable mass lesion along with compression/obliteration of the basal cistern. The majority of mass lesions (n=42) were frontotemporal contusions (70%). Forty patients of total achieved good surgical outcome (66.67%) and rest 20 patients (33.33%) had poor outcomes. Overall incidence of complications was around 40%. The most important factors associated with good outcomes were GCS of 7 and and above, patent airway, and early surgery. Conclusion: Decompressive hemicraniectomy is a novel technique of reducing ICP which acts by directly breaking the rigid box phenomenon of Monro-Kellie doctrine. However patient selection, prompt decision, earliest intervention, adoption of standard technique of DECRA and post operative critical care management are important aspects behind the successful outcome.

Contrasting Anti-obesity Effects of Smectite Clays and Mesoporous Silica in Sprague-Dawley Rats

Porous colloids have been shown to exert unique bioactivities for mediating lipid (fat) metabolism and thereby offer significant potential as anti-obesity therapies. In this study, we compare the capacity for two classes of colloids, that is, smectite clays (Laponite XLG, LAP; montmorillonite, MMT) and mesoporous silica (SBA-15 ordered silica; MPS), to impede intestinal lipid hydrolysis and provoke lipid and carbohydrate excretion through adsorption within their particle matrices. A two-stage in vitro gastrointestinal lipolysis model revealed the capacity for both smectite clays and MPS to inhibit the rate and extent of lipase-mediated digestion under simulated fed state conditions. Each system adsorbed more than its own weight of organic media (i.e., lipid and carbohydrates) after 60 min lipolysis, with MMT adsorbing >10% of all available organics through the indiscriminate adsorption of fatty acids and glycerides. When co-administered with a high-fat diet (HFD) to Sprague-Dawley rats, treatment with MMT and MPS significantly reduced normalized rodent weight gain compared to a negative control, validating their potential to restrict energy intake and serve as anti-obesity therapies. However, in vitro-in vivo correlations revealed poor associations between in vitro digestion parameters and normalized weight gain, indicating that additional/alternate anti-obesity mechanisms may exist in vivo, while also highlighting the need for improved in vitro assessment methodologies. Despite this, the current findings emphasize the potential for porous colloids to restrict weight gain and promote anti-obesity effects to subjects exposed to a HFD and should therefore drive the development of next-generation food-grade biomaterials for the treatment and prevention of obesity.

Influence of Bile Composition on Membrane Incorporation of Transient Permeability Enhancers

Transient permeability enhancers (PEs), such as caprylate, caprate, and salcaprozate sodium (SNAC), improve the bioavailability of poorly permeable macromolecular drugs. However, the effects are variable across individuals and classes of macromolecular drugs and biologics. Here, we examined the influence of bile compositions on the ability of membrane incorporation of three transient PEs—caprylate, caprate, and SNAC—using coarse-grained molecular dynamics (CG-MD). The availability of free PE monomers, which are important near the absorption site, to become incorporated into the membrane was higher in fasted-state fluids than that in fed-state fluids. The simulations also showed that transmembrane perturbation, i.e., insertion of PEs into the membrane, is a key mechanism by which caprylate and caprate increase permeability. In contrast, SNAC was mainly adsorbed onto the membrane surface, indicating a different mode of action. Membrane incorporation of caprylate and caprate was also influenced by bile composition, with more incorporation into fasted- than fed-state fluids. The simulations of transient PE interaction with membranes were further evaluated using two experimental techniques: the quartz crystal microbalance with dissipation technique and total internal reflection fluorescence microscopy. The experimental results were in good agreement with the computational simulations. Finally, the kinetics of membrane insertion was studied with CG-MD. Variation in micelle composition affected the insertion rates of caprate monomer insertion and expulsion from the micelle surface. In conclusion, this study suggests that the bile composition and the luminal composition of the intestinal fluid are important factors contributing to the interindividual variability in the absorption of macromolecular drugs administered with transient PEs.

A Comparison of Chitosan, Mesoporous Silica and Poly(lactic-co-glycolic) Acid Nanocarriers for Optimising Intestinal Uptake of Oral Protein Therapeutics

Efficacious oral delivery of therapeutic proteins remains challenging and nanoparticulate approaches are gaining interest for enhancing their permeability. In this study, we explore the ability for three comparably sized nanocarriers, with diverse physicochemical properties [i.e., chitosan (CSNP), mesoporous silica nanoparticles (MSNP) and poly(lactic-co-glycolic) acid (PLGA-NP)], to successfully facilitate epithelial uptake of a model protein, ovalbumin (OVA). We report the effect of nanoparticle surface chemistry and nanostructure on protein release, cell toxicity and the uptake mechanism in a Madin Darby Canine Kidney (MDCK) cell model of the intestinal epithelium. All nanocarriers exhibited bi-phasic OVA release kinetics with sustained and incomplete release after 4 days, and more pronounced release from MSNP than either polymeric nanocarriers. CSNP and MSNP displayed the highest cellular uptake, however CSNP was prone to significant dose-dependent toxicity attributed to the cationic surface charge. Approximately 25% of MSNP uptake was governed by a clathrin-independent endocytic mechanism, while CSNP and PLGA-NP uptake was not controlled via any endocytic mechanisms investigated herein. Furthermore, endosomal localisation was observed for CSNP and MSNP, but not for PLGA-NP. These findings may assist in the optimal choice and engineering of nanocarriers for specific intestinal permeation enhancement for oral protein delivery.

A safety, tolerability, and pharmacokinetic study of a novel simvastatin silica-lipid hybrid formulation in healthy male participants

Simvastatin (SIM) is a commonly used cholesterol-lowering drug that can reduce the risk of major cardiovascular events. However, due to its poor intrinsic water solubility, the drug is poorly absorbed from the gastrointestinal tract and exhibits a low oral bioavailability of approximately 5%. The aim of this study was to fabricate and optimize SIM encapsulated silica-lipid hybrids (SLH) as a solid-state lipid-based formulation to enhance absorption and bioavailability during a human in vivo pharmacokinetic study. SLH formulations were formulated by spray drying a submicron emulsion with either Aerosil® 300 fumed silica nanoparticles (SLH-A) or Syloid® 244 amorphous micronized silica (SLH-B). A cross-over, double-blinded study design was implemented to evaluate the performance of SLH formulations compared with a commercially available formulation in 12 healthy male participants after oral administration under fasting conditions. SLH formulations enhanced the bioavailability of SIM up to 1.6-fold and more importantly the active simvastatin acid (SIMA), 3.5-fold when compared with an equivalent dose of commercial formulation. The results demonstrate that the porous nanostructure of SLH impact systemic SIM and SIMA concentrations and may serve as a novel approach to enhance the bioavailability of specifically the parent or metabolite. No significant difference was observed in exposure when SLH formulations were administered at 10 mg in comparison with 20 mg of the commercial formulation, suggesting the potential for dose reduction. The study indicated that SLH formulations were safe and well-tolerated when administered to healthy males, confirming the commercial potential of SLH to enhance the bioavailability of poorly water-soluble drugs. Graphical abstract.

Independent Size and Fluorescence Emission Determination of Individual Biological Nanoparticles Reveals that Lipophilic Dye Incorporation Does Not Scale with Particle Size

Advancements in nanoparticle characterization techniques are critical for improving the understanding of how biological nanoparticles (BNPs) contribute to different cellular processes, such as cellular communication, viral infection, as well as various drug-delivery applications. Since BNPs are intrinsically heterogeneous, there is a need for characterization methods that are capable of providing information about multiple parameters simultaneously, preferably at the single-nanoparticle level. In this work, fluorescence microscopy was combined with surface-based two-dimensional flow nanometry, allowing for simultaneous and independent determination of size and fluorescence emission of individual BNPs. In this way, the dependence of the fluorescence emission of the commonly used self-inserting lipophilic dye 3,3'-dioctadecyl-5,5'-di(4-sulfophenyl)oxacarbocyanine (SP-DiO) could successfully be correlated with nanoparticle size for different types of BNPs, including synthetic lipid vesicles, lipid vesicles derived from cellular membrane extracts, and extracellular vesicles derived from human SH-SY5Y cell cultures; all vesicles had a radius, r, of ∼50 nm and similar size distributions. The results demonstrate that the dependence of fluorescence emission of SP-DiO on nanoparticle size varies significantly between the different types of BNPs, with the expected dependence on membrane area, r², being observed for synthetic lipid vesicles, while a significant weaker dependence on size was observed for BNPs with more complex composition. The latter observation is attributed to a size-dependent difference in membrane composition, which may influence either the optical properties of the dye and/or the insertion efficiency, indicating that the fluorescence emission of this type of self-inserting dye may not be reliable for determining size or size distribution of BNPs with complex lipid compositions.

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.

Enhancing the Cellular Uptake and Antibacterial Activity of Rifampicin through Encapsulation in Mesoporous Silica Nanoparticles

An urgent demand exists for the development of novel delivery systems that efficiently transport antibacterial agents across cellular membranes for the eradication of intracellular pathogens. In this study, the clinically relevant poorly water-soluble antibiotic, rifampicin, was confined within mesoporous silica nanoparticles (MSN) to investigate their ability to serve as an efficacious nanocarrier system against small colony variants of Staphylococcus aureus (SCV S. aureus) hosted within Caco-2 cells. The surface chemistry and particle size of MSN were varied through modifications during synthesis, where 40 nm particles with high silanol group densities promoted enhanced cellular uptake. Extensive biophysical analysis was performed, using quartz crystal microbalance with dissipation (QCM-D) and total internal reflection fluorescence (TIRF) microscopy, to elucidate the mechanism of MSN adsorption onto semi-native supported lipid bilayers (snSLB) and, thus, uncover potential cellular uptake mechanisms of MSN into Caco-2 cells. Such studies revealed that MSN with reduced silanol group densities were prone to greater particle aggregation on snSLB, which was expected to restrict endocytosis. MSN adsorption and uptake into Caco-2 cells correlated well with antibacterial efficacy against SCV S. aureus, with 40 nm hydrophilic particles triggering a ~2.5-log greater reduction in colony forming units, compared to the pure rifampicin. Thus, this study provides evidence for the potential to design silica nanocarrier systems with controlled surface chemistries that can be used to re-sensitise intracellular bacteria to antibiotics by delivering them to the site of infection.

Microporosity, Pore Size, and Diffusional Path Length Modulate Lipolysis Kinetics of Triglycerides Adsorbed onto SBA-15 Mesoporous Silica Particles

Understanding lipase-mediated hydrolysis mechanisms within solid-state nanocarriers is fundamental for the rational design of lipid-based formulations. In this study, SBA-15 ordered mesoporous silica (MPS) particles were engineered with well-controlled nanostructural properties to systematically elucidate the role of intrawall microporosity, mesopore size, and particle structure on lipase activity. The microporosity and diffusional path length were shown to be key modulators for lipase-provoked hydrolysis of medium chain triglycerides confined within MPS, with small changes in the pore size, between 9 and 13 nm, showing now a clear correlation to lipase activity. Lipid speciation within MPS after lipolysis, obtained through ¹H NMR, indicated that free fatty acids preferentially adsorbed to rod-shaped MPS (RodMPS) particles with high microporosity. MPS that formed aggregated spindle-like structures (AggMPS) had intrinsically reduced microporosity, which was hypothesized to limit lipase/lipid diffusion to and from the MPS pores and thus retard lipolysis kinetics. A linear correlation between the microporosity and the extent of lipase-provoked hydrolysis was observed within both AggMPS and RodMPS, ultimately indicating that the intricate interplay between the microporosity and lipid/lipase diffusion can be harnessed to optimize lipolysis kinetics for silica-lipid hybrid carriers. The new insights derived in this study are integral to the future development of solid-state lipid-based nanocarriers that control the lipase activity for improving the absorption of poorly soluble bio-active compounds.

Poly(lactic-co-glycolic) Acid-Lipid Hybrid Microparticles Enhance the Intracellular Uptake and Antibacterial Activity of Rifampicin

An urgent demand exists for the development of effective carrier systems that systematically enhance the cellular uptake and localization of antibiotic drugs for the treatment of intracellular pathogens. Commercially available antibiotics suffer from poor cellular penetration, restricting their efficacy against pathogens hosted and protected within phagocytic cells. In this study, the potency of the antibiotic rifampicin against intracellular small colony variants of Staphylococcus aureus was improved through encapsulation within a strategically engineered cell-penetrant delivery system, composed of lipid nanoparticles encapsulated within a poly(lactic-co-glycolic) acid (PLGA) nanoparticle matrix. PLGA-lipid hybrid (PLH) microparticles were synthesized through the process of spray drying, whereby rifampicin was loaded within both the polymer and lipid phases, to create a nanoparticle-in-microparticle system capable of efficient redispersion in aqueous biorelevant media and with programmable release kinetics. The ability of PLH particles to disintegrate into nanoscale agglomerates of the precursor nanoparticles was shown to be instrumental in optimizing rifampicin uptake in RAW264.7 macrophages, with a 7.2- and 1.6-fold increase in cellular uptake, when compared to the pure drug and PLGA microparticles (of an equivalent initial particle size), respectively. The enhanced phagocytosis and extended drug release mechanism (under the acidic macrophage environment) associated with PLH particles induced a 2.5-log reduction in colony forming units compared to initial colonies at 2.50 μg/mL rifampicin dose. Thus, the ability of PLH particles to reduce the intracellular viability of S. aureus, without demonstrating significant cellular toxicity, satisfies the requirements necessary for the safe and efficacious delivery of antibiotics to macrophages for the treatment of intracellular infections.

Doxorubicin-Loaded Delta Inulin Conjugates for Controlled and Targeted Drug Delivery: Development, Characterization, and In Vitro Evaluation

Delta inulin, also known as microparticulate inulin (MPI), was modified by covalently attaching doxorubicin to its nanostructured surface for use as a targeted drug delivery vehicle. MPI is readily endocytosed by monocytes, macrophages, and dendritic cells and in this study, we sought to utilize this property to develop a system to target anti-cancer drugs to lymphoid organs. We investigated, therefore, whether MPI could be used as a vehicle to deliver doxorubicin selectively, thereby reducing the toxicity of this antibiotic anthracycline drug. Doxorubicin was covalently attached to the surface of MPI using an acid–labile linkage to enable pH-controlled release. The MPI-doxorubicin conjugate was characterized using FTIR and SEM, confirming covalent attachment and indicating doxorubicin coupling had no obvious impact on the physical nanostructure, integrity, and cellular uptake of the MPI particles. To simulate the stability of the MPI-doxorubicin in vivo, it was stored in artificial lysosomal fluid (ALF, pH 4.5). Although the MPI-doxorubicin particles were still visible after 165 days in ALF, 53% of glycosidic bonds in the inulin particles were hydrolyzed within 12 days in ALF, reflected by the release of free glucose into solution. By contrast, the fructosidic bonds were much more stable. Drug release studies of the MPI-doxorubicin in vitro, demonstrated a successful pH-dependent controlled release effect. Confocal laser scanning microscopy studies and flow cytometric analysis confirmed that when incubated with live cells, MPI-doxorubicin was efficiently internalized by immune cells. An assay of cell metabolic activity demonstrated that the MPI carrier alone had no toxic effects on RAW 264.7 murine monocyte/macrophage-like cells, but exhibited anti-cancer effects against HCT116 human colon cancer cells. MPI-doxorubicin had a greater anti-cancer cell effect than free doxorubicin, particularly when at lower concentrations, suggesting a drug-sparing effect. This study establishes that MPI can be successfully modified with doxorubicin for chemotherapeutic drug delivery.

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.