Solid Lipid Microparticles for Oral Delivery of Catalase: Focus on the Protein Structural Integrity and Gastric Protection

An inhalable nanoparticle enabling virulence factor elimination and antibiotics delivery for pneumococcal pneumonia therapy

Streptococcus pneumoniae (S. pneumoniae) is a major cause of community-acquired pneumonia. Current standard clinical therapies mainly focus on combating S. pneumoniae through antibiotics. However, the limited delivery of antibiotics and the undetoxified hydrogen peroxide (H2O2) virulence factor secreted by S. pneumoniae impede the therapeutic outcomes. Here we report an inhalable catalase (CAT)-tannic acid (TA) nanoassembly for local antibiotic (levofloxacin) delivery and simultaneously neutralizing the secreted H2O2 virulence factors to treat pneumococcal pneumonia. After aerosol inhalation, the inhalable formulation (denoted as CT@LVX) effectively accumulates in lung tissues through TA-mediated mucoadhesion. CAT can reduce alveolar epithelial cells apoptosis by catalyzing the decomposition of accumulated H2O2 in the infected lung tissues. In synergy with antibiotic LVX-mediated S. pneumoniae elimination, CT@LVX significantly decreases lung injury companied with reduced inflammatory, resulting in 100 % survival of mice with pneumonia. In a clinically isolated S. pneumoniae strain-induced pneumonia mouse model, CT@LVX also shows superior outcomes compared to the traditional antibiotic treatment, highlighting its potential clinical application prospects.

Effect of processing and formulation factors on Catalase activity in tablets

The manufacturing of tablets containing biologics exposes the biologics to thermal and shear stresses, which are likely to induce structural changes (e.g., aggregation and denaturation), leading to the loss of their activity. Saccharides often act as stabilizers of proteins in formulations, yet their stabilizing ability throughout solid oral dosage processing, such as tableting, has been barely studied. This work aimed to investigate the effects of formulation and process (tableting and spray-drying) variables on catalase tablets containing dextran, mannitol, and trehalose as potential stabilizers. Non-spray-dried and spray-dried formulations were prepared and tableted (100, 200, and 400 MPa). The enzymatic activity, number of aggregates, reflecting protein aggregation and structure modifications were studied. A principal component analysis was performed to reveal underlying correlations. It was found that tableting and spray-drying had a notable negative effect on the activity and number of aggregates formed in catalase formulations. Overall, dextran and mannitol failed to preserve the catalase activity in any unit operation studied. On the other hand, trehalose was found to preserve the activity during spray-drying but not necessarily during tableting. The study demonstrated that formulation and process variables must be considered and optimized together to preserve the characteristics of catalase throughout processing.

Drug Release from Lipid Microparticles-Insights into Drug Incorporation and the Influence of Physiological Factors

The aim of this study was to assess the impact of physiological factors, namely tear fluid and lysozyme enzyme, as well as surfactant polysorbate, on the release profile from solid lipid microparticles (SLM), in the form of dispersion intended for ocular application. Indomethacin (Ind) was used as a model drug substance and a release study was performed by applying the dialysis bag method. Conducting release studies taking into account physiological factors is expected to improve development and screening studies, as well as support the regulatory assessment of this multi-compartment lipid dosage form. The effect of the lysozyme was directly related to its effect on lipid microparticles, as it occurred only in their presence (no effect on the solubility of Ind). Polysorbate also turned out to be an important factor interacting with the SLM surface, which determined the release of Ind from SLM. However, in study models without tear fluid or lysozyme, the release of Ind did not exceed 60% within 96 h. Ultimately, only the simultaneous application of artificial tear fluid, lysozyme, and polysorbate allowed for the release of 100% of Ind through the SLM dispersion. The examination of the residues after the release studies indicated the possibility of releasing 100% of Ind from SLM without complete degradation of the microparticles' matrix. The incubation of SLM with tear fluid confirmed a similar influence of physiological factors contained in tear fluid on the surface structure of SLM as that observed during the in vitro studies.

The use of polymorphic state modifiers in solid lipid microparticles: The role of structural modifications on drug release performance

This study investigates the correlation between the structural and release properties of solid lipid microparticles (MPs) of tristearin containing 5 % w/w of four different liquid additives used as crystal modifiers: isopropyl myristate (IM), ethyl oleate (EO), oleic acid (OA) and medium chain triglycerides (MCT). All additives accelerated the conversion of the unstable α-form of tristearin, formed after the MPs manufacturing, to the stable β-polymorph and the transformation was completed within 24 h (for IM and EO) or 48 h (for OA and MCT). The kinetic of polymorphic transition at 25 °C was investigated by simultaneous synchrotron SAXS/WAXS and DSC analysis after melting and subsequent cooling of the lipid mixture. After crystallization in the α-phase, additives accelerate the solid-solid phase transformation to β-tristearin. SAXS data showed that two types of structural modifications occurred on MPs during storage: compaction of the crystal packing (slight decrease in lamellar thickness) and crystal growth (increased number of stacked lipid lamellae). The release behavior of a model hydrophilic drug (caffeine) at two different amounts (15 % and 30 %) from MPs was studied in water and biorelevant media simulated the gastric and intestinal environment. It was particularly significant that the introduction of IM, EO and MCT were able to prolong the drug release in water, passing from a diffusion-based Higuchi kinetics to a perfect zero-order kinetic. Moreover, the overall release profiles were higher in biorelevant media, where erosion/digestion of MPs was observed. After 6 months, a moderate but statistically significant change in release profile was observed for the MPs with IM and EO, which can be correlated with the time-dependent structural alterations (i.e. larger average crystallite size) of these formulations; while MPs with OA or MCT displayed stable release profiles. These findings help to understand the correlation between release behavior, polymorphism and supramolecular-level structural modification of lipid formulations containing crystal modifiers.

Comparison of the In Vitro Drug Release Methods for the Selection of Test Conditions to Characterize Solid Lipid Microparticles

The release profiles of active substances from microspheres are one of the most important features in solid lipid microparticles (SLM) characterization. Unfortunately, the results of the dissolution tests are largely dependent on the chosen method and test conditions, which in relation to novel dosage forms, such as dispersions of lipid microspheres, are not clearly defined in international compendiums and guidelines. This makes it impossible to compare the results of different studies. The aim of the research was to identify the factors most influencing the variability of the obtained results. An attempt was also made to select the most appropriate method for testing drug substance release from SLM. Various dissolution methods were employed (method I: without a membrane, method II: in a dialysis bag, and method III: in a Side-Bi-Side chamber), and the obtained release profiles of cyclosporine and indomethacin from SLM dispersions were compared. In addition to the effect of membranes, the types of acceptor fluids were also investigated. Significant differences were observed when testing the SLM formulations under various test conditions. The results were significantly influenced by the selected membrane, the acceptor fluid, or the difference in the concentrations of active substance between the donor and acceptor compartments. The burst effect observed in some experimental methods was not noticed in other conditions. At this stage, the method with a dialysis bag has been selected as the most suitable, while the methods without the membrane can only play a complementary role.

Oxygen-supplying syringe to create hyperoxia-inducible hydrogels for in situ tissue regeneration

Recent trends in the design of regenerative materials include the development of bioactive matrices to harness the innate healing ability of the body using various biophysicochemical stimuli (defined as in situ tissue regeneration). Among these, hyperoxia (>21% pO₂) is a well-known therapeutic factor for promoting tissue regeneration, such as immune cell recruitment, cell proliferation, angiogenesis, and fibroblast differentiation into myofibroblast. Although various strategies to induce hyperoxia are reported, developing advanced hyperoxia-inducing biomaterials for tissue regeneration is still challenging. In this study, a catalase-immobilized syringe (defined as an Oxyringe) via calcium peroxide-mediated surface modification is developed as a new type of oxygen-supplying system. Hyperoxia-inducible hydrogels are fabricated utilizing Oxyringe. This hydrogel plays a role as a physical barrier for hemostasis. In addition, hyperoxic matrices induce transient hyperoxia in vivo (up to 46.0% pO₂). Interestingly, the hydrogel-induced hyperoxia boost the initial macrophage recruitment and rapid inflammation resolution. Furthermore, hyperoxic oxygen release of hydrogels facilitates neovascularization and cell proliferation involved in the proliferation phase, expediting tissue maturation related to the remodeling phase in wound healing. In summary, Oxyringe has excellent potential as an advanced oxygen-supplying platform to create hyperoxia-inducing hydrogels for in situ tissue regeneration.

Effect of drug load and lipid-wax blends on drug release and stability from spray-congealed microparticles

This study was designed to evaluate paraffin wax as a potential controlled release matrix for spray congealing and its impact on drug release and stability of the microparticles. Paraffin wax can form a hydrophobic barrier to moisture and reduce drug degradation besides retarding drug release in the gastrointestinal tract. More hydrophilic lipid-based additives can be incorporated to modulate the drug release through the paraffin wax barrier. This study reports the findings of lipid-wax formulations at preserving the stability of moisture-sensitive drugs in spray-congealed microparticles. Aspirin-loaded microparticles formulated with different drug loads, lipid additives, and lipid:wax ratios were produced by spray congealing. Stearic acid (SA), cetyl alcohol (CA), and cetyl ester (CE) were the lipid additives studied. The microparticles were evaluated for yield, encapsulation efficiency, particle size, drug stability, and release. CE exhibited the greatest effect on increasing drug release, followed by CA and SA. Dissolution profiles showed the best fit to Weibull kinetic model. The degree of drug degradation was low, with CA imparting the least protective effect, followed by SA and CE. Paraffin wax is useful for preserving the stability of moisture-sensitive aspirin and retarding its release from spray-congealed microparticles. The addition of lipid additives modulated drug release without compromising drug stability.

Development and formulation of antidiabetic property of Anarcadium occidantale-based solid lipid microparticles

Anacardium occidentale (AO) possesses potent anti-diabetic properties, owing to its high phytochemicals content. This study attempted to maximise the efficacy of AO by encapsulating it in a solid lipid microparticle (SLMs) formulation. Leaves of AO were extracted with water and formulated into SLMs using a lipid matrix composed of P90H and Dika fat. Characterisation of the SLMs include morphology, particle size, pH, encapsulation efficiency percentage, in vitro release and anti-diabetic properties. SLMs were spherical with sizes ranging from 16.7 ± 0.8 µm to 40.12 ± 2.34 µm and had a fairly stable pH over time. Highest drug entrapment was 87%_. Batch A₂ exhibited an even release of 89%, sustained over time, and a mean percentage reduction in glucose of 25.9% at 12 h after oral administration to study animals. Anacardium occidentale-loaded SLMs exhibited a good hypoglycaemic effect and can be used in the management of diabetes.

Is Oral Lipid-Based Delivery for Drug Targeting to the Brain Feasible?

This review outlines the feasibility of oral lipid-based targeted delivery of drugs to the brain, including permeation of the central nervous system's (CNS) protective blood-brain barrier (BBB). The structure of the BBB and disruption caused by varying disease states highlights the need for disease-specific approaches to alter permeation. Disruption during disease state, and the effects of certain molecules on the barrier, demonstrate the possibility of exploiting such BBB disruption for drug delivery. Many administration methods can be used to target the brain, but oral administration is considered ideal for chronic, long-term illnesses. Several lipids that have been shown to facilitate drug delivery into the brain after systemic administration, but could also be delivered orally are discussed, including oleic acid, triolein, alkylglycerol, and conjugates of linoleic and myristic acids. Current data reveal the potential for the use of such lipids as part of oral formulations for delivery to the brain by reaching sufficient plasma levels after administration to increase the permeability of the BBB. However, gaps in the literature remain regarding the concentrations and form of most lipids required to produce the desired effects. The use of lipids via oral delivery for brain targeting has not been investigated thoroughly enough to determine with certainty if similar permeability-enhancing effects would be observed as for parenteral administration. In conclusion, further research to fill research gaps is needed, but the limited evidence suggests that oral lipid-based drug delivery for brain targeting is potentially feasible.

Solvent-Free Fabrication of Biphasic Lipid-Based Microparticles with Tunable Structure

Lipid-based biphasic microparticles are generally produced by long and complex techniques based on double emulsions. In this study, spray congealing was used as a solvent-free fabrication method with improved processability to transform water-in-oil non-aqueous emulsions into spherical solid lipid-based particles with a biphasic structure (b-MPs). Emulsions were prepared by melt emulsification using different compositions of lipids (Dynasan^®118 and Compritol^®888 ATO), surfactants (Cetylstearyl alcohol and Span^®60) and hydrophilic carriers (PEGs, Gelucire^®48/16 and Poloxamer 188). First, pseudo-ternary phase diagrams were constructed to identify the area corresponding to each emulsion type (coarse emulsion or microemulsion). The hydrophobicity of the lipid mostly affected the interfacial tension, and thus the microstructure of the emulsion. Emulsions were then processed by spray congealing and the obtained b-MPs were characterized in terms of thermal and chemical properties (by DSC and FT-IR), external and internal morphology (by SEM, CLSM and Raman mapping). Solid free-flowing spherical particles (main size range 200–355 µm) with different architectures were successfully produced: microemulsions led to the formation of particles with a homogeneous internal structure, while coarse emulsions generated “multicores-shell” particles consisting of variable size hydrophilic cores evenly distributed within the crystalline lipid phase. Depending on their composition and structure, b-MPs could achieve various release profiles, representing a more versatile system than microparticles based on a single lipid phase. The formulation and technological strategy proposed, provides a feasible and cost-effective way of fabricating b-MPs with tunable internal structure and release behavior.

Solid and Semisolid Innovative Formulations Containing Miconazole-Loaded Solid Lipid Microparticles to Promote Drug Entrapment into the Buccal Mucosa

The currently available antifungal therapy for oral candidiasis (OC) has various limitations restricting its clinical use, such as short retention time, suboptimal drug concentration and low patients compliance. These issues could be overcome using micro or nanotechnology. In particular, solid lipid microparticles (SLMs) resulted as a particularly promising penetration enhancer carrier for lipophilic drugs, such as the antifungal miconazole (MCZ). Based on these considerations, cetyl decanoate (here synthesized without the use of metal catalysis) was employed together with 1-hexadecanol to prepare MCZ-loaded SLMs. These resulted in a powder composed of 45–300 µm diameter solid spherical particles, able to load a high amount of MCZ in the amorphous form and characterized by a melting temperature range perfectly compatible with oromucosal administration (35–37 °C). Moreover, when compared to Daktarin^® 2% oral gel in ex vivo experiments, SLMs were able to increase up to three-fold MCZ accumulation into the porcine buccal mucosa. The prepared SLMs were then loaded into a buccal gel or a microcomposite mucoadhesive buccal film and evaluated in terms of MCZ permeation and/or accumulation into porcine buccal mucosa by using lower doses than the conventional dosage form. The promising results obtained highlighted an enhancement in terms of MCZ accumulation even at low doses. Furthermore, the prepared buccal film was eligible as stable, reproducible and also highly mucoadhesive. Therefore, the formulated SLMs represent a penetration enhancer vehicle suitable to reduce the dose of lipophilic drugs to be administered to achieve the desired therapeutic effects, as well as being able to be effectively embedded into easily administrable solid or semisolid dosage forms.

Liquid Lipids Act as Polymorphic Modifiers of Tristearin-Based Formulations Produced by Melting Technologies

Despite the growing interest in lipid-based formulations, their polymorphism is still a challenge in the pharmaceutical industry. Understanding and controlling the polymorphic behavior of lipids is a key element for achieving the quality and preventing stability issues. This study aims to evaluate the impact of different oral-approved liquid lipids (LL) on the polymorphism, phase transitions and structure of solid lipid-based formulations and explore their influence on drug release. The LL investigated were isopropyl myristate, ethyl oleate, oleic acid, medium chain trigycerides, vitamin E acetate, glyceryl monooleate, lecithin and sorbitane monooleate. Spray-congealing was selected as an example of a melting-based solvent-free manufacturing method to produce microparticles (MPs) of tristearin (Dynasan^®118). During the production process, tristearin MPs crystallized in the metastable α-form. Stability studied evidenced a slow phase transition to the stable β-polymorph overtime, with the presence of the α-form still detected after 60 days of storage at 25 °C. The addition of 10% w/w of LL promoted the transition of tristearin from the α-form to the stable β-form with a kinetic varying from few minutes to days, depending on the specific LL. The combination of various techniques (DSC, X-ray diffraction analysis, Hot-stage polarized light microscopy, SEM) showed that the addition of LL significantly modified the crystal structure of tristearin-based formulations at different length scales. Both the polymorphic form and the LL addition had a strong influence on the release behavior of a model hydrophilic drug (caffeine). Overall, the addition of LL can be considered an interesting approach to control triglyceride crystallization in the β-form. From the industrial viewpoint, this approach might be advantageous as any polymorphic change will be complete before storage, hence enabling the production of stable lipid formulations.