Simple-by-design approach for production of stabilizer-free cubosomes from phosphatidylglycerol and docosahexaenoic acid monoacylglycerol.

Docosahexaenoic acid monoacylglycerol represents a promising lipid constituent in the development of drug nanocarriers owing to its amphiphilicity and the beneficial health effects of this docosahexaenoic acid precursor in various disorders including cancer and inflammatory diseases. Here, we describe the formation and characterization of simple-by-design and stabilizer-free lamellar and non-lamellar crystalline nanoparticles (vesicles and cubosomes, respectively) from binary mixtures of docosahexaenoic acid monoacylglycerol and phosphatidylglycerol, which is a ubiquitous amphiphilic component present in biological systems. At the physiological temperature of 37 °C, these single amphiphilic components tend to exhibit inverse hexagonal and lamellar liquid crystalline phases, respectively, on exposure to excess water. They can also be combined and dispersed in excess water by employing a high-energy emulsification method (by means of ultrasonication) to produce through an electrostatic stabilization mechanism colloidally stable nanodispersions. A colloidal transformation from vesicles to cubosomes was detected with increasing MAG-DHA content. Through use of synchrotron small-angle X-ray scattering, cryo-transmission electron microscopy, and nanoparticle tracking analysis, we report on the structural and morphological features, and size characteristics of these nanodispersions. Depending on the lipid composition, their internal liquid crystalline architectures were spanning from a lamellar (Lα) phase to biphasic features of coexisting inverse bicontinuous (Q2) cubic Pn3m and Im3m phases. Thus, a direct colloidal vesicle-cubosome transformation was detected by augmenting the concentration of docosahexaenoic acid monoacylglycerol. The produced cubosomes were thermally stable within the investigated temperature range of 5-60 °C. Collectively, our findings contribute to understanding of the imperative steps for production of stabilizer-free cubosomes from biocompatible lipids through a simple-by-design approach. We also discuss the potential therapeutic use and future implications for development of next-generation of multifunctional vesicles and cubosomes for co-delivery of docosahexaenoic acid and drugs in treatment of diseases.

Production of Omega-3 Fatty Acid Concentrates from Common Kilka Oil: Optimization of the Urea Complexation Process.

There has been an increase in interest in the application of ω-3 PUFAs, especially EPA and DHA, in the development of various food products owing to their myriad health benefits. However, most fish oils do not contain more than 30% combined levels of EPA and DHA. In this study, through the urea complexation procedure, the production of EPA and DHA concentrate in their free fatty acids (FFAs) form was achieved from an enzymatic oil extracted from common kilka (Clupeonella cultriventris caspia). To gain the maximum value of EPA and DHA, the response surface methodology (RSM), which is an effective tool to categorize the level of independent variables onto the responses of an experimental process, was also used. Different variables including the urea-fatty acids (FAs) ratio (in the range of 2-6, w/w), the temperature of crystallization (in the range of -24-8 °C), and the time of crystallization (in the range of 8-40 h) were investigated by response surface methodology (RSM) for maximizing the EPA and DHA contents. Following the model validation, the levels of the variables at which the maximum desirability function (0.907 score) was obtained for response variables were 5:1 (urea-FAs ratio), -9 °C (the temperature of crystallization), and 24 h (the time of crystallization). Under these optimal conditions, increases of 2.2 and 4.4 times in the EPA and DHA concentrations were observed, respectively, and an increase in the concentrations of EPA and DHA from 5.39 and 13.32% in the crude oil to 12.07 and 58.36% in the ω-3 PUFA concentrates were observed, respectively. These findings indicate that the urea complexation process is efficient at optimizated conditions.

Antibacterial and anti-biofilm activities of antibiotic-free phosphatidylglycerol/docosahexaenoic acid lamellar and non-lamellar liquid crystalline nanoparticles.

Infectious diseases, particularly those associated with biofilms, are challenging to treat due to an increased tolerance to commonly used antibiotics. This underscores the urgent need for innovative antimicrobial strategies. Here, we present an alternative simple-by-design approach focusing on the development of biocompatible and antibiotic-free nanocarriers from docosahexaenoic acid (DHA) that has the potential to combat microbial infections and phosphatidylglycerol (DOPG), which is attractive for use as a biocompatible prominent amphiphilic component of Gram-positive bacterial cell membranes. We assessed the anti-bacterial and anti-biofilm activities of these nanoformulations (hexosomes and vesicles) against S. aureus and S. epidermidis, which are the most common causes of infections on catheters and medical devices by different methods (including resazurin assay, time-kill assay, and confocal laser scanning microscopy on an in vitro catheter biofilm model). In a DHA-concentration-dependent manner, these nano-self-assemblies demonstrated strong anti-bacterial and anti-biofilm activities, particularly against S. aureus. A five-fold reduction of the planktonic and a four-fold reduction of biofilm populations of S. aureus were observed after treatment with hexosomes. The nanoparticles had a bacteriostatic effect against S. epidermidis planktonic cells but no anti-biofilm activity was detected. We discuss the findings in terms of nanoparticle-bacterial cell interactions, plausible alterations in the phospholipid membrane composition, and potential penetration of DHA into these membranes, leading to changes in their structural and biophysical properties. The implications for the future development of biocompatible nanocarriers for the delivery of DHA alone or in combination with other anti-bacterial agents are discussed, as novel treatment strategies of Gram-positive infections, including biofilm-associated infections.

Recent Advances in Antibacterial Coatings to Combat Orthopedic Implant-Associated Infections.

Implant-associated infections (IAIs) represent a major health burden due to the complex structural features of biofilms and their inherent tolerance to antimicrobial agents and the immune system. Thus, the viable options to eradicate biofilms embedded on medical implants are surgical operations and long-term and repeated antibiotic courses. Recent years have witnessed a growing interest in the development of robust and reliable strategies for prevention and treatment of IAIs. In particular, it seems promising to develop materials with anti-biofouling and antibacterial properties for combating IAIs on implants. In this contribution, we exclusively focus on recent advances in the development of modified and functionalized implant surfaces for inhibiting bacterial attachment and eventually biofilm formation on orthopedic implants. Further, we highlight recent progress in the development of antibacterial coatings (including self-assembled nanocoatings) for preventing biofilm formation on orthopedic implants. Among the recently introduced approaches for development of efficient and durable antibacterial coatings, we focus on the use of safe and biocompatible materials with excellent antibacterial activities for local delivery of combinatorial antimicrobial agents for preventing and treating IAIs and overcoming antimicrobial resistance.

Intrinsic and Dynamic Heterogeneity of Nonlamellar Lyotropic Liquid Crystalline Nanodispersions.

Nonlamellar lyotropic liquid crystalline (LLC) nanoparticles are a family of versatile nano-self-assemblies, which are finding increasing applications in drug solubilization and targeted drug delivery. LLC nanodispersions are heterogeneous with discrete nanoparticle subpopulations of distinct internal architecture and morphology, frequently coexisting with micelles and/or vesicles. Diversity in the internal architectural repertoire of LLC nanodispersions grants versatility in drug solubilization, encapsulation, and release rate. However, drug incorporation contributes to the heterogeneity of LLC nanodispersions, and on exposure to biological media, LLC nanodispersions often undergo nanostructural and morphological transformations. From a pharmaceutical perspective, coexistence of multiple types of nanoparticles with diverse structural attributes, together with media-driven transformations in colloidal characteristics, brings challenges in dissecting biological and therapeutic performance of LLC nanodispersions in a spatiotemporal manner. Here, we outline innate and acquired heterogeneity of LLC nanodispersions and discuss technological developments and alternative approaches needed to improve homogeneity of LLC formulations for drug delivery applications.

Lipid nanoparticles for targeted delivery of anticancer therapeutics: Recent advances in development of siRNA and lipoprotein-mimicking nanocarriers.

The limitations inherent in conventional cancer treatment methods have stimulated recent efforts towards the design of safe nanomedicines with high efficacy for combating cancer through various promising approaches. A plethora of nanoparticles has been introduced in the development of cancer nanomedicines. Among them, different lipid nanoparticles are attractive for use due to numerous advantages and unique opportunities, including biocompatibility and targeted drug delivery. However, a comprehensive understanding of nano-bio interactions is imperative to facilitate the translation of recent advancements in the development of cancer nanomedicines into clinical practice. In this contribution, we focus on lipoprotein-mimicking nanoparticles, which possess unique features and compositions facilitating drug transport through receptor binding mechanisms. Additionally, we describe potential applications of siRNA lipid nanoparticles in the future design of anticancer nanomedicines. Thus, this review highlights recent progress, challenges, and opportunities of lipid-based lipoprotein-mimicking nanoparticles and siRNA nanocarriers designed for the targeted delivery of anticancer therapeutic agents.

Perspectives on complement and phagocytic cell responses to nanoparticles: From fundamentals to adverse reactions.

The complement system, professional phagocytes and other cells such as Natural killer cells and mast cells are among the important components of the innate arm of the immune system. These constituents provide an orchestrated array of defences and responses against tissue injury and foreign particles, including nanopharmaceuticals. While interception of nanopharmaceuticals by the immune system is beneficial for immunomodulation and treatment of phagocytic cell disorders, it is imperative to understand the multifaceted mechanisms by which nanopharmaceuticals interacts with the immune system and evaluate the subsequent balance of beneficial versus adverse reactions. An example of the latter is adverse infusion reactions to regulatory-approved nanopharmaceuticals seen in human subjects. Here, we discuss collective opinions and findings from our laboratories in mapping nanoparticle-mediated complement and leucocyte/macrophage responses.

PEGylation of Phosphatidylglycerol/Docosahexaenoic Acid Hexosomes with d-α-Tocopheryl Succinate Poly(ethylene glycol)2000 Induces Morphological Transformation into Vesicles with Prolonged Circulation Times.

Considering the broad therapeutic potential of omega-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA), here we study the effect of PEGylation of DHA-incorporated hexosomes on their physicochemical characteristics and biodistribution following intravenous injection into mice. Hexosomes were formed from phosphatidylglycerol and DHA with a weight ratio of 3:2. PEGylation was achieved through the incorporation of either d-α-tocopheryl succinate poly(ethylene glycol)2000 (TPGS-mPEG2000) or 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy-poly(ethylene glycol)2000 (DSPE-mPEG2000) at a concentration of 1.5 wt %. Nanoparticle tracking analysis, synchrotron small-angle scattering, and cryo-transmission electron microscopy were employed to characterize the nanodispersions. The results show that PEGylated lipids induce a structural transition from an inverse hexagonal (H2) phase inside the nanoparticles (hexosomes) to a lamellar (Lα) phase (vesicles). We also followed the effect of mouse plasma on the nanodispersion size distribution, number, and morphology because changes brought by plasma constituents could regulate the in vivo performance of intravenously injected nanodispersions. For comparative biodistribution studies, fluorescently labeled nanodispersions of equivalent quantum yields were injected intravenously into healthy mice. TPGS-mPEG2000-induced vesicles were most effective in avoiding hepatosplenic clearance at early time points. In an orthotopic xenograft murine model of glioblastoma, TPGS-mPEG2000-induced vesicles also showed improved localization to the brain compared with native hexosomes. We discuss these observations and their implications for the future design of injectable lyotropic nonlamellar liquid crystalline drug delivery nanosystems for therapeutic interventions of brain and liver diseases.

Nanometer- and angstrom-scale characteristics that modulate complement responses to nanoparticles.

The contribution of the complement system to non-specific host defence and maintenance of homeostasis is well appreciated. Many particulate systems trigger complement activation but the underlying mechanisms are still poorly understood. Activation of the complement cascade could lead to particle opsonisation by the cleavage products of the third complement protein and might promote inflammatory reactions. Antibody binding in a controlled manner and/or sensing of particles by the complement pattern-recognition molecules such as C1q and mannose-binding lectin can trigger complement activation. Particle curvature and spacing arrangement/periodicity of surface functional groups/ligands are two important parameters that modulate complement responses through multivalent engagement with and conformational regulation of surface-bound antibodies and complement pattern-recognition molecules. Thus, a better fundamental understanding of nanometer- and angstrom-scale parameters that modulate particle interaction with antibodies and complement proteins could portend new possibilities for engineering of particulate drug carriers and biomedical platforms with tuneable complement responses and is discussed here.

Microfluidic Nanomaterial Synthesis and In Situ SAXS, WAXS, or SANS Characterization: Manipulation of Size Characteristics and Online Elucidation of Dynamic Structural Transitions.

With the ability to cross biological barriers, encapsulate and efficiently deliver drugs and nucleic acid therapeutics, and protect the loaded cargos from degradation, different soft polymer and lipid nanoparticles (including liposomes, cubosomes, and hexosomes) have received considerable interest in the last three decades as versatile platforms for drug delivery applications and for the design of vaccines. Hard nanocrystals (including gold nanoparticles and quantum dots) are also attractive for use in various biomedical applications. Here, microfluidics provides unique opportunities for the continuous synthesis of these hard and soft nanomaterials with controllable shapes and sizes, and their in situ characterization through manipulation of the flow conditions and coupling to synchrotron small-angle X-ray (SAXS), wide-angle scattering (WAXS), or neutron (SANS) scattering techniques, respectively. Two-dimensional (2D) and three-dimensional (3D) microfluidic devices are attractive not only for the continuous production of monodispersed nanomaterials, but also for improving our understanding of the involved nucleation and growth mechanisms during the formation of hard nanocrystals under confined geometry conditions. They allow further gaining insight into the involved dynamic structural transitions, mechanisms, and kinetics during the generation of self-assembled nanostructures (including drug nanocarriers) at different reaction times (ranging from fractions of seconds to minutes). This review provides an overview of recently developed 2D and 3D microfluidic platforms for the continuous production of nanomaterials, and their simultaneous use in in situ characterization investigations through coupling to nanostructural characterization techniques (e.g., SAXS, WAXS, and SANS).

Investigation of diclofenac release and dynamic structural behavior of non-lamellar liquid crystal formulations during in situ formation by UV-Vis imaging and SAXS.

In situ formation of high viscous inverse lyotropic non-lamellar liquid crystalline phases is a promising approach for sustained drug delivery in the joint. The in situ forming process on exposure of two diclofenac-loaded preformulations to aqueous media was characterized with respect to depot size and shape, initial release and structural transitions using UV-Vis imaging and spatially and time-resolved synchrotron small-angle X-ray scattering (SAXS). The preformulations consisted of 10 % (w/w) ethanol, 10 % (w/w) water and a binary lipid mixture of glycerol monooleate (GMO):1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DOPG) or GMO:medium chain triglycerides (MCT). Upon injection of preformulations into an employed injection-cell containing excess of bio-relevant medium, rapid generation of liquid crystalline depots was observed. UV-Vis images and constructed 2D SAXS maps of the injection-cell showed depots with different shapes and sizes, and features with high nanostructural heterogeneity. More extensive swelling of the GMO:DOPG-based preformulation was observed compared to the GMO:MCT-based preformulation. The UV image analysis found that a higher amount of diclofenac was released in the image area after 20 h from the GMO:MCT depot compared to the GMO:DOPG depot. The injection-cell setup employing UV-Vis imaging and synchrotron SAXS constitutes an attractive approach for evaluating the in situ forming processes of liquid crystalline depots.

Cell medium-dependent dynamic modulation of size and structural transformations of binary phospholipid/ω-3 fatty acid liquid crystalline nano-self-assemblies: Implications in interpretation of cell uptake studies.

Lyotropic non-lamellar liquid crystalline (LLC) nanoparticles, with their tunable structural features and capability of loading a wide range of drugs and reporter probes, are emerging as versatile injectable nanopharmaceuticals. Secondary emulsifiers, such as Pluronic block copolymers, are commonly used for colloidal stabilization of LLC nanoparticles, but their inclusion often compromises the biological safety (e.g., poor hemocompatibility and enhanced cytotoxicity) of the formulation. Here, we introduce a library of colloidally stable, structurally tunable, and pH-responsive lamellar and non-lamellar liquid crystalline nanoparticles from binary mixtures of a phospholipid (phosphatidylglycerol) and three types of omega-3 fatty acids (ω-3 PUFAs), prepared in the absence of a secondary emulsifier and organic solvents. We study formulation size distribution, morphological heterogeneity, and the arrangement of their internal self-assembled architectures by nanoparticle tracking analysis, synchrotron small-angle X-ray scattering, and cryo-transmission electron microscopy. The results show the influence of type and concentration of ω-3 PUFAs in nanoparticle structural transitions spanning from a lamellar (Lα) phase to inverse discontinuous (micellar) cubic Fd3m and hexagonal phase (H2) phases, respectively. We further report on cell-culture medium-dependent dynamic fluctuations in nanoparticle size, number and morphology, and simultaneously monitor uptake kinetics in two human cell lines. We discuss the role of these multiparametric biophysical transformations on nanoparticle-cell interaction kinetics and internalization mechanisms. Collectively, our findings contribute to the understanding of fundamental steps that are imperative for improved engineering of LLC nanoparticles with necessary attributes for pharmaceutical development.

Pulmonary Delivery of Anticancer Drugs via Lipid-Based Nanocarriers for the Treatment of Lung Cancer: An Update.

Lung cancer (LC) is the leading cause of cancer-related deaths, responsible for approximately 18.4% of all cancer mortalities in both sexes combined. The use of systemic therapeutics remains one of the primary treatments for LC. However, the therapeutic efficacy of these agents is limited due to their associated severe adverse effects, systemic toxicity and poor selectivity. In contrast, pulmonary delivery of anticancer drugs can provide many advantages over conventional routes. The inhalation route allows the direct delivery of chemotherapeutic agents to the target LC cells with high local concertation that may enhance the antitumor activity and lead to lower dosing and fewer systemic toxicities. Nevertheless, this route faces by many physiological barriers and technological challenges that may significantly affect the lung deposition, retention, and efficacy of anticancer drugs. The use of lipid-based nanocarriers could potentially overcome these problems owing to their unique characteristics, such as the ability to entrap drugs with various physicochemical properties, and their enhanced permeability and retention (EPR) effect for passive targeting. Besides, they can be functionalized with different targeting moieties for active targeting. This article highlights the physiological, physicochemical, and technological considerations for efficient inhalable anticancer delivery using lipid-based nanocarriers and their cutting-edge role in LC treatment.

Continuous Microfluidic Production of Citrem-Phosphatidylcholine Nano-Self-Assemblies for Thymoquinone Delivery.

Lamellar and non-lamellar liquid crystalline nanodispersions, including liposomes, cubosomes, and hexosomes are attractive platforms for drug delivery, bio-imaging, and related pharmaceutical applications. As compared to liposomes, there is a modest number of reports on the continuous production of cubosomes and hexosomes. Using a binary lipid mixture of citrem and soy phosphatidylcholine (SPC), we describe the continuous production of nanocarriers for delivering thymoquinone (TQ, a substance with various therapeutic potentials) by employing a commercial microfluidic hydrodynamic flow-focusing chip. In this study, nanoparticle tracking analysis (NTA) and synchrotron small-angle X-ray scattering (SAXS) were employed to characterize TQ-free and TQ-loaded citrem/SPC nanodispersions. Microfluidic synthesis led to formation of TQ-free and TQ-loaded nanoparticles with mean sizes around 115 and 124 nm, and NTA findings indicated comparable nanoparticle size distributions in these nanodispersions. Despite the attractiveness of the microfluidic chip for continuous production of citrem/SPC nano-self-assemblies, it was not efficient as comparable mean nanoparticle sizes were obtained on employing a batch (discontinuous) method based on low-energy emulsification method. SAXS results indicated the formation of a biphasic feature of swollen lamellar (Lα) phase in coexistence with an inverse bicontinuous cubic Pn3m phase in all continuously produced TQ-free and TQ-loaded nanodispersions. Further, a set of SAXS experiments were conducted on samples prepared using the batch method for gaining further insight into the effects of ethanol and TQ concentration on the structural features of citrem/SPC nano-self-assemblies. We discuss these effects and comment on the need to introduce efficient microfluidic platforms for producing nanocarriers for delivering TQ and other therapeutic agents.

Spatially and time-resolved SAXS for monitoring dynamic structural transitions during in situ generation of non-lamellar liquid crystalline phases in biologically relevant media.

Formation of high viscous inverse lyotropic liquid crystalline phases in situ upon exposure of low viscous drug-loaded lipid preformulations to synovial fluid provides a promising approach for design of depot formulations for intra-articular drug delivery. Rational formulation design relies on a fundamental understanding of the synovial fluid-mediated dynamic structural transitions occurring at the administration site. At conditions mimicking the in vivo situation, we investigated in real-time such transitions at multiple positions by synchrotron small-angle X-ray scattering (SAXS) combined with an injection-cell. An injectable diclofenac-loaded quaternary preformulation consisting of 72/8/10/10% (w/w) glycerol monooleate/1,2-dioleoyl-glycero-3-phospho-rac-(1-glycerol)/ethanol/water was injected into hyaluronic acid solution or synovial fluid. A fast generation of a coherent drug depot of inverse bicontinuous Im3m and Pn3m cubic phases was observed. Through construction of 2D spatial maps from measurements performed 60 min after injection of the preformulation, it was possible to differentiate liquid crystalline rich- and excess hyaluronic acid solution- or synovial fluid-rich regimes. Synchrotron SAXS findings confirmed that the exposure of the preformulation to the media leads to alterations in structural features in position- and time-dependent manners. Effects of biologically relevant medium composition on the structural features, and implications for development of formulations with sustained drug release properties are highlighted.

Recent advances in drug delivery applications of cubosomes, hexosomes, and solid lipid nanoparticles.

The use of lipid nanocarriers for drug delivery applications is an active research area, and a great interest has particularly been shown in the past two decades. Among different lipid nanocarriers, ISAsomes (Internally self-assembled somes or particles), including cubosomes and hexosomes, and solid lipid nanoparticles (SLNs) have unique structural features, making them attractive as nanocarriers for drug delivery. In this contribution, we focus exclusively on recent advances in formation and characterization of ISAsomes, mainly cubosomes and hexosomes, and their use as versatile nanocarriers for different drug delivery applications. Additionally, the advantages of SLNs and their application in oral and pulmonary drug delivery are discussed with focus on the biological fates of these lipid nanocarriers in vivo. Despite the demonstrated advantages in in vitro and in vivo evaluations including preclinical studies, further investigations on improved understanding of the interactions of these nanoparticles with biological fluids and tissues of the target sites is necessary for efficient designing of drug nanocarriers and exploring potential clinical applications.

Advances in microfluidic synthesis and coupling with synchrotron SAXS for continuous production and real-time structural characterization of nano-self-assemblies.

Microfluidic platforms have become highly attractive tools for synthesis of nanoparticles, including lipid nano-self-assemblies, owing to unique features and at least three important aspects inherent to miniaturized micro-devices. Firstly, the fluids flow under controlled conditions in the microchannels, providing well-defined flow profiles and shorter diffusion lengths that play important roles in enhancing the continuous production of lipid and polymer nanoparticles with relatively narrow size distributions. Secondly, various geometries adapted to microfluidic device designs can be utilized for enhancing the colloidal stability of nanoparticles and improving their drug loading. Thirdly, microfluidic devices are usually compatible with in situ characterization methods for real-time monitoring of processes occurring inside the microchannels. This is unlike conventional nanoparticle synthesis methods, where a final solution or withdrawn aliquots are separately analysed. These features inherent to microfluidic devices provide a tool-set allowing not only precise nanoparticle size control, but also real-time analyses for process optimization. In this review, we focus on recent advances and developments in the use of microfluidic devices for synthesis of lipid nanoparticles. We present different designs based on hydrodynamic flow focusing, droplet-based methods and controlled microvortices, and discuss integration of microfluidic platforms with synchrotron small-angle X ray scattering (SAXS) for in situ structural characterization of lipid nano-self-assemblies under continuous flow conditions, along with major challenges and future directions in this research area.

Dispersed liquid crystals as pH-adjustable antimicrobial peptide nanocarriers.

HYPOTHESIS: pH-responsive nanocarriers have the potential to provide targeted delivery of antimicrobial peptides (AMPs) to sites of bacterial infection with typically abnormal pH levels in the body. However, the local pH of the infected sites varies substantially among different infection-related diseases, calling for the development of delivery systems capable of targeting local pathological conditions in an adjustable pH range. EXPERIMENTS: In this study, a highly versatile pH-responsive nanocarrier platform, based on dispersions of oleic acid (OA) and glycerol monooleate (GMO) self-assemblies with the human cathelicidin AMP LL-37, was designed and characterized. FINDINGS: A detailed pH-composition phase diagram was constructed from small angle X-ray scattering and cryogenic transmission electron microscopy data. In addition, the protonation state and apparent pKa of OA embedded in these nano-self-assemblies were investigated by electrophoretic mobility measurements at different pHs and found to be strongly dependent on nanocarrier composition. By varying composition of these nanocarriers, the apparent pKa of embedded OA molecules could be tuned from 7.8 to 6.3, shifting the range of nanocarriers' pH-response. The study advances our fundamental understanding of self-assembly and pH-responsiveness in lipid-peptide systems containing monounsaturated long-chain fatty acids. The results may guide the future design of highly adaptable nanocarriers for patient-optimized pH-targeted AMP delivery.

In situ monitoring of the formation of lipidic non-lamellar liquid crystalline depot formulations in synovial fluid.

Administration of parenteral liquid crystalline phases, forming in-vivo with tunable nanostructural features and sustained release properties, offers an attractive approach for treatment of infections and local drug delivery. It has also a potential use for postoperative pain management after arthroscopic knee surgery. However, the optimal use of this drug delivery principle requires an improved understanding of the involved dynamic structural transitions after administration of low-viscous stimulus-responsive lipid precursors and their fate after direct contact with the biological environment. These precursors (preformulations) are typically based on a single biologically relevant lipid (or a lipid combination) with non-lamellar liquid crystalline phase forming propensity. In relation to liquid crystalline depot design for intra-articular drug delivery, it was our interest in the present study to shed light on such dynamic structural transitions by combining synchrotron SAXS with a remote controlled addition of synovial fluid (or buffer containing 2% (w/v) albumin). This combination allowed for monitoring in real-time the hydration-triggered dynamic structural events on exposure of the lipid precursor (organic stock solution consisting of the binary lipid mixture of monoolein and castor oil) to excess synovial fluid (or excess buffer). The synchrotron SAXS findings indicate a fast generation of inverse bicontinuous cubic phases within few seconds. The effects of (i) the organic solvent N-methyl-2-pyrolidone (NMP), (ii) the lipid composition, and (iii) the albumin content on modulating the structures of the self-assembled lipid aggregates and the implications of the experimental findings in the design of liquid crystalline depots for intra-articular drug delivery are discussed.