Using solution X-ray scattering to determine the high-resolution structure and morphology of PEGylated liposomal doxorubicin nanodrugs

Nanotechnology-based delivery systems to overcome drug resistance in cancer

Cancer nanomedicine is defined as the application of nanotechnology and nanomaterials for the formulation of cancer therapeutics that can overcome the impediments and restrictions of traditional chemotherapeutics. Multidrug resistance (MDR) in cancer cells can be defined as a decrease or abrogation in the efficacy of anticancer drugs that have different molecular structures and mechanisms of action and is one of the primary causes of therapeutic failure. There have been successes in the development of cancer nanomedicine to overcome MDR; however, relatively few of these formulations have been approved by the United States Food and Drug Administration for the treatment of cancer. This is primarily due to the paucity of knowledge about nanotechnology and the fundamental biology of cancer cells. Here, we discuss the advances, types of nanomedicines, and the challenges regarding the translation of in vitro to in vivo results and their relevance to effective therapies.

A preparation method for mRNA-LNPs with improved properties

The properties of mRNA lipid nanoparticles (mRNA-LNPs), including size, empty particles, morphology, storage stability, and transfection potency, are critically dependent on the preparation methods. Here, a Two-step tangential-flow filtration (TFF) method was successfully employed to improve the properties of mRNA-LNPs during the preparation process. This method involves an additional ethanol removal step prior to the particle fusion process. Notably, this innovative approach has yielded mRNA-LNPs with larger particles, a reduced proportion of empty LNPs, optimized storage stability (at least 6 months at 2-8 °C), improved in vitro transfection efficiency, and minimized distribution in the heart and blood in vivo. In summary, this study represents the implementation of the innovative Two-step TFF method in the preparation of mRNA-LNPs. Our findings indicate substantial enhancements in the properties of our mRNA-LNPs, specifically with regard to the percentage of empty LNPs, stability, transfection efficiency, and in vivo distribution. These improvements have the potential to optimize their industrial applicability and expand their clinical use.

Insight into structural biophysics from solution X-ray scattering

The current challenges of structural biophysics include determining the structure of large self-assembled complexes, resolving the structure of ensembles of complex structures and their mass fraction, and unraveling the dynamic pathways and mechanisms leading to the formation of complex structures from their subunits. Modern synchrotron solution X-ray scattering data enable simultaneous high-spatial and high-temporal structural data required to address the current challenges of structural biophysics. These data are complementary to crystallography, NMR, and cryo-TEM data. However, the analysis of solution scattering data is challenging; hence many different analysis tools, listed in the SAS Portal (http://smallangle.org/), were developed. In this review, we start by briefly summarizing classical X-ray scattering analyses providing insight into fundamental structural and interaction parameters. We then describe recent developments, integrating simulations, theory, and advanced X-ray scattering modeling, providing unique insights into the structure, energetics, and dynamics of self-assembled complexes. The structural information is essential for understanding the underlying physical chemistry principles leading to self-assembled supramolecular architectures and computational structural refinement.

Small-Angle X-ray Scattering for PEGylated Liposomal Doxorubicin Drugs: An Analytical Model Comparison Study

Liposomal delivery systems are recognized as efficient and safe platforms for chemotherapeutic agents, with doxorubicin-loaded liposomes being the most representative nanopharmaceuticals. Characterizing the structure of liposomal nanomedicines in high spatial and temporal resolution is critical to analyze and evaluate their stability and efficacy. Small-angle X-ray scattering (SAXS) is a powerful tool increasingly used to investigate liposomal delivery systems. In this study, we chose a Doxil-like PEGylated liposomal doxorubicin (PLD) as an example and characterized the liposomal drug structure using synchrotron SAXS. Classical analytical models, including the spherical-shell or flat-slab geometries with Gaussian or uniform electron density profiles, were used to model the internal structure of the liposomal membrane. A cylinder model was applied to fit the scattering from the drug crystal loaded in the liposomes. The high-resolution structures of the original drug, Caelyx, and a similar research drug prepared in our laboratory were characterized using these analytical models. The structural parameters of PLDs, including the thickness of the liposomal membrane and morphology of the drug crystal, were further compared. The results demonstrated that both spherical-shell and flat-slab geometries with Gaussian electron density distribution were suitable to elucidate the structural features of the liposomal membrane under a certain range of scattering vectors, while models with uniform electron density distribution exhibited poor fitting performance. This study highlights the technical features of SAXS, which provides structural information at the nanoscale for liposomal drugs. The demonstrated methods are reliable and easy-to-use for the structural analysis of liposomal drugs, which are helpful for a broader application of SAXS in the production and regulation of nanopharmaceuticals.

Revealing cholesterol effects on PEGylated HSPC liposomes using AF4-MALS and simultaneous small- and wide-angle X-ray scattering

Liposome development is of great interest owing to increasing requirements for efficient drug carriers. The structural features and thermal stability of such liposomes are crucial in drug transport and delivery. Reported here are the results of the structural characterization of PEGylated liposomes via small- and wide-angle X-ray scattering and an asymmetric flow field-flow fractionation (AF4) system coupled with differential refractive-index detection, multi-angle light scattering (MALS) and dynamic light scattering. This integrated analysis of the exemplar PEGylated liposome formed from hydrogenated soy phosphatid-yl-choline (HSPC) with the addition of cholesterol reveals an average hydro-dynamic radius (R h) of 52 nm with 10% polydispersity, a comparable radius of gyration (R g) and a major liposome particle mass of 118 kDa. The local bilayer structure of the liposome is found to have asymmetric electronic density profiles in the inner and outer leaflets, sandwiched by two PEGylated outer layers ca 5 nm thick. Cholesterol was found to effectively intervene in lipid chain packing, resulting in the thickening of the liposome bilayer, an increase in the area per lipid and an increase in liposome size, especially in the fluid phase of the liposome. These cholesterol effects show signs of saturation at cholesterol concentrations above ca 1:5 cholesterol:lipid molar ratio.

The development of highly dense highly protected surfactant ionizable lipid RNA loaded nanoparticles

The long quest for efficient drug administration has been looking for a universal carrier that can precisely transport traditional drugs, new genomic and proteic therapeutic agents. Today, researchers have found conditions to overcome the two main drug delivery dilemmas. On the one side, the versatility of the vehicle to efficiently load, protect and transport the drug and then release it at the target place. On the other hand, the questions related to the degree of PEGylation which are needed to avoid nanoparticle (NP) aggregation and opsonization while preventing cellular uptake. The development of different kinds of lipidic drug delivery vehicles and particles has resulted in the development of ionizable lipid nanoparticles (iLNPs), which can overcome most of the typical drug delivery problems. Proof of their success is the late approval and massive administration as the prophylactic vaccine for SARS-CoV-2. These ILNPs are built by electrostatic aggregation of surfactants, the therapeutic agent, and lipids that self-segregate from an aqueous solution, forming nanoparticles stabilized with lipid polymers, such as PEG. These vehicles overcome previous limitations such as low loading and high toxicity, likely thanks to low charge at the working pH and reduced size, and their entry into the cells via endocytosis rather than membrane perforation or fusion, always associated with higher toxicity. We herein revise their primary features, synthetic methods to prepare and characterize them, pharmacokinetic (administration, distribution, metabolization and excretion) aspects, and biodistribution and fate. Owing to their advantages, iLNPs are potential drug delivery systems to improve the management of various diseases and widely available for clinical use.

Folded, undulating, and fibrous doxorubicin sulfate crystals in liposomes

High-resolution cryogenic transmission electron microscopy (cryo-TEM) evidenced that doxorubicin sulfate crystals in liposomes (prepared by remote loading with ammonium sulfate) form folded, undulating, and fibrous crystals with a diameter of approximately 2.4 nm. An undulating, fibrous crystal considered to be undergrowth, in addition to bundles of fibrous crystals, was also observed in doxorubicin-loaded liposomes. This explains the validity of the formation of doxorubicin sulfate crystals of various shapes, e.g., curved, U-shaped, or circular, in addition to cylinder and/or rod-like crystals reported in the literature. Liposomes that do not contain crystals have inner aqueous phases with high electron density, suggesting that the doxorubicin is remotely loaded and remains as a solute without precipitation.

Dehydration does not affect lipid-based hydration lubrication

Phosphatidylcholine (PC) lipid bilayers at surfaces massively reduce sliding friction, via the hydration lubrication mechanism acting at their highly-hydrated phosphocholine headgroups, a central paradigm of biological lubrication, particularly at articular cartilage surfaces where low friction is crucial for joint well-being. Nanotribological measurements probed the effect on such lubrication of dehydration by dimethyl sulfoxide (DMSO), known to strongly dehydrate the phosphocholine headgroups of such PC bilayers, i.e. reduce the thickness of the inter-bilayer water layer, and thus expected to substantially degrade the hydration lubrication. Remarkably, and unexpectedly, we found that the dehydration has little effect on the friction. We used several approaches, including atomic force microscopy, small- and wide-angle X-ray scattering and all-atom molecular dynamics simulations to elucidate this. Our results show that while DMSO clearly removes hydration water from the lipid head-groups, this is offset by both higher areal head-group density and by rigidity-enhancement of the lipid bilayers, both of which act to reduce frictional dissipation. This sheds strong light on the robustness of lipid-based hydration lubrication in biological systems, despite the ubiquitous presence of bio-osmolytes which compete for hydration water.

MiR-199 Aggravates Doxorubicin-Induced Cardiotoxicity by Targeting TAF9b

The clinical application of doxorubicin (DOX) is limited because of its cardiotoxicity. However, the pathogenic mechanism of DOX and the role of miRNA in DOX-induced cardiotoxicity remain to be further studied. This study aimed to investigate the role of miR-199 in DOX-mediated cardiotoxicity. A mouse model of myocardial cell injury induced by DOX was established. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression changes of miR-199 and TATA-binding protein associated factor 9B (TAF9b) in DOX-induced cardiac injury. Cell apoptosis was detected by TUNEL staining and flow cytometry. The expression levels of apoptosis-related proteins, namely, Bax and Bcl-2, were detected by qPCR. The expression of Beclin-1 and LC3b was detected by western blotting. The binding effect of miR-199 with TAF9b was verified by dual-luciferase reporter gene assay. In this study, overexpression of miR-199 could promote cardiotoxicity. Inhibition of miR-199 could alleviate DOX-mediated myocardial injury. Further studies showed that miR-199 targeted TAF9b. Moreover, miR-199 promoted apoptosis of myocardial cells and aggravated autophagy. Furthermore, we demonstrated that TAF9B knockdown reversed the myocardial protective effect of miR-199 inhibitors. Therefore, miR-199 promoted DOX-mediated cardiotoxicity by targeting TAF9b, thereby aggravating apoptosis and regulating autophagy.

Fluorescence lifetime microscopy unveils the supramolecular organization of liposomal Doxorubicin

The supramolecular organization of Doxorubicin (DOX) within the standard Doxoves® liposomal formulation (DOX®) is investigated using visible light and phasor approach to fluorescence lifetime imaging (phasor-FLIM). First, the phasor-FLIM signature of DOX® is resolved into the contribution of three co-existing fluorescent species, each with its characteristic mono-exponential lifetime, namely: crystallized DOX (DOX_c, 0.2 ns), free DOX (DOX_f, 1.0 ns), and DOX bound to the liposomal membrane (DOX_b, 4.5 ns). Then, the exact molar fractions of the three species are determined by combining phasor-FLIM with quantitative absorption/fluorescence spectroscopy on DOX_c, DOX_f, and DOX_b pure standards. The final picture on DOX® comprises most of the drug in the crystallized form (∼98%), with the remaining fractions divided between free (∼1.4%) and membrane-bound drug (∼0.7%). Finally, phasor-FLIM in the presence of a DOX dynamic quencher allows us to suggest that DOX_f is both encapsulated and non-encapsulated, and that DOX_b is present on both liposome-membrane leaflets. We argue that the present experimental protocol can be applied to the investigation of the supramolecular organization of encapsulated luminescent drugs/molecules all the way from the production phase to their state within living matter.

Current Status and Challenges of Analytical Methods for Evaluation of Size and Surface Modification of Nanoparticle-Based Drug Formulations

The present review discusses the current status and difficulties of the analytical methods used to evaluate size and surface modifications of nanoparticle-based pharmaceutical products (NPs) such as liposomal drugs and new SARS-CoV-2 vaccines. We identified the challenges in the development of methods for (1) measurement of a wide range of solid-state NPs, (2) evaluation of the sizes of polydisperse NPs, and (3) measurement of non-spherical NPs. Although a few methods have been established to analyze surface modifications of NPs, the feasibility of their application to NPs is unknown. The present review also examined the trends in standardization required to validate the size and surface measurements of NPs. It was determined that there is a lack of available reference materials and it is difficult to select appropriate ones for modified NP surface characterization. Research and development are in progress on innovative surface-modified NP-based cancer and gene therapies targeting cells, tissues, and organs. Next-generation nanomedicine should compile studies on the practice and standardization of the measurement methods for NPs to design surface modifications and ensure the quality of NPs.

TPGS2000-DOX Prodrug Micelles for Improving Breast Cancer Therapy

Background

Doxorubicin (DOX) is an anthracycline antibiotic that inhibits the growth of several solid and hematologic malignant tumors. Increasing the targeting ability of DOX and reducing the multi-drug resistance (MDR) of tumor cells to DOX are major aims for researchers.

Purpose

In this study, to increase therapeutic efficiency, reduce the side effects and the MDR of tumor cells to DOX, D-alpha-tocopheryl polyethylene glycol 2000 succinate monoester (TPGS2000)-DOX prodrug micelles were developed by grafting DOX to TPGS2000 via an amide bond that release DOX in the slightly acidic conditions in tumor tissue.

Materials and Methods

The TPGS2000-DOX micelles were constructed using polyethylene glycol 12-hydroxy stearate (Solutol HS15) as the carrier. The in vitro drug release profile and dilution stability of the nanomicelles were determined. The in vitro cytotoxicity and distribution of the nanomicelles in the tumor cells were also investigated. Moreover, we explored the therapeutic outcomes using the MCF-7/ADR tumor-bearing murine model.

Results

The average particle size was approximately 30 nm with a narrow distribution, which was conducive for solid tumor accumulation. The results of in vivo imaging and in vitro cellular uptake assays demonstrated that the TPGS2000-DOX micelles increased the tumor-targeting ability and cellular uptake of DOX. The anticancer potential of TPGS2000-DOX micelles was higher than that of DOX, as revealed by in vitro cytotoxic assays with MCF-7/ADR cells and in vivo antitumor assays with MCF-7 tumor-bearing nude mice.

Conclusion

TPGS2000-DOX prodrug micelles reverse the MDR of tumor cells, achieve passive targeting by forming nanomicelles, and subsequently enhance the efficacy and reduce the toxicity of DOX.

Application of Fundamental Techniques for Physicochemical Characterizations to Understand Post-Formulation Performance of Pharmaceutical Nanocrystalline Materials

Nanocrystalline materials (NCM, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from drug delivery and electronics to optics. Drug nanocrystals (NC) and nano co-crystals (NCC) are examples of NCM with fascinating physicochemical properties and have attracted significant attention in drug delivery. NCM are categorized by advantageous properties, such as high drug-loading efficiency, good long-term physical stability, steady and predictable drug release, and long systemic circulation time. These properties make them excellent formulations for the efficient delivery of a variety of active pharmaceutical ingredients (API). In this review, we summarize the recent advances in drug NCM-based therapy options. Currently, there are three main methods to synthesize drug NCM, including top-down, bottom-up, and combination methods. The fundamental characterization methods of drug NCM are elaborated. Furthermore, the applications of these characterizations and their implications on the post-formulation performance of NCM are introduced.

Polymeric micelles in drug delivery: An insight of the techniques for their characterization and assessment in biorelevant conditions

Polymeric micelles, i.e. aggregation colloids formed in solution by self-assembling of amphiphilic polymers, represent an innovative tool to overcome several issues related to drug administration, from the low water-solubility to the poor drug permeability across biological barriers. With respect to other nanocarriers, polymeric micelles generally display smaller size, easier preparation and sterilization processes, and good solubilization properties, unfortunately associated with a lower stability in biological fluids and a more complicated characterization. Particularly challenging is the study of their interaction with the biological environment, essential to predict the real in vivo behavior after administration. In this review, after a general presentation on micelles features and properties, different characterization techniques are discussed, from the ones used for the determination of micelles basic characteristics (critical micellar concentration, size, surface charge, morphology) to the more complex approaches used to figure out micelles kinetic stability, drug release and behavior in the presence of biological substrates (fluids, cells and tissues). The techniques presented (such as dynamic light scattering, AFM, cryo-TEM, X-ray scattering, FRET, symmetrical flow field-flow fractionation (AF4) and density ultracentrifugation), each one with their own advantages and limitations, can be combined to achieve a deeper comprehension of polymeric micelles in vivo behavior. The set-up and validation of adequate methods for micelles description represent the essential starting point for their development and clinical success.

Restoring structural parameters of lipid mixtures from small-angle X-ray scattering data

Small-angle X-ray scattering (SAXS) is widely utilized to study soluble macromolecules, including those embedded into lipid carriers and delivery systems such as surfactant micelles, phospho-lipid vesicles and bilayered nanodiscs. To adequately describe the scattering from such systems, one needs to account for both the form factor (overall structure) and long-range-order Bragg reflections emerging from the organization of bilayers, which is a non-trivial task. Presently existing methods separate the analysis of lipid mixtures into distinct procedures using form-factor fitting and the fitting of the Bragg peak regions. This article describes a general approach for the computation and analysis of SAXS data from lipid mixtures over the entire angular range of an experiment. The approach allows one to restore the electron density of a lipid bilayer and simultaneously recover the corresponding size distribution and multilamellar organization of the vesicles. The method is implemented in a computer program, LIPMIX, and its performance is demonstrated on an aqueous solution of layered lipid vesicles undergoing an extrusion process. The approach is expected to be useful for the analysis of various types of lipid-based systems, e.g. for the characterization of interactions between target drug molecules and potential carrier/delivery systems.

Quantitative Cryo-TEM Reveals New Structural Details of Doxil-Like PEGylated Liposomal Doxorubicin Formulation

Nano-drugs based on nanoparticles (NP) or on nano-assemblies as carriers of the active pharmaceutical ingredient (API) are often expected to perform better compared to conventional dosage forms. Maximum realization of this potential though requires optimization of multiple physico-chemical, including structural and morphological, parameters. Meaningful distributions of these parameters derived from sufficient populations of individual NPs rather than ensemble distributions are desirable for this task, provided that relevant high-resolution data is available. In this study we demonstrate powerful capabilities of the up-to-date cryogenic transmission electron-microscopy (cryo-TEM) as well as correlations with other techniques abundant in the nano-research milieu. We explored Doxil^®-like (an anticancer drug and the first FDA-approved nano-drug) (75–100 nm) PEGylated liposomes encapsulating single doxorubicin-sulfate nano-rod-crystals (PLD). These crystals induce liposome sphere-to-ellipsoid deformation. Doxil^® was characterized by a multitude of physicochemical methods. We demonstrate, that accompanied by advanced image-analysis means, cryo-TEM can successfully enable the determination of multiple structural parameters of such complex liposomal nano-drugs with an added value of statistically-sound distributions. The latter could not be achieved by most other physicochemical approaches. It seems that cryo-TEM is capable of quantitative description of individual liposome morphological features, including meaningful distributions of all structural elements, with averages that correlate with other physical methods. Here it is demonstrated that such quantitative cryo-TEM analysis is a powerful tool in determining what is the optimal drug to lipid ratio in PLD, which is found to be the drug to lipid ratio existing in Doxil^®.

Effect of the ammonium salt anion on the structure of doxorubicin complex and PEGylated liposomal doxorubicin nanodrugs

BACKGROUND

In Doxil®, PEGylated nanoliposomes are created by hydration of the lipids in ammonium sulfate, and are remotely loaded with doxorubicin by a transmembrane ammonium gradient. The ammonium sulfate is then removed from the external aqueous phase, surrounding the liposomes, and replaced by an isoosmotic sucrose solution in 10 mM histidine buffer at pH 6.5.

METHODS

We prepared PEGylated liposomal doxorubicin (PLD) with a series of ammonium monovalent salts that after remote loading became the intraliposome doxorubicin counteranions. We analyzed the liposomes by solution X-ray scattering, differential scanning calorimetry, and electron micropscopy.

RESULTS

PLDs prepared with sulfonic acid derivatives as counteranion exhibited chemical and physical stabilities. We determined the effect of these ammonium salt counteranions on the structure, morphology, and thermotropic behavior of the PEGylated nanoliposomes, formed before and after doxorubicin loading, and the bulk properties of the doxorubicin-counteranion complexes. By comparing the structure of the doxorubicin complexes in the bulk and inside the nanoliposomes, we revealed the effect of confinement on the structure and doxorubicin release rate for each of the derivatives of the ammonium sulfonic acid counteranions.

CONCLUSIONS

We found that the extent and direction of the doxorubicin confinement effect and its release rate were strongly dependent on the type of counteranion. The counteranions, however, neither affected the structure and thermotropic behavior of the liposome membrane, nor the thickness and density of the liposome PEG layers. In an additional study, it was demonstrated that PLD made with ammonium-methane sulfonate exhibit a much lower Hand and Foot syndrome.

GENERAL SIGNIFICANCE

The structure, physical state, and pharmacokinetics of doxorubicin in PEGylated nanoliposomes, prepared by transmembrane remote loading using gradients of ammonium salts, strongly depend on the counteranions.

Targeted nanostructured lipid carriers for doxorubicin oral delivery

The treatment with anticancer drugs remains a challenge, as available drugs still entail the risk of deleterious off-target effects. The present study describes folic acid conjugated nanostructured lipid carriers (NLCs) as an effective doxorubicin delivery approach targeted to breast cancer cells. Two distinct NLCs formulations were designed and optimized leading to an encapsulation efficiency over than 65%. Cytotoxic and targeting potential of NLCs were studied in vitro, using MDA-MB-231 cell line. Results showed an enhanced cellular uptake of conjugated NLCs. In vitro release studies, mimicking the path in the body after oral administration, show that all formulations would reach the tumor microenvironment bearing 50% of the encapsulated doxorubicin. Moreover, NLCs demonstrated storage stability at 25 °C for at least 42 days. Overall, results revealed that the developed NLCs enable the possibility of oral administration and are a promising approach for the targeted delivery of doxorubicin to breast cancer cells.

Chitosan-covered liposomes as a promising drug transporter: nanoscale investigations

Liposomes are small artificial vesicles spherical shaped of 50-1000 nm in diameter. They are created from natural non-toxic phospholipids membranes. Externally, they are decorated with biocompatible polymers. Chitosan, a natural polymer, demonstrates exceptional advantages in drug delivery, in particular, as liposome cover. In this paper, Molecular Dynamics simulations (MD) are performed in the coupled NPT-NPH and NVT-NVE statistical ensembles to study the static and dynamic properties of DPPC membrane-bilayer with grafted cationic chitosan chains, with added Cl- anions to neutralize the environment, using the Martini coarse-grained force-field. From the NPT-NPH MD simulations we found a chitosan layer L DM ranging from 3.2 to 6.6 nm for graft chains of a degree of polymerization n p = 45 and different grafting molar fractions X p = 0.005, X p = 0.014 and X p = 0.1. Also, the chitosan chains showed three essential grafting regimes: mushroom, critic, and brush depending on X p. The DPPC bilayer thickness D B and the area per lipid A l increased proportionally to X p. From the NVT-NVE MD simulations, the analysis of the radial distribution function showed that the increase of X p gives a more close-packed and rigid liposome. The analysis of the mean square displacement revealed that the diffusion of lipids is anomalous. In contrast, the diffusion of chitosan chains showed a normal diffusion, just after 100 ps. The diffusion regime of ions is found to be normal and independent of time. For the three identified regimes, the chitosan showed a tendency to adhere to the membrane surface and therefore affect the properties of the liposomal membrane.

Enhanced therapeutic index of liposomal doxorubicin Myocet locally delivered by fibrin gels in immunodeficient mice bearing human neuroblastoma

Caelyx and Myocet are clinically used liposomal forms of doxorubicin (Dox). To explore ways to improve their therapeutic index, we have studied their activity in vitro and in vivo when locally delivered by fibrin gels (FBGs). In vivo local toxic and anti-tumour activities of loaded FBGs were assessed in two immunodeficient mouse orthotopic human neuroblastoma (NB) models after application in the visceral space above the adrenal gland, either still tumour-bearing or after tumour removal. In parallel, in vitro assays were used to mimic the in vivo overlaying of FBGs on the tumour surface. FBGs were prepared with different concentrations of fibrinogen (FG) and clotted in the presence of Ca2+ and thrombin. The in vitro assays showed that FBGs loaded with Myocet possess a cytotoxic activity against NB cell lines generally greater than those loaded with free Dox or Caelyx. In vivo FBGs loaded with Myocet showed lower general and local toxicities as compared to gels loaded with Caelyx or free Dox, and also to free Dox administered i.v. (all treatments with Dox at 2.5 mg/Kg). The anti-tumour activity, evaluated in the two mouse orthotopic NB models of adjuvant and neo-adjuvant therapy, resulted in a better performance of FBGs loaded with Myocet compared to the other local (FBGs loaded with Caelyx or free Dox) or systemic (free Dox) treatments (administered at 2.5 and 5 mg/Kg Dox). Specifically, the application of FBGs at 40 mg/mL in the adjuvant model caused 92 % tumour volume reduction, while by the neo-adjuvant application of FBGs at 22 mg/mL a re-growing tumour volume reduction of 89 % was obtained. Taken together, our in vitro and in vivo results indicate a significantly higher activity for the FBGs loaded with Myocet. In particular, the lower toicity coupled with the higher anti-tumour activity on both the local treatment modalities strongly suggest a better therapeutic index when Myocet is administered through FBGs. Therefore, FBGs loaded with Myocet may be considered as a possible new tool for the loco-regional treatment of NB or even other tumour histotypes treatable by loco-regional chemotherapy.

Structural Characterization of Biomaterials by Means of Small Angle X-rays and Neutron Scattering (SAXS and SANS), and Light Scattering Experiments

Scattering techniques represent non-invasive experimental approaches and powerful tools for the investigation of structure and conformation of biomaterial systems in a wide range of distances, ranging from the nanometric to micrometric scale. More specifically, small-angle X-rays and neutron scattering and light scattering techniques represent well-established experimental techniques for the investigation of the structural properties of biomaterials and, through the use of suitable models, they allow to study and mimic various biological systems under physiologically relevant conditions. They provide the ensemble averaged (and then statistically relevant) information under in situ and operando conditions, and represent useful tools complementary to the various traditional imaging techniques that, on the contrary, reveal more local structural information. Together with the classical structure characterization approaches, we introduce the basic concepts that make it possible to examine inter-particles interactions, and to study the growth processes and conformational changes in nanostructures, which have become increasingly relevant for an accurate understanding and prediction of various mechanisms in the fields of biotechnology and nanotechnology. The upgrade of the various scattering techniques, such as the contrast variation or time resolved experiments, offers unique opportunities to study the nano- and mesoscopic structure and their evolution with time in a way not accessible by other techniques. For this reason, highly performant instruments are installed at most of the facility research centers worldwide. These new insights allow to largely ameliorate the control of (chemico-physical and biologic) processes of complex (bio-)materials at the molecular length scales, and open a full potential for the development and engineering of a variety of nano-scale biomaterials for advanced applications.

Mastering the Tools: Natural versus Artificial Vesicles in Nanomedicine

Naturally occurring extracellular vesicles and artificially made vesicles represent important tools in nanomedicine for the efficient delivery of biomolecules and drugs. Since its first appearance in the literature 50 years ago, the research on vesicles is progressing at a fast pace, with the main goal of developing carriers able to protect cargoes from degradation, as well as to deliver them in a time- and space-controlled fashion. While natural occurring vesicles have the advantage of being fully compatible with their host, artificial vesicles can be easily synthetized and functionalized according to the target to reach. Research is striving to merge the advantages of natural and artificial vesicles, in order to provide a new generation of highly performing vesicles, which would improve the therapeutic index of transported molecules. This progress report summarizes current manufacturing techniques used to produce both natural and artificial vesicles, exploring the promises and pitfalls of the different production processes. Finally, pros and cons of natural versus artificial vesicles are discussed and compared, with special regard toward the current applications of both kinds of vesicles in the healthcare field.

Pegylated liposomal doxorubicin-related palmar-plantar erythrodysesthesia: a literature review of pharmaceutical and clinical aspects

OBJECTIVES

The rate of dermal toxicity has been shown to increase in patients receiving pegylated liposomal doxorubicin (PLD), particularly palmar-plantar erythrodysesthesia (PPE). However, it is difficult to diagnose and treat PLD-related PPE due to its delayed dermal performance, unclear pathogenetic mechanism, and the lack of specific preventive measures. The aim of this study was to provide potential management strategies for PPE associated with PLD.

METHODS

The current article reviews the available data regarding the pharmacological and clinical aspects of PLD, including the formulation and pharmacokinetics of PLD, dose and schedule contribution to PPE, concomitant drugs affecting skin toxicity of PLD, the pathogenesis of PPE, and preventive measures and treatment of PLD-related PPE.

RESULTS

The long circulation structure of polyethylene glycol liposomes may be one of the reasons for PPE. PLD has radically different pharmacokinetic characteristics, including prolonged blood circulation time, decreased body distribution volume, and slow clearance. Altering the schedules and doses of PLD or combining it with platinum compounds can optimise clinical efficacy and minimise the occurrence of PPE. Doses of 150-200 mg of pyridoxine daily have been widely used for the prevention and treatment of PPE. Regional cooling and plasma filtration have been used for PPE prophylaxis.

CONCLUSIONS

To date, the mechanism of PPE induced by PLD remains unclear, and no complete preventive medication has been established. Further research and prospective randomised studies are needed to understand the management options in PLD-related PPE.

Exposure of liposomes containing nanocrystallised ciprofloxacin to digestive media induces solid-state transformation and altered in vitro drug release

A recently reported approach to nanocrystallise encapsulated ciprofloxacin within liposomes has generated increased interest in the solid-state properties of drug nanocrystals within liposomal confinement. To explore the potential application of nanocrystallised drug liposomes in oral delivery, a liposomal ciprofloxacin formulation was used as a model system. An in vitro digestion model coupled to small angle X-ray scattering was used to analyse the solid-state properties of the drug nanocrystals during digestion of the liposomal ciprofloxacin nanocrystal formulations. Results showed a complete polymorphic transformation of the ciprofloxacin hydrate nanocrystals to a new salt form at a threshold sodium taurodeoxycholate to ciprofloxacin molar ratio of 0.6. The in vitro drug release from the nanocrystallised drug containing liposomes showed controlled drug release behaviour under non-digestive conditions, while a 3.5-fold increase in the drug release was seen when they were exposed to the simulated digestive environment. In conclusion, the solid state of the drug inside the liposomes is important in dictating the drug release behaviour from the liposomes. The identification of the solid state transformation during digestion in real time and the bile salt-induced polymorphic transformation of ciprofloxacin from nanocrystallised ciprofloxacin liposome are important to understand how the drug is released in vivo, as well as for future formulation design.

Formation of ciprofloxacin nanocrystals within liposomes by spray drying for controlled release via inhalation

The present study was conducted to harness spray drying technology as a novel method of producing Ciprofloxacin nanocrystals inside liposomes (CNL) for inhalation delivery. Liposomal ciprofloxacin dispersions were spray dried with sucrose as a lyoprotectant in different mass ratios (0.5:1, 1:1 and 2:1 sucrose to lipids), along with 2% w/w magnesium stearate and 5% w/w isoleucine as aerosolization enhancers. Spray drying conditions were: inlet air temperature 50 °C, outlet air temperature 33-35 °C, atomizer rate 742 L/h and aspirator 35 m³/h. After spray drying, the formation of ciprofloxacin nanocrystals inside the liposomes was confirmed by cryo- transmission electron microscopy. The physiochemical characteristics of the spray dried powder (particle size, morphology, crystallinity, moisture content, drug encapsulation efficiency (EE), in vitro aerosolization performance and drug release) were determined. The EE of the liposomes was found to vary between 44 and 87% w/w as the sucrose content was increased from 25 to 57% w/w. The powders contained partially crystalline particles with a volume median diameter of ~1 µm. The powders had low water content (~2% wt.) and were stable at high relative humidity. Aerosol delivery using the Osmohaler® inhaler at a flow rate of 100 L/min produced an aerosol fine particle fraction (% wt. <5 µm) of 58-64%. The formulation with the highest sucrose content (2:1 w/w sucrose to lipid) demonstrated extended ciprofloxacin release from liposomes (80% released within 7 h) in comparison to the original liquid formulation (80% released within 2 h). In conclusion, a stable and inhalable CNL powder with controlled drug release was successfully prepared by spray drying.

Nanomedicines and Nanosimilars: Looking for a New and Dynamic Regulatory "Astrolabe" Inspired System

The application of the nanotechnology in medicine and pharmaceutics opens new horizons in therapeutics. Several nanomedicines are in the market and an increasing number is in clinical trials. But which is the advantage of the medicines in nanoscale? The scientists and the regulatory authorities agree that the size and consequently the physiochemical/biological properties of nanomaterials play a key role in their safety and effectiveness. Additionally, all of them agree that a new scientific-based regulatory landscape is required for the establishment of nanomedicines in the market. The aim of this review is to investigate the parameters that the scientists and the regulatory authorities should take into account in order to build up a dynamic regulatory landscape for nanomedicines. For this reason, we propose an "astrolabe-like system" as the guide for establishing the regulatory approval process. Its function is based on the different physicochemical/biological properties in comparison to low molecular weight drugs.

Controlling the size and shape of liposomal ciprofloxacin nanocrystals by varying the lipid bilayer composition and drug to lipid ratio

Drug nanocrystals precipitated inside liposomes are of increasing interest in liposomal drug delivery. For liposomal nanocrystal formulations, the size and shape of the drug nanocrystals can influence the apparent drug release properties, providing opportunities for developing tailored liposomal drug release systems. Small angle X-ray scattering (SAXS) and quantitative transmission electron microscopy (TEM) can be used to analyse the size distributions of the nanoparticles. In this study, by changing the fluidity of the membrane through the use of different membrane phospholipids with varying cholesterol content, the impact of lipid phase, fluidity and permeability on the size distribution of ciprofloxacin nanocrystals were investigated using standard TEM and SAXS as orthogonal techniques. The results show that the phospholipid phase behaviour has a direct effect on the nanocrystal size distribution, where shorter and thinner nanocrystals were formed in liposomes made from hydrogenated soy phosphatidylcholine (HSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) phospholipids with higher phase transition temperatures than 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with lower transition temperatures. This is mainly due to the phase behaviour of the liposome during nanocrystal formation. The addition of cholesterol that reduces fluidity and permeability of the DOPC liposomes was also shown to restrict the growth of the ciprofloxacin nanocrystals. Moreover, increasing the drug loading of the liposomes made from HSPC and DPPC produced longer and wider nanocrystals. The findings open new opportunities to tailor nanocrystal size distributions, as well as the aspect ratio of the enclosing liposomes with potential to alter drug release and in vivo behaviour.

Doxebo (doxorubicin-free Doxil-like liposomes) is safe to use as a pre-treatment to prevent infusion reactions to PEGylated nanodrugs

The increasing use in the last decade of PEGylated nanodrugs such as Doxil® has seen a rise in the number of associated occurrences of hypersensitivity reactions (HSRs). These reactions (also called infusion reactions or IR), can range from harmless symptoms to life-threatening reactions. Current means to prevent IR include the prophylactic use of antihistamines and steroids, but they cannot ensure total prevention. We previously showed that an intravenous injection of doxorubicin-free Doxil-like PEGylated nano-liposomes (Doxebo) prior to Doxil treatment suppresses Doxil-induced complement activation-related pseudoallergy (CARPA) in pigs, a model of human hypersensitivity reactions to Doxil. However, in order to use Doxebo to prevent Doxil-induced IR, we have to prove its safety and that it does not affect Doxil's performance. Here we show that Doxebo itself does not have toxic effects on the host or tumor, and it does not interfere with Doxil's antitumor activity in mice. Blood, microscopic and macroscopic organ evaluation of rats after repeated administration confirm the lack of intrinsic adverse effect of Doxebo. Likewise, the repeated injection of Doxebo before Doxil did not impact Doxil's pharmacokinetics in plasma and therefore does not cause accelerated blood clearance (ABC). Taken together with our previous publications, these data suggest that the injection of Doxebo prior to Doxil administration can help protect against Doxil-induced IR without adversely affecting treatment efficacy and safety.

Effect of the concentration process on unloaded and doxorubicin loaded liposomal dispersions

Liposomes are lamellar nanovesicles made of phospholipids of a great interest as drug delivery carriers, able to encapsulate both hydrophilic and lipophilic compounds. Some liposomal formulations have reached the market, including the doxorubicin loaded PEGylated liposomal dispersion Doxil^®. The aim of the work was to investigate the possibility of concentrating liposomes through the ultrafiltration process under nitrogen pressure, using Doxil^® formulation as a model. The concentrated liposomal dispersions (4x and 8x) obtained from Doxil^® were characterised in terms of size evolution (dynamic light scattering), morphology (cryo-TEM) and thermal behaviour (microcalorimetry, mDSC and high-resolution ultrasonic spectroscopy, HR-US) and compared to the unloaded liposomes of the same composition. The ultrafiltration process resulted to be effective in concentrating both loaded and unloaded liposomal dispersions, which showed a particle size and thermal properties comparable to those of the non concentrated ones. Moreover, all liposomal dispersions did not show any remarkable variation in term of particle size distribution and morphology for at least 8 weeks after concentration. Altogether, results demonstrated the effectiveness in using ultrafiltration as a methodology to concentrate both loaded and unloaded liposomes without affecting the quality of the processed product.

A Simple and Easy Method of Monitoring Doxorubicin Release from a Liposomal Drug Formulation in the Serum Using Fluorescence Spectroscopy

Formulation of a drug as liposomes facilitates its delivery to the disease target. Rightly, liposomes are gaining popularity in the medical field. In order for the drug to show efficacy, release of the encapsulated drug from the liposome at the target site is required. However, the release is affected by the permeability of the lipid bilayer of the liposome, and it is important to examine the effect of the surrounding environment on the permeability. In this study, we showed the usefulness of fluorescence analysis, especially fluorescence fingerprint, for a rapid and simple monitoring of release of an encapsulated anticancer drug (doxorubicin) from its liposomal formulation (DOXIL). Our result indicated that the release is accelerated by the existence of membrane permeable ions, such as tris(hydroxymethyl)aminomethane, and blood proteins like albumin. Hence, monitoring of doxorubicin release by fluorescence analysis is useful for the efficacy evaluation of DOXIL in a biomimetic environment.

[In Vitro Release Method for Liposome Drug Products]

Over the past few decades, liposome drug delivery systems (liposome DDS) have attracted much attention as the most advanced DDS. Efficacy and toxicity profiles of liposomes are based on their characteristic pharmacokinetics, drug release, and disposition after administration. Many attempts have been made to develop these systems especially as liposomal anti-cancer drugs. In the development of liposome DDS, identification of critical quality attributes and establishment of a control strategy to ensure consistent drug product quality are crucial. Among the quality attributes, particle size, drug encapsulation, and drug release from liposomes would affect their in vivo pharmacokinetic and pharmacodynamic properties. Thus these features need to be evaluated with appropriate analytical methods to confirm the quality and performance of the drug products. This article focuses on drug release from liposomes and reviews the effects of physicochemical properties of loaded drugs on release, simulation of drug release from liposomes, and design of a simulated body fluid for drug release assay of drug products.

D+: software for high-resolution hierarchical modeling of solution X-ray scattering from complex structures

This paper presents the computer program D+ (https://scholars.huji.ac.il/uriraviv/book/d-0), where the reciprocal-grid (RG) algorithm is implemented. D+ efficiently computes, at high-resolution, the X-ray scattering curves from complex structures that are isotropically distributed in random orientations in solution. Structures are defined in hierarchical trees in which subunits can be represented by geometric or atomic models. Repeating subunits can be docked into their assembly symmetries, describing their locations and orientations in space. The scattering amplitude of the entire structure can be calculated by computing the amplitudes of the basic subunits on 3D reciprocal-space grids, moving up in the hierarchy, calculating the RGs of the larger structures, and repeating this process for all the leaves and nodes of the tree. For very large structures (containing over 100 protein subunits), a hybrid method can be used to avoid numerical artifacts. In the hybrid method, only grids of smaller subunits are summed and used as subunits in a direct computation of the scattering amplitude. D+ can accurately analyze both small- and wide-angle solution X-ray scattering data. This article describes how D+ applies the RG algorithm, accounts for rotations and translations of subunits, processes atomic models, accounts for the contribution of the solvent as well as the solvation layer of complex structures in a scalable manner, writes and accesses RGs, interpolates between grid points, computes numerical integrals, enables the use of scripts to define complicated structures, applies fitting algorithms, accounts for several coexisting uncorrelated populations, and accelerates computations using GPUs. D+ may also account for different X-ray energies to analyze anomalous solution X-ray scattering data. An accessory tool that can identify repeating subunits in a Protein Data Bank file of a complex structure is provided. The tool can compute the orientation and translation of repeating subunits needed for exploiting the advantages of the RG algorithm in D+. A Python wrapper (https://scholars.huji.ac.il/uriraviv/book/python-api) is also available, enabling more advanced computations and integration of D+ with other computational tools. Finally, a large number of tests are presented. The results of D+ are compared with those of other programs when possible, and the use of D+ to analyze solution scattering data from dynamic microtubule structures with different protofilament number is demonstrated. D+ and its source code are freely available for academic users and developers (https://bitbucket.org/uriraviv/public-dplus/src/master/).

Solid State Characterization of Ciprofloxacin Liposome Nanocrystals

Liposomes have been widely researched as drug delivery systems; however, the solid state form of drug inside the liposome, whether it is in solution or in a solid state, is often not studied. The solid state properties of the drug inside the liposomes are important, as they dictate the drug release behavior when the liposomes come into contact with physiological fluid. Recently, a new approach of making liposomal ciprofloxacin nanocrystals was proposed by the use of an additional freeze-thawing step in the liposomal preparation method. This paper aims to determine the solid state properties of ciprofloxacin inside the liposomes after this additional freeze-thawing cycle using cryo-TEM, small-angle X-ray scattering (SAXS), and cross-polarized light microscopy (CPLM). Ciprofloxacin precipitated in the ciprofloxacin hydrate crystal form with a unit cell dimension of 16.7 Å. The nanocrystals also showed a phase transition at 93 °C, which represents dehydration of the hydrate crystals to the anhydrate form of ciprofloxacin, verified by temperature-dependent SAXS measurements. Furthermore, the dependence of the solid state form of the nanocrystals on pH was investigated in situ, and it was shown that the liposomal ciprofloxacin nanocrystals retained their crystalline form at pH 6-10. Understanding the solid state attributes of nanocrystals inside liposomes provides improved understanding of drug dissolution and release as well as opening avenues to new applications where the nanosized crystals can provide a dissolution benefit.

Practical aspects in size and morphology characterization of drug-loaded nano-liposomes

Size and morphology distributions are critical to the performance of nano-drug systems, as they determine drug pharmacokinetics and biodistribution. Therefore, comprehensive and reliable analyses of these properties are required by both the US Food and Drug Administration (FDA) and European Medicines Agency (EMA). In this study, we compare two most commonly used approaches for assessing the size distribution and morphology of liposomal nano-drug systems, namely, dynamic light scattering (DLS) and cryogenic-transmission electron microscopy (cryo-TEM); an automated quantitative analysis method was developed for the latter method. We demonstrate the advantages and disadvantages of each of these two approaches for a commercial formulation of the anti-cancer drug doxorubicin - Doxil®, in which the drug is encapsulated, mostly in the form of nano-rod crystals. With increasing drug concentration, these nano-rods change the shape of the liposomes from spherical, before drug loading, to prolate (oval), post drug loading. Cryo-TEM analysis provides a detailed size distribution of both the liposomes (minor and major axes) and the nano-rod drug. Both these values are relevant to the drug performance. In this study, we show that at elevated drug concentration (2.75 mg/ml) the drug grows mainly along the major axis and that this high concentration can result, in some cases, in liposome rupture. We show that the combination of cryo-TEM and DLS constitutes a reliable tool for demonstrating the stability of the formulation in human plasma at body temperature, a characteristic that is crucial for achieving therapeutic efficacy.

Fabrication and Characterization of Hybrid Stealth Liposomes

Next-generation liposome systems for anticancer and therapeutic delivery require the precise insertion of stabilizing polymers and targeting ligands. Many of these functional macromolecules may be lost to micellization as a competing self-assembly landscape. Here, hybrid stealth liposomes, which utilize novel cholesteryl-functionalized block copolymers as the molecular stabilizer, are explored as a scalable platform to address this limitation. The employed block copolymers offer resistance to micellization through multiple liposome insertion moieties per molecule. A combination of thermodynamic and structural investigations for a series of hybrid stealth liposome systems suggests that a critical number of cholesteryl moieties per molecule defines whether the copolymer will or will not insert into the liposome bilayer. Colloidal stability of formed hybrid stealth liposomes further corroborates the critical copolymer architecture value.

Investigation on Physicochemical Characteristics of a Nanoliposome-Based System for Dual Drug Delivery

Synergistic effects of multiple drugs with different modes of action are utilized for combinatorial chemotherapy of intractable cancers. Translation of in vitro synergistic effects into the clinic can be realized using an efficient delivery system of the drugs. Despite a few studies on nano-sized liposomes containing erlotinib (ERL) and doxorubicin (DOX) in a single liposome vesicle, reliable and reproducible preparation methods as well as physicochemical characteristics of a non-PEGylated nanoliposome co-encapsulated with ERL and DOX have not been yet elucidated. In this study, ERL-encapsulated nanoliposomes were prepared using the lipid film-hydration method. By ultrasonication using a probe sonicator, the liposome diameter was reduced to less than 200 nm. DOX was loaded into the ERL-encapsulated nanoliposomes using ammonium sulfate (AS)-gradient or pH-gradient method. Effects of DOX-loading conditions on encapsulation efficiency (EE) of the DOX were investigated to determine an efficient drug-loading method. In the EE of DOX, AS-gradient method was more effective than pH gradient. The dual drug-encapsulated nanoliposomes had more than 90% EE of DOX and 30% EE of ERL, respectively. Transmission electron microscopy and selected area electron diffraction analyses of the dual drug-encapsulated nanoliposomes verified the highly oriented DOX-sulfate crystals inside the liposome as well as the less oriented small crystals of ERL in the outermost region of the nanoliposome. The nanoliposomes were stable at different temperatures without an increase of the nanoliposome diameter. The dual drug-encapsulated nanoliposomes showed a time-differential release of ERL and DOX, implying proper sequential releases for their synergism. The preparation methods and the physicochemical characteristics of the dual drug delivery system contribute to the development of the optimal process and more advanced systems for translational researches.

Cardinal Role of Intraliposome Doxorubicin-Sulfate Nanorod Crystal in Doxil Properties and Performance

The uniqueness of Doxil can be attributed, to a large extent, to its intraliposomal doxorubicin-sulfate nanorod crystal. We re-examine these nanocrystal features and their mechanism of the formation by studying pegylated liposomal doxorubicins (PLDs) of the same lipid composition, size distribution, and extraliposome medium that were prepared at different ammonium sulfate (AS) concentrations. This study includes a comparison of the thermotropic behavior, morphology, and in vitro ammonia-induced doxorubicin release (relevant to Doxil's in vivo performance) of these PLDs. In this study, we confirm that a transmembrane ammonium gradient is critical for doxorubicin remote loading, and we demonstrate that the intraliposomal concentration of sulfate counteranions and ammonium ions determine to a large extent the physical state and stability of the PLDs' remote loaded doxorubicin. "Fully-developed" intraliposome doxorubicin-sulfate nanorod crystals (as defined by cryogenic transmission electron microscopy imaging) develop only when the ammonium sulfate (AS) concentration used for PLD preparation is ≥150 mM. Less than 10% of PLDs prepared with 100 mM AS show fully developed nanorod crystals. Intraliposomal AS concentration ≥200 mM is required to support the stable nanocrystallization in PLDs. The presence of nanocrystals and their melting enthalpy and phase transition co-operativity strongly affect the ammonia-induced doxorubicin release of PLDs. A quick, biphasic release occurs for PLDs that lack the nanorod crystals or have crystals of poor crystallinity, whereas PLDs prepared with ≥200 mM AS show a monophasic, zero-order slow release. This study also demonstrates that after remote loading, residual intraliposomal ammonium concentration and the transmembrane pH gradient related to it also play an important role in doxorubicin-sulfate intraliposomal crystallization and ammonia-induced doxorubicin release.

Simulation of Stimuli-Responsive and Stoichiometrically Controlled Release Rate of Doxorubicin from Liposomes in Tumor Interstitial Fluid

PURPOSE

To simulate the stimuli-responsive and stoichiometrically controlled doxorubicin (DOX) release from liposomes in in vivo tumor interstitial fluid (TIF), the effect of ammonia concentration and pH on the DOX release from liposomes in human plasma at 37°C was quantitatively evaluated in vitro and the release rate was calculated as a function of ammonia concentration and pH.

METHODS

Human plasma samples spiked with DOX-loaded PEGylated liposomes (PLD) or Doxil^®, containing ammonia (0.3-50 mM) at different pH values, were incubated at 37°C for 24 h. After incubation, the concentration of encapsulated DOX in the samples was determined by validated solid-phase extraction (SPE)-SPE-high performance liquid chromatography.

RESULTS

Accelerated DOX release (%) from liposomes was observed as the increase of ammonia concentration and pH of the matrix, and the decrease of encapsulated DOX concentration. The release rate was expressed as a function of the ammonia concentration and pH by using Henderson-Hasselbalch equation.

CONCLUSIONS

The DOX release from PLD in TIF was expressed as a function ammonia concentration and pH at various DOX concentrations. Further, it was found that the DOX release from liposomes in a simulated TIF was more than 15 times higher than in normal plasma.

Preparation of a Sustained-Release Nebulized Aerosol of R-terbutaline Hydrochloride Liposome and Evaluation of Its Anti-asthmatic Effects via Pulmonary Delivery in Guinea Pigs

An aerosolized liposome formulation for the pulmonary delivery of an anti-asthmatic medication was developed. Asthma treatment usually requires frequent administration of medication for a sustained bronchodilator response. Liposomes are known for their sustained drug release capability and thus would be a suitable delivery system for prolonging the therapeutic effect of anti-asthmatic medication. Liposomes prepared by thin film hydration were loaded with a model drug, R-terbutaline hydrochloride(R-TBH), using an ammonium sulfate-induced transmembrane electrochemical gradient. This technique provided an encapsulation efficiency of up to 71.35% and yielded R-TBH liposomes with a particle size of approximately 145 ± 20 nm. According to stability studies, these R-TBH liposomes should be stored at 4°C before usage. Compared to R-TBH solution, which showed 90.84% release within 8 h, liposomal R-TBH had a cumulative release of 73.53% at 37°C over 192 h. A next generation impactor (NGI) was used to analyze the particle size distribution in the lungs of R-TBH liposome aerosol in vitro at 5°C. The therapeutic efficacy of the nebulized aerosol of the R-TBH liposomes was assessed via pulmonary delivery in guinea pigs. The results showed that, compared to the R-TBH solution group, the R-TBH liposome group had a prolonged anti-asthma effect.

Nanodesign of new self-assembling core-shell gellan-transfersomes loading baicalin and in vivo evaluation of repair response in skin

Gellan nanohydrogel and phospholipid vesicles were combined to incorporate baicalin in new self-assembling core-shell gellan-transfersomes obtained by an easy, scalable method. The vesicles were small in size (~107 nm) and monodispersed (P.I. ≤ 0.24), forming a viscous system (~24 mPa/s) as compared to transfersomes (~1.6 mPa/s), as confirmed by rheological studies. Gellan was anchored to the bilayer domains through cholesterol, and the polymer chains were distributed onto the outer surface of the bilayer, thus forming a core-shell structure, as suggested by SAXS analyses. The optimal carrier ability of core-shell gellan-transfersomes was established by the high deposition of baicalin in the skin (~11% in the whole skin), especially in the deeper tissue (~8% in the dermis). Moreover, their ability to improve baicalin efficacy in anti-inflammatory and skin repair tests was confirmed in vivo in mice, providing the complete skin restoration and inhibiting all the studied inflammatory markers.

Determination of Nonspherical Morphology of Doxorubicin-Loaded Liposomes by Atomic Force Microscopy

The 3-D morphology of doxorubicin (DOX)-loaded liposomes with a size of circa 100 nm was characterized by atomic force microscopy in an aqueous environment. Prolate liposomes appear in accordance with linear expansion of DOX fiber bundles precipitated inside liposomes. Oblate and concave liposomes were simultaneously observed with increased DOX concentrations; however, their morphologies were not readily determined by 2-D cryo-TEM imaging. Precise data analysis of the 3-D parameters of each liposome allowed semiquantitative evaluation of the transformation of spherical liposomes into nonspherical-prolate, oblate, and concave liposomes. In addition, nonspherical liposomes became spherical on the replacement of the liposomal outer phase consisting of a sucrose solution, with water and subsequent water influx. All spherical liposomes transformed into oblate and concave liposomes with a return to hyperosmotic conditions, when transferred from water to sucrose solution. Furthermore, the concave liposomes did not appear under DOX incubation conditions (65°C), which could be due to the amorphous and supersaturated DOX inside the liposomes that restrained liposomal shrinkage. As atomic force microscopy has improved our ability to image 3-D morphologies of liposomes in various conditions, it is an alternative analytical tool to cryo-TEM and may have future applications in regulatory tests for quality control and assurance.

Heating treatments affect the thermal behaviour of doxorubicin loaded in PEGylated liposomes

Doxil^® is a stealth marketed PEGylated liposomal formulation, containing the anticancer drug doxorubicin. After loading via a pH gradient, fibrillar supramolecular structures of doxorubicin sulfate originates inside the core of the liposomes. Recently, the crystallinity of doxorubicin sulfate has been confirmed by high-resolution calorimetry. However, no detailed information are available on the nature of doxorubicin sulfate nanocrystals and on the effect of different thermal treatments. Thus, the aim of this work was to characterize the thermal behaviour of Doxil^® in comparison to the unloaded liposomes using microcalorimetry, dynamic light scattering and high-resolution ultrasound spectroscopy (HR-US). Different thermal programmes were applied with the aim to highlight the effect of the treatments on the formulation. The used techniques confirmed the ordered state of doxorubicin nanocrystals inside PEGylated liposomes. Particularly, microcalorimetry and HR-US highlighted the changes in the thermal behaviour of the drug under different heating programmes. Doxorubicin nanocrystals were found to be stable after heating up to 80°C, but an irreversible thermal behaviour was observed after a prolonged heating at elevated temperature (2h at 80°C). The non-reversibility could be related to the formation of a different ordered structure and enhanced by the slight leakage of the drug occurring after a prolonged heating.

The new era of nanotechnology, an alternative to change cancer treatment

In the last few years, nanostructures have gained considerable interest for the safe delivery of therapeutic agents. Several therapeutic approaches have been reported, such as molecular diagnosis, disease detection, nanoscale immunotherapy and anticancer drug delivery that could be integrated into clinical use. The current paper aims to highlight the background that supports the use of nanoparticles conjugated with different types of therapeutic agents, applicable in targeted therapy and cancer research, with a special emphasis on hematological malignancies. A particular key point is the functional characterization of nonviral delivery systems, such as gold nanoparticles, liposomes and dendrimers. The paper also presents relevant published data related to microRNA and RNA interference delivery using nanoparticles in cancer therapy.

SPIN: rapid synthesis, purification, and concentration of small drug-loaded liposomes

Liposomes are one of the most studied nano-delivery systems. However, only a handful of formulations have received FDA approval. Existing liposome synthesis techniques are complex and specialized, posing a major impediment in design, implementation, and mass production of liposome delivery systems as therapeutic agents. Here, we demonstrate a unique 'synthesis and purification of injectable nanocarriers' (SPIN) technology for rapid and efficient production of small drug-loaded liposomes using common benchtop equipment. Unilamellar liposomes with mean diameter of 80 nm and polydispersity of 0.13 were synthesized without any secondary post-processing techniques. Encapsulation of dextrans (300-20,000 Da) representing small and large molecular drug formulations was demonstrated without affecting the liposome characteristics. 99.9% of the non-encapsulated molecules were removed using a novel filter centrifugation technique, largely eliminating the need for tedious ultracentrifugation protocols. Finally, the functional efficacy of loaded liposomes as drug delivery vehicles was validated by encapsulating a fluorescent cell tracker (CMFDA) and observing the liposomal release and subsequent uptake of dye by metastatic breast cancer cells (MDA-MB-231) in vitro. The proposed simplified technique addresses the existing challenges associated with liposome preparation in resource limited settings and offers significant potential for advances in translational pharmaceutical development.