Size of thermosensitive liposomes influences content release

Novel thermosensitive small multilamellar lipid nanoparticles with promising release characteristics made by dual centrifugation

Thermosensitive liposomes (TSLs) have great potential for the selective delivery of cytostatic drugs to the tumor site with greatly reduced side effects. Here we report the discovery and characterization of new thermosensitive small multilamellar lipid nanoparticles (tSMLPs) with unusually high temperature selectivity. Furthermore, the temperature-dependent release of the fluorescent marker calcein from tSMLPs is enhanced by human serum albumin. tSMLPs can easily be prepared through dual centrifugation (DC) at very high lipid concentrations using dipalmitoyl and distearoyl phosphatidylcholine (DPPC, DSPC) and the phospholipid dipalmitoyl-sn-glycero-phosphatidyldiglycerol (DPPG2). The new particles have a hydrodynamic diameter of about 175 nm and a narrow size distribution (PDI 0.02). tSMLPs consist of multiple lipid membranes, which become increasingly closer packed towards the particle center, and have no visible aqueous core. The particles are highly stable due to strong hydrogen bond-based membrane interactions mediated by DPPG2. tSMLPs can be used as carriers for water-soluble drugs (EE 25 %) entrapped within the interlamellar spaces. Based on biophysical (DSC, DLS and ITC) and morphological (cryo-EM) studies, a hypothesis is presented to explain the structural basis underlying the high temperature selectivity, as well as the unusual morphology of the new thermosensitive lipid nanoparticles.

Simultaneous separation and analysis of multiple doxorubicin hydrochloride liposomes forms in serum by circular nonuniform electric field gel electrophoresis

BACKGROUND

Liposomal formulations have traditionally been considered the most therapeutically effective drug delivery systems (DDS). However, their pharmacokinetics study and efficacy assessment are still challenging given size heterogeneity and unknown forms in vivo. The pharmacodynamic evaluation that solely analyzes total drug concentration is unfit for the liposomal formulation study. Hence, it is crucial to develop effective strategies for the separation and analysis of different forms of liposomal formulations in order to contribute to the study of pharmacokinetic profiles associated with both liposome-incorporated and non-liposomal drugs. (84) RESULTS: A laboratory-built circular nonuniform electric field gel electrophoresis (CNEFGE) system was developed in this study for simultaneous separation and analysis of various forms of doxorubicin hydrochloride (DOX•HCl) liposomes. Liposomes were effectively fractionized based on their size and higher concentration in situ in the concentration zone, obtaining liposome recovery >95 % and a 3.04 concentration factor. It was found that the technique could be used to evaluate not only the size distribution of liposomes but also the drug loading capacity related to size. The charge-to-size-based separation mechanism has also allowed the simultaneous separation of liposome-entrapped drugs, protein-bound drugs, and free drugs in various forms, and the technique has been successfully employed in serum. Moreover, the quantification analysis of liposomes incubated with serum for 72 h showed that the proportion of the ratio of DOX•HCl in liposome-entrapped drugs, protein-bound drugs, and free drugs is approximately 97:2:1. (143) SIGNIFICANCE: Using the separation principle of gel electrophoresis and the electrification characteristics of drug carriers, this study developed and implemented an efficient approach for the simultaneous separation and concentration of multiple forms of drug liposomes in vivo. This approach offers a wide range of applications in the pharmacokinetics, efficacy, and safety evaluation of drug carriers and liposomes. (56).

Preparing Size-Controlled Liposomes Modified with Polysaccharide Derivatives for pH-Responsive Drug Delivery Applications

The liposome particle size is an important parameter because it strongly affects content release from liposomes as a result of different bilayer curvatures and lipid packing. Earlier, we developed pH-responsive polysaccharide-derivative-modified liposomes that induced content release from the liposomes under weakly acidic conditions. However, the liposome used in previous studies size was adjusted to 100-200 nm. The liposome size effects on their pH-responsive properties were unclear. For this study, we controlled the polysaccharide-derivative-modified liposome size by extrusion through polycarbonate membranes having different pore sizes. The obtained liposomes exhibited different average diameters, in which the diameters mostly corresponded to the pore sizes of polycarbonate membranes used for extrusion. The amounts of polysaccharide derivatives per lipid were identical irrespective of the liposome size. Introduction of cholesterol within the liposomal lipid components suppressed the size increase in these liposomes for at least three weeks. These liposomes were stable at neutral pH, whereas the content release from liposomes was induced at weakly acidic pH. Smaller liposomes exhibited highly acidic pH-responsive content release compared with those from large liposomes. However, liposomes with 50 mol% cholesterol were not able to induce content release even under acidic conditions. These results suggest that control of the liposome size and cholesterol content is important for preparing stable liposomes at physiological conditions and for preparing highly pH-responsive liposomes for drug delivery applications.

Carbon Dots-Biomembrane Interactions and Their Implications for Cellular Drug Delivery

The effect of carbon dots (CDs) on a model blayer membrane was studied as a means of comprehending their ability to affect cell membranes. Initially, the interaction of N-doped carbon dots with a biophysical liposomal cell membrane model was investigated by dynamic light scattering, z-potential, temperature-modulated differential scanning calorimetry, and membrane permeability. CDs with a slightly positive charge interacted with the surface of the negative-charged liposomes and evidence indicated that the association of CDs with the membrane affects the structural and thermodynamic properties of the bilayer; most importantly, it enhances the bilayer's permeability against doxorubicin, a well-known anticancer drug. The results, like those of similar studies that surveyed the interaction of proteins with lipid membranes, suggest that carbon dots are partially embedded in the bilayer. In vitro experiments employing breast cancer cell lines and human healthy dermal cells corroborated the findings, as it was shown that the presence of CDs in the culture medium selectively enhanced cell internalization of doxorubicin and, subsequently, increased its cytotoxicity, acting as a drug sensitizer.

Immunomodulation and targeted drug delivery with high intensity focused ultrasound (HIFU): Principles and mechanisms

High intensity focused ultrasound (HIFU) is a non-invasive and non-ionizing sonic energy-based therapeutic technology for inducing thermal and non-thermal effects in tissues. Depending on the parameters, HIFU can ablate tissues by heating them to >55 °C to induce denaturation and coagulative necrosis, improve radio- and chemo-sensitizations and local drug delivery from nanoparticles at moderate hyperthermia (~41-43 °C), and mechanically fragment cells using acoustic cavitation (also known as histotripsy). HIFU has already emerged as an attractive modality for treating human prostate cancer, veterinary cancers, and neuromodulation. Herein, we comprehensively review the role of HIFU in enhancing drug delivery and immunotherapy in soft and calcified tissues. Specifically, the ability of HIFU to improve adjuvant treatments from various classes of drugs is described. These crucial insights highlight the opportunities and challenges of HIFU technology and its potential to support new clinical trials and translation to patients.

Review of the Delivery Kinetics of Thermosensitive Liposomes

Thermosensitive liposomes (TSL) are triggered nanoparticles that release the encapsulated drug in response to hyperthermia. Combined with localized hyperthermia, TSL enabled loco-regional drug delivery to tumors with reduced systemic toxicities. More recent TSL formulations are based on intravascular triggered release, where drug release occurs within the microvasculature. Thus, this delivery strategy does not require enhanced permeability and retention (EPR). Compared to traditional nanoparticle drug delivery systems based on EPR with passive or active tumor targeting (typically <5%ID/g tumor), TSL can achieve superior tumor drug uptake (>10%ID/g tumor). Numerous TSL formulations have been combined with various drugs and hyperthermia devices in preclinical and clinical studies over the last four decades. Here, we review how the properties of TSL dictate delivery and discuss the advantages of rapid drug release from TSL. We show the benefits of selecting a drug with rapid extraction by tissue, and with quick cellular uptake. Furthermore, the optimal characteristics of hyperthermia devices are reviewed, and impact of tumor biology and cancer cell characteristics are discussed. Thus, this review provides guidelines on how to improve drug delivery with TSL by optimizing the combination of TSL, drug, and hyperthermia method. Many of the concepts discussed are applicable to a variety of other triggered drug delivery systems.

Thermosensitive Liposomes Encapsulating Nedaplatin and Picoplatin Demonstrate Enhanced Cytotoxicity against Breast Cancer Cells

Thermosensitive liposomes (TSL) have been used for localized temperature-responsive release of chemotherapeutics into solid cancers, with a minimum of one invention currently in clinical trials (phase III). In this study, TSL was designed using a lipid blend comprising 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[maleimide(polyethylene glycol)-2000] (DSPE-PEG-2000) (molar ratio of 88:9:2.8:0.2). Either nedaplatin (ND) or p-sulfonatocalix[4]arene-nedaplatin was encapsulated in the aqueous inner layer of TSL to form (ND-TSL) or p-SC4-ND-TSL, respectively. The hydrophobic platinum-based drug picoplatin (P) was loaded into the external lipid bilayer of the TSL to develop P-TSL. The three nanosystems were studied in terms of size, PDI, surface charge, and on-shelf stability. Moreover, the entrapment efficiency (EE%) and release % at 37 and 40 °C were evaluated. In a 30 min in vitro release study, the maximum release of ND, p-SC4-ND, and picoplatin at 40 °C reached 74, 79, and 75%, respectively, compared to approximately 10% at 37 °C. This demonstrated temperature-triggered drug release from the TSL in all three developed systems. The designed TSL exhibited significant in vitro anticancer activity at 40 °C when tested on human mammary gland/breast adenocarcinoma cells (MDA-MB-231). The cytotoxicity of ND-TSL, p-SC4-ND-TSL, and P-TSL at 40 °C was approximately twice those observed at 37 °C. This study suggests that TSL is a promising nanoplatform for the temperature-triggered release of platinum-based drugs into cancer cells.

Combined Second Harmonic Generation and Fluorescence Analyses of the Structures and Dynamics of Molecules on Lipids Using Dual-Probes: A Review

Revealing the structures and dynamic behaviors of molecules on lipids is crucial for understanding the mechanism behind the biophysical processes, such as the preparation and application of drug delivery vesicles. Second harmonic generation (SHG) has been developed as a powerful tool to investigate the molecules on various lipid membranes, benefiting from its natural property of interface selectivity, which comes from the principle of even order nonlinear optics. Fluorescence emission, which is in principle not interface selective but varies with the chemical environment where the chromophores locate, can reveal the dynamics of molecules on lipids. In this contribution, we review some examples, which are mainly from our recent works focusing on the application of combined spectroscopic methods, i.e., SHG and two-photon fluorescence (TPF), in studying the dynamic behaviors of several dyes or drugs on lipids and surfactants. This review demonstrates that molecules with both SHG and TPF efficiencies may be used as intrinsic dual-probes in plotting a clear physical picture of their own behaviors, as well as the dynamics of other molecules, on lipid membranes.

USE OF ARTIFICIAL CELLS AS DRUG CARRIERS

Cells are the fundamental functional units of biological systems and mimicking their size, function and complexity is a primary goal in the development of new therapeutic strategies. Recent advances in chemistry, synthetic biology and material science have enabled the development of cell membrane-based drug delivery systems (DDSs), often referred to as "artificial cells" or protocells. Artificial cells can be made by removing functions from natural systems in a top-down manner, or assembly from synthetic, organic or inorganic materials, through a bottom-up approach where simple units are integrated to form more complex structures. This review covers the latest advances in the development of artificial cells as DDSs, highlighting how their designs have been inspired by natural cells or cell membranes. Advancement of artificial cell technologies has led to a set of drug carriers with effective and controlled release of a variety of therapeutics for a range of diseases, and with increasing complexity they will have a greater impact on therapeutic designs.

Mild Hyperthermia Responsive Liposomes for Enhanced In Vitro and In Vivo Anticancer Efficacy of Doxorubicin against Hepatocellular Carcinoma

The current study is aimed to fabricate doxorubicin (Dox) loaded mild temperature responsive liposomes (MTLs) by thin film hydration technique for enhanced in vitro and in vivo anticancer efficacy against hepatocellular carcinoma. The aforementioned Dox loaded MTLs were developed and optimized with extrusion and drug loading techniques. The optimized MTLs were in optimum size range (118.20 ± 2.81–187.13 ± 4.15 nm), colloidal stability (−13.27 ± 0.04 to −32.34 ± 0.15 mV), and enhanced entrapment of Dox (28.71 ± 2.01–79.24 ± 2.16). Furthermore, the optimized formulation (MTL1-E_(AL)) embodied improved physicochemical stability deducted by Fourier transform infra-red (FTIR) spectroscopy and mild hyperthermia-based phase transition demonstrated from differential scanning calorimetry (DSC). An in vitro drug release study revealed mild hyperthermia assisted rapid in vitro Dox release from MTLs-E_(AL) (T_100% ≈ 1 h) by Korsmeyer–Peppas model based Fickian diffusion (n < 0.45). Likewise, an in vitro cytotoxicity study and lower IC₅₀ values also symbolized mild hyperthermia (40.2 °C) based quick and improved cytotoxicity of MTL1-E_(AL) in HepG2 and MCF-7 cells than Dox. The fluorescence microscopy also represented enhanced cellular internalization of MTL1-E_(AL) at mild hyperthermia compared to the normothermia (37.2 °C). In addition, an in vivo animal study portrayed the safety, improved anticancer efficacy and healing of hepatocellular carcinoma (HCC) through MTL1-E_(AL). In brief, the Dox loaded MTLs could be utilized as safe and effective therapeutic strategy against HCC.

Furin-responsive triterpenine-based liposomal complex enhances anticervical cancer therapy through size modulation

The accumulation and penetration of antitumor drugs in tumor tissues are directly related to their antitumor effects. The particle size of the nanodrug delivery system is one of the most important factors for the accumulation and penetration of antitumor drugs within tumor tissues. Generally, nanodelivery systems of intermediate size (100–120 nm) are capable of efficient accumulation owing to prolonged circulation and enhanced permeability and retention (EPR) effect; however, smaller ones (20–40 nm) are effective for deep penetration within tumor tissue. Currently a conventional drug delivery system cannot possess two types of optimal sizes, simultaneously. To solve this and to enhance cervical cancer treatment, a furin-responsive triterpenine-based liposomal complex (PEGcleavable Tf-CTM/L), with Tf-CTM (transferrin-modified tripterine-loaded coix seed oil microemulsion) in core, coated with a thermo-sensitive lipid and a kind of PEG shell modified with a furin-cleavable peptide was developed to improve tumor-specific accumulation and penetration. Herein, PEGcleavable Tf-CTM/L was capable of efficient accumulation because of EPR effect. The PEG shells could timely detach under stimulation of overexpressed furin protein to solve the problem of the steric hindrance dilemma. The small-sized Tf-CTM released under stimulation of tumor microthermal environment in cervical cancer, which was efficient with regards to deep penetration at tumor sites. Notably, compared to the use of triterpenine alone, PEGcleavable Tf-CTM/L promoted anticervical efficacy and displayed diminished systemic toxicity by efficient accumulation and deep penetration of antitumor drugs within tumor tissues. Our study provides a new strategy, and holds promising potential for anticervical cancer treatment.

Encapsulation of Nedaplatin in Novel PEGylated Liposomes Increases Its Cytotoxicity and Genotoxicity against A549 and U2OS Human Cancer Cells

Following the discovery of cisplatin over 50 years ago, platinum-based drugs have been a widely used and effective form of cancer therapy, primarily causing cell death by inducing DNA damage and triggering apoptosis. However, the dose-limiting toxicity of these drugs has led to the development of second and third generation platinum-based drugs that maintain the cytotoxicity of cisplatin but have a more acceptable side-effect profile. In addition to the creation of new analogs, tumor delivery systems such as liposome encapsulated platinum drugs have been developed and are currently in clinical trials. In this study, we have created the first PEGylated liposomal form of nedaplatin using thin film hydration. Nedaplatin, the main focus of this study, has been exclusively used in Japan for the treatment of non-small cell lung cancer, head and neck, esophageal, bladder, ovarian and cervical cancer. Here, we investigate the cytotoxic and genotoxic effects of free and liposomal nedaplatin on the human non-small cell lung cancer cell line A549 and human osteosarcoma cell line U2OS. We use a variety of assays including ICP MS and the highly sensitive histone H2AX assay to assess drug internalization and to quantify DNA damage induction. Strikingly, we show that by encapsulating nedaplatin in PEGylated liposomes, the platinum uptake cytotoxicity and genotoxicity of nedaplatin was significantly enhanced in both cancer cell lines. Moreover, the enhanced platinum uptake as well as the cytotoxic/antiproliferative effect of liposomal nedaplatin appears to be selective to cancer cells as it was not observed on two noncancer cell lines. This is the first study to develop PEGylated liposomal nedaplatin and to demonstrate the superior cell delivery potential of this product.

A novel kinetic model to describe the ultra-fast triggered release of thermosensitive liposomal drug delivery systems

Thermosensitive liposomes, as one of the stimuli-responsive drug delivery systems, receive growing attention, due to their ability to generate rapid and massive drug release in the heated area, and marginal release of contents in non-heated parts of the body. This typical triggered release behavior cannot be fitted adequately by most of the current mathematical kinetic models. The aim of this study was to establish the proper kinetic equation to describe the rapid release of drugs from trigger-sensitive drug delivery systems. We summarized all commonly used kinetic models mentioned in the literature and fitted the release data with these models, finding that only the Korsmeyer-Peppas and the Weibull models show acceptable fitting results. To better describe the release from thermosensitive liposomes with a size below 100 nm, we took Laplace pressure as a release-driving force and proposed a new equation that demonstrates improved fitting in liposomes ranging down to a size of 70 nm. Our new kinetic model shows desirable fitting, not only at the optimal temperature but also of releases within the whole release-temperature range, providing a useful kinetic model to describe release profiles of smaller nano-sized stimuli-responsive drug delivery systems.

Self-assembled thermal gold nanorod-loaded thermosensitive liposome-encapsulated ganoderic acid for antibacterial and cancer photochemotherapy

A novel nanoparticle (Au-LTSL-GA.A) uses the thermosensitive liposome (LTSL) to encapsulate ganoderic acid A (GA.A), which successfully transforms the polarity of GA.A and has excellent water solubility. The multifunctional Au-LTSL-GA.A, a self-assembled thermal nanomaterial, was used in antibacterial and anticancer applications in combination with near-infrared (NIR) irradiation. The designed Au-LTSL-GA.A nanoparticle was used as a nano-photosensitizer to achieve synergistic photochemotherapy based on the phototherapy sensitization property of Au nanorods (NRs) and antitumour activity of GA.A. In the antibacterial experiments, the Au-LTSL-GA.A + NIR irradiation had a broad-spectrum antibacterial effect, exhibiting a strong antibacterial activity against drug-resistant Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) compared with the raw GA.A and LTSL-GA.A. In the anticancer experiments, Au-LTSL-GA.A + NIR irradiation, which combined phototherapy sensitization property of Au NRs with antitumour activity of GA.A, exhibited high anticancer activity against MCF-7 cells. The IC50 value of Au-LTSL-GA.A + NIR irradiation (12.1 ± 1.3 μg/mL) was almost similar to cisplatin in MCF-7 cells. The evaluation of the potential in vivo toxicity of Au-LTSL-GA.A revealed no toxicity in mice. The results of this study suggest that Au-LTSL-GA.A has a wide range of potential industrial and clinical applications, such as in antibacterial treatment and cancer photochemotherapy.

Polyfluorene-Based Multicolor Fluorescent Nanoparticles Activated by Temperature for Bioimaging and Drug Delivery

Multifunctional nanoparticles have been attracting growing attention in recent years because of their capability to integrate materials with different features in one entity, which leads them to be considered as the next generation of nanomedicine. In this work, we have taken advantage of the interesting properties of conjugated polyelectrolytes to develop multicolor fluorescent nanoparticles with integrating imaging and therapeutic functionalities. With this end, thermosensitive liposomes were coated with three recently synthesized polyfluorenes: copoly-((9,9-bis(6'-N,N,N-trimethylammonium)hexyl)-2,7-(fluorene)-alt-1,4-(phenylene)) bromide (HTMA-PFP), copoly-((9,9-bis(6'-N,N,N-trimethylammonium)hexyl)-2,7-(fluorene)-alt-4,7-(2- (phenyl)benzo(d) (1,2,3) triazole)) bromide (HTMA-PFBT) and copoly-((9,9-bis(6'-N,N,N- trimethylammonium)hexyl)-2,7-(fluorene)-alt-1,4-(naphtho(2,3c)-1,2,5-thiadiazole)) bromide (HTMA-PFNT), in order to obtain blue, green and red fluorescent drug carriers, respectively. The stability, size and morphology of the nanoparticles, as well as their thermotropic behavior and photophysical properties, have been characterized by Dynamic Light Scattering (DLS), Zeta Potential, transmission electron microscope (TEM) analysis and fluorescence spectroscopy. In addition, the suitability of the nanostructures to carry and release their contents when triggered by hyperthermia has been explored by using carboxyfluorescein as a hydrophilic drug model. Finally, preliminary experiments with mammalian cells demonstrate the capability of the nanoparticles to mark and visualize cells with different colors, evidencing their potential use for imaging and therapeutic applications.

Current developments in drug delivery with thermosensitive liposomes

Thermosensitive liposomes (TSLs) have been an important research area in the field of tumor targeted chemotherapy. Since the first TSLs appeared that using 1,2-dipalmitoyl-sn-glyce-ro-3-phosphocholine (DPPC) as the primary liposomal lipid, many studies have been done using this type of liposome from basic and practical aspects. While TSLs composed of DPPC enhance the cargo release near the phase transition temperature, it has been shown that many factors affect their temperature sensitivity. Thus numerous attempts have been undertaken to develop new TSLs for improving their thermal response performance. The main objective of this review is to introduce the development and recent update of innovative TSLs formulations, including combination of radiofrequency ablation (RFA), high-intensity focused ultrasound (HIFU), magnetic resonance imaging (MRI) and alternating magnetic field (AMF). In addition, various factors affecting the design of TSLs, such as lipid composition, surfactant, size and serum components are also discussed.

Potential application of nanovesicles (niosomes and liposomes) for fortification of functional beverages with Isoleucine-Proline-Proline: A comparative study with central composite design approach

In this study, the efficiency and practical utilization feasibility of niosomal and liposomal nanovesicles loading Isoleucine-Proline-Proline (IPP) as suitable ingredients of functional beverages were evaluated. Vesicles were tailored by different preparation methods using phospholipid and non-ionic surfactants. The optimization process was performed by central composite design approach. The results of Fourier transform infrared spectroscopy demonstrated the compatibility of IPP with the vesicles. The phospholipidic nanovesicles, produced by modified ethanol injection-microchannel technique, were smaller with lower polydispersity index than non-ionic surfactant vesicles developed by the method of thin film hydration and probe sonication. However, niosomal model functional beverage exhibited more proper palatability, biological activity and physicochemical properties during long-term storage than liposomal one. Moreover, niosomes exhibited more sustained release behaviour in simulated blood fluid than liposomes. These findings are of great importance for design and development of the functional foods containing IPP.

Elastin-like polypeptide incorporated thermally sensitive liposome improve antibiotic therapy against musculoskeletal bacterial pathogens

Musculoskeletal infections caused by bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa in children and adults can lead to adverse outcomes including a need for extensive surgical debridement and limb amputation. To enable targeted antimicrobial release in infected tissues, the objective of this study was to design and investigate novel elastin-like polypeptide (ELP)-based thermally sensitive liposomes in vitro. ELP biopolymers can change their phase behaviour at higher temperatures. We hypothesised that ELP-TSL will improve therapeutic efficacy by releasing antimicrobial payloads locally at higher temperatures (≥39 °C). ELP-TSL library were formulated by varying cholesterol and phospholipid composition by the thin film and extrusion method. A broad-spectrum antimicrobial (Ciprofloxacin or Cipro) was encapsulated inside the liposomes by the ammonium sulphate gradient method. Cipro release from ELP-TSLs was assessed in physiological buffers containing ∼25% serum by fluorescence spectroscopy, and efficacy against Staphylococcus aureus and Pseudomonas aeruginosa was assessed by disc diffusion and planktonic assay. Active loading of Cipro achieved an encapsulation efficiency of 40-70% in the ELP-TSL depending upon composition. ELP-TSL Cipro release was near complete at ≥39 °C; however, the release rates could be delayed by cholesterol. Triggered release of Cipro from ELP-TSL at ∼42 °C induced significant killing of S. aureus and P. aeruginosa compared to 37 °C. Our in vitro data suggest that ELP-TSL may potentially improve bacterial wound therapy in patients.

Mathematical modelling of liposomal drug release to tumour

The primary aim of liposomal drug delivery is to wisely modulate the drug delivery system in order to target diseased tissues. Temperature-sensitive liposomes function as a prospective weapon to combat toxic side effects corresponding to direct infusion of anticancer drugs. The main objective of the present study is to model liposomal drug release, subsequent drug transport in solid tumour along with integrated actions of tumour cell surface and endosomal events. Generalized mathematical model for liposomal drug delivery is proposed in which vital physical phenomena, such as kinetics of liposome-encapsulated drug, free drug release from liposomes, transport of both liposomal drug and free drug into the tumour compartment, plasma clearance, protein-drug interactions, drug-tumour cell receptor interactions, internalization of drug through endocytosis along with corresponding endosomal events. The model is expressed through a system of coupled partial differential equations along with appropriate set of initial, interface and boundary conditions which is solved numerically. Simulated results are compared with respective existing experimental data to demonstrate the potency and reliability of the proposed model. Graphical representations of time variant concentration profiles are illustrated to understand the underlying phenomena in details. Moreover, the model speaks for the sensitivity of important drug kinetic parameters, such as advection coefficients, drug release coefficient, plasma clearance rate and internalization parameters through graphical portrayals. The proposed model and the simulated results act as a tool in designing a more effective drug delivery system for cancerous tumours.

Thermosensitive liposomes for triggered release of cytotoxic proteins

Lysolipid-containing thermosensitive liposomes (LTSL) are clinically-relevant drug nanocarriers which have been used to deliver small molecule cytostatics to tumors in combination with local hyperthermia (42 °C) to trigger local drug release. The objective of this study was to investigate the feasibility of LTSL for encapsulation and triggered release of macromolecular drugs such as plant-derived cytotoxins. As therapeutic protein we used Mistletoe lectin-1 (ML1) - a ribosome-inactivating protein with potent cytotoxic activity in tumor cells. Model macromolecules (dextrans, albumin) and ML1 were encapsulated in small unilamellar LTSL with varying lipid compositions by the thin film hydration method and extrusion. LTSLs showed molecular weight dependent heat-triggered release of the loaded cargo. The most promising composition, ML1 formulated in LTSL composed of 86:10:4 %mol DPPC:MSPC:DSPE-PEG₂₀₀₀, was further studied for bioactivity against murine CT26 colon carcinoma cells. Confocal live-cell imaging showed uptake of released ML1 after mild hyperthermia at 42 °C, subsequently leading to potent cytotoxicity by LTSL-ML1. Our study shows that LTSL in combination with localized hyperthermia hold promise as local tumor delivery strategy for macromolecular cytotoxins.

Thermo-Sensitive Vesicles in Controlled Drug Delivery for Chemotherapy

Thermo-sensitive vesicles are a promising tool for triggering the release of drugs to solid tumours when used in combination with mild hyperthermia. Responsivity to temperature makes them intelligent nanodevices able to provide a site-specific chemotherapy. Following a brief introduction concerning hyperthermia and its advantageous combination with vesicular systems, recent investigations on thermo-sensitive vesicles useful for controlled drug delivery in cancer treatment are reported in this review. In particular, the influence of bilayer composition on the in vitro and in vivo behaviour of thermo-sensitive formulations currently under investigation have been extensively explored.

Chemo-immunotherapy of colon cancer with focused ultrasound and Salmonella-laden temperature sensitive liposomes (thermobots)

Using attenuated Salmonella that efficiently homes in solid tumors, here we developed thermobots that actively transported membrane attached low-temperature sensitive liposome (LTSL) inside colon cancer cells for triggered doxorubicin release and simultaneous polarized macrophages to M1 phenotype with high intensity focused ultrasound (HIFU) heating (40-42 °C). Biocompatibility studies showed that the synthesized thermobots were highly efficient in LTSL loading without impacting its viability. Thermobots demonstrated efficient intracellular trafficking, high nuclear localization of doxorubicin, and induced pro-inflammatory cytokine expression in colon cancer cells in vitro. Combination of thermobots and HIFU heating (~30 min) in murine colon tumors significantly enhanced polarization of macrophages to M1 phenotype and therapeutic efficacy in vivo compared to control. Our data suggest that the thermobots and focused ultrasound treatments have the potential to improve colon cancer therapy.

Endogenous pH-responsive nanoparticles with programmable size changes for targeted tumor therapy and imaging applications

Nanotechnology-based antitumor drug delivery systems, known as nanocarriers, have demonstrated their efficacy in recent years. Typically, the size of the nanocarriers is around 100 nm. It is imperative to achieve an optimum size of these nanocarriers which must be designed uniquely for each type of delivery process. For pH-responsive nanocarriers with programmable size, changes in pH (~6.5 for tumor tissue, ~5.5 for endosomes, and ~5.0 for lysosomes) may serve as an endogenous stimulus improving the safety and therapeutic efficacy of antitumor drugs. This review focuses on current advanced pH-responsive nanocarriers with programmable size changes for anticancer drug delivery. In particular, pH-responsive mechanisms for nanocarrier retention at tumor sites, size reduction for penetrating into tumor parenchyma, escaping from endo/lysosomes, and swelling or disassembly for drug release will be highlighted. Additional trends and challenges of employing these nanocarriers in future clinical applications are also addressed.

Ultrasonic Processing Technique as a Green Preparation Approach for Diacerein-Loaded Niosomes

In this study, the feasibility of ultrasonic processing (UP) technique as green preparation method for production of poorly soluble model drug substance, diacerein, loaded niosomes was demonstrated. Also, the effects of different surfactant systems on niosomes' characteristics were analyzed. Niosomes were prepared using both the green UP technique and traditional thin-film hydration (TFH) technique, which requires the use of environmentally hazardous organic solvents. The studied surfactant systems were Span 20, Pluronic L64, and their mixture (Span 20 and Pluronic L64). Both the production techniques produced well-defined spherical vesicles, but the UP technique produced smaller and more monodisperse niosomes than TFH. The entrapment efficiencies with the UP method were lower than with TFH, but still at a feasible level. All the niosomal formulations released diacerein faster than pure drug, and the drug release rates from the niosomes produced by the UP method were higher than those from the TFH-produced niosomes. With UP technique, the optimum process conditions for small niosomal products with low PDI values and high entrapment efficiencies were obtained when 70% amplitude and 45-min sonication time were used. The overall results demonstrated the potency of UP technique as an alternative fast, cost-effective, and green preparation approach for production of niosomes, which can be utilized as drug carrier systems for poorly soluble drug materials.

Nano-technology based carriers for nitrogen-containing bisphosphonates delivery as sensitisers of γδ T cells for anticancer immunotherapy

Nitrogen containing bisphosphonates (N-BPs) including zoledronate (ZOL) and alendronate (ALD) inhibit farnesyl diphosphate synthase, and have been shown to have a cytotoxic affect against cancer cells as a monotherapy and to also sensitise tumour cells to destruction by γδ T cells. γδ T cells are a subset of human T lymphocytes and have a diverse range of roles in the immune system including the recognition and destruction of cancer cells. This property of γδ T cells can be harnessed for use in cancer immunotherapy through in vivo expansion or the adoptive transfer of ex vivo activated γδ T cells. The use of N-BPs with γδ T cells has been shown to have a synergistic effect in in vitro, animal and clinical studies. N-BPs have limited in vivo activity due to rapid clearance from the circulation. By encapsulating N-BPs in liposomes (L) it is possible to increase the levels of N-BPs at non-osseous tumour sites. L-ZOL and L-ALD have been shown to have different toxicological profiles than free ZOL or ALD. Both L-ALD and L-ZOL led to increased spleen weight, leucocytosis, neutrophilia and lymphocytopenia in mice after intravenous injection. L-ALD was shown to be better tolerated than L-ZOL in murine studies. Biodistribution studies have been performed in order to better understand the interaction of N-BPs and γδ T cells in vivo. Additionally, in vivo therapy studies have shown that mice treated with both L-ALD and γδ T cells had a significant reduction in tumour growth compared to mice treated with L-ALD or γδ T cells alone. The use of ligand-targeted liposomes may further increase the efficacy of this combinatory immunotherapy. Liposomes targeting the αvβ6 integrin receptor using the peptide A20FMDV2 had a greater ability than untargeted liposomes in sensitising cancer cells to destruction by γδ T cells in αvβ6 positive cancer cell lines.

Hydrophobic Nanoparticles Modify the Thermal Release Behavior of Liposomes

Understanding the effect of embedded nanoparticles on the characteristics and behavior of lipid bilayers is critical to the development of lipid-nanoparticle assemblies (LNAs) for biomedical applications. In this work we investigate the effect of hydrophobic nanoparticle size and concentration on liposomal thermal release behavior. Decorated LNAs (D-LNAs) were formed by embedding 2 nm (GNP2) and 4 nm (GNP4) dodecanethiol-capped gold nanoparticles into DPPC liposomes at lipid to nanoparticle ratios (L:N) of 25,000:1, 10,000:1, and 5,000:1. D-LNA structure was investigated by cryogenic transmission electron microscopy, and lipid bilayer permeability and phase behavior were investigated based on the leakage of a model drug, carboxyfluorescein, and by differential scanning calorimetry, respectively. The presence of bilayer nanoparticles caused changes in the lipid bilayer release and phase behavior compared to pure lipid controls at very low nanoparticle to bilayer volume fractions (0.3%-4.6%). Arrhenius plots of the thermal leakage show that GNP2 led to greater increases in the leakage energy barrier compared to GNP4, consistent with GNP4 causing greater bilayer disruption due to their size relative to the bilayer thickness. Embedding hydrophobic nanoparticles as permeability modifiers is a unique approach to controlling liposomal leakage based on nanoparticle size and concentration.

Physicochemical characteristics of liposomes are decisive for their antirestenosis efficacy following local delivery

AIM

To develop an ameliorated sirolimus (SIR) liposome for intramural delivery, the effects of various carrier physicochemical parameters on the antirestenosis efficacy were evaluated.

MATERIALS & METHODS

Different liposomes were prepared, characterized and administered to balloon injured rats (12 animal groups). Their efficacies were investigated using morphometric, immunohistochemical and in vivo computed tomography imaging analyses.

RESULTS

The antirestenosis efficacy of SIR liposomes decreased in the following order: cationic 100 nm vesicles ≥ cationic 60 nm vesicles > neutral 100 nm vesicles ≥ stealth 100 nm vesicles > anionic 100 nm vesicles. The 100 µg SIR loaded in cationic liposomes showed almost no artery stenosis.

CONCLUSION

Appropriate modulation of physicochemical characteristics makes it possible to optimize the liposomes for local delivery.

Biodistribution and Efficacy of Low Temperature-Sensitive Liposome Encapsulated Docetaxel Combined with Mild Hyperthermia in a Mouse Model of Prostate Cancer

PURPOSE

Low temperature sensitive liposome (LTSL) encapsulated docetaxel were combined with mild hyperthermia (40-42°C) to investigate in vivo biodistribution and efficacy against a castrate resistant prostate cancer.

METHOD

Female athymic nude mice with human prostate PC-3 M-luciferase cells grown subcutaneously into the right hind leg were randomized into six groups: saline (+/- heat), free docetaxel (+/- heat), and LTSL docetaxel (+/- heat). Treatment (15 mg docetaxel/kg) was administered via tail vein once tumors reached a size of 200-300 mm(3). Mice tumor volumes and body weights were recorded for up to 60 days. Docetaxel concentrations of harvested tumor and organ/tissue homogenates were determined by LC-MS. Histological evaluation (Mean vessel density, Ki67 proliferation, Caspase-3 apoptosis) of saline, free Docetaxel and LTSL docetaxel (+/- heat n = 3-5) was performed to determine molecular mechanism responsible for tumor cell killing.

RESULT

LTSL/heat resulted in significantly higher tumor docetaxel concentrations (4.7-fold greater compared to free docetaxel). Adding heat to LTSL Docetaxel or free docetaxel treatment resulted in significantly greater survival and growth delay compared to other treatments (p < 0.05). Differences in body weight between all Docetaxel treatments were not reduced by >10% and were not statistically different from each other. Molecular markers such as caspase-3 were upregulated, and Ki67 expression was significantly decreased in the chemo-hyperthermia group. Vessel density was similar post treatment, but the heated group had reduced vessel area, suggesting thermal enhancement in efficacy by reduction in functional perfusion.

CONCLUSION

This technique of hyperthermia sensitization and enhanced docetaxel delivery has potential for clinical translation for prostate cancer treatment.

A pilot trial of doxorubicin containing phosphatidyldiglycerol based thermosensitive liposomes in spontaneous feline soft tissue sarcoma

PURPOSE

Doxorubicin (DOX)-loaded phosphatidyldiglycerol-based thermosensitive liposomes (DPPG₂-TSL-DOX) combined with local hyperthermia (HT) was evaluated in cats with locally advanced spontaneous fibrosarcomas (soft tissue sarcoma [STS]). The study was designed to evaluate the safety and pharmacokinetic profile of the drug. Results from four dose-levels are reported.

METHODS

Eleven client-owned cats with advanced STS were enrolled. Five cats received escalating doses of 0.1-0.4 mg/kg DOX (group I), three received 0.4 mg/kg constantly (group II) and three 0.6 mg/kg (group III) IV over 15 min. HT with a target temperature of 41.5 °C was started 15 min before drug application and continued for a total of 60 min. Six HT treatments were applied every other week using a radiofrequency applicator. Tumour growth was monitored by magnetic resonance imaging (MRI) and for dose level III also with ¹⁸F-FDG PET.

RESULTS

Treatment was generally well tolerated and reasons for premature study termination in four cats were not associated with drug-induced toxicity. No DPPG₂-TSL-DOX based hypersensitivity reaction was observed. One cat showed simultaneous partial response (PR) in MRI and positron emission tomography (PET) whereas one cat showed stable disease in MRI and PR in PET (both cats in dose level III). Pharmacokinetic measurements demonstrated DOX release triggered by HT.

CONCLUSION

DPPG₂-TSL-DOX + HT is a promising treatment option for advanced feline STS by means of targeted drug delivery. As MTD was not reached further investigation is warranted to determine if higher doses would result in even better tumour responses.

Comparative Experimental and Computational Study of Monoalkyl Chain Phosphatidylcholine-Containing Thermoresponsive Liposomes

Liposomes containing lysophospholipids are intensively studied as drug delivery systems that are stable at normal body temperature but exhibit fast release of their drug load at slightly elevated temperatures. In this study, the stability and release properties of dipalmitoylglycerophosphocholine (DPPC)-based liposomes incorporating the commonly used lysophosphatidylocholine (lyso-PC), and a series of monoalkyl chain ether-linked phosphatidylcholine, i.e., the biologically relevant monoalkyl chain platelet activating factor (PAF) and its derivatives lyso-PAF and methyl-PAF, were investigated. To this end a series of PEGylated small unilamellar liposomes with DPPC:monoalkyl lipid compositions of 5% and 10% molar ratio were prepared and compared with regard to stability (37 °C) and release properties at elevated temperatures (38-43 °C). All systems were characterized with respect to size distribution, ζ-potential, and phase transition characteristics. The presence of ether-lipids endows liposomes with superior (∼10% increase) release properties at 5% incorporation compared to lyso-PC, while at 10% molar ratio the formulations do not differ significantly, the release being close to 90%. The findings are supported by atomistic molecular dynamics simulations that suggest a correlation between the enhanced permeability and increased penetration of water molecules within the bilayers with density fluctuations resulting from the increased area-per-lipid and the disorder of the lysolipids alkyl chains.

Targeted antibiotic delivery using low temperature-sensitive liposomes and magnetic resonance-guided high-intensity focused ultrasound hyperthermia

Chronic non-healing wound infections require long duration antibiotic therapy, and are associated with significant morbidity and health-care costs. Novel approaches for efficient, readily-translatable targeted and localised antimicrobial delivery are needed. The objectives of this study were to 1) develop low temperature-sensitive liposomes (LTSLs) containing an antimicrobial agent (ciprofloxacin) for induced release at mild hyperthermia (∼42 °C), 2) characterise in vitro ciprofloxacin release, and efficacy against Staphylococcus aureus plankton and biofilms, and 3) determine the feasibility of localised ciprofloxacin delivery in combination with MR-HIFU hyperthermia in a rat model. LTSLs were loaded actively with ciprofloxacin and their efficacy was determined using a disc diffusion method, MBEC biofilm device, and scanning electron microscopy (SEM). Ciprofloxacin release from LTSLs was assessed in a physiological buffer by fluorescence spectroscopy, and in vivo in a rat model using MR-HIFU. Results indicated that < 5% ciprofloxacin was released from the LTSL at body temperature (37 °C), while >95% was released at 42 °C. Precise hyperthermia exposures in the thigh of rats using MR-HIFU during intravenous (i.v.) administration of the LTSLs resulted in a four fold greater local concentration of ciprofloxacin compared to controls (free ciprofloxacin + MR-HIFU or LTSL alone). The biodistribution of ciprofloxacin in unheated tissues was fairly similar between treatment groups. Triggered release at 42 °C from LTSL achieved significantly greater S. aureus killing and induced membrane deformation and changes in biofilm matrix compared to free ciprofloxacin or LTSL at 37 °C. This technique has potential as a method to deliver high concentration antimicrobials to chronic wounds.

Formulation and optimization of idarubicin thermosensitive liposomes provides ultrafast triggered release at mild hyperthermia and improves tumor response

Drug delivery through thermosensitive liposomes (TSL) in combination with hyperthermia (HT) has shown great potential. HT can be applied locally forcing TSL to release their content in the heated tumor resulting in high peak concentrations. To perform optimally the drug is ideally released fast (seconds) and taken up rapidly by tumor cells. The aim of this study was to develop a novel thermosensitive liposome formulation of the anthracycline idarubicin (IDA-TSL). The hydrophobicity of idarubicin may improve its release from liposomes and subsequently rapid cellular uptake when combined mild hyperthermia. Here, we investigated a series of parameters to optimize IDA-TSL formulation. The results show that the optimal formulation for IDA-TSL is DPPC/DSPC/DSPE-PEG (6/3.5/0.5 mol%), with ammonium EDTA of 6.5 pH as loading buffer and a size of ~85 nm. In vitro studies demonstrated minimal leakage of ~20% in FCS at 37 °C for 1h, while an ultrafast and complete triggered release of IDA was observed at 42 °C. On tumor cells IDA-TSL showed comparable cytotoxicity to free IDA at 42 °C, but low cytotoxicity at 37 °C. Intravital microscopy imaging demonstrated an efficient in vivo intravascular triggered drug release of IDA-TSL under mild hyperthermia, and a subsequent massive IDA uptake by tumor cells. In animal efficacy studies, IDA-TSL plus mild HT demonstrated prominent tumor growth inhibition and superior survival rate over free IDA with HT or a clinically used Doxil treatment. These results suggest beneficial potential of IDA-TSL combined with local mild HT.

Pharmacokinetics, Tissue Distribution and Therapeutic Effect of Cationic Thermosensitive Liposomal Doxorubicin Upon Mild Hyperthermia

PURPOSE

To evaluate pharmacokinetic profile, biodistribution and therapeutic effect of cationic thermosensitive liposomes (CTSL) encapsulating doxorubicin (Dox) upon mild hyperthermia (HT).

METHODS

Non-targeted thermosensitive liposomes (TSL) and CTSL were developed, loaded with Dox and characterized. Blood kinetics and biodistribution of Dox-TSL and Dox-CTSL were followed in B16BL6 tumor bearing mice upon normothermia (NT) or initial hyperthermia conditions. Efficacy study in B16BL6 tumor bearing mice was followed with Dox-TSL or Dox-CTSL upon NT or HT. Efficacy study in LLC tumor bearing mice was performed upon two HT conditions. Intravital microscopy was performed on B16BL6 tumors implanted in dorsal-skin fold window-bearing mice.

RESULTS

Targeting did not cause faster blood clearance of CTSL compared to TSL. Highest uptake of liposomes was observed in spleen, kidneys and liver. Applying HT prior to CTSL administration increased drug delivery to the tumor and CTSL delivered ~1.7 fold higher Dox concentration compared to TSL. Efficacy in B16BL6 murine melanoma showed that HT had a significant effect on CTSL in tumor suppression and prolonged survival. Efficacy in LLC Lewis lung carcinoma tumor model demonstrates that two HT treatments hold promises for a successful treatment option.

CONCLUSION

CTSL have potency to increase drug efficacy in tumors due to their targeted and drug release functions.

A systematic study of temperature sensitive liposomal delivery of doxorubicin using a mathematical model

BACKGROUND

Temperature-sensitive liposomes (TSL) in combination with hyperthermia (HT) exposure have emerged as a potentially attractive option to achieve therapeutic drug concentration at targeted tumour site while reducing adverse side effects associated with systemic administration of anticancer drugs. The aim of this study is to elucidate the interplay among different kinetic steps by means of computational modelling.

METHODS

A multi-compartment model for TSL-mediated delivery of doxorubicin (DOX) is developed, which incorporates descriptions of the pharmacokinetics of TSL and DOX, and their accumulation in tumour tissue following intravascular triggered release. By examining dynamic interactions among TSL properties, tumour physiological properties and treatment regimen, peak intracellular DOX concentration is predicted for continuous and pulse HT exposures.

RESULTS

Drug release rate from TSL has a saturable effect on peak intracellular drug concentration, and no further gain could be achieved for release rates greater than 0.1018 s(-1). A similar effect has also been found for heating duration, such that for a given bolus injection, peak intracellular drug concentration reaches its maximum and then levels off after HT duration of 2h. These results suggest that both TSL release rate and HT duration can be optimised in accordance with other parameters, e.g. clearance rate of TSL and administration mode, in order to achieve a desirable level of intracellular drug concentration. However, prolonged heating is not effective for resistant tumour cells with overexpression of ABC (ATP-binding cassette) transporter proteins.

CONCLUSIONS

The results obtained in this study can be used to guide the design and optimisation of TSL parameters and treatment regimens.

Temperature-dependent drug release from DPPC:C12H25-PNIPAM-COOH liposomes: control of the drug loading/release by modulation of the nanocarriers' components

Novel polymer-modified thermosensitive liposomes were developed for the delivery of indomethacin in order to control its release profile. When attached to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, the end functionalized C12H25-poly(N-isopropylacrylamide)-COOH (C12H25-PNIPAM-COOH) polymer was membrane-disruptive in a temperature-dependent manner. The interest for this polymer is driven by its famous lower critical solution temperature (LCST) behavior, where heating an aqueous solution of PNIPAM above 32°C induces nanophase separation and polymer chain aggregation. The physicochemical/structural behavior of these polymer-modified thermosensitive liposomes was found to depend on the PNIPAM:lipid molar ratio and the composition of the polymeric guest. The incorporation of PNIPAM has caused alterations in the thermotropic behavior of DPPC liposomes, as the differential scanning calorimetry (DSC) experiments revealed. The drug loading and the release were found to be strongly dependent on the thermotropic characteristics of the PNIPAM grafted DPPC liposomes. Namely, the in vitro release is immediate at 37°C (>LCST) ("burst" effect), while the prepared mixed nanocarriers did not release the encapsulated bioactive substance at <32°C (<LCST). Thus, the thermosensitivity and the drug loading/release properties of the prepared formulations can be modulated by varying the ratio of DPPC/PNIPAM components, as well as the molecular characteristics of the polymeric guest.