Liposomes as drug carriers

Impact of local drug delivery and natural agents as new target strategies against periodontitis: new challenges for personalized therapeutic approach

Periodontitis is a persistent inflammation of the soft tissue around the teeth that affects 60% of the population in the globe. The self-maintenance of the inflammatory process can cause periodontal damage from the alveolar bone resorption to tooth loss in order to contrast the effects of periodontitis, the main therapy used is scaling and root planing (SRP). At the same time, studying the physiopathology of periodontitis has shown the possibility of using a local drug delivery system as an adjunctive therapy. Using local drug delivery devices in conjunction with SRP therapy for periodontitis is a potential tool since it increases drug efficacy and minimizes negative effects by managing drug release. This review emphasized how the use of local drug delivery agents and natural agents could be promising adjuvants for the treatment of periodontitis patients affected or not by cardiovascular disease, diabetes, and other system problems. Moreover, the review evidences the current issues and new ideas that can inspire potential later study for both basic research and clinical practice for a tailored approach.

Modulating Inflammation-Mediated Diseases via Natural Phenolic Compounds Loaded in Nanocarrier Systems

The global increase and prevalence of inflammatory-mediated diseases have been a great menace to human welfare. Several works have demonstrated the anti-inflammatory potentials of natural polyphenolic compounds, including flavonoid derivatives (EGCG, rutin, apigenin, naringenin) and phenolic acids (GA, CA, etc.), among others (resveratrol, curcumin, etc.). In order to improve the stability and bioavailability of these natural polyphenolic compounds, their recent loading applications in both organic (liposomes, micelles, dendrimers, etc.) and inorganic (mesoporous silica, heavy metals, etc.) nanocarrier technologies are being employed. A great number of studies have highlighted that, apart from improving their stability and bioavailability, nanocarrier systems also enhance their target delivery, while reducing drug toxicity and adverse effects. This review article, therefore, covers the recent advances in the drug delivery of anti-inflammatory agents loaded with natural polyphenolics by the application of both organic and inorganic nanocarriers. Even though nanocarrier technology offers a variety of possible anti-inflammatory advantages to naturally occurring polyphenols, the complexes' inherent properties and mechanisms of action have not yet been fully investigated. Thus, expanding the quest on novel natural polyphenolic-loaded delivery systems, together with the optimization of complexes' activity toward inflammation, will be a new direction of future efforts.

Versatile Encapsulation and Synthesis of Potent Liposomes by Thermal Equilibration

The wide-scale use of liposomal delivery systems is challenged by difficulties in obtaining potent liposomal suspensions. Passive and active loading strategies have been proposed to formulate drug encapsulated liposomes but are limited by low efficiencies (passive) or high drug specificities (active). Here, we present an efficient and universal loading strategy for synthesizing therapeutic liposomes. Integrating a thermal equilibration technique with our unique liposome synthesis approach, co-loaded targeting nanovesicles can be engineered in a scalable manner with potencies 200-fold higher than typical passive encapsulation techniques. We demonstrate this capability through simultaneous co-loading of hydrophilic and hydrophobic small molecules and targeted delivery of liposomal Doxorubicin to metastatic breast cancer cell line MDA-MB-231. Molecular dynamic simulations are used to explain interactions between Doxorubicin and liposome membrane during thermal equilibration. By addressing the existing challenges, we have developed an unparalleled approach that will facilitate the formulation of novel theranostic and pharmaceutical strategies.

The Effects of Solid and Liquid Lipids on the Physicochemical Properties of Nanostructured Lipid Carriers

The aim of this work was to identify from a review of current literature the effects of lipids used in the development of Nanostructured Lipid Carriers (NLCs) on the physicochemical properties of the resulting formulation. The size of the solid lipid, affected by the molecular weight and the complexity of the structure, tends to affect the particle size of the final formulation proportionally; the higher the molecular weight and the more complex the molecular structure, the bigger the particle size of the NLCs. However, there is no straight correlation between the size and the structure of the liquid lipid and the particle size. Moreover, there seems to be a correlation of the solid to liquid lipid ratio which affects the particle size; there has been a trend of increasing particle size when more solid lipid was used. Regarding the entrapment efficiency, it is highly affected by the drug and its interaction with the lipids, as its solubility in the lipids needs to be high so the drug can stay entrapped within the lipid core. There was no direct correlation between the type of lipid used or the ratio and the zeta potential, which affects the stability of the NLCs.

Drug Carriers: Classification, Administration, Release Profiles, and Industrial Approach

This work is aimed at providing a description of the complex world of drug carriers, starting from the description of this particular market in terms of revenue. Then, a brief overview of several types of conventional and innovative drug carrier systems has been included. The types of administration routes were also analyzed, with a critical and qualitative comment on drug release kinetics and drug profile shapes. Carriers were classified according to their ability to provide a prolonged and targeted release. The concept of the therapeutic window has been presented, providing advantages of having pulsed drug release to avoid side effects to target tissues. A critical comment on the use of conventional and innovative techniques for the production of drug carriers by large industrial companies has been proposed. As a final attempt for this work, an overall unique schematization of a drug carrier production process has been added, highlighting the necessity to create a strong double link among world-requested versatility of drug carriers for human applications and the newly developed industrial processes.

Application of Pb(II) to probe the physiological responses of fungal intracellular vesicles

Vesicles (Ves) within fungal cells are the critical linkage between intracellular and extracellular systems. This study explored the application of Pb²⁺ to probe the physiology of intracellular Ves in Rhodotorula mucilaginosa (Rho). At low Pb²⁺ levels (0-500 mg/L), there was no evident change in the content of extracellular polymeric substances (EPS) or microbial activity. At medium-high levels (1000-2000 mg/L), the sizes of Ves within the Rho cells were significantly enlarged, with abundant lead nano-particles (Pb NPs) formed either on the cell surface or interior, whereas the EPS content and bioactivity were still stable. At a high level (2500 mg/L), the Rho cells were severely deformed, with cell counts reduced by more than 99%. However, the EPS contents and the respiration rate of the surviving cells dramatically increased to the maximum values (i.e., 1785 mg/10¹⁰ cells and 37 mg C 10^-10 cells h^-1, respectively). The Ves surface adsorbed Pb cations with higher density, compared with the cell membrane. Moreover, fusion of some Ves to the membrane (functioning in transport) was observed under transmission electron microscope (TEM). Three pathways of detoxification via intracellular Ves were finally proposed, i.e., Ve-mediated transport (from intracellular to extracellular) of EPS components, absorption of Pb NPs on the Ve surface, and accumulation of Pb NPs within Ves. This study sheds light on the possibility of exploring microbial physiology via Pb²⁺ cations.

Local drug delivery systems in the management of periodontitis: A scientific review

Periodontitis (PD) is a microbial disease of tooth supporting tissues that results in progressive destruction of surrounding soft and hard tissues with eventual tooth mobility and exfoliation. Perioceutics, which includes the delivery of therapeutic agents via systemic and local means as an adjunct to mechanical therapy has revolutionized the arena of periodontal therapy. Selection of a right antimicrobial agent with appropriate route of drug administration is the key to successful periodontal therapy. Irrigating systems, fibers, gels, strips, films, microparticles, nanoparticles and low dose antimicrobial agents are some of the local drug delivery systems (LDDS) available in the field, which aims to deliver antimicrobial agents to sub-gingival diseased sites with minimal or no side-effects on other body sites. The present review aim to summarize the current state-of-the-art technology on LDDS in periodontal therapy ensuring the the practitioners are able to choose LDD agents which are custom made for a specific clinical condition.

What Drives Innovation: The Canadian Touch on Liposomal Therapeutics

Liposomes are considered one of the most successful drug delivery systems (DDS) given their established utility and success in the clinic. In the past 40–50 years, Canadian scientists have made ground-breaking discoveries, many of which were successfully translated to the clinic, leading to the formation of biotech companies, the creation of research tools, such as the Lipex Extruder and the NanoAssemblr™, as well as contributing significantly to the development of pharmaceutical products, such as Abelcet^®, MyoCet^®, Marqibo^®, Vyxeos^®, and Onpattro™, which are making positive impacts on patients’ health. This review highlights the Canadian contribution to the development of these and other important liposomal technologies that have touched patients. In this review, we try to address the question of what drives innovation: Is it the individual, the teams, the funding, and/or an entrepreneurial spirit that leads to success? From this perspective, it is possible to define how innovation will translate to meaningful commercial ventures and products with impact in the future. We begin with a brief history followed by descriptions of drug delivery technologies influenced by Canadian researchers. We will discuss recent advances in liposomal technologies, including the Metaplex technology from the author’s lab. The latter exemplifies how a nanotechnology platform can be designed based on multidisciplinary groups with expertise in coordination chemistry, nanomedicines, disease, and business to create new therapeutics that can effect better outcomes in patient populations. We conclude that the team is central to the effort; arguing if the team is entrepreneurial and well positioned, the funds needed will be found, but likely not solely in Canada.

The Dimerisation of Phthalocyanines

In this review, we have shown that the dimerisation of phthalocyanine compounds, notably here the sulphonated aluminium phthalocyanines, is dependent upon concentration, on the medium in which the dye is dissolved, and upon pH. Complex equilibria between various monomer and dimer species are observed as a function of pH, and the probable structures of the dimers elucidated by semi-empirical and ab initio calculations. The formation of a red-shifted dimer leads to the quenching of monomer singlet state in concentrated solution, in reverse micelles, and in lipid vesicles, and this behaviour can account for the fluorescence intensity distributions and decay characteristics of phthalocyanine dyes in living cells as a function of irradiation time.

Antimetastatic Effect of Liposomal Recombinant Lactaptin

Antimetastatic effect of the liposomal form of recombinant lactaptin RL2 (a proteolytic fragment of human breast milk κ-casein; 8.6 kDa) was studied in A/Sn mice after intravenous transplantation of GA-1 tumor with high rate of liver metastases. Tumor growth in the liver was found in all mice. In animals dying early, the tumors were presented by multiple nodes of about the same size; in mice dying later, the tumors in the liver were presented by just few large nodes formed by cells that survived chemotherapy. A single intravenous injection of RL2 lactaptin in liposomes prolonged lifespan of animals with liver metastases of GA-1 tumor by 1.5 times in comparison with that in untreated animals.

High Antimetastatic Activity of Platin Liposomal Form after Lyophilization and Storage

Antimetastatic activity of Platin in lyophilized liposomes stored for 7 years after fabrication was evaluated. The main flaw of liposomes as vehicles for drug delivery to the tumors is their high affinity for the liver, which accumulates a great amount thereof. This property of liposomes can be used for adjuvant therapy of operable primary tumors metastasizing to the liver. It is shown on the model of mouse GA-1 tumor metastases in the liver that platinum(II) complex compound Platin in phosphatidylcholine-cholesterol liposomes, stored for 7 years after lyophilization, causes complete cure of 40% animals, while free Platin prolongs the lifespan of mice with tumors by only 31.7% vs. control (no treatment).

Nanomaterials for the Capture and Therapeutic Targeting of Circulating Tumor Cells

Circulating tumor cells are a hallmark of cancer metastasis which accounts for approximately 90% of all cancer-related deaths. Their detection and characterization have significant implications in cancer biology and clinical practice. However, CTCs are rare cells and consist of heterogeneous subpopulations, requiring highly sensitive and specific techniques to identify and isolate them with high efficiency. Nanomaterials, with unique structural and functional properties, have shown strong promise to meet the challenging demands. In this review, we discuss CTC capture and therapeutic targeting, emphasizing the significance of the nanomaterials being used for this purpose. The next generation of therapy for metastatic cancer may well involve capturing and even directly neutralizing CTCs using nanomaterials.

Different Efficiency of Liposomal Forms with Hydrophilic and Hydrophobic Antitumor Agents in Relation to Solid Transplants of Mouse Tumor and Its Metastases in the Liver

Experiments were performed on the model of transplanted mouse tumor with high incidence of liver metastases. Hydrophilic drug cycloplatam (injected intravenously in liposomes) was more potent than "free cycloplatam" (injected intravenously or intraperitoneally in physiological saline) in inhibiting the growth of natural and experimental metastases in the liver. By contrast, liposomal cycloplatam had lower efficiency than free cycloplatam in suppressing the growth of solid tumor. Liposomal and free cortifen (hydrophobic hormonal cytostatic) produced nearly the same effects on solid tumor growth. Our results suggest that liposomal forms of hydrophobic compounds producing nonselective effect on tumor cells (e.g., actinomycin D or Cosmegen), should not have advantages over free forms.

Influence of the Encapsulation Efficiency and Size of Liposome on the Oral Bioavailability of Griseofulvin-Loaded Liposomes

The objective of the present study was to investigate the influence of the encapsulation efficiency and size of liposome on the oral bioavailability of griseofulvin-loaded liposomes. Griseofulvin-loaded liposomes with desired characteristics were prepared from pro-liposome using various techniques. To study the effect of encapsulation efficiency, three preparations of griseofulvin, namely, griseofulvin aqueous suspension and two griseofulvin-loaded liposomes with different amounts of griseofulvin encapsulated [i.e., F1 (32%) and F2(98%)], were administered to rats. On the other hand, to study the effect of liposome size, the rats were given three different griseofulvin-loaded liposomes of various sizes, generated via different mechanical dispersion techniques [i.e., FTS (142 nm), MS (357 nm) and NS (813 nm)], but with essentially similar encapsulation efficiencies (about 93%). Results indicated that the extent of bioavailability of griseofulvin was improved 1.7-2.0 times when given in the form of liposomes (F1) compared to griseofulvin suspension. Besides that, there was an approximately two-fold enhancement of the extent of bioavailability following administration of griseofulvin-loaded liposomes with higher encapsulation efficiency (F2), compared to those of F1. Also, the results showed that the extent of bioavailability of liposomal formulations with smaller sizes were higher by approximately three times compared to liposomal formulation of a larger size. Nevertheless, a further size reduction of griseofulvin-loaded liposome (≤400 nm) did not promote the uptake or bioavailability of griseofulvin. In conclusion, high drug encapsulation efficiency and small liposome size could enhance the oral bioavailability of griseofulvin-loaded liposomes and therefore these two parameters deserve careful consideration during formulation.

Topical anesthesia

Topical anesthetics are being widely used in numerous medical and surgical sub-specialties such as anesthesia, ophthalmology, otorhinolaryngology, dentistry, urology, and aesthetic surgery. They cause superficial loss of pain sensation after direct application. Their delivery and effectiveness can be enhanced by using free bases; by increasing the drug concentration, lowering the melting point; by using physical and chemical permeation enhancers and lipid delivery vesicles. Various topical anesthetic agents available for use are eutectic mixture of local anesthetics, ELA-max, lidocaine, epinephrine, tetracaine, bupivanor, 4% tetracaine, benzocaine, proparacaine, Betacaine-LA, topicaine, lidoderm, S-caine patch™ and local anesthetic peel. While using them, careful attention must be paid to their pharmacology, area and duration of application, age and weight of the patients and possible side-effects.

Application of liposomes in medicine and drug delivery

Liposomes provide an established basis for the sustainable development of different commercial products for treatment of medical diseases by the smart delivery of drugs. The industrial applications include the use of liposomes as drug delivery vehicles in medicine, adjuvants in vaccination, signal enhancers/carriers in medical diagnostics and analytical biochemistry, solubilizers for various ingredients as well as support matrices for various ingredients and penetration enhancers in cosmetics. In this review, we summarize the main applications and liposome-based commercial products that are currently used in the medical field.

Oral pretreatment with liposomal glutathione attenuates reperfusion injury in rabbit isolated hearts

Reactive oxygen species are a key mediator of myocardial reperfusion injury. Endogenous cellular defenses against reactive oxygen species often become overwhelmed after ischemia and reperfusion. Therefore, exogenous supplementation of various antioxidant compounds has been hypothesized to protect against reperfusion. Reduced glutathione (GSH) is an important endogenous antioxidant that affords protection against oxidative damage. Oral administration of GSH is limited due to poor gastrointestinal absorption. A liposomal preparation of glutathione (lipGSH) capable of oral administration was investigated for its ability to attenuate tissue injury and increase myocardial glutathione levels in an isolated heart model of reperfusion injury. Male, New Zealand white rabbits were assigned randomly among 4 groups as follows: control and daily oral administration of lipGSH for 3, 7, or 14 days. At completion of the dosing regimen, hearts were harvested and perfused in a retrograde manner with the use of a Langendorff apparatus. The hearts were subjected to 30 minutes of global ischemia followed by 60 minutes of reperfusion. Hearts from lipGSH-treated rabbits exhibited better recovery of left ventricular contractile function during reperfusion and had attenuated oxidative damage. Furthermore, hearts from lipGSH-treated animals had increased myocardial tissue levels of GSH demonstrating effective absorption of lipGSH.

Cyclodextrin as membrane protectant in spray-drying and freeze-drying of PEGylated liposomes

In this study it was investigated whether hydroxypropyl-β-cyclodextrin (HPβCD) is able to stabilize the liposomal membranes during drying of long circulating polyethylene glycol (PEG) coated liposomes, as compared to the disaccharides trehalose and sucrose. PEGylated liposomes loaded with prednisolone disodium phosphate (PLP) were dried by spray-drying or freeze-drying. The dried powders were tested on their residual moisture content, glass transition temperature and amorphous character. Upon reconstitution the liposomal size, size distribution and drug retention were determined and the results were compared to the characteristics of the formulation solution before drying. In contrast to the disaccharides, HPβCD stabilizes the liposomal membranes of the PEGylated liposomes during the drying process of both spray drying and freeze-drying when present in a lipid:carbohydrate ratio of 1:6 (w/w). The resulting powder can be stored at room temperature. No changes in size and size distribution were seen upon reconstitution of the HPβCD containing formulations. Drying resulted in a minimal leaking of PLP from the liposomes. Its relatively high [Formula: see text] and T(g) of HPβCD, as compared to the disaccharides, make HPβCD an excellent membrane protectant for dry PEGylated liposomal formulations.

Lipid-based carriers: manufacturing and applications for pulmonary route

INTRODUCTION

Recent advances in aerosol therapy have sparked considerable interest in the development of novel drug delivery systems for pulmonary route. Development of colloidal carriers as pharmaceutical drug delivery systems has spurred an exponential growth; the encapsulation of bioactive molecules into relatively inert and non-toxic carriers for in vivo delivery constitutes a promising approach for improving their therapeutic index while reducing the side effects. Extraordinary success has been made toward improving efficacy by developing lipid-based carriers (LBCs); among classical examples are liposomes and solid lipid nanoparticles (SLNs).

AREAS COVERED

The authors review lipid-based colloidal carriers - liposomes and SLNs - as pulmonary drug delivery systems. Conventional methods of liposome preparation and recently developed systems are discussed. Special attention is given to SLNs and their main manufacturing techniques. Finally, a summary of recent scientific publications and important results in the field of pulmonary lipidic carriers are presented. Some practical considerations regarding the toxicological concerns of such systems are briefly cited.

EXPERT OPINION

Despite several scientific investigations, numerous advantages and encouraging results, LBCs for pulmonary route have attained only few great achievements as many challenges still remain. Problems limiting the use of such system seem to be the complexity of the respiratory tract as well as the lack of toxicity assessment risks of colloidal carriers.

Multifunctional nanoemulsion platform for imaging guided therapy evaluated in experimental cancer

Nanoparticle applications in medicine have seen a tremendous growth in the past decade. In addition to their drug targeting application and their ability to improve bioavailability of drugs, nanoparticles can be designed to allow their detection with a variety of imaging methodologies. In the current study, we developed a multimodal nanoparticle platform to enable imaging guided therapy, which was evaluated in a colon cancer mouse model. This "theranostic" platform is based on oil-in-water nanoemulsions and carries iron oxide nanocrystals for MRI, the fluorescent dye Cy7 for NIRF imaging, and the hydrophobic glucocorticoid prednisolone acetate valerate (PAV) for therapeutic purposes. Angiogenesis-targeted nanoemulsions functionalized with αvβ(3)-specific RGD peptides were evaluated, as well. When subcutaneous tumors were palpable, the nanoemulsions were administered at a dose of 30 mg of FeO/kg and 10 mg of PAV/kg. MRI and NIRF imaging showed significant nanoparticle accumulation in the tumors, while tumor growth profiles revealed a potent inhibitory effect in all of the PAV nanoemulsion-treated animals as compared to the ones treated with control nanoemulsions, the free drug, or saline. This study demonstrated that our nanoemulsions, when loaded with PAV, iron oxide nanocrystals, and Cy7, represent a flexible and unique theranostic nanoparticle platform that can be applied for imaging guided therapy of cancer.

Liposomal drug formulations in the treatment of rheumatoid arthritis

Liposomes have been extensively investigated as drug delivery systems in the treatment of rheumatoid arthritis (RA). Low bioavailability, high clearance rates and limited selectivity of several important drugs used for RA treatment require high and frequent dosing to achieve sufficient therapeutic efficacy. However, high doses also increase the risk for systemic side effects. The use of liposomes as drug carriers may increase the therapeutic index of these antirheumatic drugs. Liposomal physicochemical properties can be changed to optimize penetration through biological barriers and retention at the site of administration, and to prevent premature degradation and toxicity to nontarget tissues. Optimal liposomal properties depend on the administration route: large-sized liposomes show good retention upon local injection, small-sized liposomes are better suited to achieve passive targeting. PEGylation reduces the uptake of the liposomes by liver and spleen, and increases the circulation time, resulting in increased localization at the inflamed site due to the enhanced permeability and retention (EPR) effect. Additionally liposomal surfaces can be modified to achieve selective delivery of the encapsulated drug to specific target cells in RA. This review gives an overview of liposomal drug formulations studied in a preclinical setting as well as in clinical practice. It covers the use of liposomes for existing antirheumatic drugs as well as for new possible treatment strategies for RA. Both local administration of liposomal depot formulations and intravenous administration of passively and actively targeted liposomes are reviewed.

Polymerized surfactant vesicles: novel membrane mimetic systems

Vesicles formed from dialkyl surfactants containing vinyl, methacrylate, diacetylene, isocyano, and styrene groups have been stabilized by polymerization across their bilayers of head groups. Polymerized vesicles have shelf lives of many months and controllable permeabilities and sizes. The kinetics of surfactant vesicle photopolymerzation have been determined, and the mechanism of photopolymerization has been discussed as a two-dimensional surface process. Polymerized surfactant vesicles concentrate reagents in their aqueous interiors, in bilayers, and in their inner or outer surfaces. This, in turn, leads to altered reaction rates and sites. Polymerized surfactant vesicles also provide a good media for the generation, in situ, of small, uniform, and efficient colloidal catalysts.

A new trial liposteroid (dexamethasone palmitate) therapy for intractable epileptic seizures in infancy

West syndrome (WS) is a severe age-dependent intractable epilepsy in infants that frequently results in mental retardation. ACTH or glucocorticoids are among several effective treatments in WS, but the relative advantages and disadvantages of these two therapies are still unknown. In a previous study, liposteroid (LS; dexamethasone palmitate) was used for the treatment of WS and compared with ACTH therapy in relation to therapeutic effect and adverse reactions. In this study, a new regimen of LS therapy was tried for WS and its related syndrome in an attempt to hasten the onset of the therapeutic effect and reduce the relapse rate. A single intravenous injection of LS (0.25mg/kg) was administered 12 times in 1 month (total dosage 3.0mg/kg) to four patients with WS and with post-WS aged 5-25 months, and one patient with Lennox-Gastaut syndrome (post-WS) aged 84 months. All five patients had daily seizures uncontrolled by conventional antiepileptic drugs, such as VPA, CZP or ZNS. Nodding spasm and hypsarrhythmia on EEG disappeared in one patient with WS within four doses. More than 50% decrease in seizures, and EEG improvement, were found in other two patients. No notable effects were seen in the other two patients. There were no clinically significant adverse reactions throughout the therapy. Efficacy can be determined in this new experimental LS therapy earlier than with conventional LS therapy. In this small study, a new protocol for LS therapy could be completed safely. This regimen may be useful for those susceptible to adverse reactions from conventional treatment or those unresponsive to other treatments.

DDS for anti-aging and regenerative medicine (review)

In this paper we summarized, first the present status and history of the development of research in anti-aging and regenerative medicine in Japan, and secondly some of our research using DDS in the field of both medicine. The regenerative medicine has been developed in Japan by using the fund from the Government, particularly as the Millennium Project. While anti-aging medicine developed following the social interest on it in Japan and it was influenced by American Society (A4M). Next, we summarized our research on DDS for anti-aging and regenerative medicine. In most cases we used oily or solid nanoparticles as carriers of drug. Those particles have a property of both of targeting and slow release in the DDS technology. The two properties are important for anti-aging and regenerative medicine, since drugs have to be administered safely and for long time. We applied prostaglandin E1, granulocyte-colony stimulate factor (G-CSF), and retinoid into the systems.

The effect of surface charge on the disposition of liposome-encapsulated gentamicin to the rat liver, brain, lungs and kidneys after intraperitoneal administration

The disposition of gentamicin to the normal rat brain, lung, kidney and liver was studied at intervals of 1, 2, 4, 6 and 8h after intraperitoneal injection of gentamicin encapsulated in positive, negative and neutral liposomes. Compared with the control, which was treated with free gentamicin, liposomes were associated with higher concentrations of gentamicin in the brain and liver, while concentrations were lower in the kidney. The average concentrations of gentamicin in the liver and the brain were highest with positive liposomes, while, gentamicin concentrations in the kidneys and lungs were not influenced by surface charge of the liposomes. These observations have important implications on the selective delivery of gentamicin to tissues and on the intraperitoneal route of administration.

Lipid microspheres incorporated by U937 cells via their specific receptors

Lipid microspheres (LM), currently in clinical use as drug carriers, mainly consist of soybean oil as a core and lecithin as a surfactant. The purpose of our study wass to determine whether or not LM incorporation is receptor-mediated. U937 cells resuspended in a serum-free medium abundantly took up unmodulated LM. A binding study showed that U937 cells had a single binding site for LM (410 sites/cell at 24°C; 100 sites/cell at 4°C). Inhibition assays revealed that lecithin liposome, lysophosphatidylcholines, activated α2-macroglobulin, and HDL did not affect the binding of LM to U937 cells. VLDL strongly, and LDL and AcLDL moderately, inhibited the binding of LM to U937 cells. Ligand blotting analysis revealed that unmodulated LM in an apoprotein-free buffer directly bound to a 40 kDa protein in the cell membrane fraction. These results suggest that LM that is not modulated by any protein is incorporated by specific cells via receptor-mediated processes.Key words: lipid emulsion, drug delivery system, monocyte, free fatty acids.

Effects of lipo prostaglandin E1 on distribution of cis-diamminedichloroplatinum in lung metastasis derived from Dunn osteosarcoma cell-inoculated mouse foot-pad

This study was designed to determine the effect of lipid microspheres containing prostaglandin E1 (lipo PGE1) on cis-diamminedichloroplatinum (CDDP) accumulation in primary and lung metastatic lesions. Sixty mice were divided into four groups, depending on whether or not an intra-foot-pad injection of Dunn osteosarcoma cells had been administered and on whether or not an intraperitoneal injection of lipo PGE1 had been administered. CDDP was injected intraperitoneally into all the mice 6 weeks after the inoculation. Tumor colonies of spontaneous metastases in the left lung were found in 21 out of 30 tumor-inoculated mice at autopsy. Tissue platinum concentrations in the lungs with metastatic colonies and in the foot-pad tumors were significantly higher in the lipo PGE1-administered mice than in those without treatment. Terminal deoxytransferase-mediated dUTP nick end labeling (TUNEL) assay showed marked localization of dying cells in the lung metastatic lesions of the lipo PGE1-administered mice. The results of this study showed that pretreatment with lipo PGE1 may augment the antitumor effects of CDDP at the tumor site.

Liposteroid (dexamethasone palmitate) therapy for West syndrome: a comparative study with ACTH therapy

Dexamethasone palmitate (liposteroid) was used for the treatment of West syndrome and compared with adrenocorticotropic hormone (ACTH) therapy. A single intravenous injection of liposteroid (0.25 mg/kg) was administered seven times in 3 months (total dosage = 1.75 mg/kg) to five symptomatic patients with West syndrome, aged 4-11 months. ACTH (0.025 mg/kg/day) was administered intramuscularly for 6 weeks according to the conventional therapy in Japan (total dosage = 0.625 mg/kg) to five symptomatic patients with West syndrome, aged 6-10 months. Nodding spasm and hypsarrhythmia on EEG disappeared in all patients in the liposteroid therapy group within four doses; however, partial seizures and focal spikes on EEG reappeared in three patients 2 months after the end of liposteroid therapy. In the ACTH therapy group, nodding spasm and hypsarrhythmia on EEG similarly disappeared during treatment in all patients, but nodding spasm reappeared 2 months after therapy in two patients and partial seizures reappeared in one patient 3 months after therapy. No notable adverse reactions occurred in the liposteroid group, but transient dysfunction of the thyroid and anterior pituitary gland and increased levels of serum cortisol were experienced in the ACTH group. These results suggest that glucocorticoid incorporated in a lipid emulsion is useful for the treatment of West syndrome.

Effects of liposteroid on skin lesions in autoimmune MRLlpr/lpr mice

Dexamethasone palmitate (D-PAL) incorporated into lipid microspheres (D-PAL emulsion) is taken up by the reticuloendothelial system and by some inflammatory cells. Therefore, it has a stronger anti-inflammatory activity than free corticosteroids in vivo. To study the effect of D-PAL emulsion on systemic lupus erythematosus (SLE), we administered D-PAL emulsion to MRLlpr/lpr mice, an animal model for human SLE. The effect of D-PAL emulsion was compared with that of methylprednisolone (m-PSL), a water-soluble steroid. Percent survival was higher in the group treated with 0.25 mg of D-PAL emulsion intravenously once every 4 weeks than in those groups treated similarly with m-PSL or PBS control. Swelling of lymph nodes was frequent in the group treated with m-PSL or with PBS, while rarely observed in the group treated with D-PAL emulsion. Proteinuria was more frequent in the groups treated with m-PSL or PBS than in the group treated with D-PAL emulsion. Although the frequency of skin lesions was not different between these three groups, the control and m-PSL treated mice had severe skin lesions, such as hair loss of erythematous skin with scales and crusts at the nape, while D-PAL emulsion treated animals showed only facial alopecia without inflammatory skin changes. These data demonstrate that D-PAL emulsion was more effective than a corresponding dose of m-PSL on autoimmune prone mice. This suggests that intermittent administration of D-PAL emulsion may be effective in the treatment of human SLE.

Activity of liposomal nystatin against disseminated Aspergillus fumigatus infection in neutropenic mice

The purpose of this study was to examine the activity of liposomal nystatin against a disseminated Aspergillus fumigatus infection in neutropenic mice. Mice were made neutropenic with 5-fluorouracil and were administered the antifungal drug intravenously for 5 consecutive days beginning 24 h following infection. Liposomal nystatin, at doses as low as 2 mg/kg of body weight/day, protected neutropenic mice against Aspergillus-induced death in a statistically significant manner at the 50-day time point compared to either the no-treatment, the saline, or the empty-liposome group. This protection was approximately the same as that for free nystatin, a positive control. Histopathological results showed that liposomal nystatin cleared the lungs, spleen, pancreas, kidney, and liver of Aspergillus and that there was no organ damage at the day 5 time point, which was after only three doses of liposomal nystatin. Based on these results in mice, it is probable that liposomal nystatin will be effective against Aspergillus infection in humans.

Randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of AS-013, a prostaglandin E1 prodrug, in patients with intermittent claudication

BACKGROUND

Intermittent claudication due to peripheral arterial occlusive disease (PAOD) is a common cause of pain and disability in the middle-aged. Clinical trials of the potent vasodilator prostaglandin E1 have been disappointing. This is the first report of a controlled clinical trial of AS-0:3, a novel prodrug of prostaglandin E1 incorporated into lipid microspheres that has been developed to improve delivery of the active compound to blood vessel walls.

METHODS AND RESULTS

Eighty patients with stenosis or occlusion, symptoms of intermittent claudication, and maximum walking distance of > or = 30 and < or = 300 m on a standard treadmill test were randomized to placebo or one of three dosage regimens of AS-013. Drug was administered by intravenous injection 5 d/wk for 4 weeks. Treadmill tests and other assessments were completed at weeks 0, 4, and 8. A statistically significant increase in maximum walking distance was observed at 4 weeks (for placebo: median, 4.5 m; interquartile range [IQR], 20; for active treatment: median, 28.0 m; IQR, 81; P < .01, Mann-Whitney test). A similar response was seen at 8 weeks (for placebo; median, -11.2 m; IQR, 35; for active treatment: median, 35 m; IQR, 68; P < .01, Mann-Whitney test). Dose-related improvements in pain-free walking distance and quality of life were observed. No serious safety issues were noted.

CONCLUSIONS

These promising clinical data indicate that AS-013, a new prodrug of prostaglandin E1, could provide an effective and acceptable treatment for patients with intermittent claudication. Studies to investigate the optimal dosing regimen, duration of clinical benefit, and effects in more severe forms of peripheral arterial disease are warranted.

Activated CD4+ T cells preferentially take up lipid microspheres, but resting cells do not

Lipid microspheres (LM) used as drug carriers increase the effectiveness and reduce the toxicity of incorporated drugs. The present study is designed to determine whether or not activated T lymphocytes, which were the cells chosen first from the 'inflammatory cells', can take up LM in vitro. LM were labelled with a fluorescent probe, DiI (DiI-LM), to examine the kinetics. Flow cytometric analysis demonstrated that in freshly isolated peripheral blood mononuclear cells (PBMC), monocytes principally took up DiI-LM, while lymphocytes and granulocytes did not. When PBMC were stimulated with immobilized anti-CD3 MoAb and IL-2, cells expressing CD3, CD4, CD8 and CD16 incorporated DiI-LM. Purified CD4+ T cells, obtained by positive panning selection, were stimulated with this system. They were CD25, CD71, LFA-1-positive, and also showed an ability to take up DiI-LM, which resting cells did not. The findings were confirmed by flow cytometry and quantitative analysis of DiI. Confocal micrographs showed fluorescent granules from the probe in the cytoplasm of stimulated CD4+ T cells after incubation with DiI-LM. These results suggest that immunomodulatory agents incorporated into LM might selectively regulate the function of CD4+ or CD8+ T cells when these are activated.

Liposome-complement interactions in rat serum: implications for liposome survival studies

Serum complement opsonizes particles such as bacteria for clearance by the reticuloendothelial system. Complement has been reported to interact with liposomes and therefore may mediate the reticuloendothelial system clearance of liposomes. This study has used a rat serum model to define some of the characteristics of liposomes which modulate their ability to activate complement. Using functional hemolytic assays and C3/C3b crossed immunoelectrophoresis, we have demonstrated that liposomes activated rat complement in a dose-dependent manner with higher concentrations of liposomes activating higher levels of complement. The detection of complement activation required the inclusion of phospholipids bearing a net charge. Complement activation occurred via the classical pathway; no alternative pathway activation was detected. The presence of cholesterol contributed to complement activation in a dose-dependent manner. Phospholipid fatty acyl chain length did not influence complement activation while the introduction of unsaturated acyl chains markedly decreased levels of complement activation. Liposome size also influenced complement activation with 400 nm unilamellar vesicles more effectively activating complement than 50 nm vesicles for equivalent amounts of exposed lipid. These studies demonstrate that the composition of the liposome greatly affects the in vitro activation of rat serum complement and suggest that the biological half-life of liposomes in the circulation of rats may be altered by changing the liposome composition to reduce complement activation.

Fluorescent probe-labeled lipid microsphere uptake by human endothelial cells: a flow cytometric study

Lipid microspheres have been used as carriers of drugs such as prostaglandin E1 (lipo-PGE1) and corticosteroid (liposteroid). Lipo-PGE1 is used for the treatment of chronic arterial occlusive diseases because its activity is far greater than that of free PGE1 in vivo. To verify the fact that the drug carriers, lipid microspheres, are preferentially taken up by endothelial cells, we labeled lipid microspheres with a fluorescent probe, DiI (DiI-LM), and observed them in some in vitro models. Stoichiometric fluorescence was obtainable, and the fluorescence was stable between pH 3.3 and pH 8.9. Human umbilical vein endothelial cells and cells of a human endothelial cell line, ECV304, showed increased uptake of DiI-LM, 81% and 61%, respectively. In contrast, uptakes were less than 7% in human skin fibroblasts, 3T3 cells, and human neutrophils. Prominent perinuclear fluorescence was also observed in endothelial cells by fluorescence microscopy. DiI-LM and flow cytometric analysis will be useful for studies to elucidate the precise mechanism of the selective accumulation of lipid microspheres by cells in blood vessel walls.