Biodistribution of dual radiolabeled lipidic nanocapsules in the rat using scintigraphy and gamma counting

Elimination study of intact lipid nanocapsules after intravenous rat administration

Aim: The present study investigated renal elimination after intravenous administration of four different formulations of lipid nanocapsules (LNCs) containing dyes adapted to Förster resonance energy transfer (FRET-LNCs). Materials & methods: FRET-LNCs of 85 or 50 nm with or without a pegylated surface were injected and collected in the blood or urine of rats at different time points. Quantitative analysis was performed to measure intact FRET-LNCs. Results & conclusion: No intact LNCs were found in urine (0 particles/ml) for all formulations. The 50-nm pegylated LNCs were eliminated faster from the blood, whereas 85-nm pegylated LNCS were eliminated slower than nonpegylated LNCs. Elimination of FRET-LNCs was mainly due to liver tissue interaction and not renal elimination.

[99mTc]Technetium-Labeled Niosomes: Radiolabeling, Quality Control, and In Vitro Evaluation

The aim of this research was to develop technetium-99m ([^99mTc]Tc)-radiolabeled niosomes and evaluate the cancer cell incorporation capacity of radiolabeled niosomes. For this purpose, niosome formulations were developed by film hydration method, and prepared niosomes were characterized to particle size, polydispersity index (PdI), ζ-potential value, and image profile. Then, niosomes were radiolabeled with [^99mTc]Tc using stannous salts (chloride) as a reducing agent. The radiochemical purity (RP) and stability in different mediums of the niosomes were assessed by ascending radioactive thin-layer chromatography (RTLC) and radioactive ultrahigh-performance liquid chromatography (R-UPLC) methods. Also, the partition coefficient value of radiolabeled niosomes was determined. The cell incorporation of [^99mTc]Tc-labeled niosome formulations, as well as reduced/hydrolyzed (R/H)-[^99mTc]NaTcO₄ in the HT-29 (human colorectal adenocarcinoma) cells, was then assessed. According to the obtained results, the spherical niosomes had a particle size of 130.5 ± 1.364 nm, a PdI value of 0.250 ± 0.023, and a negative charge of -35.4 ± 1.06 mV. The niosome formulations were effectively radiolabeled with [^99mTc]Tc using 500 μg mL^-1 stannous chloride for 15 min, and RP was found to be over 95%. [^99mTc]Tc-niosomes showed good in vitro stability in every system for up to 6 h. The log P value of radiolabeled niosomes was found as -0.66 ± 0.02. Compared to R/H-[^99mTc]NaTcO₄ (34.18 ± 1.56%), the incorporation percentages of [^99mTc]Tc-niosomes (88.45 ± 2.54%) were shown to be higher in cancer cells. In conclusion, the newly developed [^99mTc]Tc-niosomes showed good prototype for potential use in nuclear medicine imaging in the near future. However, further investigations, such as drug encapsulation and biodistribution studies, should be performed, and our studies are continuing.

Improved Bioavailability of Poorly Soluble Drugs through Gastrointestinal Muco-Adhesion of Lipid Nanoparticles

Gastrointestinal absorption remains indispensable in the systemic delivery of most drugs, even though it presents several challenges that, paradoxically, may also provide opportunities that can be exploited to achieve maximal bioavailability. Drug delivery systems made from nanoparticle carriers and especially, lipid carriers, have the potential to traverse gastrointestinal barriers and deploy in the lymphatic pathway, which aptly, is free from first pass via the liver. Several poorly soluble drugs have presented improved systemic bioavailability when couriered in lipid nanoparticle carriers. In this review, we propose an additional frontier to enhancing the bioavailability of poorly soluble drugs when encapsulated in lipid nano-carriers by imparting muco-adhesion to the particles through application of appropriate polymeric coating to the lipid carrier. The combined effect of gastrointestinal muco-adhesion followed by lymphatic absorption is a promising approach to improving systemic bioavailability of poorly soluble drugs following oral administration. Evidence to the potential of this approach is backed-up by recent studies within the review.

Labeling of Hinokitiol with 90Y for Potential Radionuclide Therapy of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC), the most common form of primary liver tumors, is the fifth cancer in the world in terms of incidence, and third in terms of mortality. Despite significant advances in the treatment of HCC, its prognosis remains bleak. Transarterial radioembolization with radiolabeled microspheres and Lipiodol has demonstrated significant effectiveness. Here we present a new, simple radiolabeling of Lipiodol with Yttrium-90, for the potential treatment of HCC.

Lipid nanocapsules as in vivo oxygen sensors using magnetic resonance imaging

Hypoxia is common occurrence of the tumour microenvironment, wherein heterogeneous gradients of O₂ give rise to tumoural cells which are highly malignant, metastatic, and resistant to therapeutic efforts. Thus, the assessment and imaging of hypoxia is essential for tumour diagnosis and treatment. Magnetic resonance imaging and, more specifically, the quantitative assessment of longitudinal relaxation time enhancement, was shown to enable the mapping of oxygen in tumours with increased sensitivity for lipids as compared to water signal. Unfortunately, this can only be applied to tumours with high lipid content. To overcome this issue, we propose the use of lipid nanocapsules (LNCs). LNCs have been demonstrated as excellent core-shell nanocarriers, wherein the lipidic-core is used for lipophilic drug encapsulation, enabling treatment of highly malignant tumours. Herein, however, we exploited the lipidic-core of the LNCs to develop a simple but effective technique to increase the lipidic content within tissues to enable the assessment and mapping of pO₂. LNCs were prepared using the phase-inversion technique to produce 60 nm sized nanoparticles, and in vitro studies demonstrated the permeability and responsiveness of LNCs to O₂. To evaluate the ability of LNCs to respond to changes in pO₂in vivo, after a hyperoxic challenge, three animal models, namely a normal tissue model (gastrocnemius muscle tissue) and two tumour tissue models (subcutaneous fibrosarcoma and intracerebral glioblastoma) were explored. LNCs were found to be responsive to variation of O₂in vivo. Moreover, the use of MRI enabled the mapping of oxygen gradients and heterogeneity within tumours.

Influence of Nanotoxicity on Human Health and Environment: The Alternative Strategies

Currently, nanotechnology revolutionizing both scientific and industrial community due to their applications in the fields of medicine, environmental protection, energy, and space exploration. Despite of the evident benefits of nanoparticles, there are still open questions about the influence of these nanoparticles on human health and environment. This is one of the critical issues that have to be addressed in the near future, before massive production of nanomaterials. Manufactured nanoparticles, which are finding ever-increasing applications in industry and consumer products fall into the category of emerging contaminants with ecological and toxicological effects on populations, communities and ecosystems. The existing experimental knowledge gave evidence that inhaled nanoparticles are less efficiently separated than larger particles by the macrophage clearance mechanisms and these nanoparticles are known to translocate through the lymphatic, circulatory and nervous systems to many tissues and organs, including the brain. In this review we highlight adverse impacts of nanoparticles on human and the environment with special emphasis on green nanoscience as a sustainable alternative.

Conventional versus stealth lipid nanoparticles: formulation and in vivo fate prediction through FRET monitoring

The determination of the nanocarrier fate in preclinical models is required before any translation from laboratory to clinical trials. Modern fluorescent imaging techniques have gained considerable advances becoming a powerful technology for non-invasive visualization in living subjects. Among them, Forster (fluorescence) resonance energy transfer (FRET) is a particular fluorescence imaging which involves energy transfer between 2 fluorophores in a distance-dependent manner. Considering this feature, the encapsulation of an acceptor/donor pair in lipid nanoparticles (LNEs: lipid nanoemulsions, LNCs: lipid nanocapsules) allowed the carrier integrity to be tracked. Accordingly, we used this FRET technique to evaluate the behavior of LNEs, conventional LNCs and newly designed stealth LNCs. After the development through a one-step (OS) PEGylation process of these stealth LNCs (OS LNCs), in vitro guest exchange dynamics and release kinetics were evaluated for both LNC formulations. We thereafter assessed in vivo biodistribution of all types of lipid nanoparticles. Results showed enhanced stability of encapsulation in OS LNCs in comparison to conventional LNCs. Additionally, the presence of the long PEG chains on the lipid nanoparticle surface altered the biodistribution pattern. Despite different release kinetic profiles, OS LNCs and LNEs showed extended blood circulation time associated with a good structure stability over several hours after intravenous injection.

Gene therapy and DNA delivery systems

Gene therapy is a promising new technique for treating many serious incurable diseases, such as cancer and genetic disorders. The main problem limiting the application of this strategy in vivo is the difficulty of transporting large, fragile and negatively charged molecules like DNA into the nucleus of the cell without degradation. The key to success of gene therapy is to create safe and efficient gene delivery vehicles. Ideally, the vehicle must be able to remain in the bloodstream for a long time and avoid uptake by the mononuclear phagocyte system, in order to ensure its arrival at the desired targets. Moreover, this carrier must also be able to transport the DNA efficiently into the cell cytoplasm, avoiding lysosomal degradation. Viral vehicles are the most commonly used carriers for delivering DNA and have long been used for their high efficiency. However, these vehicles can trigger dangerous immunological responses. Scientists need to find safer and cheaper alternatives. Consequently, the non-viral carriers are being prepared and developed until techniques for encapsulating DNA can be found. This review highlights gene therapy as a new promising technique used to treat many incurable diseases and the different strategies used to transfer DNA, taking into account that introducing DNA into the cell nucleus without degradation is essential for the success of this therapeutic technique.

Emerging role of radiolabeled nanoparticles as an effective diagnostic technique

Nanomedicine is emerging as a promising approach for diagnostic applications. Nanoparticles are structures in the nanometer size range, which can present different shapes, compositions, charges, surface modifications, in vitro and in vivo stabilities, and in vivo performances. Nanoparticles can be made of materials of diverse chemical nature, the most common being metals, metal oxides, silicates, polymers, carbon, lipids, and biomolecules. Nanoparticles exist in various morphologies, such as spheres, cylinders, platelets, and tubes. Radiolabeled nanoparticles represent a new class of agent with great potential for clinical applications. This is partly due to their long blood circulation time and plasma stability. In addition, because of the high sensitivity of imaging with radiolabeled compounds, their use has promise of achieving accurate and early diagnosis. This review article focuses on the application of radiolabeled nanoparticles in detecting diseases such as cancer and cardiovascular diseases and also presents an overview about the formulation, stability, and biological properties of the nanoparticles used for diagnostic purposes.

ICP-MS analysis of lanthanide-doped nanoparticles as a non-radiative, multiplex approach to quantify biodistribution and blood clearance

Recent advances in material science and chemistry have led to the development of nanoparticles with diverse physicochemical properties, e.g. size, charge, shape, and surface chemistry. Evaluating which physicochemical properties are best for imaging and therapeutic studies is challenging not only because of the multitude of samples to evaluate, but also because of the large experimental variability associated with in vivo studies (e.g. differences in tumor size, injected dose, subject weight, etc.). To address this issue, we have developed a lanthanide-doped nanoparticle system and analytical method that allows for the quantitative comparison of multiple nanoparticle compositions simultaneously. Specifically, superparamagnetic iron oxide (SPIO) with a range of different sizes and charges were synthesized, each with a unique lanthanide dopant. Following the simultaneous injection of the various SPIO compositions into tumor-bearing mice, inductively coupled plasma mass spectroscopy (ICP-MS) was used to quantitatively and orthogonally assess the concentration of each SPIO composition in serial blood samples and the resected tumor and organs. The method proved generalizable to other nanoparticle platforms, including dendrimers, liposomes, and polymersomes. This approach provides a simple, cost-effective, and non-radiative method to quantitatively compare tumor localization, biodistribution, and blood clearance of more than 10 nanoparticle compositions simultaneously, removing subject-to-subject variability.

The encapsulation of DNA molecules within biomimetic lipid nanocapsules

Most of DNA synthetic complexes result from the self-assembly of DNA molecules with cationic lipids or polymers in an aqueous controlled medium. However, injection of such self-assembled complexes in medium like blood that differ from that of their formulation leads to strong instability. Therefore, DNA vectors that have physico-chemical properties and structural organisation that will not be sensitive to a completely different medium in terms of ionic and protein composition are actively sought. To this end, the goal here was to discover and optimize a nanostructured system where DNA molecules would be encapsulated in nanocapsules consisting in an oily core and a shell covered by PEG stretches obtained through a nanoemulsion process in the absence of organic solvent. This encapsulation form of DNA molecules would prevent interactions with external hostile biological fluid. The results show the entrapment of lipoplexes into lipid nanocapsules, leading to the formation of neutral 110 nm-DNA nanocapsules. They were weakly removed by the immune system, displaying an increased blood half-life, and improved carcinoma cell transfection, in comparison to the parent lipoplexes. Our results demonstrate that the fabrication of nanocapsules encapsulating hydrophilic DNA in an oily core that meet criteria for blood injection is possible.

Computer-aided applications of nanoscale smart materials for biomedical applications

Nanotechnology has the potential to impact the treatment of many diseases that currently plague society: cancer, AIDS, dementia of various kinds and so on. Nanoscale smart materials, such as carbon nanotubes, C60, dendrimers and cyclodextrins, hold great promise for use in the development of better diagnostics, drug delivery and the alteration of biological function. Although experimentation is being used to explore the potential offered by these materials, it is by its very nature expensive in terms of time, resources and expertise. Insight with respect to the behavior of these materials in the presence of biological entities can be obtained much more rapidly by molecular dynamics simulation. Furthermore, the results of simulation may be used to guide experimentation so that it is much more productive than it might be in the absence of such information. The interactions of several nanoscale structures with biological macromolecules can already be probed effectively using molecular dynamics simulation. The results obtained should form the basis for significant new developments in the treatment of disease.

In vivo evaluation of lipid nanocapsules as a promising colloidal carrier for paclitaxel

Paclitaxel-loaded lipid nanocapsules (PX-LNC) exhibit interesting in vitro characteristics with improved antitumoral activity compared with free PX formulation. Biodistribution studies were realized with the use of (14)C-trimyristin ((14)C-TM) or (14)C-phosphatidylcholine ((14)C-PC) whereas antitumoral activity of PX-LNC formulations was based on the animal survival in a chemically induced hepatocellular carcinoma (HCC) model in Wistar rats. Blood concentration-time profiles for both labeled (14)C-TM-LNC and (14)C-PC-LNC were similar; the t(1/2) and MRT values (over 2h and close to 3h, respectively, for both formulations) indicated the long circulating properties of the LNC carrier with a slow distribution and elimination phase. Survival curves of paclitaxel treated groups showed a statistical significant difference compared to the control survival curve (P=0.0036 and 0.0408). Animals treated with 4x 70 mg/m(2) of PX-LNC showed the most significant increase in mean survival times compared to the controls (IST(mean) 72%) and cases of long-term survivors were preferentially observed in the PX-LNC treated group (37.5%; 3/8). These results demonstrate the great interest to use LNC as drug delivery system for paclitaxel, permitting with an equivalent therapeutic efficiency to avoid the use of excipients such as polyoxyethylated castor oil for its formulation.

99mTc/188Re-labelled lipid nanocapsules as promising radiotracers for imaging and therapy: formulation and biodistribution

PURPOSE

This study focuses on a promising carrier system for imaging and therapeutic purposes using lipid nanocapsules. To assess their potential for clinical use, we labelled nanocapsules with (99m)Tc and (188)Re and analysed some kinetic biodistribution parameters after intravenous injection in rats.

METHODS

Lipophilic complexes [(99m)Tc/(188)Re(S(3)CPh)(2)(S(2)CPh)] ((99m)Tc/(188)Re-SSS) were encapsulated within the nanoparticles during their manufacture with quantitative yield and satisfactory radiochemical purity. Rats were injected intravenously with 3.7 MBq (99m)Tc/(188)Re-labelled nanocapsules and sacrificed at 5, 15 and 30 min and 1, 2, 4, 8, 12, 16, 20 and 24 h.

RESULTS

Dynamic scintigraphic acquisitions showed predominant hepatic uptake, and ex vivo counting indicated a long circulation time of labelled nanocapsules, with a half-life of 21+/-1 min for (99m)Tc and 22+/-2 min for (188)Re. Very weak urinary elimination was observed, indicating good stability of (99m)Tc and (188)Re labelling.

CONCLUSION

(99m)Tc/(188)Re-SSS nanocapsules can be obtained with high yield and satisfactory radiochemical purity. The biodistributions of (99m)Tc/(188)Re-labelled nanocapsules are close to those of classical PEG-coated particles and show good stability of (188)Re/(99m)Tc-SSS labelling.

Evaluation of pegylated lipid nanocapsules versus complement system activation and macrophage uptake

This work consisted in defining the in vitro behavior of pegylated lipid nanocapsules (LNC) toward the immune system. LNC were composed of an oily core surrounded by a shell of lecithin and polyethylene glycol (PEG) known to decrease the recognition of nanoparticles by the immune system. The "stealth" properties were evaluated by measuring complement activation (CH50 technique and crossed-immunoelectrophoresis (C3 cleavage)) and macrophage uptake. These experiments were performed on 20-, 50-, and 100-nm LNC before and after dialysis. A high density of PEG at the surface led to very low complement activation by LNC with a slight effect of size. This size effect, associated to a dialysis effect in macrophage uptake, was due to differences in density and flexibility of PEG chains related to LNC curvature radius. Thanks to a high density, 660-Da PEG provided LNC a steric stabilization and a protective effect versus complement protein opsonization, but this protection decreased with the increase of LNC size, especially versus macrophage uptake.

Tissue distribution of indinavir administered as solid lipid nanocapsule formulation in mdr1a (+/+) and mdr1a (-/-) CF-1 mice

PURPOSE

Due to protease inhibitor (PI) efflux transport by P-glycoprotein (P-gp), insufficient PI concentrations result in low ongoing HIV replication in the so-called virus sanctuaries (brain and testes). The aim of the present study was to evaluate indinavir-loaded nanocapsules (Ind-LNC) including Solutol HS15, an excipient reported to possess in vitro P-gp inhibiting properties, as a means to improve indinavir distribution into brain and testes of mice.

METHODS

Normal mdr1a (+/+) or P-gp-deficient mdr1a (-/-) CF-1 mice were dosed with Ind-LNC (10 mg indinavir/kg, i.v.). At 30 min post-administration, indinavir was determined in plasma, brain, testes, as well as in kidneys, liver, and heart by LC-MS/MS, and tissue/plasma concentration ratios were calculated. Results were compared with those of control groups that received an indinavir solution (Ind-Sol).

RESULTS

Using Ind-Sol, ratios were 21.3- and 3.3-fold higher in brains and testes of mdr1a (-/-) mice than of mdr1a (+/+) mice, respectively, whereas in the other organs ratios were not significantly different between the two substrains. When Ind-LNC was used, a similar [mdr1a(-/-) vs. mdr1a (+/+) mice] trend was observed. Moreover, ratios were found to be significantly increased (1.9-fold increase in average) in most organs (brain and testes in particular) with Ind-LNC compared to Ind-Sol, regardless of the substrain used.

CONCLUSIONS

In agreement with previous works, P-gp governs at least in part indinavir uptake into brain and testes. LNC formulation increased indinavir uptake in brain and testes by mechanisms other than, or additional to, P-gp inhibition.

Reorganization of lipid nanocapsules at air–water interface

The size, the electrical properties and the behaviour at air-water interface of lipid nanocapsules (LNC) with various compositions were investigated. Two populations of LNC are presented in the suspension after the preparation: with (LNC II) and without (LNC I) phospholipid molecules. After the spreading at air-water interface, a rapid disaggregation of LNC I, located in the vicinity of interface, occurs leading to formation of surface film. The phospholipid molecules stabilize the structure of nanocapsules and LNC II are more stable at the interface in comparison with LNC I. The formation of a surface film was followed after by measuring the evolution of the surface pressure, relative surface area change and surface potential. A kinetic approach describing the various processes during the surface film formation was proposed. The corresponding kinetic constants were estimated.

Reorganization of lipid nanocapsules at air–water interface

The state, electrical and dilatational rheological properties of surface films formed at air-water interface from lipid nanocapsules (LNC) with various compositions as well as model monolayers formed by the LNC constituents-Labrafac, Solutol and Lipoid are investigated. These nanocapsules constitute potential drug delivery systems where lypophilic drug will be loaded in their core. The study of the model Labrafac/Solutol (Lab/Sol) mixed monolayers shows behavior close to the ideal. Small negative deviations in the mean molecular areas a and dipole moments mu are observed. All studied monolayers have elastic behavior during the small continuous compressions. The comparison between the properties of surface films formed from LNC with those of the model monolayers confirms the idea developed in the kinetic study that the surface films formed after a rapid disaggregation of the unstable nanocapsule fraction (LNC I) contains mainly Labrafac and Solutol. The Labrafac molar part (xLab) in the formed Lab/Sol mixed layer is established.

Electrokinetic properties of noncharged lipid nanocapsules: Influence of the dipolar distribution at the interface

Lipid nanocapsules (LNCs) containing poly(ethylene glycol) (PEG) were developed according to a phase inversion process without organic solvent. The distribution of PEG chains at the surface was determined due to electrokinetic properties, in order to correlate it with protein adsorption potentiality. In this aim, electrophoretic mobilities were measured as a function of ionic strength and pH, for particles differing by their size, dialysis effects, and the presence or not of lecithin in their shell. The study allowed the determination of the isoelectric point (pI) as well as the charge density (ZN) in relation with the dipolar distribution in the polyelectrolyte accessible layer (depth = 1/lambda), by using soft-particle electrophoresis analysis. These parameters pointed out that the PEG surface organization was dependent on the particle size. Moreover, this organization could be modified by dialyzing particles and/or by formulating them with or without lecithin. Lecithin was found to be present in the inner part of the polyelectrolyte layer and to play a role in the outer part disorganization. Dialyzing LNCs formulated with lecithin allowed to obtain stable and well-structured nanocapsules, ready to an in vivo use as drug delivery system.

Lipid nanocarriers as drug delivery system for ibuprofen in pain treatment

Due to their small size, lipid nanocapsules (LNC) might be promising for an injectable as well as for an oral drug delivery system, providing both sufficient drug solubility avoiding vessel embolisation for the intravenous injection and a positive effect of drug absorption after oral administration. Biocompatible ibuprofen LNC were developed in a size range of around 50 nm with a new preparation method. Drug incorporation into LNC was successful to a high degree in all formulations tested (94-98%) and the in vitro drug release in phosphate buffer occurred within 24 h. Pharmacokinetic data were recorded in vivo from rats after intravenous or oral administration, while the antinociceptive efficiency of the LNC formulation was compared with ibuprofen solution by the tail flick test. The AUC and half-life of intravenously injected ibuprofen LNC were found to be 16 and 19%, respectively, higher than a simple drug solution, while the mean residence time was not changed. Oral administration of LNC showed an 18% increase of AUC and a 27% higher mean residence time. The antinociceptive effect was similar for oral administration, drug solution, and LNC at 30 min after administration, and was prolonged up to 4 h in the LNC group. The pain relief after intravenous administration was prolonged when administering LNC formulation for at least 2 h. A drug delivery system for intravenous administration of ibuprofen has been developed which exhibits sustained release properties by either oral or intravenous route and may be interesting in the treatment of postoperative pain.