Polysorbate-stabilized solid lipid nanoparticles as colloidal carriers for intravenous targeting of drugs to the brain: comparison of plasma protein adsorption patterns

Plasma proteins enriched on the surface of drug-delivery-purpose nanoparticles are regarded as key factors for determination of in vivo organ distribution after intravenous injection. Polysorbate 80-coated polybutylcyanoacrylate (PBCA) nanoparticles, preferentially adsorbing apolipoprotein E (apoE) on their surface, have previously been considered to deliver various drugs to the brain. In the present study, in vivo well tolerable solid lipid nanoparticles (SLN) using different types of polysorbates as stabilizers were produced. The influence of the different surfactants on in vitro adsorption of human plasma proteins was investigated using two-dimensional polyacrylamide gel electrophoresis (2-DE). Possible correlations of different amounts of adsorbed apoE to the hydrophilic-lipophilic balance (HLB) of the polysorbates are shown and discussed. Apolipoprotein C-II, albumin and immunoglobulin G, which are also decisive plasma proteins with regard to site-specific drug delivery of intravenously injected carriers to the brain, are compared with regard to adsorption. Moreover, certain similarities to the plasma protein adsorption patterns of previously analysed brain-specific PBCA nanoparticles could be detected. Despite some differences in adsorption behavior of proteins on the surface of polysorbate-stabilized SLN and PBCA nanoparticles, we conclude that in both cases polysorbate 80 might have the highest potential to deliver drugs to the brain.     

Direct Evidence That Polysorbate-80-Coated Poly(Butylcyanoacrylate) Nanoparticles Deliver Drugs to the CNS via Specific Mechanisms Requiring Prior Binding of Drug to the Nanoparticles

Purpose. It has recently been suggested that the poly(butylcyanoacrylate) (PBCA) nanoparticle drug delivery system has a generalized toxic effect on the blood-brain barrier (BBB) (8) and that this effect forms the basis of an apparent enhanced drug delivery to the brain. The purpose of this study is to explore more fully the mechanism by which PBCA nanoparticles can deliver drugs to the brain. Methods. Both in vivo and in vitro methods have been applied to examine the possible toxic effects of PBCA nanoparticles and polysorbate-80 on cerebral endothelial cells. Human, bovine, and rat models have been used in this study. Results. In bovine primary cerebral endothelial cells, nontoxic levels of PBCA particles and polysorbate-80 did not increase paracellular transport of sucrose and inulin in the monolayers. Electron microscopic studies confirm cell viability. In vivo studies using the antinociceptive opioid peptide dalargin showed that both empty PBCA nanoparticles and polysorbate-80 did not allow dalargin to enter the brain in quantities sufficient to cause antinociception. Only dalargin preadsorbed to PBCA nanoparticles was able to induce an antinociceptive effect in the animals. Conclusion. At concentrations of PBCA nanoparticles and polysorbate-80 that achieve significant drug delivery to the brain, there is little in vivo or in vitro evidence to suggest that a generalized toxic effect on the BBB is the primary mechanism for drug delivery to the brain. The fact that dalargin has to be preadsorbed onto nanoparticles before it is effective in inducing antinociception suggests specific mechanisms of delivery to the CNS rather than a simple disruption of the BBB allowing a diffusional drug entry.     

Drug delivery to the brain with nanoparticles

Drugs can be delivered to brain with the aid of poly(butylcyanoacrylate) (PBCA) nanoparticles coated with polysorbate 80. These carriers can penetrate BBB and deliver drugs of various structures, including peptides, hydrophilic compounds, and lipophilic compounds eliminated from brain with P-glycoprotein. When a suspension of polysorbate-coated PBCA nanoparticles is introduced into blood, apolipoproteins of the blood plasma adsorb on the particle surface and then interact with receptors of low-density lipoproteins situated in endothelial cells of cerebral vessels, thus stimulating endocytosis.     

Protein adsorption patterns on poloxamer- and poloxamine-stabilized solid lipid nanoparticles (SLN)

Solid lipid nanoparticles (SLN) were produced using a full range of poloxamer polymers and poloxamine 908 for stabilization. The protein adsorption pattern acquired on the surface of these particles after intravenous injection is the key factor determining the organ distribution. Two-dimensional polyacrylamide gel electrophoresis (2-DE) was employed for determination of particle interactions with human plasma proteins. The objective of this study was to investigate changes in the plasma protein adsorption patterns in the course of variation of the polymers stabilizing the SLN. Considerable differences in the protein adsorption with regard to preferential adsorbed proteins were detected for the different stabilizers. Possible correlations between the polyethylene oxide (PEO) chain length and the adsorption of various proteins (first of all apolipoproteins) are shown and discussed. Besides the study of protein adsorption patterns, the total protein mass adsorbed to the SLN was also evaluated using the bicinchoninic acid (BCA)-protein assay. The knowledge concerning the interactions of proteins and nanoparticles can be used for a rational development of particulate drug carriers. Based on the findings presented in this paper, we anticipate that the in vivo well-tolerable SLN are a promising site-specific drug delivery system for intravenous injection.     

Lactoferrin bioconjugated solid lipid nanoparticles: a new drug delivery system for potential brain targeting

Background: Delivery of drugs to brain is a subtle task in the therapy of many severe neurological disorders. Solid lipid nanoparticles (SLN) easily diffuse the blood–brain barrier (BBB) due to their lipophilic nature. Furthermore, ligand conjugation on SLN surface enhances the targeting efficiency. Lactoferin (Lf) conjugated SLN system is first time attempted for effective brain targeting in this study.

Purpose: Preparation of Lf-modified docetaxel (DTX)-loaded SLN for proficient delivery of DTX to brain.

Methods: DTX-loaded SLN were prepared using emulsification and solvent evaporation method and conjugation of Lf on SLN surface (C-SLN) was attained through carbodiimide chemistry. These lipidic nanoparticles were evaluated by DLS, AFM, FTIR, XRD techniques and in vitro release studies. Colloidal stability study was performed in biologically simulated environment (normal saline and serum). These lipidic nanoparticles were further evaluated for its targeting mechanism for uptake in brain tumour cells and brain via receptor saturation studies and distribution studies in brain, respectively.

Results: Particle size of lipidic nanoparticles was found to be optimum. Surface morphology (zeta potential, AFM) and surface chemistry (FTIR) confirmed conjugation of Lf on SLN surface. Cytotoxicity studies revealed augmented apoptotic activity of C-SLN than SLN and DTX. Enhanced cytotoxicity was demonstrated by receptor saturation and uptake studies. Brain concentration of DTX was elevated significantly with C-SLN than marketed formulation.

Conclusions: It is evident from the cytotoxicity, uptake that SLN has potential to deliver drug to brain than marketed formulation but conjugating Lf on SLN surface (C-SLN) further increased the targeting potential for brain tumour. Moreover, brain distribution studies corroborated the use of C-SLN as a viable vehicle to target drug to brain. Hence, C-SLN was demonstrated to be a promising DTX delivery system to brain as it possessed remarkable biocompatibility, stability and efficacy than other reported delivery systems.     

Solid lipid nanoparticles as a drug delivery system for the treatment of neurodegenerative diseases

ABSTRACT

Introduction: The failure of many molecules as CNS bioactive compounds is due to many restrictions: poor water solubility, intestinal absorption, in vivo stability, bioavailability, therapeutic effectiveness, side effects, plasma fluctuations, and difficulty crossing physiological barriers, like the brain blood barrier (BBB), to deliver the drug directly to the site of action.

Area covered: Nanotechnology-based approaches with the employment of liposomes, micelles, dendrimers, and solid lipid nanoparticles (SLN) as drug delivery systems, are used to overcome the above reported limitations. Here, we focus on the delivery of drugs based on SLN formulation to treat neurodegenerative diseases. Notably, SLN have the ability to protect drugs from chemical and enzymatic degradation, direct the active compound towards the target site with a substantial reduction of toxicity for the adjacent tissues, and pass physiological barriers increasing bioavailability without resorting to high dosage forms.

Expert opinion: We believe that SLN could represent a suitable tool to pass the BBB and permit drugs to reach damaged areas of the CNS in patients affected by neurodegenerative pathologies, such as Alzheimer’s and Parkinson’s diseases.     

Plasma protein adsorption of Tween 80- and poloxamer 188-stabilized solid lipid nanoparticles

The plasma proteins adsorbing onto intravenously injected carriers are considered to be crucial factors determining the organ distribution. Plasma protein adsorption patterns were analyzed on solid lipid nanoparticles (SLN) stabilized with Tween 80 or stabilized with poloxamer 188. The binding patterns were determined by applying two different sample preparation methods, i.e. removal of the SLN from the plasma by (a) centrifugation and (b) gel filtration to assess, if the separation method has an effect on the patterns obtained. The Tween 80-modified SLN adsorbed the major plasma proteins known from particles with blood-brain barrier specificity. Poloxamer 188-surface modified SLN adsorbed the proteins known from model particles that exhibit prolonged circulation time in the blood. It is concluded that the biodegradable SLN stabilized with Tween 80 can potentially be used as drug carriers to the blood-brain barrier having a relatively long residence time in the blood stream. For the poloxamer 188-stabilized SLN a relatively long resistance time in the blood is predicted leading to potential accumulation in the bone marrow when looking at the distinct CII/CIII adsorption.     

Indirect Evidence that Drug Brain Targeting Using Polysorbate 80-Coated Polybutylcyanoacrylate Nanoparticles Is Related to Toxicity

Purpose. To investigate the mechanism underlying the entry of the analgesic peptide dalargin into brain using biodegradable polybutylcyanoacrylate (PBCA) nanoparticles (NP) overcoated with polysorbate 80. Methods. The investigations were carried out with PBCA NP and with non biodegradable polystyrene (PS) NP (200 nm diameter). Dalargin adsorption was assessed by HPLC. Its entry into the CNS in mice was evaluated using the tail-flick procedure. Locomotor activity measurements were performed to compare NP toxicities. BBB permeabilization by PBCA NP was studied in vitro using a coculture of bovine brain capillary endothelial cells and rat astrocytes. Results. Dalargin loading was 11.7 µg/mg on PBCA NP and 16.5µg/ mg on PS NP. Adding polysorbate 80 to NP led to a complete desorption. Nevertheless, dalargin associated with PBCA NP and polysorbate 80 induced a potent and prolonged analgesia, which could not be obtained using PS NP in place of PBCA NP. Locomotor activity dramatically decreased in mice dosed with PBCA NP, but not with PS NP. PBCA NP also caused occasional mortality. In vitro, PBCA NP (10 µg/ml) induced a permeabilization of the BBB model. Conclusions. A non specific permeabilization of the BBB, probably related to the toxicity of the carrier, may account for the CNS penetration of dalargin associated with PBCA NP and polysorbate 80.     

Nanoparticulate systems for brain delivery of drugs

The blood–brain barrier (BBB) represents an insurmountable obstacle for a large number of drugs, including antibiotics, antineoplastic agents, and a variety of central nervous system (CNS)-active drugs, especially neuropeptides. One of the possibilities to overcome this barrier is a drug delivery to the brain using nanoparticles. Drugs that have successfully been transported into the brain using this carrier include the hexapeptide dalargin, the dipeptide Kyotorphin, loperamide, tubocurarine, the NMDA receptor antagonist MRZ 2/576, and doxorubicin. The nanoparticles may be especially helpful for the treatment of the disseminated and very aggressive brain tumors. Intravenously injected doxorubicin-loaded polysorbate 80-coated nanoparticles were able to lead to a 40% cure in rats with intracranially transplanted glioblastomas 101/8. The mechanism of the nanoparticle-mediated transport of the drugs across the blood–brain barrier at present is not fully elucidated. The most likely mechanism is endocytosis by the endothelial cells lining the brain blood capillaries. Nanoparticle-mediated drug transport to the brain depends on the overcoating of the particles with polysorbates, especially polysorbate 80. Overcoating with these materials seems to lead to the adsorption of apolipoprotein E from blood plasma onto the nanoparticle surface. The particles then seem to mimic low density lipoprotein (LDL) particles and could interact with the LDL receptor leading to their uptake by the endothelial cells. After this the drug may be released in these cells and diffuse into the brain interior or the particles may be transcytosed. Other processes such as tight junction modulation or P-glycoprotein (Pgp) inhibition also may occur. Moreover, these mechanisms may run in parallel or may be cooperative thus enabling a drug delivery to the brain.     

Nanoparticulate systems for brain delivery of drugs

The blood--brain barrier (BBB) represents an insurmountable obstacle for a large number of drugs, including antibiotics, antineoplastic agents, and a variety of central nervous system (CNS)-active drugs, especially neuropeptides. One of the possibilities to overcome this barrier is a drug delivery to the brain using nanoparticles. Drugs that have successfully been transported into the brain using this carrier include the hexapeptide dalargin, the dipeptide kytorphin, loperamide, tubocurarine, the NMDA receptor antagonist MRZ 2/576, and doxorubicin. The nanoparticles may be especially helpful for the treatment of the disseminated and very aggressive brain tumors. Intravenously injected doxorubicin-loaded polysorbate 80-coated nanoparticles were able to lead to a 40% cure in rats with intracranially transplanted glioblastomas 101/8. The mechanism of the nanoparticle-mediated transport of the drugs across the blood-brain barrier at present is not fully elucidated. The most likely mechanism is endocytosis by the endothelial cells lining the brain blood capillaries. Nanoparticle-mediated drug transport to the brain depends on the overcoating of the particles with polysorbates, especially polysorbate 80. Overcoating with these materials seems to lead to the adsorption of apolipoprotein E from blood plasma onto the nanoparticle surface. The particles then seem to mimic low density lipoprotein (LDL) particles and could interact with the LDL receptor leading to their uptake by the endothelial cells. After this the drug may be released in these cells and diffuse into the brain interior or the particles may be transcytosed. Other processes such as tight junction modulation or P-glycoprotein (Pgp) inhibition also may occur. Moreover, these mechanisms may run in parallel or may be cooperative thus enabling a drug delivery to the brain.     

Adsorption kinetics of plasma proteins on solid lipid nanoparticles for drug targeting

The interactions of intravenously injected carriers with plasma proteins are the determining factor for the in vivo fate of the particles. In this study the adsorption kinetics on solid lipid nanoparticles (SLN) were investigated and compared to the adsorption kinetics on previously analyzed polymeric model particles and O/W-emulsions. The adsorbed proteins were determined using two-dimensional polyacrylamide gel electrophoresis (2-DE). Employing diluted human plasma, a transient adsorption of fibrinogen was observed on the surface of SLN stabilized with the surfactant Tego Care 450, which in plasma of higher concentrations was displaced by apolipoproteins. This was in agreement with the "Vroman-effect" previously determined on solid surfaces. It says that in the early stages of adsorption, more plentiful proteins with low affinity are displaced by less plentiful with higher affinity to the surface. Over a period of time (0.5 min to 4 h) more interesting for the organ distribution of long circulating carriers, no relevant changes in the composition of the adsorption patterns of SLN, surface-modified with poloxamine 908 and poloxamer 407, respectively, were detected. This is in contrast to the chemically similar surface-modified polymeric particles but well in agreement with the surface-modified O/W-emulsions. As there is no competitive displacement of apolipoproteins on these modified SLN, the stable adsorption patterns may be better exploited for drug targeting than particles with an adsorption pattern being very dependent on contact time with plasma.     

TAT-based drug delivery system – new directions in protein delivery for new hopes?

There has been great progress in the use of TAT-based drug delivery systems for the delivery of different macromolecules into cells in vitro and in vivo, thus circumventing the bioavailability barrier that is a problem for so many drugs. There are many advantages to using this system, such as the ability to deliver these cargoes into all types of cells in culture and into all organs in vivo. This system can even deliver cargoes into the brain across the blood–brain barrier. In addition, the ability to target specific intracellular sub-localizations such as the nuclei, the mitochondria and lysosomes further expands the possibilities of this drug delivery system to the development of sub-cellular organelle-targeted therapy. The therapeutic applications seem almost unlimited, and the use of the TAT-based delivery system has extended from proteins to a large variety of cargoes such as oligonucleotides, imaging agents, low molecular mass drugs, nanoparticles, micelles and liposomes. In this review the most recent advances in the use of the TAT-based drug delivery system will be described, mainly discussing TAT-mediated protein delivery and the use of the TAT system for enzyme replacement therapy.     

Major effects on blood-retina barrier passage by minor alterations in design of polybutylcyanoacrylate nanoparticles

Abstract

Because the blood-brain barrier (BBB) is an obstacle for drug-delivery, carrier systems such as polybutylcyanoacrylate (PBCA) nanoparticles (NPs) have been studied. Yet, little is known of how physiochemical features such as size, surfactants and surface charge influence BBB passage in vivo. We now used a rat model of in vivo imaging of the retina - which is brain tissue and can reflect the situation at the BBB - to study how size and surface charge determine NPs’ ability to cross the blood-retina barrier (BRB). Interestingly, for poloxamer 188-modified, DEAE-dextran-stabilised, fluorescent PBCA NPs, decreasing the average zeta-size from 272?nm to 172?nm by centrifugation reduced the BRB passage of the NPs substantially. Varying the zeta potential within the narrow range of 0–15?mV by adding different amounts of stabiliser revealed that 0?mV and 15?mV were less desirable than 5?mV which facilitated the BRB passage. Moreover, whether the fluorescent marker was adsorbed or incorporated also influenced the transport into the retina tissue. Thus, minor changes in design of nano-carriers can alter physicochemical parameters such as size or zeta potential, thus substantially influencing NPs’ biological distribution in vivo, possibly by interactions with blood constituents and peripheral organs.     

Delivery of Loperamide Across the Blood-Brain Barrier with Polysorbate 80-Coated Polybutylcyanoacrylate Nanoparticles

Purpose. The possibility of using polysorbate 80-coated nanoparticles for the delivery of the water insoluble opioid agonist loperamide across the blood-brain barrier was investigated. The analgesic effect after i.v. injection of the preparations was used to indicate drug transport through this barrier. Methods. Loperamide was incorporated into PBCA nanoparticles. Drug-containing nanoparticles were coated with polysorbate 80 and injected intravenously into mice. Analgesia was then measured by the tail-flick test. Results. Intravenous injection of the particulate formulation resulted in a long and significant analgesic effect. A polysorbate 80 loperamide solution induced a much less pronounced and very short analgesia. Uncoated nanoparticles loaded with loperamide were unable to produce analgesia. Conclusions. Polysorbate 80-coated PBCA nanoparticles loaded with loperamide enabled the transport of loperamide to the brain.     

The role of plasma proteins in brain targeting: species dependent protein adsorption patterns on brain-specific lipid drug conjugate (LDC) nanoparticles

The in vivo organ distribution of particulate drug carriers is decisively influenced by the interaction with plasma proteins after i.v. administration. Serum protein adsorption on lipid drug conjugate nanoparticles, a new carrier system for i.v. application, was investigated by 2-dimensional electrophoresis (2-DE). The particles were surface-modified to target them to the brain. To assess the protein adsorption pattern after i.v. injection in mice prior to in vivo studies, the particles were incubated in mouse serum. Incubation in human serum was carried out in parallel to investigate similarities or differences in the protein patterns obtained from men and mice. Distinct differences were found. Particles incubated in human serum showed preferential adsorption of apolipoproteins A-I, A-IV and E. Previously, preferential adsorption of ApoE was reported as one important factor for targeting of Tween(R)80 modified polybutylcyanoacrylate nanoparticles to the brain. Preferential adsorption of ApoA-I and A-IV took place after incubation in mouse serum, adsorption of ApoE could not be clearly confirmed. In vivo localization of the LDC nanoparticles at the blood-brain barrier and diffusion of the marker Nile Red into the brain could be shown by confocal laser-scanning microscopy. Differences of the obtained adsorption patterns are discussed with regard to their relevance for correlations of in vitro and in vivo data obtained from different species.     

In situ apolipoprotein E-enriched corona guides dihydroartemisinin-decorating nanoparticles towards LDLr-mediated tumor-homing chemotherapy

The therapeutic efficiency of active targeting nanoparticulate drug delivery systems (nano-DDS) is highly compromised by the plasma proteins adsorption on nanoparticles (NPs) surface, which significantly hinders cell membrane receptors to recognize the designed ligands, and provokes the off-target toxicity and rapid clearance of NPs in vivo. Herein, we report a novel dihydroartemisinin (DHA)-decorating nano-DDS that in situ specifically recruits endogenous apolipoprotein E (apoE) on the NPs surface. The apoE-anchored corona is able to prolong PLGA-PEG2000-DHA (PPD) NPs circulation capability in blood, facilitate NPs accumulating in tumor cells by the passive enhanced permeability and retention (EPR) effect and low-density lipoprotein receptor (LDLr)-mediated target transport, and ultimately improve the in vivo antitumor activity. Our findings demonstrate that the strategy of in situ regulated apoE-enriched corona ensures NPs an efficient LDLr-mediated tumor-homing chemotherapy.     

Body distribution of polysorbate‐80 and doxorubicin-loaded [14C]poly(butyl cyanoacrylate) nanoparticles after i.v. administration in rats

Previously it was shown that poly(butyl cyanoacrylate) (PBCA) nanoparticles coated with polysorbate 80 are able to cross the blood-brain barrier (BBB) after i.v. administration. The objective of the present study was to investigate the influence of polysorbate 80 and doxorubicin-loading on the body distribution in rats. The biodistribution profile and brain concentration of ¹⁴C-radiolabeled PBCA nanoparticles, polysorbate 80 coated ¹⁴C-PBCA nanoparticles, and doxorubicin-loaded ¹⁴C-PBCA nanoparticles were determined by radioactivity counting after i.v. administration in rats. The ¹⁴C-PBCA nanoparticles showed a significant accumulation in the organs of the reticuloendothelial system (RES). Polysorbate 80 coating of the ¹⁴C-PBCA nanoparticles decreased this accumulation to about 40% after 1 h post injection. The brain concentration was increased about 2-fold after polysorbate 80-coating at this time point. The presence of doxorubicin in this preparation, however, decreased the brain concentration to levels similar to uncoated particles, probably caused by the positive charge of this compound. After longer time periods after injection the differences between the three preparations decreased.     

Body distribution of polysorbate-80 and doxorubicin-loaded [14C]poly(butyl cyanoacrylate) nanoparticles after i.v. administration in rats

Previously it was shown that poly(butyl cyanoacrylate) (PBCA) nanoparticles coated with polysorbate 80 are able to cross the blood-brain barrier (BBB) after i.v. administration. The objective of the present study was to investigate the influence of polysorbate 80 and doxorubicin-loading on the body distribution in rats. The biodistribution profile and brain concentration of (14)C-radiolabeled PBCA nanoparticles, polysorbate 80 coated (14)C-PBCA nanoparticles, and doxorubicin-loaded (14)C-PBCA nanoparticles were determined by radioactivity counting after i.v. administration in rats. The (14)C-PBCA nanoparticles showed a significant accumulation in the organs of the reticuloendothelial system (RES). Polysorbate 80 coating of the (14)C-PBCA nanoparticles decreased this accumulation to about 40% after 1 h post injection. The brain concentration was increased about 2-fold after polysorbate 80-coating at this time point. The presence of doxorubicin in this preparation, however, decreased the brain concentration to levels similar to uncoated particles, probably caused by the positive charge of this compound. After longer time periods after injection the differences between the three preparations decreased.     

A Comparative Study of Orally Delivered PBCA and ApoE Coupled BSA Nanoparticles for Brain Targeting of Sumatriptan Succinate in Therapeutic Management of Migraine

Purpose

The present investigation aimed at brain targeting of sumatriptan succinate (SS) for its optimal therapeutic effect in migraine through nanoparticulate drug delivery system using poly (butyl cyanoacrylate) (PBCA) and bovine serum albumin linked with apolipoprotein E3 (BSA-ApoE).

Method

The study involved formulation optimization of PBCA nanoparticles (NPs) using central composite design for achieving minimum particle size, maximum entrapment efficiency along with sustained drug release. SS incorporated in BSA-ApoE NPs (S-AA-NP) were prepared by desolvation technique and compared with SS loaded polysorbate 80 coated optimized PBCA NPs (FP_opt) in terms of their brain uptake potential, upon oral administration in male Wistar rats. The NPs were characterized by FTIR, thermal, powder XRD and TEM analysis.

Results

The in vivo studies of FP_opt and S-AA-NP on male Wistar rats demonstrated a fairly high brain/plasma drug ratio of 9.45 and 12.67 respectively 2 h post oral drug administration. The behavioural studies on male Swiss albino mice affirmed the enhanced anti-migraine potential of S-AA-NP than FP_opt (P?<?0.001).

Conclusion

The results of this work, therefore, indicate that BSA-ApoE NPs are significantly better than polysorbate 80 coated PBCA NPs for brain targeting of SS (P?<?0.05) and also offer an improved therapeutic strategy for migraine management.

     

Tamoxifen Citrate Loaded Solid Lipid Nanoparticles (SLN™): Preparation,Characterization, In Vitro Drug Release,and Pharmacokinetic Evaluation

Solid lipid nanoparticles (SLN) were prepared by emulsification and high pressure homogenization technique and characterized by size analysis and differential scanning calorimetry. The influence of experimental factors such as homogenization pressure, time, and surfactant concentration on the nanoparticle size and distribution were investigated to optimize the formulation. Homogenization at 15,000 psi for 3 cycles was found to be optimum and resulted in smaller sized nanoparticles. In case of tristearin SLN (TSSLN), tripalmitin SLN (TPSLN), and glycerol behenate SLN (GBSLN), the relatively smaller sized nanoparticles were obtained with 3% sodium tauroglycocholate. The SLN were loaded with an anticancer agent, tamoxifen citrate (TC). The TC-loaded TSSLN shown lower entrapment efficiency (78.78%) compared to the TPSLN (86.75%) and GBSLN (98.64%). Short term stability studies indicated a significant increase in size of nanoparticles when stored at 50°C, compared to those stored at 30°C and 4°C. The particle destabilization upon storage in case of all the types of nanoparticles studied was in the order of day light > artificial light > dark. An ultraviolet (UV) spectrophotometric method of estimation of tamoxifen in rat plasma was developed and validated. The TC‐loaded TSSLN was administered to the rats intravenously and the pharmacokinetic parameters in the plasma were determined. The t_1/2 and mean residence time of TC-loaded TSSLN in plasma was about 3.5-fold (p < 0.001) and 3-fold (p < 0.001) higher, respectively, than the free tamoxifen, indicating the potential of TC-loaded TSSLN as a long circulating system in blood. Thus the above mentioned solid lipid nanoparticles can be a beneficial system to deliver tamoxifen to cancer tissues through enhanced permeability and retention (EPR) effect.