Synthesis of a novel galactosylated lipid and its application to the hepatocyte-selective targeting of liposomal doxorubicin

Effect of hydrophile-lipophile balance of the linker in Gal/GalNAc ligands on high-affinity binding of galactosylated liposomes by the asialoglycoprotein receptor

In this study, we explored the effect of the hydrophile-lipophile balance (HLB) in the linker unit of Galactose (Gal)/N-acetylgalactosamine (GalNAc) ligands on their affinity toward asialoglycoprotein receptors (ASGPRs). Two Gal/GalNAc ligands with lipophilic linkers-{(5-cholesten-3b-ol)[(2-acetamido-2-deoxy-d-galactopyranose-6-o)sebacate]} (CHS-6-GalNAc) and {(5-cholesten-3b-ol)[(d-galactopyranose-6-o)sebacate]} (CHS-6-Gal)-and two with hydrophilic linkers-{(5-cholesten-yl)[(4-O-b-D-galactopyranosyl)-D-glucitol-6-yl]sebacate} (CHS-1-Gal) and {(5-cholesten-3a-ol)[(2-acetamido-2-deoxy-d-galactopyranose-6-o)3,6-dioxa-octanedioate]} (CHS-PEG₂-6-GalNAc)-were synthesized by enzymatic catalysis. Compared with unmodified liposomes, all Gal/GalNAc ligand-modified liposomes showed higher efficiency toward the hepatocyte target as evaluated by weighted-average overall drug-targeting efficiency (Te*) in vivo and HepG2 cell uptake efficiency in vitro. The ligands containing linkers with high HLB values (i.e., CHS-PEG₂-6-GalNAc and CHS-1-Gal) exhibited higher ASGPR affinity than those containing linkers with low HLB values (i.e., CHS-6-GalNAc and CHS-6-Gal). We used molecular-dynamics (MD) simulations to investigate the structure-activity relationship between the HLB value of the linker in a ligand and ASGPR affinity. MD simulation results indicated that a Gal/GalNAc ligand with a more hydrophilic linker (i.e., higher HLB value) unit tended to have a higher solvent-accessible surface area (SASA), leading to lower steric hindrance for effective ASGPR recognition. The results of this study will provide an improved design for Gal/GalNAc ligand-based surface-modified liposomes with high ASGPR affinity.

Polysaccharide conjugates surpass monosaccharide ligands in hepatospecific targeting - Synthesis and comparative in silico and in vitro assessment

Ligands with the polysaccharide headgroups have been recently reported by our group to possess enhanced interaction with asialoglycoprotein receptor (ASGPR) in silico as compared to ligands having galactose moieties. This enhanced interaction is a result of the polymer's backbone support in anchoring the ligand in a specific orientation within the bilayer. In this paper, we have attempted to provide an in vitro proof of concept by performing a comparative evaluation of polysaccharide and monosaccharide-based ligands. Docking was performed to understand interaction with ASGPR in silico. Agarose and galactose conjugates with behenic acid were synthesized, purified, and characterized to yield biocompatible hepatospecific ligands which were incorporated into nanoliposomes. Cellular internalization of these targeted liposomes was studied using confocal microscopy and flow cytometry. The toxicity potential was assessed in vivo. Results indicated that the polysaccharide-based ligand increased cellular uptake due to better interaction with the receptor as compared to ligand bearing a single galactose group. In addition to developing novel liver targeting ligands, the study also established proof of concept that has been suggested by earlier in silico investigations. The approach can be used to design targeting ligands and develop formulations with improved targeting efficacy.

Ligand Decorated Primaquine Loaded Nanocarriers for Liver Targeting for Triggered Anti-Malarial Activity

OBJECTIVE

The aim of the current research is to formulate a nano delivery system for effective delivery of primaquine for liver targeting to achieve the potential anti-malarial activity. Another objective of current development is to formulate a lactobionic acid conjugated polyphosphazene based nano delivery of primaquine for liver targeting to distinguish anti-malarial activity.

METHOD

The particle size, entrapment efficiency, in-vitro drug release pattern, hepatotoxicity, MTT assay, erythrocyte toxicity assay, histopathology study, HepG2 cell uptake study, anti-- malarial study, and organ-distribution was also carried out to estimate the activity and potential features of a nanoparticle system.

RESULTS

The results obtained from the above analysis justify the efficiency and effectiveness of the system. The NMR studies confirm the conjugation pattern and the TEM represents the spherical morphological features of nanoparticles. The controlled release pattern from the in-vitro release study was observed and found to be 73.25% of drug release in 20 hrs and in the nano-size range (61.6± 1.56 nm) by particle size analysis.SGOT level, SGPT, ALP, and Parasitemia level of optimized drug-loaded PEGylated lactobionic acid conjugated polyphosphazene derivatized nanoparticles (FF) was found to lie in the safe range, showing that the formulation is non-toxic to the liver. Primaquine drug-loaded PEGylated lactobionic acid conjugated polyphosphazene polymeric nanoparticles showed higher cell uptake on HepG2 cell lines as compared to the drug-loaded in PEGylated polyphosphazene polymeric nanoparticles and plain drug.Percentage cell viability of drugloaded PEGylated lactobionic acid conjugated polyphosphazene derivatized nanoparticles was decreased by enhancing the concentration of prepared nanoparticle system accessed by MTT assay.

CONCLUSION

From the studies, it can be concluded that the optimized formulation of drug-loaded PEGylated lactobionic acid conjugated polyphosphazene derivatized nanoparticles showed high liver targeting, least toxicity to the liver, controlled release of the drug, higher anti-malarial activity against hepatocytes at a low dose, more effectiveness, and can be treated as a potential candidate for anti-malarial therapy.

Inositol hexanicotinate self-micelle solid dispersion is an efficient drug delivery system in the mouse model of non-alcoholic fatty liver disease

Inositol hexanicotinate (IHN) self-micelle solid dispersion (SD) with glycyrrhizic acid (GA) and arabic gum (AG) was prepared by mechanical ball milling process to improve the solubility, stability of amorphous state, and bioavailability of IHN, which enhanced the treatment of IHN on hyperlipidemia and nonalcoholic fatty liver disease (NAFLD). The physicochemical properties of IHN/GA/AG SDs in solid state were characterized by differential scanning calorimetry, X-ray diffraction studies, and scanning electron microscopy. The characteristics of the sample solutions were analyzed by reverse-phase HPLC, particle characterization, critical micelle concentration, and transmission electron microscopy. Further pharmacokinetic study of this SD formulation in rats showed a significant 3.3-fold increase in bioavailability compared to pure IHN. Moreover, biomarkers in serum and liver of NAFLD mice were significantly ameliorated after oral administration of IHN/GA/AG SDs for 15 days. Altogether, these results establish the mechanochemically prepared IHN/GA/AG SDs as an efficacious formulation for the treatment of hyperlipidemia and NAFLD.

Lipoproteins-Nanocarriers as a Promising Approach for Targeting Liver Cancer: Present Status and Application Prospects

The prevalence of liver cancer is increasing over the years and it is the fifth leading cause of mortality worldwide. The intrusive features and burden of low survival rate make it a global health issue in both developing and developed countries. The recommended chemotherapy drugs for patients in the intermediate and advanced stages of various liver cancers yield a low response rate due to the nonspecific nature of drug delivery, thus warranting the search for new therapeutic strategies and potential drug delivery carriers. There are several new drug delivery methods available to ferry the targeted molecules to the specific biological environment. In recent years, the nano assembly of lipoprotein moieties (lipidic nanoparticles) has emerged as a promising and efficiently tailored drug delivery system in liver cancer treatment. This increased precision of nano lipoproteins conjugates in chemotherapeutic targeting offers new avenues for the treatment of liver cancer with high specificity and efficiency. This present review is focused on concisely outlining the knowledge of liver cancer diagnosis, existing treatment strategies, lipoproteins, their preparation, mechanism and their potential application in the treatment of liver cancer.

Effect of gal/GalNAc regioisomerism in galactosylated liposomes on asialoglycoprotein receptor-mediated hepatocyte-selective targeting in vivo

In this study, we describe a novel synthesis of galactosylated lipids by lipase catalysis. Lactitol (Lac), galactose (Gal), or N-acetyl galactosamine (GalNAc) was coupled with cholesterol (CHS) as target head groups by enzyme-catalyzed regioselective esterification to produce three kinds of lipids: CHS-1-Gal, CHS-6-Gal, or CHS-6-GalNAc¹. The biological effects of galactosylated lipids carrying different constitutional isomers of the pendent sugar species were investigated. LP-1-Gal (liposomes containing 5.0 molar% of CHS-1-Gal) showed strong binding to tetrameric lectins of Ricinus communis agglutinin (RCA120) in vitro, while LP-6-Gal (liposomes containing 5.0 molar% of CHS-6-Gal) and LP-6-GalNAc (liposomes containing 5.0 molar% of CHS-6-GalNAc) did not. After intravenous injection, LP-6-GalNAc, LP-1-Gal and LP-6-Gal rapidly disappeared from the blood and accumulated rapidly in liver (up to 74.88 ± 4.11%, 58.67 ± 5.75%, and 47.66 ± 4.56% of injected dose/g organ within 4 h, respectively). This is significantly higher than the uptake of unmodified liposomes (Unmod-LP) (18.67 ± 6.07%). Pre-injection of asialofetuin significantly inhibits liver uptake of Gal-liposomes (P < 0.01), with the degree of inhibition appearing in the following order: LP-6-GalNAc (73.29%) > LP-1-Gal (67.06%) > LP-6-Gal (53.61%). More importantly, LP-6-GalNAc was preferentially taken up by hepatocytes and the uptake ratio by parenchymal cells (PC) and nonparenchymal cells (NPC) (PC/NPC ratio) was 11.03 higher than LP-1-Gal (7.32), LP-6-Gal (5.83) and Unmod-LP (2.39). We suggest that liposomes containing the novel galactosylated lipid CHS-6-GalNAc have potential as drug delivery carriers for hepatocyte-selective targeting.

Modifying glycyrrhetinic acid liposomes with liver-targeting ligand of galactosylated derivative: preparation and evaluations

In this study, novel glycyrrhetinic acid (GA) liposomes modified with a liver-targeting galactosylated derivative ligand (Gal) were prepared using a film-dispersion method. To characterize the samples, particle size, zeta potential, drug loading, and encapsulation efficiency were performed. Moreover, plasma and tissues were pre-treated by liquid-liquid extraction and analyzed by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that the mean residence times (MRTs) and the area under the curve (AUC) of GA liposomes with Gal (Gal-GA-LP), and GA liposomes (GA-LP) were higher than the GA solution (GA-S) in plasma. The tissue (liver) distribution of Gal-GA-LP was significantly different in contrast to GA-LP. The relative intake rate (Re) of Gal-GA-LP and GA-LP in the liver was 4.752 and 2.196, respectively. The peak concentration ratio (Ce) of Gal-GA-LP and GA-LP in the liver was 2.796 and 1.083, respectively. The targeting efficiency (Te) of Gal-GA-LP and GA-LP in the liver was 48.193% and 34.718%, respectively. Taken together, the results indicate that Gal-GA-LP is an ideal complex for liver-targeting, and has great potential application in the clinical treatment of hepatic diseases. Drug loading and releasing experiments also indicated that most liposomes are spherical structures and have good dispersity under physiologic conditions, which could prolong GA release efficiency in vitro.

Design, characterization and antimalarial efficacy of PEGylated galactosylated nano lipid carriers of primaquine phosphate

This study was aimed to design and optimize primaquine phosphate (PQ) loaded nanostructured lipid carriers (NLCs) using response surface methodology. The optimized NLCs were evaluated for various physical and morphological characterizations. The in vitro studies for drug release showed that PQ loaded NLCs had a sustained release up to 72 h and the stability studies confirmed that the PQ-NLCs were stable for 90 d at 4 °C and 25 °C. In vitro erythrocyte toxicity revealed that PQ-NLCs were less toxic than the pure drug. In vitro parasite growth inhibition assay showed an IC₅₀ value of 71.11 ± 6.47 ng/ml for the 3D7 Plasmodium falciparum (CQ sensitive) strain and 263.86 ± 5.68 ng/ml for RKL9 P. falciparum (CQ resistant) strain for the PQ-NLCs. Enhanced parasitaemia suppression of 99.46% at 2 mg/kg/d, a better suppression of parasitaemia of about 28% more than pure drug and a higher survivality rate of 66.66% even after the 35th day was observed for the PQ loaded NLCs. Also from the comparative fluorescent imaging study, it was clearly observed that accumulation of PQ-NLCs in the liver was more that of the pure drug. These results clearly indicated that the limitations of antimalarial drug PQ can be overcomed by loading it into the NLCs.

Surface-Modified Liposomal Formulation of Amphotericin B: In vitro Evaluation of Potential Against Visceral Leishmaniasis

Surface modification of liposomes with targeting ligands is known to improve the efficacy with reduced untoward effects in treating infective diseases like visceral leishmaniasis (VL). In the present study, modified ligand (ML), designed by modifying polysaccharide with a long chain lipid was incorporated in liposomes with the objective to target amphotericin B (Amp B) to reticuloendothelial system and macrophages. Conventional liposomes (CL) and surface modified liposomes (SML) were characterized for size, shape, and entrapment efficiency (E.E.). Amp B SML with 3% w/w of ML retained the vesicular nature with particle size of ∼205 nm, E.E. of ∼95% and good stability. SML showed increased cellular uptake in RAW 264.7 cells which could be attributed to receptor-mediated endocytosis. Compared to Amp B solution, Amp B liposomes exhibited tenfold increased safety in vitro in RAW 264.7 and J774A.1 cell lines. Pharmacokinetics and biodistribution studies revealed high t _1/2, area under the curve (AUC)_0-24, reduced clearance and prolonged retention in liver and spleen with Amp B SML compared to other formulations. In promastigote and amastigote models, Amp B SML showed enhanced performance with low 50% inhibitory concentration (IC₅₀) compared to Amp B solution and Amp B CL. Thus, due to the targeting ability of ML, SML has the potential to achieve enhanced efficacy in treating VL.

Nanoparticle-liver interactions: Cellular uptake and hepatobiliary elimination

30-99% of administered nanoparticles will accumulate and sequester in the liver after administration into the body. This results in reduced delivery to the targeted diseased tissue and potentially leads to increased toxicity at the hepatic cellular level. This review article focuses on the inter- and intra-cellular interaction between nanoparticles and hepatic cells, the elimination mechanism of nanoparticles through the hepatobiliary system, and current strategies to manipulate liver sequestration. The ability to solve the "nanoparticle-liver" interaction is critical to the clinical translation of nanotechnology for diagnosing and treating cancer, diabetes, cardiovascular disorders, and other diseases.

Docetaxel (DTX)-loaded polydopamine-modified TPGS-PLA nanoparticles as a targeted drug delivery system for the treatment of liver cancer

Polydopamine-based surface modification is a simple way to functionalize polymeric nanoparticle (NP) surfaces with ligands and/or additional polymeric layers. In this work, we developed DTX-loaded formulations using polydopamine-modified NPs synthesized using D-α-tocopherol polyethylene glycol 1000 succinate-poly(lactide) (pD-TPGS-PLA/NPs). To target liver cancer cells, galactosamine was conjugated on the prepared NPs (Gal-pD-TPGS-PLA/NPs) to enhance the delivery of DTX via ligand-mediated endocytosis. The size and morphology of pD-TPGS-PLA/NPs and Gal-pD-TPGS-PLA/NPs changed obviously compared with TPGS-PLA/NPs. In vitro studies showed that TPGS-PLA/NPs, pD-TPGS-PLA/NPs and Gal-pD-TPGS-PLA/NPs had similar release profiles of DTX. Both confocal laser scanning microscopy and flow cytometric results showed that coumarin 6-loaded Gal-pD-TPGS-PLA/NPs had the highest cellular uptake efficiency in liver cancer cell line HepG2. Moreover, DTX-loaded Gal-pD-TPGS-PLA/NPs inhibited the growth of HepG2 cells more potently than TPGS-PLA/NPs, pD-TPGS-PLA/NPs, and a clinically available DTX formulation (Taxotere®). The in vivo biodistribution experiments show that the Gal-pD-TPGS-PLA/NPs are specifically targeted to the tumor. Furthermore, the in vivo anti-tumor effects study showed that injecting DTX-loaded Gal-pD-TPGS-PLA/NPs reduced the tumor size most significantly on hepatoma-bearing nude mice. These results suggest that Gal-pD-TPGS-PLA/NPs prepared in the study specifically interacted with the hepatocellular carcinoma cells through ligand-receptor recognition and they may be used as a potentially eligible drug delivery system targeting liver cancers.

STATEMENT OF SIGNIFICANCE

Polydopamine-based surface modification is a simple way to functionalize polymeric nanoparticle surfaces with ligands and/or additional polymeric layers. In this work, we developed docetaxel (DTX)-loaded formulations using polydopamine-modified NPs synthesized from D-α-tocopherol polyethylene glycol 1000 succinate-poly(lactide) (pD-TPGS-PLA/NPs). To target liver cancer cells, galactosamine was conjugated on the prepared NPs (Gal-pD-TPGS-PLA/NPs) to enhance the delivery of DTX via ligand-mediated endocytosis. Both confocal laser scanning microscopy and flow cytometric results showed that coumarin 6-loaded Gal-pD-TPGS-PLA/NPs had the highest cellular uptake efficiency for liver cancer cell line HepG2. The in vivo biodistribution experiments show that the Gal-pD-TPGS-PLA/NPs are specifically targeted to the tumor. Furthermore, the in vivo anti-tumor effects study showed that injecting DTX-loaded Gal-pD-TPGS-PLA/NPs reduced the tumor size most significantly on hepatoma-bearing nude mice. These results suggest that Gal-pD-TPGS-PLA/NPs prepared in the study specifically interacted with the hepatocellular carcinoma cells through ligand-receptor recognition and they could be used as a potentially eligible drug delivery system targeting liver cancers.

Gum arabic-curcumin conjugate micelles with enhanced loading for curcumin delivery to hepatocarcinoma cells

Curcumin is conjugated to gum arabic, a highly water soluble polysaccharide to enhance the solubility and stability of curcumin. Conjugation of curcumin to gum arabic is confirmed by (1)H NMR, fluorescence and UV spectroscopy studies. The conjugate self assembles to spherical nano-micelles (270 ± 5 nm) spontaneously, when dispersed in aqueous medium. Spherical morphology of the self assembled conjugate is evidenced by field emission scanning electron microscopy and transmission electron microscopy. The self assembly of the amphiphilic conjugate into micelle in aqueous medium significantly enhances the solubility (900 fold of that of free curcumin) and stability of curcumin in physiological pH. The anticancer activity of the conjugate micelles is found to be higher in human hepatocellular carcinoma (HepG2) cells than in human breast carcinoma (MCF-7) cells. The conjugate exhibits enhanced accumulation and toxicity in HepG2 cells due to the targeting efficiency of the galactose groups present in gum arabic.

Translational Nano-Medicines: Targeted Therapeutic Delivery for Cancer and Inflammatory Diseases

With the advent of novel and personalized therapeutic approaches for cancer and inflammatory diseases, there is a growing demand for designing delivery systems that circumvent some of the limitation with the current therapeutic strategies. Nanoparticle-based delivery of drugs has provided means of overcoming some of these limitations by ensuring the drug payload is directed to the disease site and insuring reduced off-target activity. This review highlights the challenges posed by the solid tumor microenvironment and the systemic limitations for effective chemotherapy. It then assesses the basis of nanoparticle-based targeting to the tumor tissues, which helps to overcome some of the microenvironmental and systemic limitations to therapy. We have extensively focused on some of the tumor multidrug resistance mechanisms (e.g., hypoxia and aerobic glycolysis) that contribute to the development of multidrug resistance and how targeted nano-approaches can be adopted to overcome drug resistance. Finally, we assess the combinatorial approach and how this platform has been used to develop multifunctional delivery systems for cancer therapy. The review article also focuses on inflammatory diseases, the biological therapies available for its treatment, and the concept of macrophage repolarization for the treatment of inflammatory diseases.

Diagnostic imaging and therapeutic application of nanoparticles targeting the liver

Liver diseases, particularly viral hepatitis, cirrhosis and hepatocellular carcinoma, are common in clinical practice with high morbidity and mortality worldwide. Many substances for diagnostic imaging and therapy of liver diseases may have either severe adverse effects or insufficient effectiveness in vivo because of their nonspecific uptake. Therefore, by targeting the delivery of drugs into the liver or specific liver cells, drug efficiency may be largely improved. This review summarizes the up-to-date research progress focusing on nanoparticles targeting the liver for both diagnostic and therapeutic purposes. Targeting strategies, mechanisms of enhanced effects, and clinical applications of nanoparticles are discussed specifically. We believe that new targeting nanotechnology such as nanoprobes for multi-modality imaging and multifunctional nanoparticles would facilitate significant advancements in this active research area in the near future.

Enzyme-responsive nanomaterials for controlled drug delivery

Enzymes underpin physiological function and exhibit dysregulation in many disease-associated microenvironments and aberrant cell processes. Exploiting altered enzyme activity and expression for diagnostics, drug targeting, and drug release is tremendously promising. When combined with booming research in nanobiotechnology, enzyme-responsive nanomaterials used for controlled drug release have achieved significant development and have been studied as an important class of drug delivery strategies in nanomedicine. In this review, we describe enzymes such as proteases, phospholipases and oxidoreductases that serve as delivery triggers. Subsequently, we explore recently developed enzyme-responsive nanomaterials with versatile applications for extracellular and intracellular drug delivery. We conclude by discussing future opportunities and challenges in this area.

Tamoxifen guided liposomes for targeting encapsulated anticancer agent to estrogen receptor positive breast cancer cells: in vitro and in vivo evaluation

Tamoxifen (TMX), an estrogen receptor (ER) antagonist, incorporated at surface of liposomes loaded with Doxorubicin (DOX), was hypothesized to serve as ligand for targeting overexpressed ERs on surface and cytosol of breast cancer cells, in addition to its synergism with DOX in killing MCF-7 cells. The TMX-DOX liposomes demonstrated mean size of 188.8±2.2nm and positive potential of+47mV, both suitable for better cellular interaction. TMX-DOX liposomes sustained DOX release in vitro (25.9%) in pH 7.4 at 48h, in comparison with 64.5% DOX release at pH 5.5. In vitro cell line studies demonstrated that TMX-DOX liposomes were more cytotoxic to ER+ve MCF-7 cells as compared to DOX liposomes, DOX solution and TMX-DOX solution (P<0.05). However, there was no statistical difference in cyto-toxicity of TMX-DOX liposomes and DOX liposomes towards ER-ve MDA-MB-231 cells. Flow cytometry and confocal studies in MCF-7 cells revealed greater cell and nuclear uptake of DOX, with TMX guided liposomes as compared to DOX liposomes and DOX solution. TMX-DOX liposomes demonstrated significantly increased inhibition of MCF-7 cell based tumor growth in nude mice (P<0.05) in comparison to DOX solution and DOX liposomes, indicative of target specificity and higher DOX accumulation at tumor site.

Efficient hepatic delivery of drugs: novel strategies and their significance

Liver is a vital organ responsible for plethora of functions including detoxification, protein synthesis, and the production of biochemicals necessary for the sustenance of life. Therefore, patients with chronic liver diseases such as viral hepatitis, liver cirrhosis, and hepatocellular carcinoma need immediate attention to sustain life and as a result are often exposed to the prolonged treatment with drugs/herbal medications. Lack of site-specific delivery of these medications to the hepatocytes/nonparenchymal cells and adverse effects associated with their off-target interactions limit their continuous use. This calls for the development and fabrication of targeted delivery systems which can deliver the drug payload at the desired site of action for defined period of time. The primary aim of drug targeting is to manipulate the whole body distribution of drugs, that is, to prevent distribution to non-target cells and concomitantly increase the drug concentration at the targeted site. Carrier molecules are designed for their selective cellular uptake, taking advantage of specific receptors or binding sites present on the surface membrane of the target cell. In this review, various aspects of liver targeting of drug molecules and herbal medications have been discussed which elucidate the importance of delivering the drugs/herbal medications at their desired site of action.

Local targeted therapy of liver metastasis from colon cancer by galactosylated liposome encapsulated with doxorubicin

Since regional drug administration enables to maintain a high drug concentration within tumors, we compared the plasma concentration and biodistribution of doxorubicin (Dox) from drug-loaded conventional liposomes by local or systemic administration. The results demonstrated that drug concentration was substantially improved in liver as well as a decrease in blood and other organs by spleen injection mimicking portal vein perfusion (regional administration). To further investigate the targeted therapeutic effect of galactosylated liposome encapsulated doxorubicin (Dox) by regional administration, liver targeting liposomes were prepared by incorporating galactosylated-DPPE to conventional liposomes. Liposome uptake and targeting were verified in vitro and in vivo by fluorescence microscopy and xenogen IVIS imaging system, respectively. The results showed that galactose targeted liposomes presented a stronger specific cell uptake by human hepatocellular carcinoma HepG2 cells compared to the non-targeted liposomes. In vivo fluorescence imaging showed that the intra-hepatic deposition of conventional and galactosylated liposomes via spleen injection was more than that via tail vein administration, and galactosylated liposomes had higher fluorescent intensity over conventional liposomes in the liver post spleen administration. The anti-tumor effect of various drug administration routes for both liposomal formulations was evaluated using a murine liver metastasis model of colon cancer. The results indicated that tumor progression in the liver and mesenteric lymph nodes was significantly suppressed by Dox-loaded galactosylated liposomes via spleen injection, while no significance was observed in non-targeted formulations. Our data indicated that local perfusion of galactosylated liposomal doxorubicin had a great promise for the treatment of liver metastasis from colon cancer.

Galactosylated chitosan-polycaprolactone nanoparticles for hepatocyte-targeted delivery of curcumin

Galactosylated chitosan-polycaprolactone (Gal-CH-PCL) copolymers with a galactosylation degree of around 10% and varied PCL percentages less than 40 wt% were synthesized and used to produce nanoparticles for delivering curcumin. Some nanoparticles with encapsulation efficiency of 70% or higher and sizes changing from 100 to 250 nm were able to deliver curcumin in a controlled manner. PCL content in Gal-CH-PCLs was found to be a key factor for governing the release behavior of nanoparticles. Hepatocyte-targeted characteristic of nanoparticles was confirmed using human hepatocellular carcinoma (HepG2) cells. In comparison to free curcumin, curcumin-loaded Gal-CH-PCL nanoparticles well retained its anticancer activity. At an equivalent curcumin-dose of around 20 μg/mL that was found to be relatively safe to human normal liver cells, the results obtained from flow-cytometry revealed that some optimized Gal-CH-PCL nanoparticles showed more than 6-fold increasing abilities to induce the apoptosis and necrosis of HepG2 cells during 72 h treatment compared to free curcumin.

Lactosylated liposomes for targeted delivery of doxorubicin to hepatocellular carcinoma

Background

N-lactosyl-dioleoylphosphatidylethanolamine (Lac-DOPE) was synthesized and evaluated as a liver-specific targeting ligand via asialoglycoprotein receptors for liposomal delivery of doxorubicin.

Methods

Lactosylated liposomes encapsulating calcein (Lac-L-calcein) or doxorubicin (Lac-L-DOX) composed of egg phosphatidylcholine, cholesterol, monomethoxy polyethylene glycol 2000-distearoyl phosphatidylethanolamine, and Lac-DOPE at 50:35:5:10 (mol/mol) were prepared by polycarbonate membrane extrusion and evaluated in human hepatocellular carcinoma HepG2 cells. Cellular uptake of Lac-L-calcein was monitored by confocal microscopy and by flow cytometry. The cytotoxicity of Lac-L-DOX was evaluated by MTT assay. The pharmacokinetic properties of Lac-L-DOX were studied in normal mice, and its biodistribution and antitumor activity were studied in nude mice with HepG2 xenografts.

Results

The size of Lac-L-DOX was less than 100 nm and the liposomes demonstrated excellent colloidal stability. In vitro uptake of Lac-L-calcein by HepG2 cells was four times greater than that of non-targeted L-calcein. In the presence of 20 mM lactose, the uptake of Lac-L-calcein was inhibited, suggesting that asialoglycoprotein receptors mediated the observed cellular uptake. Lac-L-DOX exhibited enhanced in vivo cytotoxicity compared with the nontargeted liposomal doxorubicin (L-DOX), and its pharmacokinetic parameters indicate that Lac-L-DOX has a long blood circulation time (t_1/2 8.73 hours). Tissue distribution and therapeutic efficacy studies in nude mice bearing HepG2 xenografts show that Lac-L-DOX had significantly stronger tumor inhibitory activity compared with L-DOX and free doxorubicin, along with a higher accumulation of drug within the tumor site and greater cellular uptake by tumor cells.

Conclusion

These data suggest that lactosylated liposomes are promising drug delivery vehicles for hepatocellular carcinoma.

Novel materials which possess the ability to target liver cells

INTRODUCTION

Hepatic-targeted drug delivery systems are designed to treat diseases of the liver. However, since there are several different types of liver diseases that are caused by different cells, it is important to select the proper materials to target these different cells.

AREAS COVERED

This review addresses novel materials that possess the ability to target liver cells via receptor-ligand processes and offers an insight into the aspects of formulation design. It also discusses several approaches used to enhance the targeting efficiency of drug delivery systems to receptors in the liver cells. In addition, the delivery efficiency and therapeutic efficacy of these materials in the treatment of acute or chronic liver diseases is highlighted.

EXPERT OPINION

Further research into the use of clinical materials and the design of smart materials for multi-drug delivery to different organelles is important for future studies on these new materials. It is hoped that these targeted therapeutics will benefit patients with liver disorders in the near future.

Galactosylated nanostructured lipid carriers for delivery of 5-FU to hepatocellular carcinoma

The aim of the present study was to design a targeted delivery system of 5-fluorouracil (5-FU) for hepatocellular carcinoma (HCC). Lactobionic acid (LB) was conjugated to stearyl amine (SA) by a chemical reaction. The nanostructured lipid carriers (NLCs), containing LB conjugate, lecithin, glyceryl monostearate, oil [oleic acid (OA) or Labrafac 5 or 10%], and 5-FU, were dissolved in alcohol/acetone, the oil phase was added to the aqueous phase containing Tween 80 or Solutol(®) HS15 (0.25 or 0.5%), and NLCs were prepared by an emulsification-solvent diffusion method. Physical properties and drug release were studied in NLCs. The thiazolyl blue tetrazolium bromide assay was used to study the cytotoxicity of NLCs on HepG(2) cells, and the cellular uptake of NLCs was determined by flow cytometry. Fourier transform infrared spectroscopy and (1)H-NMR spectra confirmed the successful conjugation of LB and SA. The optimized NLCs consisted of 0.5% Solutol HS15 and 10% OA oil. The particle size of these nanoparticles was 139.2 nm, with a zeta potential of -18 mV, loading efficiency of 34.2%, release efficiency after 2 hours of the release test was 72.6%, and crystallinity was 0.63%. The galactosylated NLCs of 5-FU were cytotoxic on the HepG(2) cell line in a half concentration of 5-FU and seems promising in reducing 5-FU dose in HCC.

Mannosylated liposomes for targeted gene delivery

Background

Liposomes can be modified with different ligands to control their biological properties, such as longevity, targeting ability, and intracellular penetration, in a desired fashion. The aim of this study was to modify liposomes with a novel mannosylated polyethylene glycol-phosphatidylethanolamine (M-PEG-PE) ligand to achieve active targeted gene delivery.

Methods

Rat Kupffer cells were isolated and used as model cells for in vitro evaluation of cytotoxicity and transfection efficiency. The modified liposomes were intravenously injected into the rats, and Kupffer cells were isolated and analyzed by flow cytometry for in vivo gene delivery and expression.

Results

The M-PEG-PE-modified liposome-enhanced green fluorescence protein plasmid (M-PEG-PE-Lipo-pEGFP) complexes had a particle size of 237 nm and a loading efficiency of 90%. The M-PEG-PE-Lipo-pEGFP complexes displayed remarkably higher transfection efficiency than unmodified Lipo-pEGFP, both in vitro (51%–30%) and in vivo (43%–27%).

Conclusion

M-PEG-PE could function as an excellent active targeting ligand, and M-PEG-PE-modified liposomes could be promising active targeted drug delivery vectors.

pH- and sugar-sensitive layer-by-layer films and microcapsules for drug delivery

The present review provides an overview on the recent progress in the development of pH- and sugar-sensitive layer-by-layer (LbL) thin films and microcapsules in relation to their potential applications in drug delivery. pH-sensitive LbL films and microcapsules have been studied for the development of peptide and protein drug delivery systems to the gastrointestinal tract, anti-cancer drugs to tumor cells, anti-inflammatory drugs to inflamed tissues, and the intracellular delivery of DNA, where pH is shifted from neutral to acidic. pH-induced decomposition or permeability changes of LbL films and microcapsules form the basis for the pH-sensitive release of drugs. Sugar-sensitive LbL films and microcapsules have been studied mainly for the development of an artificial pancreas that can release insulin in response to the presence of glucose. Therefore, glucose oxidase, lectin, and phenylboronic acid have been used for the construction of glucose-sensitive LbL films and microcapsules. LbL film-coated islet cells are also candidates for an artificial pancreas. An artificial pancreas would make a significant contribution to improving the quality of life of diabetic patients by replacing repeated subcutaneous insulin injections.

Sustained liver targeting and improved antiproliferative effect of doxorubicin liposomes modified with galactosylated lipid and PEG-lipid

In this study, a cleavable PEG-lipid (methoxypolyethyleneglycol 2000-cholesteryl hemisuccinate, PEG(2000)-CHEMS) linked via ester bond and galactosylated lipid ((5-cholesten-3beta-yl) 4-oxo-4-[2-(lactobionyl amido) ethylamido] butanoate, CHS-ED-LA) were used to modify doxorubicin (DOX) liposome. DOX was encapsulated into conventional liposomes (CL), galactosylated liposomes (modified with CHS-ED-LA, GalL), pegylated liposomes (modified with PEG(2000)-CHEMS, PEG-CL), and pegylated galactosylated liposomes (modified with CHS-ED-LA and PEG(2000)-CHEMS, PEG-GalL) using an ammonium sulfate gradient loading method and then intravenously injected to normal mice. Both PEG-GalL DOX and GalL DOX gave relatively high overall drug targeting efficiencies to liver ((T(e))(liver)) and were mainly taken up by hepatocyte. However, PEG-GalL DOX showed unique "sustained targeting" characterized by slowed transfer of DOX to liver and reduced peak concentrations in the liver. The biodistribution and antitumor efficacy of various DOX preparations were studied in hepatocarcinoma 22 (H22) tumor-bearing mice. The inhibitory rate of PEG-GalL DOX to H22 tumors was up to 94%, significantly higher than that of PEG-CL DOX, GalL DOX, CL DOX, and free DOX, although the tumor distribution of DOX revealed no difference between PEG-GalL DOX and PEG-CL DOX. Meanwhile, the gradual increase in the liver DOX concentration due to the sustained uptake of PEG-GalL DOX formulations resulted in lower damage to liver. In conclusion, the present investigation indicated that double modification of liposomes with PEG(2000)-CHEMS, and CHS-ED-LA represents a potentially advantageous strategy in the therapy of liver cancers or other liver diseases.

Sustained liver targeting and improved antiproliferative effect of doxorubicin liposomes modified with galactosylated lipid and PEG-lipid

In this study, a cleavable PEG-lipid (methoxypolyethyleneglycol 2000-cholesteryl hemisuccinate, PEG(2000)-CHEMS) linked via ester bond and galactosylated lipid ((5-cholesten-3beta-yl) 4-oxo-4-[2-(lactobionyl amido) ethylamido] butanoate, CHS-ED-LA) were used to modify doxorubicin (DOX) liposome. DOX was encapsulated into conventional liposomes (CL), galactosylated liposomes (modified with CHS-ED-LA, GalL), pegylated liposomes (modified with PEG(2000)-CHEMS, PEG-CL), and pegylated galactosylated liposomes (modified with CHS-ED-LA and PEG(2000)-CHEMS, PEG-GalL) using an ammonium sulfate gradient loading method and then intravenously injected to normal mice. Both PEG-GalL DOX and GalL DOX gave relatively high overall drug targeting efficiencies to liver ((T(e))(liver)) and were mainly taken up by hepatocyte. However, PEG-GalL DOX showed unique "sustained targeting" characterized by slowed transfer of DOX to liver and reduced peak concentrations in the liver. The biodistribution and antitumor efficacy of various DOX preparations were studied in hepatocarcinoma 22 (H22) tumor-bearing mice. The inhibitory rate of PEG-GalL DOX to H22 tumors was up to 94%, significantly higher than that of PEG-CL DOX, GalL DOX, CL DOX, and free DOX, although the tumor distribution of DOX revealed no difference between PEG-GalL DOX and PEG-CL DOX. Meanwhile, the gradual increase in the liver DOX concentration due to the sustained uptake of PEG-GalL DOX formulations resulted in lower damage to liver. In conclusion, the present investigation indicated that double modification of liposomes with PEG(2000)-CHEMS, and CHS-ED-LA represents a potentially advantageous strategy in the therapy of liver cancers or other liver diseases.

Glycyrrhetinic acid-modified chitosan/poly(ethylene glycol) nanoparticles for liver-targeted delivery

A liver-targeted drug delivery carrier, composed of chitosan/poly(ethylene glycol)-glycyrrhetinic acid (CTS/PEG-GA) nanoparticles, was prepared by an ionic gelation process, in which glycyrrhetinic acid (GA) acted as the targeting ligand. The formation and characterization of these nanoparticles were confirmed by FT-IR, dynamic light scattering (DLS) and zeta potential measurements. The biodistribution of the nanoparticles was assessed by single-photon emission computed tomography (SPECT), and the cellular uptake was evaluated using human hepatic carcinoma cells (QGY-7703 cells). The anti-neoplastic effect of the doxorubicin.HCl-loaded nanoparticles (DOX-loaded nanoparticles) was also investigated in vitro and in vivo. The results showed that the CTS/PEG-GA nanoparticles were remarkably targeted to the liver, and keep at a high level during the experiment. The accumulation in the liver was 51.3% at 3 h after injection; this was nearly 2.6 times that obtained with the CTS/PEG nanoparticles. The DOX-loaded nanoparticles were greatly cytotoxic to QGY-7703 cells, and the IC(50) (50% inhibitory concentration) for the free doxorubicin.HCl (DOX.HCl) and the DOX-loaded CTS/PEG-GA nanoparticles were 47 and 79 ng/mL, respectively. Moreover, the DOX-loaded CTS/PEG-GA nanoparticles could effectively inhibit tumor growth in H22 cell-bearing mice.

In vitro photothermal study of gold nanoshells functionalized with small targeting peptides to liver cancer cells

Gold nanoshells functionalized with a small peptide as a targeting agent were designed and synthesized for photothermal therapy of hepatocarcinoma. The nanoshells exhibited high absorption in the near-infrared (NIR) range, 800-1,100 nm, and were functionalized with 12-amino acid sequence peptides for targeting liver cancer cells. The nanoshells were characterized by Dynamic Light Scattering (DLS), Transmission Electron Microscope (TEM) and IR spectra. The functionalized gold nanoshells showed good targeting ability to liver cancer cells BEL-7404 and BEL-7402 while not to the normal healthy liver cell HL-7702, and also had a low cytotoxic activity. The fluorescence images showed that the gold nanoshells caused death to the liver cancer cells efficiently after being treated with a NIR light in vitro. These simple, stable, low cytotoxic, cancer-cell targeting gold nanoshells present a great promise as delivery agents for the selective photothermal treatment of liver cancer cells.

Design and synthesis of novel galactosylated polymers for liposomes as gene drug carriers targeting the hepatic asialoglycoprotein receptor

The 18-mer oligodeoxynucleotides (ODNs) that can inhibit survivin gene expression were selected as a model gene drug to study hepatic-targeting drug delivery system. Novel galactosylated polymers (cholesteryloxycarbonylamino) ethylamine-alpha,beta-polyasparthydrazied (CHE-PAHy-Lacs), which target asialoglycoprotein receptor on hepatic parenchymal cells (PC), were designed and synthesized as non-toxic, non-antigenic and non-teratogenic ligands for liposomes. The liposomes incorporating different CHE-PAHy-Lacs were prepared and characterized by zeta potential and particle size analyzer. The drug encapsulation efficiency was measured by gel filtration method. 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate was used as a marker for all the liposome preparations in the in vivo experiments. The CHE-PAHy-Lac liposomes produced a significant improvement in the encapsulation efficiency of ODNs (28.73-51.37%) compared with conventional liposomes (9.88%). The in vivo results showed that the liposomes incorporating CHE-PAHy-Lac, which contained about 30% (w/w) galactosyl residues, exhibited marked accumulation in the liver and hepatic PC. These results suggest that the novel galactosylated polymers used for liposomes have a great potential as a gene delivery system for hepatic targeting.