Lipid nanocarrier targeting activated macrophages for antiretroviral therapy of HIV reservoir.

Aim: To develop lipid nano-antiretrovirals (LNAs) for the treatment of HIV-infected macrophages. Materials & methods: LNAs were prepared with docosahexaenoic acid to facilitate brain penetration and surface-decorated with folate considering that infected macrophages often overexpress folate receptors. Results: Folate-decorated LNAs loading rilpivirine (RPV) were efficiently taken up by folate receptor-expressing cell types including activated macrophages. The intracellular Cmax of the RPV-LNAs in activated macrophages was 2.54-fold and the area under the curve was 3.4-fold versus free RPV, translating to comparable or higher (p < 0.01; RPV ≤6.5 ng/ml) activities against HIV infectivity and superior protection (p < 0.05) against HIV cytotoxicity. LNAs were also effective in monocyte-derived macrophages. Conclusion: These findings demonstrate the potential of LNAs for the treatment of infected macrophages, which are key players in HIV reservoirs.

HIV can infect and hide inside certain types of white blood cells that make up the immune system and help defend our body, such as macrophages. Because these infected cells tend to carry the virus to certain organs where antiviral drugs have a hard time reaching, the virus is able to avoid treatment from the drug. In this study, the authors developed very small devices known as nanocarriers to carry antiviral drugs. These nanocarriers were designed to seek out infected macrophages. The nanocarriers were successfully built with oils and lipids that are safe for patients and could easily deliver antiviral drugs to macrophages infected by HIV. Excellent anti-HIV effects were observed using these nanocarriers. In summary, the authors developed a promising device with the potential to fight HIV in a smart and safe manner.

Development of local injectable, bone-targeting nanocarriers of triptolide for treatment of bone-only metastasis.

Triptolide (TP) is known for its diverse pharmacological activities but also its delivery and toxicity issues. This study aimed at exploiting TP's anticancer effects at lower risk of systemic toxicity by developing local-injectable "bone-targeting TP nanoparticle" (TPN) for bone-only metastasis treatment. The lipid/oil-based TPNs decorated with alendronate (ALE) achieved size of 70.4-111.2 nm with good dispersion stability. The drug encapsulation efficiency reached 97 % and drug release profiles were in biphasic, controlled manner lasting for 5 days in medium with serum proteins and calcium. TPNs were more cytotoxic than free TP against MDA-MB-231 breast cancer cells (IC50: 16.40 ± 0.80 nM vs 25.45 ± 1.83 nM, P < 0.05) but less cytotoxic against MC3T3-E1 osteoblasts (P < 0.05). When combined with paclitaxel or docetaxel, low dose TPN (containing 10 nM) significantly increased the effectiveness of the two chemotherapy drugs against MDA-MB-231 (IC50 values decreased from 7.3 nM to 2.5 nM for docetaxel; from 4.6 nM to 1.1 nM), indicating potent chemosensitization effects. Retardation of in vitro cancer cell migration by TPN was also observed in the standard scratch assay. ALE decoration significantly enhanced the TPN affinity for both calcium hydroxyapatite and porcine bone chip models, which led to enhancement in TP retention in the bones up to 8.1-fold versus free drug. Overall, TPN demonstrated good potential as a local-injectable, bone-targeted nanotherapy tailored for eradication of bone-only metastasis at reduced risk of systemic toxicity.

Development of a high payload, cancer-targeting liposomes of methyl aminolevulinate for intraoperative photodynamic diagnosis/therapy of peritoneal carcinomatosis.

Methyl aminolevulinate (MAL) is a photosensitizer topically used for photodynamic diagnosis (PDD) and photodynamic therapy (PDT) of skin pre-cancers and cancers. In this study, our goal is to expand the application of MAL to dual intraoperative PDD and PDT of peritoneal carcinomatosis. A new liposomal MAL formulation (lipMAL) designed for systemic or intraperitoneal administration was developed. LipMALs prepared by ammonium sulfate gradient technique achieved MAL payload up to 18% (w/w) with drug encapsulation efficiency in the range of 15.1-31.5%. All lipMALs demonstrated controlled MAL release behavior, and achieved strong fluorescence in cancer cells (SKOV3) but minimal fluorescence in non-cancer peritoneal cells (B14FAF28-G3). LipMALs led to significantly higher fluorescence levels than free MAL groups (P < 0.05), up to 6.8-fold of the free MAL fluorescence levels in SKOV3 cells. The PDD performance of lipMALs was also compared with free MAL in SKOV3/ B14FAF28-G3 co-cultures simulating ovarian cancer micrometastases on peritoneal surface. The lipMAL-treated cancer colonies glew more brightly than the free MAL treated colonies and were clearly distinguishable from the dim peritoneum background with unaided eyes. LipMAL also achieved significantly stronger anticancer PDT effects than free MAL both in terms of cell viability and colony-formation (P < 0.05) while demonstrating minimal dark toxicity. To conclude, a new promising aid for the surgeons to achieve more complete resection of tumors and PC micrometastases and clean up any residual cancer cells undetected was developed.

Incorporation of docosahexaenoic acid (DHA) enhances nanodelivery of antiretroviral across the blood-brain barrier for treatment of HIV reservoir in brain.

Although the newer antiretroviral (ARV) drugs are highly active against the human immunodeficiency virus (HIV) in the body compartment, they often fail to effectively tackle the HIV reservoir in the brain because of inefficient penetration to the blood-brain barrier (BBB). In this study, we investigated the potential benefits of incorporating docosahexaenoic acid (DHA), an omega-3 fatty acid essential for brain development, in lipid nanocarriers for facilitating the BBB passage of an ARV darunavir. The resulting nanocarriers (nanoARVs) containing 5-15% DHA were 90-140 nm in size, had high darunavir payload (~11-13% w/w), good stability and minimal cellular toxicity, and could be further decorated with transferrin (Tf) for Tf-receptor targeting. In BBB models of hCMEC/d3 cells, nanoARVs with higher DHA content achieved increased nanocarrier uptake and up to 8.99-fold higher darunavir permeation than free darunavir. In animals, nanoARVs were able to achieve 3.38-5.93-fold increase in brain darunavir level over free darunavir. Tf-conjugated nanoARVs also achieved significantly higher anti-HIV activity than free darunavir (viral titer 2 to 2.6-fold higher in latter group). Comparison of DHA incorporation and Tf-receptor targeting showed that while both strategies could enhance the cellular uptake and brain accumulation of the nanocarriers, DHA was more effective (P < 0.05) for improving BBB permeation and brain accumulation of the darunavir payload. Substituting DHA with another oil noticeably reduced the cellular uptake of nanoARVs. Overall, this proof-of-concept study has supported the development of DHA-based nanoARVs as an effective, safe yet technically simple strategy to enhance brain delivery of darunavir and potentially other lipophilic ARVs for treatment of HIV reservoir.

Enhanced eradication of intracellular and biofilm-residing methicillin-resistant Staphylococcus aureus (MRSA) reservoirs with hybrid nanoparticles delivering rifampicin.

Osteomyelitis carries a high risk of recurrence even after extended, aggressive antibiotic therapy. One of the key challenges is to eradicate the reservoirs of methicillin-resistant Staphylococcus aureus (MRSA) inside the host bone cells and their biofilms. Our goal is to develop rifampicin loaded lipid-polymer hybrid nanocarriers (Rf-LPN) and evaluate if they can achieve enhanced rifampicin delivery to eradicate these intracellular and biofilm-residing MRSA. After optimization of the composition, Rf-LPN demonstrated size around 110 nm in diameter that remained stable in serum-supplemented medium, drug payload up to 11.7% and sustained rifampicin release for 2 weeks. When comparing Rf-LPN with free rifampicin, moderate but significant (p < 0.05) improvement of the activities against three osteomyelitis-causing bacteria (USA300-0114, CDC-587, RP-62A) in planktonic form were observed. In comparison, the enhancements in the activities against the biofilms and intracellular MRSA by Rf-LPN were even more substantial. The MBEC50 values against USA300-0114, CDC-587, and RP-62A were 42 vs 155, 70 vs 388, and 265 ng/ml vs over 400 ng/ml, respectively, and up to 18.5-fold reduction in the intracellular MRSA counts in osteoblasts was obtained. Confocal microscope images confirmed extensive accumulation of Rf-LPN inside the biofilm matrix and MRSA-infected osteoblasts. Overall, in this proof-of-concept study we have developed and validated the strategy to exploit the nanoparticle-cell and nanoparticle-biofilm interactions with a new rifampicin nanoformulation for prevention of osteomyelitis recurrence and chronicity caused by the elusive MRSA.

Lipid-polymer hybrid nanoparticles carrying linezolid improve treatment of methicillin-resistant Staphylococcus aureus (MRSA) harbored inside bone cells and biofilms.

Methicillin-resistant Staphylococcus aureus (MRSA) is the most prevalent pathogen causing osteomyelitis. The tendency of MRSA to evade standard antibiotic treatment by hiding inside bone cells and biofilms is a major cause of frequent osteomyelitis recurrence. In this study, we developed a lipid-polymer hybrid nanoparticle loading the antibiotic linezolid (LIN-LPN), and focused on evaluating if this new nanoantibiotic can achieve significant in vitro activities against these intracellular and biofilm-embedded MRSA. The optimal LIN-LPN formulation demonstrated both high linezolid payload (12.0% by weight of nanoparticles) and controlled release characteristics (gradually released the entrapped antibiotic in 120 h). Although it achieved lower activities against bacteria including USA300-0114, CDC-587, RP-62A in planktonic form, it was substantially superior against the intracellular MRSA reservoir inside osteoblast cells. The differences of intracellular activities between LIN-LPN and linezolid were 87.0-fold, 12.3-fold, and 12.6-fold in CFU/ml (p < 0.05 or < 0.01) at 2 µg/ml, 4 µg/ml, and 8 µg/ml linezolid concentrations, respectively. LIN-LPN also suppressed the MRSA biofilm growth to 35-60% of the values achieved with free linezolid (p < 0.05). These enhanced intracellular and anti-biofilm activities of LIN-LPN were likely contributed by the extensive accumulation of LIN-LPN inside the MRSA-infected osteoblasts and biofilms as revealed in the confocal microscope images. The study thus validates the feasibility of exploiting the good nanoparticle-host cell and nanoparticle-biofilm interactions for improving the antibiotic drug activities against the poorly accessible bacteria, and supports LIN-LPN as a new alternative therapy for preventing the recurrence of MRSA-mediated bone infections.

Therapeutic Nanotechnology for Bone Infection Treatment - State of the Art.

Despite extended, aggressive use of conventional antibiotics, drug treatment of bone infections frequently fails as a combined result of the widespread of drug-resistant bacteria, poor accessibility of many antimicrobials to the deeper portion of the bones, the ease of biofilm formation on the bone surface, and high risk of drug toxicity. Emerging therapeutic nanotechnology offers potential solutions to these issues. In recent years, a number of nanoantimicrobials, i.e. nanoscale devices with intrinsic antibacterial activities or capacity for delivering antibiotics, have been developed for the treatment and prevention of bone infections. These nanoantimicrobials can be designed to have controlled and sustained drug release kinetics, surface-modifications for bone or bacteria targeting, and increased affinity for biofilms. Given the potential value of nanoantimicrobials, clinical application of nanoantimicrobials for bone infection treatment remains scant when compared with the number of ongoing research. It is, therefore, a good time to carefully examine this promising yet relatively uncharted area. This review will extensively discuss the development and state of the art of different classes of nanoantimicrobials for bone infections with emphasis on the treatment aspect and identify the factors that prevent the clinical translation of nanoantimicrobial therapy from bench to bedside.

Nanomedicine applications in the treatment of breast cancer: current state of the art.

Breast cancer is the most common malignant disease in women worldwide, but the current drug therapy is far from optimal as indicated by the high death rate of breast cancer patients. Nanomedicine is a promising alternative for breast cancer treatment. Nanomedicine products such as Doxil® and Abraxane® have already been extensively used for breast cancer adjuvant therapy with favorable clinical outcomes. However, these products were originally designed for generic anticancer purpose and not specifically for breast cancer treatment. With better understanding of the molecular biology of breast cancer, a number of novel promising nanotherapeutic strategies and devices have been developed in recent years. In this review, we will first give an overview of the current breast cancer treatment and the updated status of nanomedicine use in clinical setting, then discuss the latest important trends in designing breast cancer nanomedicine, including passive and active cancer cell targeting, breast cancer stem cell targeting, tumor microenvironment-based nanotherapy and combination nanotherapy of drug-resistant breast cancer. Researchers may get insight from these strategies to design and develop nanomedicine that is more tailored for breast cancer to achieve further improvements in cancer specificity, antitumorigenic effect, antimetastasis effect and drug resistance reversal effect.

A biodistribution study of solid lipid-polyethyleneimine hybrid nanocarrier for cancer RNAi therapy.

Solid lipid-polymer hybrid nanocarrier (LPN) was previously reported to achieve high siRNA transfection efficiency and induce sustained RNAi-based chemosensitizing effect at cellular level. In this study, our objectives were to evaluate the in vivo biodistribution of LPNs in a prostate cancer model and determine the factors that potentially affect tumor penetration by LPNs. The LPN formulation with the highest transfection efficiency (64%) and stability was selected for the study. Mice bearing tumors of PC-3Mcells were treated with LPNs labeled with IR780 or AF647-siRNA. Near infrared imaging showed that LPNs achieved favorable in vivo biodistribution with high tumor/low organ ratios. LPN accumulation was also observed in liver metastatic tissue. Result of extravasation study confirmed that encapsulated siRNA molecules were able to escape into the tumor tissue at the extravascular area. When LPN levels in large (volume>750mm3) and small (<500mm3) tumors were compared, no significant difference was observed. However, both docetaxel pretreatment (72hbefore LPN) and concurrent docetaxel treatment significantly enhanced the tumor LPN levels by 3.9- and 3.1-fold, respectively (both p<0.01). In conclusion, LPN is a promising carrier system to deliver RNAi therapy to solid malignancies that also receive chemotherapy.

Development and evaluation of viscosity-enhanced nanocarrier (VEN) for oral insulin delivery.

Solid lipid nanoparticles (SLN) have demonstrated good potential for oral peptide delivery. However, their hydrophobic nature generally accounts for low peptide entrapment efficiency (EE%). In this study, a new strategy was adopted to improve peptide EE% by incorporating a hydrophilic viscosity-enhancing agent (VA) within SLN cores to develop viscosity enhanced nanocarriers (VEN). Three agents namely, propylene glycol (PG), polyethylene glycol (PEG) 400 and PEG 600, were tested with human insulin serving as a model peptide drug. The effects of VA were both concentration- and type-dependent. 70% w/w PG had achieved the highest EE% (54.5%), versus the two PEGs, compared to only 20.4% in unmodified SLN. PG based VEN had demonstrated good dispersion stability at gastrointestinal (GI) pHs and preferential uptake by intestinal Caco2 cells while showing low cytotoxicity. Additionally, they preserved the integrity of insulin and significantly protected it against GI enzymatic degradation. Freeze dried VEN had shown good stability upon storage at -20°C. Orally administered insulin-VEN had achieved good hypoglycemic effect in fasted rats with relative bioavailability of 5.1%. To conclude, an easily implementable technique to improve peptide entrapment within SLN has been validated, and the resulting VEN had proved promising efficacy for oral peptide delivery.

Nanomedicine of synergistic drug combinations for cancer therapy - Strategies and perspectives.

Nanomedicine of synergistic drug combinations has shown increasing significance in cancer therapy due to its promise in providing superior therapeutic benefits to the current drug combination therapy used in clinical practice. In this article, we will examine the rationale, principles, and advantages of applying nanocarriers to improve anticancer drug combination therapy, review the use of nanocarriers for delivery of a variety of combinations of different classes of anticancer agents including small molecule drugs and biologics, and discuss the challenges and future perspectives of the nanocarrier-based combination therapy. The goal of this review is to provide better understanding of this increasingly important new paradigm of cancer treatment and key considerations for rational design of nanomedicine of synergistic drug combinations for cancer therapy.

Methocel-Lipid Hybrid Nanocarrier for Efficient Oral Insulin Delivery.

Even with the use of double-emulsion technique for preparation, the hydrophobic nature of solid lipid nanoparticles (SLNs) limits their encapsulation efficiency (EE%) for peptides such as insulin. In this study, we hypothesize that inclusion of Methocel into SLN to form Methocel-lipid hybrid nanocarriers (MLNs) will significantly enhance insulin EE% without compromising the various characteristics of SLN favorable for oral drug delivery. Our data show that incorporation of 2% wt/wt of Methocel A15C had doubled insulin EE% (around 40%) versus conventional SLN prepared using standard double emulsion technique. MLN significantly protected the entrapped insulin against chymotrypsin degradation at gastrointestinal pH. Using intestinal epithelial cells Caco2 as a model, it was shown that MLN could be extensively taken up by Caco2 cells while demonstrating low cytotoxicity. The results indicate that MLN have preserved the key advantages of SLN (biocompatibility, low cytotoxicity, good drug protection, and good interaction with cells) while overcoming their key limitation for efficient peptide entrapment. Based on this, MLN may serve as a promising nanocarrier for oral delivery of peptides.

Lipid-Based Nanocarriers for RNA Delivery.

RNA-interference (RNAi) agents such as small-interfering RNA (siRNA) and micro-RNA (miRNA) have strong potential as therapeutic agents for the treatment of a broad range of diseases such as malignancies, infections, autoimmune diseases and neurological diseases that are associated with undesirable gene expression. In recent years, several clinical trials of RNAi therapeutics especially siRNAs have been conducted with limited success so far. For systemic administration of these poorly permeable and easily degradable macromolecules, it is obvious that a safe and efficient delivery platform is highly desirable. Because of high biocompatibility, biodegradability and solid track record for clinical use, nanocarriers made of lipids and/or phospholipids have been commonly employed to facilitate RNA delivery. In this article, the key features of the major sub-classes of lipid-based nanocarriers, e.g. liposomes, lipid nanoparticles and lipid nanoemulsions, will be reviewed. Focus of the discussion is on the various challenges researchers face when developing lipid-based RNA nanocarriers, such as the toxicity of cationic lipids and issues related to PEGylated lipids, as well as the strategies employed in tackling these challenges. It is hoped that by understanding more about the pros and cons of these most frequently used RNA delivery systems, the pharmaceutical scientists, biomedical researchers and clinicians will be more successful in overcoming some of the obstacles that currently limit the clinical translation of RNAi therapy.

A new nanostructured carrier design including oil to enhance the pharmaceutical properties of retinoid therapy and its therapeutic effects on chemo-resistant ovarian cancer.

All-trans retinoic acid (ATRA) is an appealing alternative drug for the cancers that have failed the conventional chemotherapy and become chemo-resistant and more tumorigenic. In this study, we specifically addressed two issues commonly associated with ATRA nanotherapeutics: (1) insufficient, unstable entrapment and uncontrolled release of the highly lipophilic ATRA and (2) lack of studies in therapeutically relevant chemo-resistant cancer cell models. A polymer-oil nanostructured carrier (PONC) composed of oil and PLGA was designed and studied in an ovarian cancer cell subline SKOV-3PR that could withstand up to 300 nM paclitaxel and expressed high levels of multidrug resistance transporter ABCB1 and tumorigenic marker CD133. Differential scanning calorimetry of PONC revealed superior polymer amorphosity and dispersion of the entrapped ATRA in a manner comparable to nanostructured lipid carriers. With this design, the ATRA encapsulation efficiency was increased up to 8.5-fold and a 5-day controlled release profile was obtained. ATRA-PONC was able to induce extensive apoptotic cell death and exert substantially higher long-term anti-tumorigenic effects (IC50 of ATRA-PONC: 2 µg/ml versus free ATRA: 17.5 µg/ml; p<0.05) in SKOV-3PR cells. Mechanistic studies indicated that these enhanced anticancer effects were likely attributable to higher cell permeation by the well-dispersed drug/oil steadily released from PONC. To conclude, a nanostructured, oil-in-polymer hybrid carrier design has been developed for efficient ATRA delivery and treatment of the chemo-exposed, chemo-resistant sub-population of ovarian cancer, exemplifying a convenient strategy to vastly improve the pharmaceutical and therapeutic properties of tough-to-deliver lipophilic, poorly water-soluble anticancer compounds.

Nanocarrier for poorly water-soluble anticancer drugs--barriers of translation and solutions.

Many existing chemotherapeutic drugs, repurposed drugs and newly developed small-molecule anticancer compounds have high lipophilicity and low water-solubility. Currently, these poorly water-soluble anticancer drugs (PWSAD) are generally solubilized using high concentrations of surfactants and co-solvents, which frequently lead to adverse side effects. In recent years, researchers have been actively exploring the use of nanotechnology as an alternative to the solvent-based drug solubilization approach. Several classes of nanocarrier systems (lipid-based, polymer-based and albumin-based) are widely studied for encapsulation and delivery of the existing and new PWSAD. These nanocarriers were also shown to offer several additional advantages such as enhanced tumour accumulation, reduced systemic toxicity and improved therapeutic effectiveness. In this article, the recent nanotechnological advances in PWSAD delivery will be reviewed. The barriers commonly encountered in the development of PWSAD nanoformulations (e.g. formulation issues and nanotoxicity issues) and the strategies to overcome these barriers will also be discussed. It is our goal to provide the pharmaceutical scientists and clinicians with more in-depth information about the nanodelivery approach, thus, more efficacious and safe PWSAD nanoformulations can be developed with improved translational success.

Nanotoxicity: a key obstacle to clinical translation of siRNA-based nanomedicine.

siRNAs have immense therapeutic potential for the treatment of various gene-related diseases ranging from cancer, viral infections and neuropathy to autoimmune diseases. However, their bench-to-bedside translation in recent years has faced several challenges, with inefficient siRNA delivery being one of the most frequently encountered issues. In order to improve the siRNA delivery especially for systemic treatment, nanocarriers made of polymers, lipids or inorganic materials have become almost essential. The 'negative' aspects of these carriers such as their nanotoxicity and immunogenicity thus can no longer be overlooked. In this article, we will extensively review the nanotoxicity of siRNA carriers. The strategies for mitigating the risks of nanotoxicity and the methodology for evaluating these strategies will also be discussed. By addressing this often overlooked but important issue, it will help clear the way for siRNAs to fulfill their promise as a versatile class of therapeutic agents.

Lipid encapsulation of cationic polymers in hybrid nanocarriers reduces their non-specific toxicity to breast epithelial cells.

PURPOSE: Clinical application of cationic polymers for delivery of nucleic acids has been limited by their toxicity. The purpose of this study is to evaluate whether the polymer-in-lipid hybrid nanotechnology recently developed for controlled siRNA delivery can tackle this toxicity issue by reducing exposure of the cellular components to free cationic polymers. METHODS: Lipid-polymer hybrid nanocarriers (LPNs) encapsulating complexes of hexadecylated polyethylenimine (H-PEI) and biologically inactive siRNA in lipids were prepared at different lipid-polymer ratios. Comparative toxicity of these LPNs and unencapsulated cationic materials on breast epithelial cell lines MDA-MB-231 and MCF-10a was evaluated. RESULTS: Even at a low lipid-polymer ratio (3:1 w/w), encapsulation of H-PEI improved its LC(50) values measured within hours by 3-5 fold, and caused less reduction in the colony-formation rates in 10-14 days. The observed reductions in the acute and delayed carrier toxicity were associated with significantly less membrane damages, improved mitochondrial functions, reduced reactive oxidative species production, and lower caspase-3 activity (all p < 0.05) without sacrificing the siRNA transfection efficiency. CONCLUSIONS: This study has validated the hybrid nanotechnology for controlled RNA delivery from a toxicological perspective. This is especially valuable if local or long-term RNA therapy is intended for which low carrier toxicity is essential.

A novel hybrid delivery system: polymer-oil nanostructured carrier for controlled delivery of highly lipophilic drug all-trans-retinoic acid (ATRA).

Many recently developed drugs encounter delivery issues due to their high lipophilicity and poor aqueous solubility. This study reports the development of a novel hybrid nanocarrier known as polymer-oil nanostructured carrier (PONC), in which highly lipophilic drugs such as all-trans-retinoic acid (ATRA) and indomethacin pre-solubilized in oil phase were dispersed in a polymeric matrix of poly(D,L-lactic-co-glycolic acid) (PLGA). In comparison to the standard PLGA only nanoparticles, PONC substantially increased the encapsulation efficiency of ATRA and indomethacin by up to 259% and 124%, respectively. Differential scanning calorimetry analysis revealed that the inclusion of oil introduced nanostructure into the polymeric matrix of the carrier. This feature facilitated more uniform distribution of the drug molecules which subsequently led to improved drug release kinetics with significantly reduced burst release effects (p<0.05). PONC was lyophilizable, remained physically stable when stored at low temperatures, and demonstrated low non-specific carrier toxicity. Delivery of ATRA by PONC also significantly improved its anticancer activity over the standard PLGA only nanoparticles (p<0.05). Our findings have therefore validated a promising delivery system that integrates the advantages of lipid-based (e.g. efficient encapsulation of highly lipophilic drugs) and polymeric colloidal carriers (e.g. uniform size, good stability), plus potential therapeutic benefits for delivery of poorly water-soluble anticancer drugs like ATRA.

Targeting megalin to enhance delivery of anti-clusterin small-interfering RNA nanomedicine to chemo-treated breast cancer.

The goal of this study is to evaluate a new targeting strategy to improve nanomedicine delivery to breast cancer cells that survive prior exposure to chemotherapy. These cells are particularly difficult to treat because they often develop drug resistance by upregulation of chemoresistant factors such as clusterin and should be preferably eradicated before they further spread out. In this study, the surface endocytotic receptor megalin was studied for the first time for targeted delivery of anti-clusterin small-interfering RNAs (siRNAs) to these chemo-treated cells. Lipid-polyethylenimine hybrid nanocarriers decorated with apolipoprotein E (Ap-LPNs) were developed for this purpose. Using immunoblotting, we demonstrated induction of both megalin and clusterin in MCF-7 cells by previous paclitaxel treatment. The siRNA transfection of these megalin-rich chemo-treated cancer cells was improved by three-fold when the siRNAs were delivered by Ap-LPNs. This trend was translatable into enhanced clusterin knockdown and improved chemosensitization to subsequent paclitaxel treatment (both p<0.05 versus uncoated LPNs). This proof-of-principle study has validated a novel "chemoresistance-targeting" strategy for siRNA delivery to the cancer cell subpopulation that begins to acquire chemoresistance and is in strong need for chemosensitization.

Solid lipid-PEI hybrid nanocarrier: an integrated approach to provide extended, targeted, and safer siRNA therapy of prostate cancer in an all-in-one manner.

Small-interfering RNA (siRNA) has a high application potential for therapeutic silencing of pathologic or drug-resistance genes. However, although recent research has led to several nonviral nucleic acid delivery systems with encouraging transfection performance, there remains a substantial gap between these systems and an ideal siRNA carrier that can be safely and effectively used for the more complex delivery tasks such as cancer management. We hypothesized that by integrating the high transfection performance of linear polyethylenimine (PEI) with the controlled release properties of solid lipid components, and complementing the resulting lipid-PEI hybrid nanocarrier (LPN) with receptor-targeting capability, multiple limitations of the conventional siRNA carriers would be simultaneously overcome. Data comparing this new hybrid system with the conventional siRNA-PEI polyplexes showed 15 to 21% less loss of siRNA, higher selectivity for prostate cancer cells over noncancerous prostate cells, and significant reduction in both acute and delayed carrier toxicity especially to the noncancerous RWPE1 cells (e.g., 71.2% of LPN-treated cells preserved proliferative capacity versus ≤30.2% in other groups). We further demonstrated sustained intracellular siRNA release from LPNs, which was shown translatable into extended in vitro and in vivo RNA-interference effects for a minimum of one week. Our findings generally support the use of LPN technology to achieve a longer-acting, less toxic, more efficient, and cancer-specific form of siRNA therapy in an "all-in-one" manner. This brings the nonviral siRNA delivery approach one important step closer to its clinical application.