Targeting breast cancer using pirarubicin-loaded vasoactive intestinal peptide grafted sterically stabilized micelles.

In this study the chemotherapeutic agent Pirarubicin (PRB) which is known for its serious side effects was actively targeted to the breast cancer cells by uploading it to the biocompatible and biodegradable Sterically Stabilized Micelles (SSMs) made of 1,2- Distearoyl- sn- glycero­3- phosphoethanolamine- N- methoxy­ polyethylene glycol 2000 (DSPE-PEG2000) to enhance efficacy and reduce toxicity. Vasoactive intestinal peptide (VIP), the receptors of which are overexpressed on the breast cancer cells, was grafted on the surface of the micelles. To the best of our knowledge this is the first report on active targeting of PRB to tumor site. For this purpose, PRB loaded VIP grafted SSMs (PRB-SSM-VIP) were synthesized and characterized. The in vitro efficiency of PRB-SSM-VIP along with SSM and free PRB was investigated on the MCF-7 breast cancer cells and the in vivo effects were studied on the 4T1 breast cancer bearing nude mice. Solubilizing 300 µg of PRB using 2.81 mg of DSPE-PEG2000 resulted in obtaining monodispersed particles of 12.16 ± 2.7 nm with slow drug release profile. Incorporation of PRB within the hydrophobic DSPE core of SSM was confirmed using differential scanning calorimetry (DSC) and the spherical shape of the synthesized particles was demonstrated using atomic force microscope (AFM). Both in vitro and in vivo studies showed significantly higher activity of PRB-SSM-VIP compared to free PRB. In vivo imaging showed successful accumulation of PRB-SSM-VIP at the tumor site and 98.8% tumor eradication was obtained with no signs of side effects. Current study suggests that SSM-VIP could be used as new drug delivery system for targeting PRB to the breast cancer cells.

Colonic delivery of vasoactive intestinal peptide nanomedicine alleviates colitis and shows promise as an oral capsule.

Aim: To evaluate the efficacy of locally delivered nanomedicine, vasoactive intestinal peptide in sterically stabilized micelles (VIP-SSM) to the colon and conduct in vitro release studies of a potential oral formulation. Materials & methods: Intracolonic instillation of VIP-SSM was tested in a mouse model of dextran sulfate sodium-induced colitis. Based on the effective mouse dose, human equivalent dose containing nanomedicine powder was filled into enteric coated capsules for in vitro release testing. Results: Colonic delivery of VIP-SSM significantly alleviated colitis. VIP-SSM containing capsules completely dissolved at colonic pH allowing micelles to reform with active VIP. Capsule formulations exhibited reproducible release profiles when stored up to 6 weeks demonstrating stability. Conclusion: VIP-SSM is an effective nanomedicine formulation which appears to have potential for oral treatment of colitis in humans. [Formula: see text].

Targeted Nanomedicines for Cancer Therapy, From Basics to Clinical Trials.

Traditional systemic chemotherapy involves the wide distribution of drug molecules in the body, causing toxic side effects in the healthy tissues and limiting the therapeutic dose required at the site of drug action. In order to decrease side effects and increase the drug efficacy, recent research on chemotherapy focuses on drug targeting. Targeted therapy can be achieved by several mechanisms including; 1) using an antibody as a drug that is specific to a disease biomarker, 2) using an antibody (or peptide) as a targeting agent conjugated to the drug molecule, 3) delivering the drug molecules to the target tissue in a nano-carrier with or without the targeting agent attached on its surface. The third approach involves the nanomedicines that can be targeted to diseased tissues by both passive (extravasating at diseased sites due to leaky vasculature) and active (specific interaction of the targeting agent with disease biomarker) targeting mechanisms. In this review we will cover the passively targeted nanomedicines prepared using nano drug carriers. Ideally the carrier particle should be in the right size (1-100nm), stable enough to prevent drug leakage during circulation, and safe not to cause any damage to healthy tissues. Competition for all these properties generated many different types of materials to be used as nanodrug delivery systems. After a brief review of most commonly used drug carriers, we discuss the clinical use of the targeted nanomedicines with regard to their pharmacokinetic and pharmacodynamics properties, and how these properties vary from conventional formulations providing free drugs in the circulation after administration.

Proteomic analysis reveals a role for PAX8 in peritoneal colonization of high grade serous ovarian cancer that can be targeted with micelle encapsulated thiostrepton.

High grade serous ovarian cancer (HGSOC) is the fifth leading cause of cancer deaths among women yet effective targeted therapies against this disease are limited. The heterogeneity of HGSOC, including few shared oncogenic drivers and origination from both the fallopian tube epithelium (FTE) and ovarian surface epithelium (OSE), has hampered development of targeted drug therapies. PAX8 is a lineage-specific transcription factor expressed in the FTE that is also ubiquitously expressed in HGSOC where it is an important driver of proliferation, migration, and cell survival. PAX8 is not normally expressed in the OSE, but it is turned on after malignant transformation. In this study, we use proteomic and transcriptomic analysis to examine the role of PAX8 leading to increased migratory capabilities in a human ovarian cancer model, as well as in tumor models derived from the OSE and FTE. We find that PAX8 is a master regulator of migration with unique downstream transcriptional targets that are dependent on the cell's site of origin. Importantly, we show that targeting PAX8, either through CRISPR genomic alteration or through drug treatment with micelle encapsulated thiostrepton, leads to a reduction in tumor burden. These findings suggest PAX8 is a unifying protein driving metastasis in ovarian tumors that could be developed as an effective drug target to treat HGSOC derived from both the OSE and FTE.

Phospholipid Micelles for Peptide Drug Delivery.

Sterically stabilized micelle (SSM) is a self-assembled nanoparticle ideal for the delivery of therapeutic peptides. The PEGylated phospholipid forming the particle, DSPE-PEG2000, is a safe, biocompatible, and biodegradable ingredient already approved for human use in the marketed product Doxil®. SSM can overcome formulation difficulties such as instability associated with peptide drugs, enabling their development for clinical application. The key advantage of this lipid-based nanocarrier is its simple preparation even at large scales, which allows easy transition to the clinics and the pharmaceutical market. In this chapter, we describe methods for preparation and characterization of peptides self-associated with SSM (peptide-SSM). We also discuss approaches to evaluate the biological activity of the peptide nanomedicines in vitro and in vivo.

Development of co-solvent freeze-drying method for the encapsulation of water-insoluble thiostrepton in sterically stabilized micelles.

The purpose of this work was to develop a practical and scalable method to encapsulate the hydrophobic antibiotic thiostrepton (TST) in sterically stabilized micelles (SSM). Using the conventional method of thin-film hydration, we encapsulated up to 5 drug molecules per SSM (diameter ∼ 16 nm). However, since this method is not suitable for large-scale production - a limiting factor for clinical translation - we applied the co-solvent freeze-drying method using tert-butanol (TBA): water co-solvent system. We found that the presence of phosphate-buffered saline (PBS) salts in the lyophilized cake accelerated the reconstitution time and allowed efficient drug encapsulation without the formation of larger drug particles. In addition, TBA proportion of 50% (v/v) was sufficient to maintain both phospholipid and drug in solution prior to the freeze-drying. The increase of drug and phospholipid concentrations in the formulation extended the reconstitution time and led to drug precipitation. Therefore, to increase the strength of the formulation, we prepared lyophilized cakes with lower phospholipid content (5 mM) and reconstituted them in one-third of the fill volume. In conclusion, we found optimum conditions to prepare TST-SSM using the co-solvent freeze-drying method. This scalable production method can facilitate the further clinical development and industrial production of TST-SSM nanomedicine.

Vasoactive Intestinal Peptide Nanomedicine for the Management of Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD) is a chronic relapsing disorder of the intestine, with increasing incidence worldwide. At present, the management of IBD is an unmet medical need due to the ineffectiveness of currently available drugs in treating all patients, and there is strong demand for novel therapeutics. In this regard, vasoactive intestinal peptide, a potent anti-inflammatory endogenous hormone, has shown promise in managing multiple immune disorders in animal models. However, when administered in the free form, VIP undergoes rapid degradation in vivo, and with continuous infusion, it causes severe dose limiting side effects. To overcome these barriers, we have developed a superior mode to deliver VIP in its native form, using sterically stabilized micelles (VIP-SSM). Our previous studies demonstrated that, VIP, when administered in SSM, prevented joint damage and inflammation in a mouse model of rheumatoid arthritis at a significantly lower dose than the free peptide, completely abrogating the serious side effect of hypotension associated with VIP. In the current study, we demonstrate the therapeutic benefit of VIP-SSM over free peptide in reversing severe colitis associated with IBD. First, we conducted preliminary studies with dextran sulfate sodium (DSS) induced colitis in mice, to determine the effectiveness of VIP administered on alternate days in reducing disease severity. Thereafter, a single intra peritoneal injection of VIP-SSM or the free peptide was used to determine its therapeutic effect on the reversal of colitis and associated diarrhea. The results demonstrated that when administered on alternate days, both VIP-SSM and VIP were capable of alleviating DSS colitis in mice. However, when administered as a single dose, in a therapeutic setting, VIP-SSM showed superior benefits compared to the free peptide in ameliorating colitis phenotype. Namely, the loss of solid fecal pellets and increased fluid accumulation in colon resulting from DSS insult was abrogated in VIP-SSM treated mice and not with free VIP. Furthermore, reduced protein and mRNA levels of the major chloride bicarbonate exchanger, down regulated in adenoma (DRA), seen with DSS was reversed with VIP-SSM, but not with the free peptide. Similarly, VIP-SSM treatment significantly reduced the elevated mRNA levels of pro-inflammatory cytokines and showed significant histologic recovery when compared to mice treated with free VIP. Therefore, these results demonstrated that as a single dose, the anti-inflammatory and antidiarrheal effects of VIP can be achieved effectively when administered as a nanomedicine. Therefore, we propose VIP-SSM to be developed as a potential therapeutic tool for treating ulcerative colitis, a type of IBD.

Expression and localization of VPAC1, the major receptor of vasoactive intestinal peptide along the length of the intestine.

Vasoactive intestinal peptide (VIP) is an endogenous neuropeptide with a broad array of physiological functions in many organs including the intestine. Its actions are mediated via G protein-coupled receptors, and vasoactive intestinal peptide receptor 1 (VPAC1) is the key receptor responsible for majority of VIP's biological activity. The distribution of VPAC1 along the length of the gastrointestinal tract and its subcellular localization in intestinal epithelial cells have not been fully characterized. The current studies were undertaken to determine VPAC1 distribution and localization so that VIP-based therapies can be targeted to specific regions of the intestine. The results indicated that the mRNA levels of VPAC1 showed an abundance pattern of colon > ileum > jejunum in the mouse intestine. In parallel, the VPAC1 protein levels were higher in the mouse colon, followed by the ileum and jejunum. Immunofluorescence studies in mouse colon demonstrated that the receptor was specifically localized to the luminal surface, as was evident by colocalization with the apical marker villin but not with the basolateral marker Na+/K+-ATPase. In the human intestine, VPAC1 mRNA expression exhibited a distribution similar to that in mouse intestine and was highest in the sigmoid colon. Furthermore, in the human colon, VPAC1 also showed predominantly apical localization. The physiological relevance of the expression and apical localization of VPAC1 remains elusive. We speculate that apical VPAC1 in intestinal epithelial cells may have relevance in recognizing secreted peptides in the intestinal lumen and therefore supports the feasibility of potential therapeutic and targeting use of VIP formulations via oral route to treat gastrointestinal diseases.NEW & NOTEWORTHY These studies for the first time present comprehensive data on the relative characterization of vasoactive intestinal peptide (VIP) receptors in the intestinal mucosa. Vasoactive intestinal peptide receptor 1 (VPAC1) was identified as the predominant receptor with higher levels in the colon compared with the small intestine and was mainly localized to the apical membrane. In addition, the findings in the human tissues were consistent with VPAC1 expression in the mouse intestine and open possibilities to target colonic tissues with VIP for treating diseases such as inflammatory bowel disease.

Cytotoxic, Apoptotic and Genotoxic Effects of Lipid-Based and Polymeric Nano Micelles, an In Vitro Evaluation.

Self-assembly systems (SAS) mainly consist of micelles, and liposomes are the classes of Nano Drug Delivery Systems with superior properties compared to traditional therapeutics in targeting cancer tumors. All commercially available nano-formulations of chemotherapeutics currently consist of SAS. According to our knowledge, a specific toxicity comparison based on material differences has not yet been performed. The purpose of this study was to evaluate and compare the toxicity of two SAS consisting of Sterically Stabilized Micelles (SSM) made of a lipid-based amphiphilic distearoyl-sn-glycero-phosphatidylethanolamine-polyethylene glycol (PEG)-2000 and a polymeric micelle (PM) consisting of Y-shape amphiphilic block copolymer, synthesized using poly ε-caprolactone and PEG. The mechanism of cytotoxicity and genotoxicity of micelles on L-929 healthy mouse fibroblast cells was assessed using Sulforhodamine-B, WST-1, Acridine Orange/Ethidium Bromide and alkaline single-cell gel electrophoresis assays. Results showed that SSM in conc. of 40 mg/mL shows very low cytotoxicity at the end of 24, 48 and 72 h. The DNA damage caused by SSM was much lower than PM while the latter one showed significant toxicity by causing apoptosis with the ED50 value of 3 mg/mL. While the DNA damage caused by SSM was ignorable, some DNA chain breaks were detected on cells treated with PM.

GLP-1 nanomedicine alleviates gut inflammation.

The gut hormone, glucagon like peptide-1 (GLP-1) exerts anti-inflammatory effects. However, its clinical use is limited by its short half-life. Previously, we have shown that GLP-1 as a nanomedicine (GLP-1 in sterically stabilized phospholipid micelles, GLP-1-SSM) has increased in vivo stability. The current study was aimed at testing the efficacy of this GLP-1 nanomedicine in alleviating colonic inflammation and associated diarrhea in dextran sodium sulfate (DSS) induced mouse colitis model. Our results show that GLP-1-SSM treatment markedly alleviated the colitis phenotype by reducing the expression of pro-inflammatory cytokine IL-1ß, increasing goblet cells and preserving intestinal epithelial architecture in colitis model. Further, GLP-1-SSM alleviated diarrhea (as assessed by luminal fluid) by increasing protein expression of intestinal chloride transporter DRA (down regulated in adenoma). Our results indicate that GLP-1 nanomedicine may act as a novel therapeutic tool in alleviating gut inflammation and associated diarrhea in inflammatory bowel disease (IBD).

TREM-1-accentuated lung injury via miR-155 is inhibited by LP17 nanomedicine.

Triggering receptors expressed on myeloid cell-1 (TREM-1) is a superimmunoglobulin receptor expressed on myeloid cells. Synergy between TREM-1 and Toll-like receptor amplifies the inflammatory response; however, the mechanisms by which TREM-1 accentuates inflammation are not fully understood. In this study, we investigated the role of TREM-1 in a model of LPS-induced lung injury and neutrophilic inflammation. We show that TREM-1 is induced in lungs of mice with LPS-induced acute neutrophilic inflammation. TREM-1 knockout mice showed an improved survival after lethal doses of LPS with an attenuated inflammatory response in the lungs. Deletion of TREM-1 gene resulted in significantly reduced neutrophils and proinflammatory cytokines and chemokines, particularly IL-1ß, TNF-α, and IL-6. Physiologically deletion of TREM-1 conferred an immunometabolic advantage with low oxygen consumption rate (OCR) sparing the respiratory capacity of macrophages challenged with LPS. Furthermore, we show that TREM-1 deletion results in significant attenuation of expression of miR-155 in macrophages and lungs of mice treated with LPS. Experiments with antagomir-155 confirmed that TREM-1-mediated changes were indeed dependent on miR-155 and are mediated by downregulation of suppressor of cytokine signaling-1 (SOCS-1) a key miR-155 target. These data for the first time show that TREM-1 accentuates inflammatory response by inducing the expression of miR-155 in macrophages and suggest a novel mechanism by which TREM-1 signaling contributes to lung injury. Inhibition of TREM-1 using a nanomicellar approach resulted in ablation of neutrophilic inflammation suggesting that TREM-1 inhibition is a potential therapeutic target for neutrophilic lung inflammation and acute respiratory distress syndrome (ARDS).

Targeted Sterically Stabilized Phospholipid siRNA Nanomedicine for Hepatic and Renal Fibrosis.

Since its discovery, small interfering RNA (siRNA) has been considered a potent tool for modulating gene expression. It has the ability to specifically target proteins via selective degradation of messenger RNA (mRNA) not easily accessed by conventional drugs. Hence, RNA interference (RNAi) therapeutics have great potential in the treatment of many diseases caused by faulty protein expression such as fibrosis and cancer. However, for clinical application siRNA faces a number of obstacles, such as poor in vivo stability, and off-target effects. Here we developed a unique targeted nanomedicine to tackle current siRNA delivery issues by formulating a biocompatible, biodegradable and relatively inexpensive nanocarrier of sterically stabilized phospholipid nanoparticles (SSLNPs). This nanocarrier is capable of incorporating siRNA in its core through self-association with a novel cationic lipid composed of naturally occuring phospholipids and amino acids. This overall assembly protects and delivers sufficient amounts of siRNA to knockdown over-expressed protein in target cells. The siRNA used in this study, targets connective tissue growth factor (CTGF), an important regulator of fibrosis in both hepatic and renal cells. Furthermore, asialoglycoprotein receptors are targeted by attaching the galactosamine ligand to the nanocarries which enhances the uptake of nanoparticles by hepatocytes and renal tubular epithelial cells, the major producers of CTGF in fibrosis. On animals this innovative nanoconstruct, small interfering RNA in sterically stabilized phospholipid nanoparticles (siRNA-SSLNP), showed favorable pharmacokinetic properties and accumulated mostly in hepatic and renal tissues making siRNA-SSLNP a suitable system for targeting liver and kidney fibrotic diseases.

A new lipid-based nano formulation of vinorelbine.

Vinorelbine (VLB) is a semi-synthetic Vinca alkaloid which is currently used in treatment of different cancer types mainly advanced breast cancer (ABC) and advanced/metastatic non-small cell lung cancer (NSCLC). However, its marketed formulation has been reported to have serious side effects, such as granulocytopenia, which is the major dose-limiting toxicity. Other unwanted effects include venous discoloration and phlebitis proximal to the site of injection, as well as localized rashes and urticaria, blistering, and skin sloughing. Our long-term aim in synthesizing a novel nanomicellar vinorelbine formulation is to reduce or even eliminate these side effects and increase drug activity by formulating the drug in a lipid-based system as a nanomedicine targeted to the site of action. To this end, the purpose of this study was to prepare, characterize, and determine the in vitro efficacy of vinorelbine-loaded sterically stabilized, biocompatible, and biodegradable phospholipid nanomicelles (SSM; size, ∼15 nm). Our results indicated that vinorelbine incorporate at high quantities and within the interface between the core and palisade sections of the micelles. Incorporation ratio of drug within sterically stabilized micelles increased as the total amount of drug in the system increased, and no drug particles were formed at the highest drug concentrations tested. The nanomicellar formulation of vinorelbine was ∼6.7-fold more potent than vinorelbine dissolved in DMSO on MCF-7 cell line. Collectively, these data indicate that vinorelbine-loaded SSM can be developed as a new, safe, stable, and effective nanomedicine for the treatment of breast and lung cancers.

Curcumin in VIP-targeted sterically stabilized phospholipid nanomicelles: a novel therapeutic approach for breast cancer and breast cancer stem cells.

Breast cancer is a leading cause of cancer deaths among women in the US, with 40 % chance of relapse after treatment. Recent studies outline the role of cancer stem cells (CSCs) in tumor initiation, propagation, and regeneration of cancer. Moreover, it has been established that breast CSCs reside in a quiescent state that makes them more resistant to conventional cancer therapies than bulk cancer cells resulting in tumor relapse. In this study, we establish that CSCs are associated with the overexpression of vasoactive intestinal peptide (VIP) receptors which can be used to actively target these cells. We investigated the potential of using a novel curcumin nanomedicine (C-SSM) surface conjugated with VIP to target and hinder breast cancer with CSCs. Here, we formulated, characterized, and evaluated the feasibility of C-SSM nanomedicine in vitro. We investigated the cytotoxicity of C-SSM on breast cancer cells and CSCs by tumorsphere formation assay. Our results suggest that curcumin can be encapsulated in SSM up to 200 µg/ml with 1 mM lipid concentration. C-SSM nanomedicine is easy to prepare and maintains its original physicochemical properties after lyophilization, with an IC50 that is significantly improved from that of free curcumin (14.2±1.2 vs. 26.1±3.0 µM). Furthermore, C-SSM-VIP resulted in up to 20 % inhibition of tumorsphere formation at a dose of 5 µM. To this end, our findings demonstrate the feasibility of employing our actively targeted nanomedicine as a potential therapy for CSCs-enriched breast cancer.

Solubilization of therapeutic agents in micellar nanomedicines.

We use atomistic molecular dynamics simulations to reveal the binding mechanisms of therapeutic agents in PEG-ylated micellar nanocarriers (SSM). In our experiments, SSM in buffer solutions can solubilize either ≈11 small bexarotene molecules or ≈6 (2 in low ionic strength buffer) human vasoactive intestinal peptide (VIP) molecules. Free energy calculations reveal that molecules of the poorly water-soluble drug bexarotene can reside at the micellar ionic interface of the PEG corona, with their polar ends pointing out. Alternatively, they can reside in the alkane core center, where several bexarotene molecules can self-stabilize by forming a cluster held together by a network of hydrogen bonds. We also show that highly charged molecules, such as VIP, can be stabilized at the SSM ionic interface by Coulombic coupling between their positively charged residues and the negatively charged phosphate headgroups of the lipids. The obtained results illustrate that atomistic simulations can reveal drug solubilization character in nanocarriers and be used in efficient optimization of novel nanomedicines.

A novel peptide nanomedicine for treatment of pancreatogenic diabetes.

Pancreatogenic diabetes (PD) is a potentially fatal disease that occurs secondary to pancreatic disorders. The current anti-diabetic therapy for PD is fraught with adverse effects that can increase morbidity. Here we investigated the efficacy of novel peptide nanomedicine: pancreatic polypeptide (PP) in sterically stabilized micelles (SSM) for management of PD. PP exhibits significant anti-diabetic efficacy but its short plasma half-life curtails its therapeutic application. To prolong and improve activity of PP in vivo, we evaluated the delivery of PP in SSM. PP-SSM administered to rats with PD, significantly improved glucose tolerance, insulin sensitivity and hepatic glycogen content compared to peptide in buffer. The studies established the importance of micellar nanocarriers in protecting enzyme-labile peptides in vivo and delivering them to target site, thereby enhancing their therapeutic efficacy. In summary, this study demonstrated that PP-SSM is a promising novel anti-diabetic nanomedicine and therefore should be further developed for management of PD. FROM THE CLINICAL EDITOR: Pancreatic peptide was earlier demonstrated to address pancreatogenic diabetes, but its short half-life represented major difficulties in further development for therapeutic use. PP-SSM (pancreatic polypeptide in sterically stabilized micelles) is a promising novel anti-diabetic nanomedicine that enables prolonged half-life and increased bioactivity of PP, as shown in this novel study, paving the way toward clinical studies in the near future.

Novel, biocompatible, and disease modifying VIP nanomedicine for rheumatoid arthritis.

Despite advances in rheumatoid arthritis (RA) treatment, efficacious and safe disease-modifying therapy still represents an unmet medical need. Here, we describe an innovative strategy to treat RA by targeting low doses of vasoactive intestinal peptide (VIP) self-associated with sterically stabilized micelles (SSMs). This spontaneous interaction of VIP with SSM protects the peptide from degradation or inactivation in biological fluids and prolongs circulation half-life. Treatment with targeted low doses of nanosized SSM-VIP but not free VIP in buffer significantly reduced the incidence and severity of arthritis in an experimental model, completely abrogating joint swelling and destruction of cartilage and bone. In addition, SSM associated VIP, unlike free VIP, had no side-effects on the systemic functions due to selective targeting to inflamed joints. Finally, low doses of VIP in SSM successfully downregulated both inflammatory and autoimmune components of RA. Collectively, our data clearly indicate that VIP-SSM should be developed to be used as a novel nanomedicine for the treatment of RA.

Peptide delivery using phospholipid micelles.

Peptide based drugs are an important class of therapeutic agents but their development into commercial products is often hampered due to their inherent physico-chemical and biological instabilities. Phospholipid micelles can be used to address these delivery concerns. Peptides self-associate with micelles that serve to thwart the aggregation of these biomolecules. Self-association with micelles does not modify the peptide chemically; therefore the process does not denature or compromise the bioactivity of peptides. Additionally, many amphiphilic peptides adopt α-helical conformation in phospholipid micelles which is not only the most favorable conformation for receptor interaction but also improves their stability against proteolytic degradation, thus making them long-circulating. Furthermore, the nanosize of micelles enables passive targeting of peptides to the desired site of action through leaky vasculature present at tumor and inflamed tissues. All these factors alter the pharmacokinetic and biodistribution profiles of peptides therefore enhance their efficacy, reduce the dose required to obtain a therapeutic response and prevent adverse effects due to interaction of the peptide with receptors present in other physiological sites of the body. These phospholipid micelle based peptide nanomedicines can be easily scaled-up and lyophilized, thus setting the stage for further development of the formulation for clinical use. All things considered, it can be concluded that phospholipid micelles are a safe, stable and effective delivery option for peptide drugs and they form a great promise for future peptide nanomedicines.

Improvement of drug safety by the use of lipid-based nanocarriers.

Drug toxicity is an important factor that contributes significantly to adverse drug events in current healthcare practice. Application of lipid-based nanocarriers in drug formulation is one approach to improve drug safety. Lipid-based delivery systems include micelles, liposomes, solid lipid nanoparticles, nanoemulsions and nanosuspensions. These carriers are generally composed of physiological lipids well tolerated by human body. Delivery of water-insoluble drugs in these formulations increases their solubility and stability in aqueous media and eliminates the need for toxic co-solvents or pH adjustment to solubilize hydrophobic drugs. Association or encapsulation of peptides/proteins within lipid-based carriers protects the labile biologics against enzymatic degradation, hence reducing the therapeutic dose required and risk of dose-dependent toxicity. Most importantly, lipid-based nanocarriers alter the pharmacokinetics and biodistribution of drugs through passive and active targeting, leading to increased drug accumulation at target sites while significantly decreasing non-specific distribution to other tissues. Furthermore, surface modification of these nanocarriers reduces immunogenicity of drug-carrier complexes, imparts stealth by preventing opsonization and removal by phagocytes and minimizes interaction with circulating blood components. In view of heightening attention on drug safety in patient treatment, lipid-based nanocarrier is therefore an important and promising option for formulation of pharmaceutical products to improve treatment safety and efficacy.

Human pancreatic polypeptide in a phospholipid-based micellar formulation.

PURPOSE: Pancreatic polypeptide (PP) has important glucoregulatory functions and thereby holds significance in the treatment of diabetes and obesity. However, short plasma half-life and aggregation propensity of PP in aqueous solution, limits its therapeutic application. To address these issues, we prepared and characterized a formulation of PP in sterically stabilized micelles (SSM) that protects and stabilizes PP in its active conformation. METHODS: PP-SSM was prepared by incubating PP with SSM dispersion in buffer. Peptide-micelle association and freeze-drying efficacy of the formulation was characterized in phosphate buffers with or without sodium chloride using dynamic light scattering, fluorescence spectroscopy and circular dichroism. The degradation kinetics of PP-SSM in presence of proteolytic enzyme was determined using HPLC and bioactivity of the formulation was evaluated by in vitro cAMP inhibition study. RESULTS: PP self-associated with SSM and this interaction was influenced by presence/absence of sodium chloride in the buffer. The formulation was effectively lyophilized, demonstrating feasibility for its long-term storage. The stability of peptide against proteolytic degradation was significantly improved and PP in SSM retained its bioactivity in vitro. CONCLUSIONS: Self-association of PP with phospholipid micelles addressed the delivery issues of the peptide. This nanomedicine should be further developed for the treatment of diabetes.