Octreotide-Modified Polymeric Micelles as Potential Carriers for Targeted Docetaxel Delivery to Somatostatin Receptor Overexpressing Tumor Cells

Octreotide and Octreotide-derived delivery systems

Pharmaceutical peptide Octreotide is a somatostatin analog with targeting and therapeutic abilities. Over the last decades, Octreotide has been developed and approved to treat acromegaly and neuroendocrine tumours, and Octreotide-based radioactive conjugates have been leveraged clinically to detect small neuroendocrine tumour sites. Meanwhile, variety of Octreotide-derived delivery strategies have been proposed and explored for tumour targeted therapeutics or diagnostics in preclinical or clinical settings. In this review, we especially focus on the preclinical development and applications of Octreotide-derived drug delivery systems, diagnostic nanosystems, therapeutic nanosystems and multifunctional nanosystems, we also briefly discuss challenges and prospects of these Octreotide-derived delivery systems.

Forward Precision Medicine: Micelles for Active Targeting Driven by Peptides

Precision medicine is based on innovative administration methods of active principles. Drug delivery on tissue of interest allows improving the therapeutic index and reducing the side effects. Active targeting by means of drug-encapsulated micelles decorated with targeting bioactive moieties represents a new frontier. Between the bioactive moieties, peptides, for their versatility, easy synthesis and immunogenicity, can be selected to direct a drug toward a considerable number of molecular targets overexpressed on both cancer vasculature and cancer cells. Moreover, short peptide sequences can facilitate cellular intake. This review focuses on micelles achieved by self-assembling or mixing peptide-grafted surfactants or peptide-decorated amphiphilic copolymers. Nanovectors loaded with hydrophobic or hydrophilic cytotoxic drugs or with gene silence sequences and externally functionalized with natural or synthetic peptides are described based on their formulation and in vitro and in vivo behaviors.

Identification of somatostatin receptors using labeled PEGylated octreotide, as an active internalization

Numerous normal and tumors cells are well-known to express the somatostatin receptors (SSTRs) on their surface which makes the receptor be useful for tumor scintigraphy. Thus, the identification of SSTRs is beneficial, especially SSTR₂. The somatostatin analog, Octreotide (OCT), was chosen as a ligand, as it is known to selectively bind to SSTR₂. Moreover, polyethylene glycol (PEG), 8armPEG, was used as a branched PEG to provide a low nonspecific cell binding and easily chemical modification. OCT and fluorescein (Flu) were conjugated to branched PEG using a water-soluble carbodiimide (EDC) and N-hydroxy succinimide (NHS) so as to activate its carboxylic acid group. 8armPEG-tagged Flu and OCT was characterized by gel permeation chromatography (GPC) to proof the conjugation of OCT to 8armPEG. Finally, cellular uptake was studied using pancreatic cancer cells with well-expressed somatostatin receptors using a confocal laser scanning microscope (CLMS) and fluorescence activated cell sorting (FACS). GPC showed increases in molecular mass since it showed a difference in elution time of 8armPEG itself and 8armPEG labeled with Flu. CLMS and FACS showed high binding with the positive SSTR₂ cells expression and showed negative results with negative expressing SSTR₂. These bindings were decreased when the receptors were occupied with free OCT which confirms the specific binding to SSTR₂. Therefore, we formulated a novel model to easily identify SSTR₂ and other receptors which serves as a promising platform for identification of tumor cells overexpressing the SSTR₂, which would be a hopeful target for cancer therapy and tumor scintigraphy.

Dual-template cascade synthesis of highly multi-branched Au nanoshells with ultrastrong NIR absorption and efficient photothermal therapeutic intervention

A universal dual-template cascade strategy for the synthesis of multi-branched gold nanoshells with ultrastrong NIR absorption for tumor photothermal therapy.

Somatostatin receptors as a new active targeting sites for nanoparticles

The delivery of nanoparticles through receptor-mediated cell interactions has nowadays a major attention in the area of drug targeting applications. This specific kind of targeting is mediated by localized receptors impeded into the target site with subsequent drugs internalization. Hence, this type of interaction would diminish side effects and enhance drug delivery efficacy to the target site. Somatostatin receptors (SSTRs) are one type of G protein-coupled receptors, which could be active targeted for various purposes. There are five SSTRs types (SSTR1-5) which are localized at various organs in the body and spread into different tissues. SSTRs could be considered as a promising target to various nanoparticles which is facilitated when nanoparticles are modified through specific ligand or coating to allow better binding. This review discusses the exploration of SSTRs for active targeting of nanoparticles with certain emphasize on their interaction at the cellular level.

Targeting Somatostatin Receptors By Functionalized Mesoporous Silica Nanoparticles - Are We Striking Home?

The concept of delivering nanoformulations to desired tissues by means of targeting membrane receptors of high local abundance by ligands anchored to the nanocarrier has gained a lot of attention over the last decade. Currently, there is no unanimous opinion on whether surface functionalization of nanocarriers by targeting ligands translates into any real benefit in terms of pharmacokinetics or treatment outcomes. Having examined the published nanocarriers designed to engage with somatostatin receptors, we realized that in the majority of cases targetability claims were not supported by solid evidence of targeting ligand-targeted receptor coupling, which is the very crux of a targetability concept. Here, we present an approach to characterize targetability of mesoporous silica-based nanocarriers functionalized with ligands of somatostatin receptors. The targetability proof in our case comes from a functional assay based on a genetically-encoded cAMP probe, which allows for real-time capture of receptor activation in living cells, triggered by targeting ligands on nanoparticles. We elaborate on the development and validation of the assay, highlighting the power of proper functional tests in the characterization pipeline of targeted nanoformulations.

α-Conotoxin ImI-modified polymeric micelles as potential nanocarriers for targeted docetaxel delivery to α7-nAChR overexpressed non-small cell lung cancer

A micelle system modified with α-Conotoxin ImI (ImI), a potently antagonist for alpha7 nicotinic acetylcholine receptor (α7-nAChR) previously utilized for targeting breast cancer, was constructed. Its targeting efficiency and cytotoxicity against non-small cell lung cancer (NSCLC) highly expressing α7-nAChR was investigated. A549, a non-small cell lung cancer cell line, was selected as the cell model. The cellular uptake study showed that the optimal modification ratio of ImI on micelle surface was 5% and ImI-modification increased intracellular delivery efficiency to A549 cells via receptor-mediated endocytosis. Intracellular Ca²⁺ transient assay demonstrated that ImI modification led to enhanced molecular interaction between nanocarriers and A549 cells. The in vivo near-infrared fluorescence imaging further revealed that ImI-modified micelles could facilitate the drug accumulation in tumor sites compared with non-modified micelles via α7-nAChR mediation. Moreover, docetaxel (DTX) was loaded in ImI-modified nanomedicines to evaluate its in vitro cytotoxicity. As a result, DTX-loaded ImI-PMs exhibited greater anti-proliferation effect on A549 cells compared with non-modified micelles. Generally, our study proved that ImI-modified micelles had targeting ability to NSCLC in addition to breast cancer and it may provide a promising strategy to deliver drugs to NSCLC overexpressing α7-nAChR.

Cancer-targeted delivery systems based on peptides

There is a growing interest for the discovery of new cancer-targeted delivery systems for drug delivery and diagnosis. A synopsis of the bibliographic data will be presented on bombesin, neurotensin, octreotide, Arg-Gly-Asp, luteinizing hormone-releasing hormone and other peptides. Many of them have reached the clinics for therapeutic or diagnostic purposes, and have been utilized as carriers of known cytotoxic agents such as doxorubicin, paclitaxel, cisplatin, methotrexate or dyes and radioisotopes. In our article, recent advances in the development of peptides as carriers of cytotoxic drugs or radiometals will be analyzed.

Poly(Ethylene Glycol)-Polylactide Micelles for Cancer Therapy

For the treatment of malignancy, many therapeutic agents, including small molecules, photosensitizers, immunomodulators, proteins and genes, and so forth, have been loaded into nanocarriers for controllable cancer therapy. Among these nanocarriers, polymeric micelles have been considered as one of the most promising nanocarriers, some of which have already been applied in different stages of clinical trials. The successful advantages of polymeric micelles from bench to bedside are due to their special core/shell structures, which can carry specific drugs in certain disease conditions. Particularly, poly(ethylene glycol)–polylactide (PEG–PLA) micelles have been considered as one of the most promising platforms for drug delivery. The PEG shell effectively prevents the adsorption of proteins and phagocytes, thereby evidently extending the blood circulation period. Meanwhile, the hydrophobic PLA core can effectively encapsulate many therapeutic agents. This review summarizes recent advances in PEG–PLA micelles for the treatment of malignancy. In addition, future perspectives for the development of PEG–PLA micelles as drug delivery systems are also presented.

Targeted therapy of octreotide-modified oleanolic acid liposomes to somatostatin receptor overexpressing tumor cells

AIM

To prepare and validate the efficacy of a novel targeted drug delivery system - octreotide (Oct)-modified oleanolic acid (OA) liposomes.

MATERIALS & METHODS

OA liposomes (OA-L) were prepared by an ethanol injection method. The Oct-modified OA liposomes (O-OA-L) were synthesized and their properties were evaluated. Cellular uptake and competition inhibition studies were performed.

RESULTS

The OA vesicles presented satisfactory particles size (100-200 nm), stability and drug release characteristics; their ζ potential was -1.42 ± 0.08 mV. The O-OA-L had a higher cell proliferation inhibitory activity and cellular uptake than that of OA-L for somatostatin receptor-positive A549 cells.

CONCLUSION

The O-OA-L, as a promising agent, can target actively the lesion site with safe and high-efficiency pattern.

Somatostatin Receptor-Mediated Tumor-Targeting Nanocarriers Based on Octreotide-PEG Conjugated Nanographene Oxide for Combined Chemo and Photothermal Therapy

Nano-sized in vivo active targeting drug delivery systems have been developed to a high anti-tumor efficacy strategy against certain cancer-cells-specific. Graphene based nanocarriers with unique physical and chemical properties have shown significant potentials in this aspect. Here, octreotide (OCT), an efficient biotarget molecule, is conjugated to PEGylated nanographene oxide (NGO) drug carriers for the first time. The obtained NGO-PEG-OCT complex shows low toxicity and excellent stability in vivo and is able to achieve somatostatin receptor-mediated tumor-specific targeting delivery. Owing to the high loading efficiency and accurate targeting delivery of anti-cancer drug doxorubicin (DOX), our DOX loaded NGO-PEG-OCT complex offers a remarkably improved cancer-cell-specific cellular uptake, chemo-cytotoxicity, and decreased systemic toxicity compared to free DOX or NGO-PEG. More importantly, due to its strong near-infrared absorption, the NGO-PEG-OCT complex further enhances efficient photothermal ablation of tumors, delivering combined chemo and photothermal therapeutic effect against cancer cells.

Development of octreotide-conjugated polymeric prodrug of bufalin for targeted delivery to somatostatin receptor 2 overexpressing breast cancer in vitro and in vivo

BACKGROUND

Development of polymeric prodrugs of small molecular anticancer drugs has become one of the most promising strategies to overcome the intrinsic shortcomings of small molecular anticancer drugs and improve their anticancer performance.

MATERIALS AND METHODS

In the current work, we fabricated a novel octreotide (Oct)-modified esterase-sensitive tumor-targeting polymeric prodrug of bufalin (BUF) and explored its anticancer performance against somatostatin receptor 2 overexpressing breast cancer.

RESULTS

The obtained tumor-targeting polymeric prodrug of BUF, P(oligo[ethylene glycol] monomethyl ether methacrylate [OEGMA]-co-BUF-co-Oct), showed a nanosize dimension and controlled drug release features in the presence of esterase. It was demonstrated by in vitro experiment that P(OEGMA-co-BUF-co-Oct) showed enhanced cytotoxicity, cellular uptake, and apoptosis in comparison with those of free BUF. In vivo experiment further revealed the improved accumulation of drugs in tumor tissues and enhanced anticancer performance of P(OEGMA-co-BUF-co-Oct).

CONCLUSION

Taken together, this study indicated that polymeric prodrug of BUF holds promising potential toward the treatment of somatostatin receptor 2 overexpressing breast cancer.

Drug delivery system targeting advanced hepatocellular carcinoma: Current and future

Hepatocellular carcinoma (HCC) has a fairly high morbidity and is notoriously difficult to treat due to long latent period before detection, multidrug resistance and severe drug-related adverse effects from chemotherapy. Targeted drug delivery systems (DDS) that can selectively deliver therapeutic drugs into tumor sites have demonstrated a great potential in cancer treatment, which could be utilized to resolve the limitations of conventional chemotherapy. Numerous preclinical studies of DDS have been published, but targeted DDS for HCC has yet to be made for practical clinical use. Since rational targeted DDS design should take cancer-specific properties into consideration, we have reviewed the biological and physicochemical properties of HCC extensively to provide a comprehensive understanding on HCC, and recent DDS studies on HCC, aiming to find some potential targeted DDSs for HCC treatment and a meaningful platform for further development of HCC treatments.

FROM THE CLINICAL EDITOR

Hepatocellular carcinoma has a high incidence worldwide and is known to be multidrug resistant. Thus, intensive research is being carried out to find better chemotherapeutic agents as well as new drug delivery systems. In this article, the authors reviewed in depth the current challenges facing new drug designs and also outlined novel targeted drug delivery systems (DDS) in the fight against HCC.

The influence of bile salt on the chemotherapeutic response of docetaxel-loaded thermosensitive nanomicelles

The primary aim of this work was to investigate the potential of bile salt, sodium taurocholate (NaTC), in improving the bioavailability and anti-tumor efficacy of docetaxel (DCT) upon rectal administration. Poloxamer-based nanomicelles with thermosensitive and mucoadhesive properties were prepared using the cold method. The optimized nanomicellar formulation was evaluated in terms of physicochemical and viscoelastic parameters. Nanomicelles containing bile salt maintained sufficient gelation strength (234×10² mPa·s) and mucoadhesive force (17.3×10² dyne/cm²) to be retained in the upper part of the rectum. They significantly enhanced the DCT internalization across the rectal mucosa and showed a high plasma level during the first 4 hours of the study period, compared to nanomicelles with no bile salt. As a result, a slightly higher rectal bioavailability of ~33% was observed in nanomicelles containing bile salt, compared to ~28% from the latter system. The higher pharmacokinetic parameters for rectally administered DCT/P407/P188/Tween 80/NaTC (0.25%/11%/15%/10%/0.1% by weight, respectively) resulted in significant anti-tumor efficacy. However, the tumor regression rate for the NaTC group was not statistically different from that for nanomicelles without NaTC. Therefore, overall results suggest that thermosensitive nanomicelles could be a potential dosage form for improvement of the bioavailability and chemotherapeutic profile of DCT.

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.

Combinational delivery of c-myc siRNA and nucleoside analogs in a single, synthetic nanocarrier for targeted cancer therapy

The treatment of aggressive non-small-cell lung cancer (NSCLC) depends on the creation of new therapeutic regimens in clinical settings. In this study, we developed a Lipid/Calcium/Phosphate (LCP) nanoparticle that combines chemotherapy with gene therapy. By encapsulating a chemodrug, gemcitabine monophosphate (GMP), and siRNA specific to the undruggable cMyc oncogene (cMyc siRNA) into a single nano-sized vesicle and systemically administering them to nude mice, we achieved potent anti-tumor activity in both subcutaneous and orthotopic models of NSCLC. The improvements in therapeutic response over either cMyc siRNA or GMP therapy alone, were demonstrated by the ability to effectively induce the apoptosis of tumor cells and the significant reduction of proliferation of tumor cells. The combination therapy led to dramatic inhibition of tumor growth, with little in vivo toxicity. Additionally, the current studies demonstrated the possibility of incorporating both nucleic acid molecules and phosphorylated small molecule drugs into the inner core of a single nanoparticle formulation. Co-encapsulation of an oncogene-modulating siRNA and a chemotherapeutic agent will allow simultaneous interruption of diverse anti-cancer pathways, leading to increased therapeutic efficacy and reduced toxicities.

How nanotechnology can enhance docetaxel therapy

Docetaxel has been recognized as one of the most efficient anticancer drugs over the past decade; however, its poor water solubility and systemic toxicity have greatly limited its clinical application. In recent decades, the emergence of nanotechnology has provided new drug delivery systems for docetaxel, which can improve its water solubility, minimize the side effects and increase the tumor-targeting distribution by passive or active targeting. This review focuses on the research progress in nanoformulations related to docetaxel delivery – such as polymer-based, lipid-based, and lipid-polymer hybrid nanocarriers, as well as inorganic nanoparticles – addressing their structures, characteristics, preparation, physicochemical properties, methods by which drugs are loaded into them, and their in vitro and in vivo efficacies. Further, the targeted ligands used in the docetaxel nanoformulations, such as monoclonal antibodies, peptides, folic acid, transferrin, aptamers and hyaluronic acid, are described. The issues to overcome before docetaxel nanoformulations can be used in clinical and commercial applications are also discussed.

Codelivery of VEGF siRNA and gemcitabine monophosphate in a single nanoparticle formulation for effective treatment of NSCLC

There is an urgent need for new therapeutics for the treatment of aggressive and metastatic refractory human non-small-cell lung cancer (NSCLC). Antiangiogenesis therapy and chemotherapy are the two major treatment options. Unfortunately, both types of therapies when used individually have their disadvantages. Integrating antiangiogenesis therapy with chemotherapy is expected to target the tumor's vascular endothelial cells and the tumor cells simultaneously. In this study, we coformulated Vascular endothelial growth factor (VEGF) siRNA targeting VEGFs and gemcitabine monophosphate (GMP) into a single cell-specific, targeted lipid/calcium/phosphate (LCP) nanoparticle formulation. Antitumor effect of the combination therapy using LCP loaded with both VEGF siRNA and GMP was evaluated in both subcutaneous and orthotopic xenograft models of NSCLC with systemic administration. The improved therapeutic response, as compared with either VEGF siRNA or GMP therapy alone, was supported by the observation of 30-40% induction of tumor cell apoptosis, eightfold reduction of tumor cell proliferation and significant decrease of tumor microvessel density (MVD). The combination therapy led to dramatic inhibition of tumor growth, with little in vivo toxicity. In addition, the current studies demonstrated the possibility of incorporating multiple nucleic acid molecules and phosphorylated small-molecule drugs, targeting to different pathways, into a single nanoparticle formulation for profound therapeutic effect.

Peptide modified polymeric micelles specific for breast cancer cells

The specific targeting ability of novel breast cancer targeting peptides as ligands coupled to polymeric micelles was evaluated in the present study. In this context, engineered breast cancer cell targeting peptides, denoted as peptide 11 (RGDPAYQGRFL) and peptide 18 (WXEAAYQRFL), were compared with the lead 12-mer p160 peptide and cyclic RGDfK peptide. All four peptides were conjugated individually to poly(ethylene oxide)-b-poly(caprolactone) (PEO-b-PCL) diblock polymeric micelles to obtain targeted carrier systems PM11, PM18, PM 160, and PM c-RGD. Physical blending of the peptides 11 and 18 with PEO-b-PCL was also done to yield combination micelles, comPM11 and comPM18. The structural confirmation of polymer was carried out using (1)H NMR and MALDI-TOF, and the size distribution and zeta potential of the micelles were determined using dynamic light scattering. Lipophilic cyanine fluorescent probe DiI was physically incorporated in the polymeric micelles to imitate the hydrophobic drug loaded in the micellar core. The cellular uptake of DiI-loaded peptide-containing polymeric micelles by MDA-MB-435, MDA-MB-231, and MCF7 breast cancer cell lines, as well as HUVEC and MCF10A noncancerous cells, were analyzed using flow cytometry and confocal microscopy techniques. Modification of polymeric micelles with peptide 11 or 18 led to an increase in micellar uptake specifically in breast cancer cells compared to p160, c-RGD modified, or naked micelles. The peptide-micelle combinations (comPM11 and comPM18) displayed better uptake by the cells compared to the covalently conjugated PM11 and PM18 micelles; however, the combinations were less selective toward cancer cells. The results point to a potential for peptides 11- and 18-micelle conjugates as attractive platforms for improved performance of a wide range of chemotherapeutic drugs and/or imaging agents in cancer therapy and diagnosis.

Systemic delivery of gemcitabine triphosphate via LCP nanoparticles for NSCLC and pancreatic cancer therapy

Nucleoside analogs are a significant class of anti-cancer agent. As prodrugs, they terminate the DNA synthesis upon transforming to their active triphosphate metabolites. We have encapsulated a biologically activate nucleotide analog (i.e. gemcitabine triphosphate (GTP)), instead of the nucleoside (i.e. gemcitabine) derivative, into a novel Lipid/Calcium/Phosphate nanoparticle (LCP) platform. The therapeutic efficacy of LCP-formulated GTP was evaluated in a panel of human non-small-cell lung cancer (NSCLC) and human pancreatic cancer models after systemic administrations. GTP-loaded LCPs induced cell death and arrested the cell cycle in the S phase. In vivo efficacy studies showed that intravenously injected GTP-loaded LCPs triggered effective apoptosis of tumor cells, significant reduction of tumor cell proliferation and cell cycle progression, leading to dramatic inhibition of tumor growth, with little in vivo toxicity. Broadly speaking, the current study offers preclinical proof-of-principle that many active nucleotide or phosphorylated nucleoside analogs could be encapsulated in the LCP nanoplatform and delivered systemically for a wide variety of therapeutic applications.

Self-assembled methoxy poly(ethylene glycol)-cholesterol micelles for hydrophobic drug delivery

To promote the application of methoxy poly(ethylene glycol)-cholesterol (mPEG-Chol), mPEG-Chol was used to prepare core-shell micelles encapsulating poorly water-soluble docetaxel (DTX-PM) by modified cosolvent evaporation method. Approaches to enhance DTX entrapment efficiency (EE) and minimize particle size were investigated in detail, including organic and aqueous phase composition, organic/aqueous phase ratio, and polymer concentration. In optimal formulation, micelles had higher EE (97.6%) and drug loading (4.76%) with the diameter of 13.76 ± 0.68 nm and polydispersity index of 0.213 ± 0.006. Transmission electron microscopy (TEM) showed that the micelles were spherical, and differential scanning calorimetry (DSC) analysis proved that DTX was successfully entrapped into mPEG-Chol micelles. The in vitro cytotoxicity experiments displayed that blank micelles had no effect on the growth of SKOV-3, BXPC-3, A549, and HepG-2 cells, demonstrating that mPEG-Chol was one of the biocompatible biomaterials. The half inhibition concentration of DTX-PM on SKOV-3, BXPC-3, A549, and HepG-2 cells were 10.08, 7.6, 28.37, and 125.75 ng/mL, respectively. DTX-PM had the similar antitumor activity to free DTX, indicating that mPEG-Chol was a promising micellar vector for hydrophobic drug delivery. In addition, this work provided a new and facile approach to prepare drug-loaded micelles with controllable performances.

Somatostatin subtype-2 receptor-targeted metal-based anticancer complexes

Conjugates of a dicarba analogue of octreotide, a potent somatostatin agonist whose receptors are overexpressed on tumor cells, with [PtCl(2)(dap)] (dap = 1-(carboxylic acid)-1,2-diaminoethane) (3), [(η(6)-bip)Os(4-CO(2)-pico)Cl] (bip = biphenyl, pico = picolinate) (4), [(η(6)-p-cym)RuCl(dap)](+) (p-cym = p-cymene) (5), and [(η(6)-p-cym)RuCl(imidazole-CO(2)H)(PPh(3))](+) (6), were synthesized by using a solid-phase approach. Conjugates 3-5 readily underwent hydrolysis and DNA binding, whereas conjugate 6 was inert to ligand substitution. NMR spectroscopy and molecular dynamics calculations showed that conjugate formation does not perturb the overall peptide structure. Only 6 exhibited antiproliferative activity in human tumor cells (IC(50) = 63 ± 2 μM in MCF-7 cells and IC(50) = 26 ± 3 μM in DU-145 cells) with active participation of somatostatin receptors in cellular uptake. Similar cytotoxic activity was found in a normal cell line (IC(50) = 45 ± 2.6 μM in CHO cells), which can be attributed to a similar level of expression of somatostatin subtype-2 receptor. These studies provide new insights into the effect of receptor-binding peptide conjugation on the activity of metal-based anticancer drugs, and demonstrate the potential of such hybrid compounds to target tumor cells specifically.

Fatty acid-RGD peptide amphiphile micelles as potential paclitaxel delivery carriers to α(v)β₃ integrin overexpressing tumors

PURPOSE

To design and synthesize fatty acid-RGD peptide amphiphiles with ADA linker for their potential delivery of hydrophobic drugs like paclitaxel targeted to α(v)β(3) integrin overexpressing tumors.

METHODS

Four amphiphiles - C16 or C18 fatty acid-RGD peptide and ADA linker were designed and synthesized. CMC, size and zeta potential of the amphiphiles were determined. FITC loaded micelles uptake into A2058 melanoma cells was investigated at 4°C and 37°C using confocal microscopy. Paclitaxel was loaded into micelles, their encapsulation efficiency and cytotoxicity of micelles was evaluated. The stability of the micelles was determined using FRET method.

RESULTS

Mass, (1)H NMR and HPLC analysis confirmed the formation of amphiphiles and their purity. Among the amphiphiles, C18-(ADA)(2)-RGD amphiphile exhibited lowest CMC (9.00 ± 1.73 μM) and its micelles had suitable size (194.63 ± 44.86 nm) and zeta potential (0.27 ± 1.96 mV) for targeting. The cellular uptake of the micelles was temperature dependent and the micelles were stable. The IC50 of paclitaxel loaded in micelles decreased 50% in α(v)β(3) integrin overexpressing cells and showed a 4 fold increase in normal cells when compared to free paclitaxel.

CONCLUSION

Amphiphiles of fatty acids-ADA-RGD were synthesized. These amphiphiles formed stable micelles and were effective as targeted delivery carriers to α(v)β(3) integrin overexpressing tumors.

Amorphous amphiphilic P(3HV-co-4HB)-b-mPEG block copolymer synthesized from bacterial copolyester via melt transesterification: nanoparticle preparation, cisplatin-loading for cancer therapy and in vitro evaluation

Cisplatin is a chemotherapeutic agent used against a variety of tumors. We determined the efficacy and bioavailability of cisplatin in the form of cisplatin-loaded self-assembled amphiphilic copolymer nanoparticles (NPs). Non-crystallizing bacterial copolyester was employed as hydrophobic segment to increase drug loading efficiency. Novel amorphous amphiphilic block copolymer P(3HV-co-4HB)-b-mPEG was synthesized from bacterial copolyester poly(3-hydroxyvalerate-co-4-hydroxybutyrate) coupled via transesterification reaction using bis(2-ethylhexanoate) tin catalyst to monomethoxypoly(ethylene glycol). The product was characterized, and core-shell particles with nanometer size range were prepared by emulsification-solvent evaporation method. Transmission electron microscopy (TEM) examination revealed that the NPs took the shape of spheres with inner concealed core of hydrophobic P(3HV-co-4HB) polymer and the outer shell formed by hydrophilic mPEG segment. The in vitro release profile of cisplatin from the core hydrophobic domain showed a sustained release of the drug. TEM and confocal microscopy examination revealed clearly the internalization of cisplatin-loaded NPs into the tumor cells. MTT assay, flow cytometry, western blot and confocal microscopy revealed a suppression effect by the NPs on tumor cell growth, and enhancement of apoptotic process of the tumor cells compared to free drug treated cells. The amorphous polymeric NPs could be effective vehicles for the sustained delivery of toxic anticancer drugs.