Active Targeting Moiety Research Articles

Ligand-directed stearic acid grafted chitosan micelles to increase therapeutic efficacy in hepatic cancer.

Targeted delivery system would be an interesting platform to enhance the therapeutic effect and to reduce the side effects of anticancer drugs. In this study, we have developed lactobionic acid (LA)-modified chitosan-stearic acid (CS-SA) (CSS-LA) to deliver doxorubicin (DOX) to hepatic cancer cells. The average particle size of CSS-LA/DOX was ∼100 nm with a high entrapment efficiency of >95%. Drug release studies showed that DOX release from pH-sensitive micelles is significantly faster at pH 5.0 than at pH 7.4. The LA conjugated micelles showed enhanced cellular uptake in HepG2 and BEL-7402 liver cancer cells than free drug and unconjugated micelles. Consistently, CSS-LA/DOX showed enhanced cell cytotoxicity in these two cell lines. Annexin-V/FITC and PI based apoptosis assay showed that the number of living cells greatly reduced in this group with marked presence of necrotic and apoptotic cells. LA-conjugated carrier induced typical chromatic condensation of cells; membrane blebbing and apoptotic bodies began to appear. In vivo, CSS-LA/DOX showed an excellent tumor regression profile with no toxic side effects. The active targeting moiety, long circulation profile, and EPR effect contributed to its superior anticancer effect in HepG2 based tumor. Our results showed that polymeric micelles conjugated with LA increased the therapeutic availability of DOX in the liver cancer cell based solid tumor without any toxic side effects. The active targeting ligand conjugated nanoparticulate system could be a promising therapeutic strategy in the treatment of hepatic cancers.

Abstract LB-196: Preventing breast cancer metastases with an anti-angiogenic and anticancer RGD-bearing nanomedicine

Abstract Overcoming drug resistance, emerging either on recurring cancer or metastasis, is a major challenge of cancer treatments. The combination of anti-angiogenic agents with chemotherapeutic ones offers a promising therapeutic approach. Such combination can be achieved exploiting the multivalency of polymer therapeutics. We have recently showed that polymer conjugation of paclitaxel (PTX), a potent cytotoxic and anti-angiogenic drug, improved its pharmacokinetic profile. We hypothesized that actively targeting PTX to αvβ3-integrin, presents an attractive therapeutic strategy for breast cancer. Interestingly, overexpression of αvβ3-integrin, occurring on tumor endothelial and some epithelial cells during tumor growth, invasion, and metastasis, was found to correlate with PTX-resistance of breast cancer cells. We designed and synthesized a novel polyglutamic acid (PGA)-PTX-E-[c(RGDfK)2] nano-sized conjugate. Polymer conjugation converted PTX to a water-soluble macromolecule, which passively targeted the tumor tissue exploiting the enhanced permeability and retention (EPR) effect. The E-[c(RGDfK)2] was utilized as an additional active targeting moiety to αvβ3 integrin. PGA is enzymatically-degradable by cathepsin B, leading to PTX release. PGA-PTX-E-[c(RGDfK)2] displayed a potent anti-angiogenic activity, determined by several well-established in vitro assays. Preferential tumor accumulation of the RGD-bearing conjugate in orthotopic mammary tumors inoculated in mice, lead to enhanced antitumor efficacy and a marked decrease in toxicity compared with free PTX. We found that metastasis establishment was dependent on αvβ3-integrin expression as determined in vitro and ex vivo. PGA-PTX-E-[c(RGDfK)2] conjugate inhibited metastatic growth in an experimental breast cancer metastases model in mice. Taken together, inclusion of an active targeting moiety to integrin expressing-cells has the potential to decrease breast cancer metastases establishment by displaying an anti-angiogenic and anticancer activity. Citation Format: Anat Eldar-Boock, Dikla Ben-Shushan, Joaquin Sanchis, Ruth Lupu, Maria J. Vicent, Ronit Satchi-Fainaro. Preventing breast cancer metastases with an anti-angiogenic and anticancer RGD-bearing nanomedicine. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-196. doi:10.1158/1538-7445.AM2014-LB-196

Tuning pharmacokinetics and biodistribution of a targeted drug delivery system through incorporation of a passive targeting component.

Major challenges in the development of drug delivery systems (DDSs) have been the short half-life, poor bioavailability, insufficient accumulation and penetration of the DDSs into the tumor tissue. Understanding the pharmacokinetic (PK) parameters of the DDS is essential to overcome these challenges. Herein we investigate how surface chemistry affects the PK profile and organ distribution of a gold nanoparticle-based DDS containing both a passive and active targeting moiety via two common routes of administration: intravenous and intraperitoneal injections. Using LC/MS/MS, ELISA and INAA we report the half-life, peak plasma concentrations, area under the curve, ability to cross the peritoneal barrier and biodistribution of the nanoconjugates. The results highlight the design criteria for fine-tuning the PK parameters of a targeted drug delivery system that exploits the benefits of both active and passive targeting.

Structure related transport properties and cellular uptake of hyperbranched polyglycerol sulfates with hydrophobic cores

A set of six hydrophobically derivatized polymers based on polyglycerol sulfates have been investigated to determine the influence of scaffold architecture on the encapsulation properties of hydrophobic guests. Each of three block and statistical copolymers has been synthesized with phenyl, naphthyl, and biphenyl substituents in a one-pot procedure. The copolymers have been functionalized with sulfate groups in order to introduce an electrostatically repulsive surface that can stabilize the aggregated carriers. In addition, sulfates provide a highly active targeting moiety for inflammation and cellular uptake. UV measurements show a supramolecular encapsulation of the investigated guest molecules in the low μM range. The transport studies with pyrene and an indocarbocyanine dye further indicated a core–shell-type architecture which provides a distinct amphiphilicity as required for supramolecular guest complexation. The combination of a host functionality with an active sulfate targeting moiety has been used to investigate the structure related cellular transport properties.

Intrinsically active nanobody-modified polymeric micelles for tumor-targeted combination therapy

Various different passively and actively targeted nanomedicines have been designed and evaluated over the years, in particular for the treatment of cancer. Reasoning that the potential of ligand-modified nanomedicines can be substantially improved if intrinsically active targeting moieties are used, we have here set out to assess the in vivo efficacy of nanobody-modified core-crosslinked polymeric micelles containing covalently entrapped doxorubicin. Nanobody-modified polymeric micelles were found to inhibit tumor growth even in the absence of a drug, and nanobody-modified micelles containing doxorubicin were significantly more effective than nanobody-free micelles containing doxorubicin. Based on these findings, we propose that the combination of two therapeutic strategies within one nanomedicine formulation, i.e. the intrinsic pharmacological activity of ligand-modified carrier materials with the cytostatic activity of the incorporated chemotherapeutic agents, is a highly promising approach for improving the efficacy of tumor-targeted combination therapy.

Synthesis and characterization of a poly(lactic-co-glycolic acid) core + poly(N-isopropylacrylamide) shell nanoparticle system

Poly(lactic-co-glycolic acid) (PLGA) is a popular material used to prepare nanoparticles for drug delivery. However, PLGA nanoparticles lack desirable attributes including active targeting abilities, resistance to aggregation during lyophilization, and the ability to respond to dynamic environmental stimuli. To overcome these issues, we fabricated a nanoparticle consisting of a PLGA core encapsulated within a shell of poly(N-isopropylacrylamide). Dynamic light scattering and transmission electron microscope imaging were used to characterize the nanoparticles, while an MTT assay and ELISA suggested biocompatibility in THP1 cells. Finally, a collagen type II binding assay showed successful modification of these nanoparticles with an active targeting moiety.

Nanophotosensitizers toward advanced photodynamic therapy of Cancer

AbstractPhotodynamic therapy (PDT) is a non-invasive treatment modality for selective destruction of cancer and other diseases and involves the colocalization of light, oxygen, and a photosensitizer (PS) to achieve photocytotoxicity. Although this therapeutic method has considerably improved the quality of life and life expectancy of cancer patients, further advances in selectivity and therapeutic efficacy are required to overcome numerous side effects related to classical PDT. The application of nanoscale photosensitizers (NPSs) comprising molecular PSs and nanocarriers with or without other biological/photophysical functions is a promising approach for improving PDT. In this review, we focus on four nanomedical approaches for advanced PDT: (1) nanocarriers for targeted delivery of PS, (2) introduction of active targeting moieties for disease-specific PDT, (3) stimulus-responsive NPSs for selective PDT, and (4) photophysical improvements in NPS for enhanced PDT efficacy. Highlights► Conservation of normal tissues demands non-invasive therapeutic methods. ► PDT is a light-activated, non-invasive modality for selective destruction of cancers.► Success of PDT requires further advances to overcome the limitations of classical PDT. ►Nanophotosensitizers help improve target selectivity and therapeutic efficacy of PDT.

Vascular-targeted nanotherapy for obesity: Unexpected passive targeting mechanism to obese fat for the enhancement of active drug delivery

We previously reported that nanoparticles (NPs) modified with a prohibitin-homing peptide ligand via a short PEG2kDa-spacer could deliver its pay-load into the cytoplasm of endothelial cells in murine adipose tissue and escape from endosomes/lysosomes in vitro. We herein report, for the first time, on a dual-targeting strategy for mediating the enhanced targeting activity of NPs to adipose endothelial cells in diet-induced obesity (DIO). The targeted accumulation of prohibitin-targeted nanoparticles (PTNP), modified with a peptide ligand via a long PEG-linker, was significantly increased in white fat vessels of normal healthy mice compared to the other non-PEGylated targeted NPs, whereas the undesired accumulation of PTNP in the liver was considerably reduced. These results demonstrate that the PEGylation of targeted NPs is a critical factor in maximizing the in vivo targeted delivery of NPs and can be attributed to a significant decrease in recognition by the reticuloendothelial system. After systemic administration to DIO mice, PTNP exclusively accumulated in both adipose vessels and angiogenic clusters of obese fat cells. Surprisingly, PEGylated NPs with no active targeting moieties also accumulated in these clusters, demonstrating that the nanoscaled carriers passively accumulate in clusters via a mechanism similar to that for the enhanced permeability and retention effect, as has been well established in tumor targeting. Therefore, the enhanced delivery of PTNP appears to be mediated by both passive accumulation to angiogenic regions and active recognition by endothelial cells. Thus, the systemic administration of a proapoptotic peptide with the delivery via PTNP significantly reduced the body weight of DIO mice, as evidenced by the targeted ablation of adipose endothelial cells. These findings are potentially useful in terms of the design and development of vascular-targeted nanotherapy in the effective control of obesity.

Abstract 5225: Correlation between αvβ3 integrin expression, paclitaxel resistance and RGD-bearing conjugate efficacy

Abstract Overcoming drug resistance, emerging either on recurring cancer or metastasis, is a major target of cancer treatments. The combination of anti-angiogenic therapy with cytotoxic therapy offers a promising therapeutic approach. Paclitaxel (PTX) is a widely-used potent cytotoxic drug, which also exhibits anti-angiogenic activity at low doses. The use of the hydrophobic PTX to its full potential is limited by severe side effects, caused by the drug and its solubilizing agents. Integrins play a key role in cell matrix interactions. The highly restricted expression of integrin αvβ3, overexpressed on tumor endothelial and some epithelial cells, during tumor growth, invasion, and metastasis present an interesting molecular target for metastatic breast tumors. In addition, PTX acquired resistance correlated with integrin αvβ3 overexpression on breast cancer cells. We designed and synthesized a novel polyglutamic acid (PGA)-PTX-E-[c(RGDfK)2] nano-scaled conjugate. Polymer conjugation converted PTX to a water-soluble macromolecule, which passively targeted the tumor tissue exploiting the enhanced permeability and retention (EPR) effect, while extravasating via the leaky tumor neovasculature. The E-[c(RGDfK)2] enhanced the effects previously seen for PGA-PTX alone, utilizing the additional active targeting to the αvβ3 integrin. PGA is enzymatically-degradable by cathepsin B, leading to PTX release. PGA-PTX-E-[c(RGDfK)2] displayed a potent anti-angiogenic therapy, determined by several, well-established, in vitro assays. Mice bearing orthotopic mammary tumors demonstrated preferential tumor accumulation of the RGD-bearing conjugate, leading to enhanced antitumor efficacy and a marked decreased in toxicity compared with free PTX. The correlation between αvβ3 integrin expression on tumor cells and acquired PTX-resistance was determined by in vitro manipulation of αvβ3 overexpressing-cells and by examining subsets of primary versus metastatic or recurring tumors of PTX-treated patients as well as free and conjugated-PTX-treated tumor-bearing mice. Taken together, our conjugate alters the pharmacokinetics of free PTX. Inclusion of an active targeting moiety to integrin expressing-cells, have the potential to manipulate and overcome acquired drug resistance, which will hopefully warrant it as a novel targeted, anti-angiogenic and anticancer therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5225. doi:1538-7445.AM2012-5225

Multistage Nanovectors: From Concept to Novel Imaging Contrast Agents and Therapeutics

Over the last few decades a great variety of nanotechnology based platforms have been synthesized and fabricated to improve the delivery of active compounds to a disease site. Nanoparticles currently used in the clinic, and the majority of nanotherapeutics/nanodiagnostics under investigation, accommodate single- or multiple- functionalities on the same entity. Because many heterogeneous biological barriers can prevent therapeutic and imaging agents from reaching their intended targets in sufficient concentrations, there is an emerging requirement to develop a multimodular nanoassembly, in which different components with individual specific functions act in a synergistic manner. The multistage nanovectors (MSVs) were introduced in 2008 as the first system of this type. It comprises several nanocomponents or "stages", each of which is designed to negotiate one or more biological barriers. Stage 1 mesoporous silicon particles (S1MPs) were rationally designed and fabricated in a nonspherical geometry to enable superior blood margination and to increase cell surface adhesion. The main task of S1MPs is to efficiently transport nanoparticles that are loaded into their porous structure and to protect them during transport from the administration site to the disease lesion. Semiconductor fabrication techniques including photolithography and electrochemical etching allow for the exquisite control and precise reproducibility of S1MP physical characteristics such as geometry and porosity. Furthermore, S1MPs can be chemically modified with negatively/positively charged groups, PEG and other polymers, fluorescent probes, contrast agents, and biologically active targeting moieties including antibodies, peptides, aptamers, and phage. The payload nanoparticles, termed stage 2 nanoparticles (S2NPs), can be any currently available nanoparticles such as liposomes, micelles, inorganic/metallic nanoparticles, dendrimers, and carbon structures, within the approximate size range of 5-100 nm in diameter. Depending upon the physicochemical features of the S1MP (geometry, porosity, and surface modifications), a variety of S2NPs or nanoparticle "cocktails" can be loaded and efficiently delivered to the disease site. As demonstrated in the studies reviewed here, once the S2NPs are loaded into the S1MPs, a variety of novel properties emerge, which enable the design of new and improved imaging contrast agents and therapeutics. For example, the loading of the MRI Gd-based contrast agents onto hemispherical and discoidal S1MPs significantly increased the longitudal relaxivity (r1) to values of up to 50 times larger than those of clinically available gadolinium-based agents (~4 mM(-1) s(-1)/Gd(3+) ion). Furthermore, administration of a single dose of MSVs loaded with neutral nanoliposomes containing small interfering RNA (siRNA) targeted against the EphA2 oncoprotein enabled sustained EphA2 gene silencing for at least 21 days. As a result, the tumor burden was reduced in an orthotopic mouse model of ovarian cancer. We envision that the versatility of the MSV platform and its emerging properties will enable the creation of personalized solutions with broad clinical implications within and beyond the realm of cancer theranostics.

Pulmonary Formulations: What Remains to be Done?

Significant advances have been made in the last 50 years in developing safe and efficacious aerosol formulations for pulmonary delivery. The key to future innovation may lie at the interface between biology and particle engineering. Improved understanding of biological processes including particle clearance, cellular targeting, intracellular trafficking, and drug absorption are needed to better design formulations that deliver to the "target" with the optimal balance of pharmacodynamic, pharmacokinetic, and safety profiles. More specifically, continued advances are needed in the development of: (1) controlled release formulations; (2) formulations with improved regional targeting within the lungs (e.g., airway versus alveoli and vice versa); (3) formulations containing active targeting moieties; (4) formulation strategies for improving the systemic bioavailability of inhaled macromolecules; (5) formulation strategies for delivering macromolecules, including siRNA and DNA into cells; and (f) formulations with improved dose consistency. It is likely that such innovation will require the development of novel excipients and particle engineering strategies. Future innovation must also take into the account the changing marketplace and the diverse set of customers (patient, healthcare professional, heath authorities, payers, and politicians) who must be satisfied. The pharmacoeconomics of new delivery systems will be closely scrutinized, so it is imperative that cost factors be taken into account. Otherwise, the new technology option may overshoot the evolving inhalation marketplace.

Introduction 1000 Years of Pharmaceutical Aerosols: What Remains to Be Done?

Introduction 1000 Years of Pharmaceutical Aerosols: What Remains to Be Done?

VIP-grafted sterically stabilized phospholipid nanomicellar 17-allylamino-17-demethoxy geldanamycin: A novel targeted nanomedicine for breast cancer

17-Allylamino-17-demethoxy geldanamycin (17-AAG), an inhibitor of heat shock protein 90 (Hsp90) function, is being developed as antitumor drug in patients with breast cancer. However, water-insolubility and hepatotoxicity limit its use. The purpose of this study was to begin to address these issues by determining whether 17-AAG can be formulated in long-circulating (PEGylated), biocompatible and biodegradable sterically stabilized phospholipid nanomicelles (SSM) to which vasoactive intestinal peptide (VIP) was grafted as an active targeting moiety and, if so, whether these nanomicelles are cytotoxic to MCF-7 human breast cancer cells. We found that particle size of 17-AAG loaded in VIP surface-grafted SSM was 16 ± 1 nm and drug content was 97 ± 2% (300 μg/ml). Cytotoxicity of 17-AAG loaded in VIP surface-grafted SSM to MCF-7 cells was significantly higher than that of 17-AAG loaded in non-targeted SSM ( p < 0.05) and similar to that of 17-AAG dissolved in dimethylsulfoxide. Collectively, these data demonstrate that 17-AAG is solubilized at therapeutically relevant concentrations in actively targeted VIP surface-grafted SSM. Cytotoxicity of these nanomicelles to MCF-7 cells is retained implying high affinity VIP receptors overexpressed on these cells mediate, in part, their intracellular uptake thereby amplifying drug potency. We propose that 17-AAG loaded in VIP surface-grafted SSM should be further developed as actively targeted nanomedicine for breast cancer.

Prodrugs of Anthracyclines in Cancer Chemotherapy

Designing and developing truly tumor-specific prodrugs remains a challenge in the field of cancer chemotherapy. Active targeting strategies, on the one hand, aim at exploiting membrane-associated receptors or antigens for drug delivery; on the other hand, the enhanced vascular permeability and retention of macromolecules in tumor tissue substantiates the concept of passive targeting. Consequently, research efforts have concentrated on conjugating anticancer agents with a wide spectrum of carriers including antibodies, peptides, serum proteins, and synthetic polymers. Conversely, low-molecular weight prodrugs of anticancer agents have been developed that do not bear an active or passive targeting moiety, but are activated by tumor-associated enzymes at the tumor site. Anthracyclines probably represent the class of anticancer agents that has been most widely used for the development of prodrugs. This overview gives an update of the various low- and high-molecular weight prodrugs of anthracyclines, e.g. with antibodies, peptides, carbohydrates, serum proteins or synthetic polymers, that have been developed over the past 20 years and that exemplify the salient features of a respective drug delivery system. A detailed description will be dedicated to anthracycline prodrugs that have reached an advanced stage of preclinical testing or that have entered clinical trials.

All d-VIP mitigates vasodilation elicited by l-VIP, micellar l-VIP and micellar PACAP 1–38, but not PACAP 1–38, in vivo

The purpose of this study was to determine whether all d-vasoactive intestinal peptide (VIP), an inactive optical isomer of l-VIP, modulates the vasorelaxant effects of human l-VIP and pituitary adenylate cyclase activating peptide (PACAP) 1–38, two ubiquitous and pleiotropic neuropeptides that activate VPAC 1 and VPAC 2, two VIP subtype receptors, in the intact peripheral microcirculation. Using intravital microscopy, we found that suffusion of all d-VIP had no significant effects on arteriolar diameter in the intact hamster cheek pouch. However, all d-VIP significantly attenuated l-VIP-induced vasodilation in a concentration-dependent fashion ( P < 0.05). Likewise, all d-VIP significantly attenuated the vasorelaxant effects of l-VIP associated with sterically stabilized phospholipid micelles (SSM; P < 0.05). Although all d-VIP had no significant effects on l-PACAP 1–38-induced vasodilation, it abrogated PACAP 1–38 in SSM-induced responses ( P < 0.05). The effects of all d-VIP were specific because it had no significant effects on acetylcholine-, nitroglycerin- and bradykinin-induced vasodilation. Taken together, these data indicate that all d-VIP attenuates the vasorelaxant effects of random coil and α-helix l-VIP as well as those of α-helix but not random coil PACAP in the intact peripheral microcirculation in a specific fashion. These effects are mediated, most likely, through interactions with VPAC 1/VPAC 2 receptors. We suggest that all d-VIP could be exploited as a novel, safe and active targeting moiety of VPAC 1/VPAC 2 receptors in vivo.