Click chemistry functionalized polymeric nanoparticles target corneal epithelial cells through RGD-cell surface receptors

Targeting cancer cells: controlling the binding and internalization of antibody-functionalized capsules

The development of nanoengineered particles, such as polymersomes, liposomes, and polymer capsules, has the potential to offer significant advances in vaccine and cancer therapy. However, the effectiveness of these carriers has the potential to be greatly improved if they can be specifically delivered to target cells. We describe a general method for functionalizing nanoengineered polymer capsules with antibodies using click chemistry and investigate their interaction with cancer cells in vitro. The binding efficiency to cells was found to be dependent on both the capsule-to-cell ratio and the density of antibody on the capsule surface. In mixed cell populations, more than 90% of target cells bound capsules when the capsule-to-target cell ratio was 1:1. Strikingly, greater than 50% of target cells exhibited capsules on the cell surface even when the target cells were present as less than 0.1% of the total cell population. Imaging flow cytometry was used to quantify the internalization of the capsules, and the target cells were found to internalize capsules efficiently. However, the role of the antibody in this process was determined to enhance accumulation of capsules on the cell surface rather than promote endocytosis. This represents a significant finding, as this is the first study into the role antibodies play in internalization of such capsules. It also opens up the possibility of targeting these capsules to cancer cells using targeting molecules that do not trigger an endocytic pathway. We envisage that this approach will be generally applicable to the specific targeting of a variety of nanoengineered materials to cells.

α(V)β(3) integrin-targeted PLGA-PEG nanoparticles for enhanced anti-tumor efficacy of a Pt(IV) prodrug

Targeted delivery of therapeutics to tumor neovasculature is potentially a powerful approach for selective cancer treatment. Integrins are heterodimeric transmembrane proteins involved in cell adhesion and cell signaling, and their expression is commonly upregulated in cancers and inflammatory diseases. The α(v)β(3) integrin is differentially upregulated on angiogenic endothelial cells as well as on many cancer cells. Here we demonstrate the differential targeting of cisplatin prodrug-encapsulated poly(d,l-lactic-co-glycolic acid)-block-polyethylene glycol (PLGA-PEG) nanoparticles (NPs) to the α(v)β(3) integrin on cancer cells using the cyclic pentapeptide c(RGDfK). Cisplatin is one of the most widely used anticancer drugs, and approaches that can improve its therapeutic index are of broad importance. The RGD-targeted Pt(IV)-encapsulated NPs displayed enhanced cytotoxicity as compared to cisplatin administered in its conventional dosage form in model prostate and breast cancer epithelial cells in vitro. Cytotoxicities were also elevated in comparison to those of previously reported systems, a small molecule Pt(IV)-RGD conjugate and a Pt(IV) nanoscale coordination polymer carrying RGD moieties. This result encouraged us also to evaluate the anticancer effect of the new construct in an animal model. The RGD-targeted PLGA-PEG NPs were more efficacious and better tolerated by comparison to cisplatin in an orthotopic human breast cancer xenograft model in vivo.

Targeted polymeric therapeutic nanoparticles: design, development and clinical translation

Polymeric materials have been used in a range of pharmaceutical and biotechnology products for more than 40 years. These materials have evolved from their earlier use as biodegradable products such as resorbable sutures, orthopaedic implants, macroscale and microscale drug delivery systems such as microparticles and wafers used as controlled drug release depots, to multifunctional nanoparticles (NPs) capable of targeting, and controlled release of therapeutic and diagnostic agents. These newer generations of targeted and controlled release polymeric NPs are now engineered to navigate the complex in vivo environment, and incorporate functionalities for achieving target specificity, control of drug concentration and exposure kinetics at the tissue, cell, and subcellular levels. Indeed this optimization of drug pharmacology as aided by careful design of multifunctional NPs can lead to improved drug safety and efficacy, and may be complimentary to drug enhancements that are traditionally achieved by medicinal chemistry. In this regard, polymeric NPs have the potential to result in a highly differentiated new class of therapeutics, distinct from the original active drugs used in their composition, and distinct from first generation NPs that largely facilitated drug formulation. A greater flexibility in the design of drug molecules themselves may also be facilitated following their incorporation into NPs, as drug properties (solubility, metabolism, plasma binding, biodistribution, target tissue accumulation) will no longer be constrained to the same extent by drug chemical composition, but also become in-part the function of the physicochemical properties of the NP. The combination of optimally designed drugs with optimally engineered polymeric NPs opens up the possibility of improved clinical outcomes that may not be achievable with the administration of drugs in their conventional form. In this critical review, we aim to provide insights into the design and development of targeted polymeric NPs and to highlight the challenges associated with the engineering of this novel class of therapeutics, including considerations of NP design optimization, development and biophysicochemical properties. Additionally, we highlight some recent examples from the literature, which demonstrate current trends and novel concepts in both the design and utility of targeted polymeric NPs (444 references).

Orthogonally bifunctionalised polyacrylamide nanoparticles: a support for the assembly of multifunctional nanodevices

Polyacrylamide nanoparticles bearing two orthogonal reactive functionalities were prepared by reverse microemulsion polymerisation. Water-soluble photosensitisers and peptide or carbohydrate moieties were sequentially attached to the new nanospecies by orthogonal conjugations based on copper-catalysed azide-alkyne cycloaddition and isothiocyanate chemistry.

"OA02" peptide facilitates the precise targeting of paclitaxel-loaded micellar nanoparticles to ovarian cancer in vivo

Micellar nanoparticles based on linear polyethylene glycol (PEG) block dendritic cholic acids (CA) copolymers (telodendrimers), for the targeted delivery of chemotherapeutic drugs in the treatment of cancers, are reported. The micellar nanoparticles have been decorated with a high-affinity "OA02" peptide against α-3 integrin receptor to improve the tumor-targeting specificity which is overexpressed on the surface of ovarian cancer cells. "Click chemistry" was used to conjugate alkyne-containing OA02 peptide to the azide group at the distal terminus of the PEG chain in a representative PEG(5k)-CA(8) telodendrimer (micelle-forming unit). The conjugation of OA02 peptide had negligible influence on the physicochemical properties of PEG(5k)-CA(8) nanoparticles and as hypothesized, OA02 peptide dramatically enhanced the uptake efficiency of PEG(5k)-CA(8) nanoparticles (NP) in SKOV-3 and ES-2 ovarian cancer cells via receptor-mediated endocytosis, but not in α-3 integrin-negative K562 leukemia cells. When loaded with paclitaxel, OA02-NPs had significantly higher in vitro cytotoxicity against both SKOV-3 and ES-2 ovarian cancer cells as compared with nontargeted nanoparticles. Furthermore, the in vivo biodistribution study showed OA02 peptide greatly facilitated tumor localization and the intracellular uptake of PEG(5k)-CA(8) nanoparticles into ovarian cancer cells as validated in SKOV3-luc tumor-bearing mice. Finally, paclitaxel (PTX)-loaded OA02-NPs exhibited superior antitumor efficacy and lower systemic toxicity profile in nude mice bearing SKOV-3 tumor xenografts, when compared with equivalent doses of nontargeted PTX-NPs as well as clinical paclitaxel formulation (Taxol). Therefore, OA02-targeted telodendrimers loaded with paclitaxel have great potential as a new therapeutic approach for patients with ovarian cancer.

Stability of Self-Assembled Polymeric Micelles in Serum

The stability of polymeric nanoparticles in serum is critical to their use in drug delivery where dilution after intravenous injection often results in nanoparticle disassembly and drug unloading; however, few investigate this in biologically relevant media. To gain greater insight into nanoparticle stability in blood, the stability of self-assembled polymeric micelles of poly(d,l-lactide-co-2-methyl-2-carboxytrimethylene carbonate)-g-poly(ethylene glycol), P(LA-co-TMCC)-g-PEG, were tested in both serum and individual serum protein solutions. By encapsulating Förster resonance energy transfer pairs and following their release by fluorescence, these micelles demonstrated excellent thermodynamic and kinetic stability in the presence of serum. Further analyses by fast protein liquid chromatography and dynamic light scattering confirmed these data. Moreover, these micelles are compatible with red blood cells, as shown by a hemolysis assay. The stability and compatibility demonstrated in blood suggest that these micelles may be stable in vivo, which is critical for intravenous drug delivery applications. This comprehensive approach to understanding micelle stability and compatibility is broadly applicable.

Antibody-targeted nanoparticles for cancer therapy

In recent years, nanoparticulate-mediated drug delivery research has examined a full spectrum of nanoparticles that can be used in diagnostic and therapeutic cancer applications. A key aspect of this technology is in the potential to specifically target the nanoparticles to diseased cells using a range of molecules, in particular antibodies. Antibody–nanoparticle conjugates have the potential to elicit effective targeting and release of therapeutic targets at the disease site, while minimizing off-target side effects caused by dosing of normal tissues. This article provides an overview of various antibody-conjugated nanoparticle strategies, focusing on the rationale of cell-surface receptors targeted and their potential clinical application.

A novel size-tunable nanocarrier system for targeted anticancer drug delivery

We have developed a nanocarrier drug-delivery system based on micelles formed by a new class of well-defined linear PEGylated two-arm oligomer of cholic acids in aqueous solution. By varying the length of the linear PEG chains and the configuration of cholic acid oligomer, one can easily fine-tune the physicochemical properties of the amphiphilic polymers and the resulting micelles. These include particle size, critical micelle concentration, and drug-loading capacity. High level of hydrophobic anticancer drugs such as PTX, etoposide and SN-38 can be readily loaded into such nanocarriers. The loading capacity of the nanocarrier for PTX (PTX) is extremely high (12.0mg/mL), which is equivalent to 37.5% (w/w) of the total mass of the micelle. PTX-loaded nanocarriers are much more stable than Abraxane (PTX/human serum albumin nanoaggregate) when stored in bovine serum albumin solution or dog plasma. PTX release profile from the micelles is burst-free and sustained over a period of seven days. The anti-tumor activity of PTX-loaded nanocarriers against ovarian cancer cell line in vitro, with continuous drug exposure, is similar to Taxol (formulation of PTX dissolved in Cremophor EL and ethanol) or Abraxane. Targeted drug delivery to tumor site with these novel micelles was demonstrated by near infrared fluorescence (NIRF) imaging in nude mice bearing ovarian cancer xenograft. Furthermore, PTX-loaded nanocarriers demonstrated superior anti-tumor efficacy compared to Taxol at equivalent PTX dose in ovarian cancer xenograft model.

Click chemistry for the synthesis of RGD-containing integrin ligands

In the last few years click chemistry reactions, and in particular copper-catalyzed cycloadditions, have been used intensively for the preparation of new bioconjugate molecules and materials applicable to biomedical and pharmaceutical areas. This review will be focused on conjugates of the tripeptide Arg-Gly-Asp formed by means of click chemistry reactions. This sequence is a well known binding motif for specific transmembrane proteins and is involved in cellular adhesion to the extracellular matrix, allowing the selective recognition of the biomolecule or polymer in which it is incorporated.