Functionalization of the PEG Corona of Nanoparticles by Clip Photochemistry in Water: Application to the Grafting of RGD Ligands on PEGylated USPIO Imaging Agent.

The fast development of nanomedicines requires more and more reliable chemical tools in order to accurately design materials and control the surface properties of the nano-objects used in biomedical applications. In this study we describe a smooth and simple photografting technique, i.e., the clip photochemistry, that allows the introduction of molecules of interest in inert polymers or on stealth nanoparticles directly in aqueous solution. First we developed the methodology on polyethylene glycol (PEG) and looked for critical parameters of the process (irradiation times, concentrations, washings) by using several molecular probes and adapted analytical techniques ((19)F qNMR, EA, LSC). We found that the clip photochemistry in water is a robust and efficient method to functionalize PEG. Second we applied it on PEGylated USPIO (USPIO-PEG) magnetic resonance imaging agent and succeeded in introducing RGD peptide and homemade peptidomimetics on their PEG segments. The magnetic abilities of the conjugated nanoparticles were unchanged by the derivatization process as evidenced by their relaxometric properties and their NMRD profile. When tested on Jurkat lymphocyte T Cells, which express αvß3 integrins, the USPIO conjugated with RGD ligands leads to an increase of the transverse relaxation rate (R2) by a factor 10 to 14 as compared to USPIO-PEG. Consequently, it makes them good candidates for targeted imaging technology in cancer therapy.

Self-assembling doxorubicin-tocopherol succinate prodrug as a new drug delivery system: synthesis, characterization, and in vitro and in vivo anticancer activity.

Self-assembled prodrugs forming nanoaggregates are a promising approach to enhance the antitumor efficacy and to reduce the toxicity of anticancer drugs. To achieve this goal, doxorubicin was chemically conjugated to d-α-tocopherol succinate through an amide bond to form N-doxorubicin-α-d-tocopherol succinate (N-DOX-TOS). The prodrug self-assembled in water into 250 nm nanostructures when stabilized with d-α-tocopherol poly(ethylene glycol) 2000 succinate. Cryo-TEM analysis revealed the formation of nanoparticles with a highly ordered lamellar inner structure. NMR spectra of the N-DOX-TOS nanoparticles indicated that N-DOX-TOS is located in the core of the nanoparticles while PEG chains and part of the tocopherol are in the corona. High drug loading (34% w/w) and low in vitro drug release were achieved. In vitro biological assessment showed significant anticancer activity and temperature-dependent cellular uptake of N-DOX-TOS nanoparticles. In vivo, these nanoparticles showed a greater antitumor efficacy than free DOX. N-DOX-TOS nanoparticles might have the potential to improve DOX-based chemotherapy.

Pharmacological characterization of 7-(4-(Piperazin-1-yl)) ciprofloxacin derivatives: antibacterial activity, cellular accumulation, susceptibility to efflux transporters, and intracellular activity.

PURPOSE: To evaluate pharmacological properties (antibacterial activity; accumulation in phagocytic cells; activity against intracellular bacteria; susceptibility to fluoroquinolone efflux transporters) of ciprofloxacin derivatives modified at C-7 of the piperazine ring. METHODS: N-acetyl- (1), N-benzoyl- (2), N-ethyl- (3), and N-benzyl- (4) ciprofloxacin were synthesized. MICs against Escherichia coli and Staphylococcus aureus were determined following CLSI guidelines. Cellular accumulation, subcellular distribution, and intracellular activity (towards S. aureus and Listeria monocytogenes) were determined in J774 mouse macrophages. Efflux in bacteria (NorA [S. aureus], Lde [L. monocytogenes]) and in macrophages (Mrp4) was assessed using the corresponding inhibitors reserpine and gemfibrozil, respectively. RESULTS: All derivatives were active, though less than ciprofloxacin. 2 and 3 accumulated 2-3 fold more than ciprofloxacin in mouse macrophages but remained substrates for efflux by Mrp4. 4 was insensitive to NorA and Lde, accumulated approx 50-fold more than ciprofloxacin in macrophages, was barely affected by Mrp4, localized in the soluble fraction of cells, and was equipotent to ciprofloxacin against intracellular bacteria. CONCLUSIONS: Benzyl substitution at C7 markedly affects the pharmacological profile of ciprofloxacin with respect to recognition by efflux transporters and cellular accumulation. N-benzyl-ciprofloxacin may serve as basis for designing molecules with higher intrinsic activity while remaining poorly susceptible to efflux.

Synthesis of poly(lactide-co-glycolide-co-ε-caprolactone)-graft-mannosylated poly(ethylene oxide) copolymers by combination of "clip" and "click" chemistries.

Poly(lactide-co-glycolide) (PLGA) is extensively used in pharmaceutical applications, for example, in targeted drug delivery, because of biocompatibility and degradation rate, which is easily tuned by the copolymer composition. Nevertheless, synthesis of sugar-labeled amphiphilic copolymers with a PLGA backbone is quite a challenge because of high sensitivity to hydrolytic degradation. This Article reports on the synthesis of a new amphiphilic copolymer of PLGA grafted by mannosylated poly(ethylene oxide) (PEO). A novel building block, that is, α-methoxy-ω-alkyne PEO-clip-N-hydroxysuccinimide (NHS) ester, was prepared on purpose by photoreaction of a diazirine containing molecular clip. This PEO block was mannosylated by reaction of the NHS ester groups with an aminated sugar, that is, 2-aminoethyl-α-d-mannopyroside. Then, the alkyne ω-end-group of PEO was involved in a copper alkyne- azide coupling (CuAAC) with the pendent azides of the aliphatic copolyester. The targeted mannose-labeled poly(lactide-co-glycolide-co-ε-caprolactone)-graft-poly(ethylene oxide) copolymer was accordingly formed. Copolymerization of d,l-lactide and glycolide with α-chloro-ε-caprolactone, followed by substitution of chlorides by azides provided the azido-functional PLGA backbone. Finally, micelles of the amphiphilic mannosylated graft copolymer were prepared in water, and their interaction with Concanavalin A (ConA), a glyco-receptor protein, was studied by quartz crystal microbalance. This study concluded to the prospect of using this novel bioconjugate in targeted drug delivery.

"Clip" and "click" chemistries combination: toward easy PEGylation of degradable aliphatic polyesters.

α-Methoxy-ω-alkyne poly(ethylene glycol) (PEG) was tagged with pendent N-hydroxy-succinimidyl activated esters by photografting of a molecular clip. This easily synthesized heterofunctional PEG was found to be a versatile building block for (i) conjugation with an amino derivative and (ii) grafting to azido functional aliphatic polyesters backbone by Huisgen's 1,3-dipolar cycloaddition. This original combination of "clip" and "click" reactions provides a versatile and straightforward pathway for the synthesis of functional amphiphilic and degradable copolymers valuable for biomedical applications such as in drug-delivery.

Ultrasmall particle of iron oxide--RGD peptidomimetic conjugate: synthesis and characterisation.

Ultrasmall particles of iron oxide (USPIOs) coated with 3,3'-bis(phosphonate)propionic acid were covalently coupled to a home-made Arg-Gly-Asp (RGD) peptidomimetic molecule via a short oligoethylene-glycol (OEG) spacer. The conjugation rate was measured by X-ray photoelectron spectroscopy (XPS). The particle size and magnetic characteristics were kept. Our novel conjugate targeted efficiently Jurkat cells (increase of 229% vs the control).

Light induced functionalization of PCL-PEG block copolymers for the covalent immobilization of biomolecules.

Functionalized poly-epsilon-caprolactone-block-polyethyleneglycol (PCL-PEG) amphiphilic copolymers were prepared to be constituents of nanocarriers used for the targeting of specific cells. Hence, we conceived a smooth and simple photografting methodology on these copolymers using a bifunctional molecular clip (O-succinimidyl-4-(p-azido-phenyl)butanoate). We prepared PCL-PEGs with pendent N-hydroxysuccinimide esters and studied the grafting with 3H-lysine, which radioactivity was counted by LSC. Several parameters were investigated, such as behavior of homopolymers, initial concentrations, irradiation, and incubation durations. Evidences of a "PEG directed photografting" are discussed and this selectivity could be improved by a selective solvent technique. The photografting on different PCL-PEGs revealed a dependency of the rates to the crystallinity of the copolymers. Several controls by SEC, DLS, and TEM of the treated copolymers were realized. Lastly, the coupling of alpha-D-mannopyranoside ligand was performed, reaching amounts of 5400 nmol/g of PCL-PEG. This derivatized PCL-PEG enters in the preparation of nanocarriers used for the targeting of antigen presenting cells.

A graftable LDV peptidomimetic: design, synthesis and application to a blood filtration membrane.

A graftable LDV (Leu-Asp-Val) peptidomimetic molecule (B-c) has been prepared from 3-(5-amino-2-hydroxy)phenyl-propionic acid, as alpha(4)beta(1) (VLA-4) integrin ligand. For that purpose, the mechanism of 3-(4-azidophenyl)propionic acid rearrangement has been revisited. Activation of Durapore DVPP-hydrophilic membrane, by surface wet chemistry using triazine trifluoride, followed by covalent coupling of B-c produced a modified filter (0.8% of derivatisation from XPS analysis) with improved capacity of leukocyte retention.

Delivery of siRNA targeting tumor metabolism using non-covalent PEGylated chitosan nanoparticles: Identification of an optimal combination of ligand structure, linker and grafting method.

PEGylated chitosan-based nanoparticles offer attractive platforms for siRNA cocktail delivery into tumors. Still, therapeutic efficacy requires us to select a rational combination of siRNAs and an efficient tumor delivery after systemic administration. Here, we showed that non-covalent PEGylation of chitosan-based nanoparticles loaded with siRNA targeting two key transporters of energy fuels for cancer cells, namely the lactate transporter MCT1 and the glutamine transporter ASCT2, could lead to significant antitumor effects. As a ligand, we tested variations of the prototypical RGD peptidomimetic (RGDp). A higher siRNA delivery was obtained with naphthyridine-containing RGDp randomly conjugated on the PEG chain by clip photochemistry and the use of a lipophilic linker than when using traditional chain-end grafting and RGDp with a hydrophilic linker. The antiproliferative effects resulting from ASCT2 and MCT1 silencing were validated separately in vitro in conditions mimicking specific metabolic profiles of cancer cells and in vivo upon concomitant delivery. The combination of those siRNA and the selected components of targeted RGDp nanoparticles led to a dramatic tumor growth inhibition upon peri-tumoral but also systemic administration in mice. Altogether these data emphasize the convenience of using non-covalent PEGylated chitosan particles to produce sheddable stealth protection compatible with an efficient siRNA delivery in tumors.

Intracellular siRNA delivery dynamics of integrin-targeted, PEGylated chitosan-poly(ethylene imine) hybrid nanoparticles: A mechanistic insight.

Integrin-targeted nanoparticles are promising for the delivery of small interfering RNA (siRNA) to tumor cells or tumor endothelium in cancer therapy aiming at silencing genes essential for tumor growth. However, during the process of optimizing and realizing their full potential, it is pertinent to gain a basic mechanistic understanding of the bottlenecks existing for nanoparticle-mediated intracellular delivery. We designed αvß3 integrin-targeted nanoparticles by coupling arginine-glycine-aspartate (RGD) or RGD peptidomimetic (RGDp) ligands to the surface of poly(ethylene glycol) (PEG) grafted chitosan-poly(ethylene imine) hybrid nanoparticles. The amount of intracellular siRNA delivered by αvß3-targeted versus non-targeted nanoparticles was quantified in the human non-small cell lung carcinoma cell line H1299 expressing enhanced green fluorescent protein (EGFP) using a stem-loop reverse transcription quantitative polymerase chain reaction (RT-qPCR) approach. Data demonstrated that the internalization of αvß3-targeted nanoparticles was highly dependent on the surface concentration of the ligand. Above a certain threshold concentration, the use of targeted nanoparticles provided a two-fold increase in the number of siRNA copies/cell, subsequently resulting in as much as 90% silencing of EGFP at well-tolerated carrier concentrations. In contrast, non-targeted nanoparticles mediated low levels of gene silencing, despite relatively high intracellular siRNA concentrations, indicating that these nanoparticles might end up in late endosomes or lysosomes without releasing their cargo to the cell cytoplasm. Thus, the silencing efficiency of the chitosan-based nanoparticles is strongly dependent on the uptake and the intracellular trafficking in H1299 EGFP cells, which is critical information towards a more complete understanding of the delivery mechanism that can facilitate the future design of efficient siRNA delivery systems.

Targeted nanoparticles with novel non-peptidic ligands for oral delivery.

Orally administered targeted nanoparticles have a large number of potential biomedical applications and display several putative advantages for oral drug delivery, such as the protection of fragile drugs or modification of drug pharmacokinetics. These advantages notwithstanding, oral drug delivery by nanoparticles remains challenging. The optimization of particle size and surface properties and targeting by ligand grafting have been shown to enhance nanoparticle transport across the intestinal epithelium. Here, different grafting strategies for non-peptidic ligands, e.g., peptidomimetics, lectin mimetics, sugars and vitamins, that are stable in the gastrointestinal tract are discussed. We demonstrate that the grafting of these non-peptidic ligands allows nanoparticles to be targeted to M cells, enterocytes, immune cells or L cells. We show that these grafted nanoparticles could be promising vehicles for oral vaccination by targeting M cells or for the delivery of therapeutic proteins. We suggest that targeting L cells could be useful for the treatment of type 2 diabetes or obesity.

Drug delivery to inflamed colon by nanoparticles: comparison of different strategies.

For inflammatory bowel disease (IBD) treatment, local delivery of molecules loaded in nanoparticles to the inflamed colon could be a promising strategy. The aim of this study was to investigate how drug-loaded polymeric nanoparticles target the site of inflammation and to analyse the influence of different colon-specific delivery strategies. Three different polymeric nanoparticles were formulated using ovalbumin (OVA) as a model drug. pH-sensitive nanoparticles were made with Eudragit(®) S100. Mucoadhesive nanoparticles were created with trimethylchitosan (TMC). A mix of polymers, PLGA, PEG-PLGA and PEG-PCL, were used to obtain a sustained drug delivery. Furthermore, ligands targeting immune cells (i.e. mannose) or the inflamed colon (i.e. a specific peptide) were grafted on the PEG chain of PCL. Interaction of nanoparticles with the intestinal epithelium was explored using Caco-2 monolayers designed to mimic an inflamed epithelium and then visualized using confocal laser microscopy. TMC nanoparticles had the highest apparent permeability for OVA in the untreated model. However, in the inflamed model, there were no difference between TMC, PLGA-based and Eudragit(®) nanoparticles. The uptake of nanoparticles in the inflamed mouse colon was assessed in a horizontal diffusion chamber. Mannose-grafted PLGA nanoparticles showed the highest accumulation of OVA in inflamed colon. Based on these results, active targeting of macrophages and dendritic cells may be a promising approach for targeting the colon in IBD.

Targeting of tumor endothelium by RGD-grafted PLGA-nanoparticles.

The destruction of the neovessels in solid tumors can cause the death of tumor cells resulting from the lack of oxygen and nutrients. Peculiarities of the tumor vasculature, however, also position angiogenic endothelial cells as obvious targets to address cytotoxic drugs into the tumor. In particular, the identification of a three-amino acids sequence, arginine-glycine-aspartate (RGD), as a fundamental recognition site for proliferating endothelial attachment to the extracellular matrix leads to the development of tumor-targeting ligands for nanoparticles. The RGD peptide can target the α(v)ß(3) integrin overexpressed by the tumor endothelium, and thereby increases the accumulation of drug-loaded RGD-grafted nanoparticles. RGD-nanoparticles may thus extravasate more efficiently and enter the tumor via the enhanced permeability and retention (EPR) effect. This combination of active and passive processes leads to the penetration of nanoparticles into the tumor tissue, followed by cellular uptake and intracellular delivery of the cytotoxic payload. Since cancer cells may also express α(v)ß(3) integrin, the entrapping of RGD-nanoparticles into the tumor interstitial fluid may yet be facilitated through direct binding to cancer cells. Here, we describe methods used for the preparation of RGD-nanoparticles and for the validation of their potential of tumor endothelium targeting both in vitro and in vivo. We also illustrate how RGD-nanoparticles may be more suited than nontargeted modalities for the tumor delivery of poorly soluble and/or highly cytotoxic drugs, using different mouse tumor xenograft models.

Targeting of tumor endothelium by RGD-grafted PLGA-nanoparticles loaded with paclitaxel.

Paclitaxel (PTX)-loaded PEGylated PLGA-based nanoparticles (NP) have been previously described as more effective in vitro and in vivo than taxol. The aim of this study was to test the hypothesis that our PEGylated PLGA-based nanoparticles grafted with the RGD peptide or RGD-peptidomimetic (RGDp) would target the tumor endothelium and would further enhance the anti-tumor efficacy of PTX. The ligands were grafted on the PEG chain of PCL-b-PEG included in the nanoparticles. We observed in vitro that RGD-grafted nanoparticles were more associated to human umbilical vein endothelial cells (HUVEC) by binding to alpha(v)beta(3) integrin than non-targeted nanoparticles. Doxorubicin was also used to confirm the findings observed for PTX. In vivo, we demonstrated the targeting of RGD and RGDp-grafted nanoparticles to tumor vessels as well as the effective retardation of TLT tumor growth and prolonged survival times of mice treated by PTX-loaded RGD-nanoparticles when compared to non-targeted nanoparticles. Hence, the targeting of anti-cancer drug to tumor endothelium by RGD-labeled NP is a promising approach.

Targeting nanoparticles to M cells with non-peptidic ligands for oral vaccination.

The presence of RGD on nanoparticles allows the targeting of beta1 integrins at the apical surface of human M cells and the enhancement of an immune response after oral immunization. To check the hypothesis that non-peptidic ligands targeting intestinal M cells or APCs would be more efficient for oral immunization than RGD, novel non-peptidic and peptidic analogs (RGD peptidomimitic (RGDp), LDV derivative (LDVd) and LDV peptidomimetic (LDVp)) as well as mannose were grafted on the PEG chain of PCL-PEG and incorporated in PLGA-based nanoparticles. RGD and RGDp significantly increased the transport of nanoparticles across an in vitro model of human M cells as compared to enterocytes. RGD, LDVp, LDVd and mannose enhanced nanoparticle uptake by macrophages in vitro. The intraduodenal immunization with RGDp-, LDVd- or mannose-labeled nanoparticles elicited a higher production of IgG antibodies than the intramuscular injection of free ovalbumin or intraduodenal administration of either non-targeted or RGD-nanoparticles. Targeted formulations were also able to induce a cellular immune response. In conclusion, the in vitro transport of nanoparticles, uptake by macrophages and the immune response were positively influenced by the presence of ligands at the surface of nanoparticles. These targeted-nanoparticles could thus represent a promising delivery system for oral immunization.

Surface functionalization of a poly(butylene terephthalate) (PBT) melt-blown filtration membrane by wet chemistry and photo-grafting.

The surface functionalization of PBT melt-blown membrane, making up a whole filter of blood components, was achieved via two methods. Hydroxyl chain-end activation by tosylation (method A), followed by coupling of F- and (3)H-tagged molecules (probes), led to 1% of surface derivatization (XPS) and 290 pmol/cm(2) of lysine fixation (LSC). Deposition of O-succinimidyl 4-(p-azido-phenyl)butanoate ("molecular clip") and 2 h irradiation at 254 nm led to the implanting of activated ester functions, randomly on the polymer surface (method B). Further coupling of F- and (3)H-probes by wet chemistry gave highly functionalized surface (4% by XPS and 1000 pmol/cm(2) by LSC). However, control experiments showed that about 80% of the surface derivatization resulted from the UV treatment alone. Thus, the effect of UV irradiation on PBT membrane was systematically studied and analyzed by XPS, contact angle measurements, GPC and surface reactivity assays. The optimized conditions of "molecular clip" photo-grafting (negligible polymer photo-oxidation/photo-degradation) led to the covalent fixation of 45 pmol/cm(2) of (3)H-probe. Throughout our study, the behaviour of PBT melt-blown membrane was compared to PBT film and PET track-etched membrane similarly treated. Lastly, the method B was applied to couple GRGDS peptide on the PBT membrane; this material showed improved properties of leukocyte depletion in buffy coat filtration experiments.

PEGylated PLGA-based nanoparticles targeting M cells for oral vaccination.

To improve the efficiency of orally delivered vaccines, PEGylated PLGA-based nanoparticles displaying RGD molecules at their surface were designed to target human M cells. RGD grafting was performed by an original method called "photografting" which covalently linked RGD peptides mainly on the PEG moiety of the PCL-PEG, included in the formulation. First, three non-targeted formulations with size and zeta potential adapted to M cell uptake and stable in gastro-intestinal fluids, were developed. Their transport by an in vitro model of the human Follicle associated epithelium (co-cultures) was largely increased as compared to mono-cultures (Caco-2 cells). RGD-labelling of nanoparticles significantly increased their transport by co-cultures, due to interactions between the RGD ligand and the beta(1) intregrins detected at the apical surface of co-cultures. In vivo studies demonstrated that RGD-labelled nanoparticles particularly concentrated in M cells. Finally, ovalbumin-loaded nanoparticles were orally administrated to mice and induced an IgG response, attesting antigen ability to elicit an immune response after oral delivery.