Nanoencapsulation of a Far-Red Absorbing Phthalocyanine into Poly(benzylmalate) Biopolymers and Modulation of Their Photodynamic Efficiency.

Two different poly(benzylmalate) biopolymers, a hydrophobic non-PEGylated (PMLABe73) and an amphiphilic PEGylated derivative (PEG42-b-PMLABe73), have been used to encapsulate a phthalocyanine chosen for its substitution pattern that is highly suitable for photodynamic therapy. Different phthalocyanine/(co)polymers ratios have been used for the nanoprecipitation. A set of six nanoparticles has been obtained. If the amphiphilic PEGylated copolymer proved to be slightly more efficient for the encapsulation and to lower the aggregation of the phthalocyanine inside the nanoparticles, it is, however, the hydrophobic PMLABe73-based nanoparticles that exhibited the best photodynamic efficiency.

Investigations of the Photothermal Properties of a Series of Molecular Gold-bis(dithiolene) Complexes Absorbing in the NIR-III Region.

The photothermal properties of a series of neutral radical gold-bis(dithiolene) complexes absorbing in the near-infrared-III window (1550-1870 nm) have been investigated. This class of complexes was found to be good photothermal agents (PTAs) in toluene under 1600 nm laser irradiation with photothermal efficiencies around 40 and 60 % depending on the nature of the dithiolene ligand. To the best of our knowledge, these complexes are the first small molecular photothermal agents to absorb so far into the near infrared. To test their applicability in water, these hydrophobic complexes have been encapsulated into nanoparticles constituted by amphiphilic block-copolymers. Stable suspensions of polymeric nanoparticles (NPs) encapsulating the gold-bis(dithiolene) complexes have been prepared which show a diameter around 100 nm. The encapsulation rate was found to be strongly dependent on the nature of the dithiolene ligands. The photothermal properties of the aqueous suspensions containing gold-bis(dithiolene) complexes were then studied under 1600 nm laser irradiation. These studies demonstrate that water has strong photothermal activity in the NIR-III region that, cannot be overcome even with the addition of gold complexes displaying good photothermal properties.

Nanoprecipitation of Biocompatible Poly(malic acid) Derivative, Its Ability to Encapsulate a Molecular Photothermal Agent and Photothermal Properties of the Resulting Nanoparticles.

Biocompatible nanoparticles (NPs) of hydrophobic poly(benzyl malate) (PMLABe) were prepared by nanoprecipitation. The influence of nanoprecipitation parameters (initial PMLABe, addition rate, organic solvent/water ratio and stirring speed) were studied to optimize the resulting formulations in terms of hydrodynamic diameter (Dh) and dispersity (PDI). PMLABe NPs with a Dh of 160 nm and a PDI of 0.11 were isolated using the optimized nanoprecipitation conditions. A hydrophobic near infra-red (NIR) photothermally active nickel-bis(dithiolene) complex (Ni8C12) was then encapsulated into PMLABe NPs using the optimized nanoprecipitation conditions. The size and encapsulation efficiency of the NPs were measured, revealing that up to 50 weight percent (wt%) of Ni8C12 complex can efficiently be encapsulated with a slight increase in Dh of the corresponding Ni8C12-loaded NPs. Moreover, we have shown that NP encapsulating Ni8C12 were stable under storage conditions (4 °C) for at least 10 days. Finally, the photothermal properties of Ni8C12-loaded NPs were evaluated and a high photothermal efficiency (62.7 ± 6.0%) waswas measured with NPs incorporating 10 wt% of the Ni8C12 complex.

Lipase-Catalyzed Ring-Opening Polymerization of Benzyl Malolactonate: An Unusual Mechanism?

The use of safe natural catalyst such as enzymes for ring opening polymerization (ROP) of ß-substituted ß-lactones such as benzyl malolactonate (MLABe) is an important objective considering the biomedical applications of the resulting (co)polymers. However, the preparation of well-defined polymeric materials using such systems requires an understanding of enzyme-substrate interactions. In this context, we investigated the mechanism of lipase-catalyzed ROP of MLABe, because it appears that it is probably not the same as the one widely described for other lactones such ε-caprolactone, propiolactone. and lactide. Enzymatic-catalyzed ROPs of MLABe in the presence of the lipase/acyltransferase CpLip2 and its serine knockout (serine KO) mutant (CpLip2_180A) have led to poly(benzyl malate) (PMLABe) terminated by a monobenzyl fumarate group with monomer conversion higher than 70% and weight-average molar mass of about 3600 g/mol (D = 1.42). On the other hand, only less than 7% of MLABe conversion and no polymer formation were observed when the polymerization reaction was conducted in the presence of inactivated CpLip2 (heated at 100 °C). Moreover, the ROP of MLABe in the presence of imidazole, a synthetic mimic of the catalytic histidine, led to a PMLABe terminated by a monobenzyl fumarate group. On the contrary, neither the enzymatic-catalyzed ROP of benzyl dimethylmalolactonate (diMeMLABe), a MLABe with two methyl groups instead of the two "acidic" protons on the lactone's ring, in the presence of CpLip2 and CpLip2_180A nor its chemical ROP in the presence of imidazole were successful. Together, all these results suggested that the lipase-catalyzed polymerization of malolactonates occurred through the abstraction of one of the two "acidic" protons of the lactone's ring by the histidine of the catalytic triad leading to the corresponding monobenzyl fumarate responsible for the polymerization of the remaining monomer. Finally, molecular modeling of the positioning of the monomer into the catalytic site of the CpLip2 and DFT quantum-chemical calculations highlighted an interaction of (R)- and (S)-MLABe with the catalytic histidine of the enzyme preferentially to serine, in the form of a strong hydrogen bond with one of the "acidic" protons of MLABe, thus, supporting the important role of the catalytic histidine in the polymerization of such cyclic lactones.

Liposomes Containing Nickel-Bis(dithiolene) Complexes for Photothermal Theranostics.

New thermosensitive liposomes with a phase transition at 42 °C, containing nickel-bis(dithiolene) complexes as efficient and stable photothermal agents, have been formulated and characterized. These liposomes are highly stable and keep their contents at 37 °C for more than 30 days. On the contrary, the mild hyperthermia generated by the nickel-bis(dithiolene) complex under 940 nm NIR irradiation allows for the fine controlled release of the liposome contents, making such liposomes highly suitable for on-demand drug delivery in the human body under NIR laser irradiation. These liposomes can also be directly used, as shown here, as nanoagents for photothermal therapy. In fact, strong cell death can be generated under laser irradiation in the presence of these photothermally active nanocargos containing less than 10% w/w of metal complex. We also demonstrate, for the first time, that nickel-bis(dithiolene) complexes are good photoacoustic agents, generating easily detectable ultrasonic signals directly proportional to the concentration of complexes and the used laser power.

Poly(trimethylene carbonate)/Poly(malic acid) Amphiphilic Diblock Copolymers as Biocompatible Nanoparticles.

Amphiphilic polycarbonate-poly(hydroxyalkanoate) diblock copolymers, namely, poly(trimethylene carbonate) (PTMC)-b-poly(ß-malic acid) (PMLA), are reported for the first time. The synthetic strategy relies on commercially available catalysts and initiator. The controlled ring-opening polymerization (ROP) of trimethylene carbonate (TMC) catalyzed by the organic guanidine base 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), associated with iPrOH as an initiator, provided iPrO-PTMC-OH, which served as a macroinitiator in the controlled ROP of benzyl ß-malolactonate (MLABe) catalyzed by the neodymium triflate salt (Nd(OTf)3). The resulting hydrophobic iPrO-PTMC-b-PMLABe-OH copolymers were then hydrogenolyzed into the parent iPrO-PTMC-b-PMLA-OH copolymers. A range of well-defined copolymers, featuring different sizes of segments (Mn,NMR up to 9300 g mol(-1) ; ÐM =1.28-1.40), were thus isolated in gram quantities, as evidenced by NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry, and contact angle analyses. Subsequently, PTMC-b-PMLA copolymers with different hydrophilic weight fractions (11-75 %) self-assembled in phosphate-buffered saline upon nanoprecipitation into well-defined nano-objects with Dh =61-176 nm, a polydispersity index <0.25, and a negative surface charge, as characterized by dynamic light scattering and zeta-potential analyses. In addition, these nanoparticles demonstrated no significant effect on cell viability at low concentrations, and a very low cytotoxicity at high concentrations only for PTMC-b-PMLA copolymers exhibiting hydrophilic fractions over 47 %, thus illustrating the potential of these copolymers as promising nanoparticles.

Development of Multifunctional Nanoparticles for Therapy and/or Diagnosis.

The design of multifunctional nanoparticles for diagnostic and/or therapeutic purposes continues to be a subject of tremendous research [...].

Circumsporozoite Protein of Plasmodium berghei- and George Baker Virus A-Derived Peptides Trigger Efficient Cell Internalization of Bioconjugates and Functionalized Poly(ethylene glycol)-b-poly(benzyl malate)-Based Nanoparticles in Human Hepatoma Cells.

In order to identify the peptides, selected from the literature, that exhibit the strongest tropism towards human hepatoma cells, cell uptake assays were performed using biotinylated synthetic peptides bound to fluorescent streptavidin or engrafted onto nanoparticles (NPs), prepared from biotin-poly(ethylene glycol)-block-poly(benzyl malate) (Biot-PEG-b-PMLABe) via streptavidin bridging. Two peptides, derived from the circumsporozoite protein of Plasmodium berghei- (CPB) and George Baker (GB) Virus A (GBVA10-9), strongly enhanced the endocytosis of both streptavidin conjugates and NPs in hepatoma cells, compared to primary human hepatocytes and non-hepatic cells. Unexpectedly, the uptake of CPB- and GBVA10-9 functionalized PEG-b-PMLABe-based NPs by hepatoma cells involved, at least in part, the peptide binding to apolipoproteins, which would promote NP's interactions with cell membrane receptors of HDL particles. In addition, CPB and GBVA10-9 peptide-streptavidin conjugates favored the uptake by hepatoma cells over that of the human macrophages, known to strongly internalize nanoparticles by phagocytosis. These two peptides are promising candidate ligands for targeting hepatocellular carcinomas.

Hepatotropic Peptides Grafted onto Maleimide-Decorated Nanoparticles: Preparation, Characterization and In Vitro Uptake by Human HepaRG Hepatoma Cells.

We recently demonstrated the strong tropism of George Baker (GB) Virus A (GBVA10-9) and Plasmodium circumsporozoite protein (CPB) derived synthetic peptides towards hepatoma cells. In a first approach, these peptides were covalently bound to poly(benzyl malate) (PMLABe73) and poly(ethylene glycol)-block-PMLABe73 (PEG62-b-PMLABe73) (co)polymers, and corresponding peptide-decorated nanoparticles (NPs) were prepared by nanoprecipitation. We showed that peptide enhanced NPs internalization by hepatoma cells. In the present work, we set up a second strategy to functionalize NPs prepared from PMLABe73 derivates. First, maleimide-functionalized PMLABe73 (Mal-PMLABe73) and PEG62-b-PMLABe73 (Mal-PEG62-b-PMLABe73) were synthesized and corresponding NPs were prepared by nanoprecipitation. Then, peptides (GBVA10-9, CPB and their scramble controls GBVA10-9scr and CPBscr) with a thiol group were engrafted onto the NPs' maleimide groups using the Michael addition to obtain peptide functionalized NPs by post-formulation procedure. These peptide-modified NPs varied in diameter and dispersity depending on the considered peptides and/or (co)polymers but kept their spherical shape. The peptide-functionalized NPs were more efficiently internalized by HepaRG hepatoma cells than native and maleimide-NPs with various levels relying on the peptide's nature and the presence of PEG. We also observed important differences in internalization of NPs functionalized by the maleimide-thiol-peptide reaction compared to that of NPs prepared from peptide-functionalized PMLABe73 derivatives.

Encapsulation of Hydrophobic Porphyrins into Biocompatible Nanoparticles: An Easy Way to Benefit of Their Two-Photon Phototherapeutic Effect without Hydrophilic Functionalization.

Star-shaped hydrophobic porphyrins, acting as powerful fluorescent two-photon photosensitizers for oxygen in organic solvents, can easily be loaded into PMLABe polymeric nanoparticles at various concentrations. In this contribution, the performance of these porphyrin-containing nanoparticles in terms of photodynamic therapy (PDT) is compared to those of the corresponding water-soluble porphyrin analogues when irradiated in MCF-7 cancer cells. While quite promising results are obtained for performing PDT with these nanoparticles, validating this approach as a mean for using more easily accessible and less expensive photosensitizers, from a synthetic perspective, we also show that their luminescence can still be used for bioimaging purposes in spite of their confinement in the nanoparticles, validating also the use of these nano-objects for theranostic purposes.

Synthesis of Poly(Malic Acid) Derivatives End-Functionalized with Peptides and Preparation of Biocompatible Nanoparticles to Target Hepatoma Cells.

Recently, short synthetic peptides have gained interest as targeting agents in the design of site-specific nanomedicines. In this context, our work aimed at developing new tools for the diagnosis and/or therapy of hepatocellular carcinoma (HCC) by grafting the hepatotropic George Baker (GB) virus A (GBVA10-9) and Plasmodium circumsporozoite protein (CPB)-derived peptides to the biocompatible poly(benzyl malate), PMLABe. We successfully synthesized PMLABe derivatives end-functionalized with peptides GBVA10-9, CPB, and their corresponding scrambled peptides through a thiol/maleimide reaction. The corresponding nanoparticles (NPs), varying by the nature of the peptide (GBVA10-9, CPB, and their scrambled peptides) and the absence or presence of poly(ethylene glycol) were also successfully formulated using nanoprecipitation technique. NPs were further characterized by dynamic light scattering (DLS), electrophoretic light scattering (ELS) and transmission electron microscopy (TEM), highlighting a diameter lower than 150 nm, a negative surface charge, and a more or less spherical shape. Moreover, a fluorescent probe (DiD Oil) has been encapsulated during the nanoprecipitation process. Finally, preliminary in vitro internalisation assays using HepaRG hepatoma cells demonstrated that CPB peptide-functionalized PMLABe NPs were efficiently internalized by endocytosis, and that such nanoobjects may be promising drug delivery systems for the theranostics of HCC.

Synthesis of Poly(Dimethylmalic Acid) Homo- and Copolymers to Produce Biodegradable Nanoparticles for Drug Delivery: Cell Uptake and Biocompatibility Evaluation in Human Heparg Hepatoma Cells.

Hydrophobic and amphiphilic derivatives of the biocompatible and biodegradable poly(dimethylmalic acid) (PdiMeMLA), varying by the nature of the lateral chains and the length of each block, respectively, have been synthesized by anionic ring-opening polymerization (aROP) of the corresponding monomers using an initiator/base system, which allowed for very good control over the (co)polymers' characteristics (molar masses, dispersity, nature of end-chains). Hydrophobic and core-shell nanoparticles (NPs) were then prepared by nanoprecipitation of hydrophobic homopolymers and amphiphilic block copolymers, respectively. Negatively charged NPs, showing hydrodynamic diameters (Dh) between 50 and 130 nm and narrow size distributions (0.08 < PDI < 0.22) depending on the (co)polymers nature, were obtained and characterized by dynamic light scattering (DLS), zetametry, and transmission electron microscopy (TEM). Finally, the cytotoxicity and cellular uptake of the obtained NPs were evaluated in vitro using the hepatoma HepaRG cell line. Our results showed that both cytotoxicity and cellular uptake were influenced by the nature of the (co)polymer constituting the NPs.

PEGylated degradable composite nanoparticles based on mixtures of PEG-b-poly(γ-benzyl L-glutamate) and poly(γ-benzyl L-glutamate).

In the present work, the possibility to obtain PEGylated nanoparticles from two PBLG derivatives, PEG-b-poly(γ-benzyl L-glutamate), PBLG-PEG-60, and poly(γ-benzyl L-glutamate), PBLG-Bnz-50, by nanoprecipitation has been investigated. Particles were prepared not only from one polymer (PBLG-PEG-60 or PBLG-Bnz-50), but also from mixtures of two PBLG derivatives, PBLG-PEG-60 and PBLG-Bnz-50, in different ratios (90/10, 77/23, and 40/60 wt %). Because of the presence of PEG chains, hydrophilic particles were obtained, which was confirmed by ζ potential measurements (ζ from -13 mV and -21 mV) and by isothermal titration microcalorimetry (ITC). This last technique has shown no heat exchange when BSA was added to PEGylated nanoparticles. Further, complement activation has been evaluated by crossed immuno-electrophoresis demonstrating that the introduction of 77 wt % of PEGylated PBLG chains in the particles was enough to ensure a low complement activation activity. This effect was strongly correlated to the ζ potential of the particles, which decreased with an increase of PEG chains content. Interestingly, such properties are of interest for the preparation of degradable stealth nanocarriers. Moreover, it is suggested that the introduction of a reasonable amount (up to 20 wt %) of a second copolymer in the particle composition can be possible without modifying their stealth character. Moreover, the presence of this second copolymer would help to introduce a second functionality to the particles.

Biocompatible nanoparticles containing hydrophobic nickel-bis(dithiolene) complexes for NIR-mediated doxorubicin release and photothermal therapy.

Biocompatible nanoparticles (NPs) constituted by amphiphilic poly(ethylene glycol)-block-poly(benzyl malate), PEG-b-PMLABe, have been designed for site-specific PhotoThermal Controlled Release (PTCR) of drugs thanks to the presence of a near infra-red (NIR) photothermally active nickel-bis(dithiolene) complex in the inner core of the NPs, together with doxorubicin (Dox). A nanoprecipitation technique was used to prepare well-defined nickel-bis(dithiolene) and nickel-bis(dithiolene)/Dox loaded NPs, which were characterized by dynamic light scattering (DLS), zeta-potential measurements and Transmission Electron Microscopy (TEM). We have shown that the Dox release was effectively controlled by NIR irradiation (long or pulsed NIR laser irradiation). Cytotoxicity experiments on HeLa and MDA-MB-231 cells have shown that the incorporation of more than 10 w% of nickel-bis(dithiolene) complexes does not increase the intrinsic toxicity of the polymer nanoparticles. Finally, the viability of MDA-MB-231 cells was assessed after their incubation, for 24 hours, with empty NPs, Ni4C12 loaded NPs, Dox loaded NPs or Ni4C12/Dox loaded NPs, without or with NIR irradiation. Above all, the results have highlighted that the Ni4C12 loaded NPs after 5 min NIR laser irradiation can induce strong cell death up to 80% at 50 µg mL-1. These results demonstrate that these NPs are good candidates for photothermal therapy.

Cell Uptake and Biocompatibility of Nanoparticles Prepared from Poly(benzyl malate) (Co)polymers Obtained through Chemical and Enzymatic Polymerization in Human HepaRG Cells and Primary Macrophages.

The design of drug-loaded nanoparticles (NPs) appears to be a suitable strategy for the prolonged plasma concentration of therapeutic payloads, higher bioavailability, and the reduction of side effects compared with classical chemotherapies. In most cases, NPs are prepared from (co)polymers obtained through chemical polymerization. However, procedures have been developed to synthesize some polymers via enzymatic polymerization in the absence of chemical initiators. The aim of this work was to compare the acute in vitro cytotoxicities and cell uptake of NPs prepared from poly(benzyl malate) (PMLABe) synthesized by chemical and enzymatic polymerization. Herein, we report the synthesis and characterization of eight PMLABe-based polymers. Corresponding NPs were produced, their cytotoxicity was studied in hepatoma HepaRG cells, and their uptake by primary macrophages and HepaRG cells was measured. In vitro cell viability evidenced a mild toxicity of the NPs only at high concentrations/densities of NPs in culture media. These data did not evidence a higher biocompatibility of the NPs prepared from enzymatic polymerization, and further demonstrated that chemical polymerization and the nanoprecipitation procedure led to biocompatible PMLABe-based NPs. In contrast, NPs produced from enzymatically synthesized polymers were more efficiently internalized than NPs produced from chemically synthesized polymers. The efficient uptake, combined with low cytotoxicity, indicate that PMLABe-based NPs are suitable nanovectors for drug delivery, deserving further evaluation in vivo to target either hepatocytes or resident liver macrophages.

Fine and Clean Photothermally Controlled NIR Drug Delivery from Biocompatible Nickel-bis(dithiolene)-Containing Liposomes.

This work demonstrates that metal-bis(dithiolene) complexes can be efficiently incorporated inside organic nanocarriers and, that under near-infrared (NIR) irradiation, their high photothermal activity can be finely used to release encapsulated drugs on demand. In contrast to gold nanoparticles and other organic NIR dyes, nickel-bis(dithiolene) complexes do not produce singlet oxygen under irradiation, a highly desirable characteristic to preserve the chemical integrity and activity of the loaded drug during the NIR-triggered release from the nanocarriers. Finally, cytotoxicity experiments performed on various cell lines have shown that the incorporation of such metal complexes do not increase the toxicity of the final liposomal formulation. These results offer great promise for the development of innovative biocompatible drug nanocargos that are able to safely deliver their content on demand under NIR laser irradiation. Moreover, this work demonstrates that metal-bis(dithiolene) complexes, owing to their versatility of functionalization and metal complexation, are attractive photothermal agents for the development of original NIR-responsive materials for application not only in biotechnology but also in materials science.

Poly(malic acid) bearing Doxorubicin and N-Acetyl Galactosamine as a site-specific prodrug for targeting hepatocellular carcinoma.

In the past, several systems of drug delivery carriers have been designed with a high capacity to target specific cells and/or tissues and a reduced non-specific toxicity. In this context, we synthesized and characterized novel poly(malic acid) derivatives bearing Doxorubicin (Dox), Poly(ethylene glycol) (PEG) and/or N-Acetyl Galactosamine (NAcGal) for drug delivery. These poly(malic acid) derivatives were obtained by chemical modification of the carboxylic acid lateral groups of poly(malic acid) (PMLA). The resulting nanoplatforms were evaluated for their in vitro cytotoxicity using the human HepaRG hepatoma cell line. Results reveal that the PMLA nanoplatform modified with PEG and Dox has an IC50 of 936 nM corresponding to a Dox concentration of 47 nM, while the grafting of NAcGal onto the nanoplatform reduced the IC50 to 527 nM corresponding to a Dox concentration of 26 nM. The presence of the targeting moiety, NAcGal, thus improves the cellular toxicity of the Dox.

Opsonisation of nanoparticles prepared from poly(ß-hydroxybutyrate) and poly(trimethylene carbonate)-b-poly(malic acid) amphiphilic diblock copolymers: Impact on the in vitro cell uptake by primary human macrophages and HepaRG hepatoma cells.

The present work reports the investigation of the biocompatibility, opsonisation and cell uptake by human primary macrophages and HepaRG cells of nanoparticles (NPs) formulated from poly(ß-malic acid)-b-poly(ß-hydroxybutyrate) (PMLA-b-PHB) and poly(ß-malic acid)-b-poly(trimethylene carbonate) (PMLA-b-PTMC) diblock copolymers, namely PMLA800-b-PHB7300, PMLA4500-b-PHB4400, PMLA2500-b-PTMC2800 and PMLA4300-b-PTMC1400. NPs derived from PMLA-b-PHB and PMLA-b-PTMC do not trigger lactate dehydrogenase release and do not activate the secretion of pro-inflammatory cytokines demonstrating the excellent biocompatibility of these copolymers derived nano-objects. Using a protein adsorption assay, we demonstrate that the binding of plasma proteins is very low for PMLA-b-PHB-based nano-objects, and higher for those prepared from PMLA-b-PTMC copolymers. Moreover, a more efficient uptake by macrophages and HepaRG cells is observed for NPs formulated from PMLA-b-PHB copolymers compared to that of PMLA-b-PTMC-based NPs. Interestingly, the uptake in HepaRG cells of NPs formulated from PMLA800-b-PHB7300 is much higher than that of NPs based on PMLA4500-b-PHB4400. In addition, the cell internalization of PMLA800-b-PHB7300 based-NPs, probably through endocytosis, is strongly increased by serum pre-coating in HepaRG cells but not in macrophages. Together, these data strongly suggest that the binding of a specific subset of plasmatic proteins onto the PMLA800-b-PHB7300-based NPs favors the HepaRG cell uptake while reducing that of macrophages.

Development of Biocompatible and Functional Polymeric Nanoparticles for Site-Specific Delivery of Radionuclides.

INTRODUCTION: Encapsulation of biologically active molecules into nanoparticles (NPs), for site-specific delivery, is a fast growing area. These NPs must be biocompatible, non-toxic, and able to release their load in a controlled way. We have developed a series of NPs based on (bio)degradable and biocompatible poly(malic acid) derivatives, poly(benzyl malate) (PMLABe), with its PEG-grafted stealth analog and target-specific biotin-PEG-b-PMLABe one. A lipophilic radiotracer has then been encapsulated into these NPs. METHODS: Monomers were synthesized from dl-aspartic acid. PEG42-b-PMLABe73 and Biot-PEG66-b-PMLABe73 block copolymers were obtained by anionic ring-opening polymerization of benzyl malolactonate in presence of α-methoxy-ω-carboxy-PEG42 and α-biotin-ω-carboxy-PEG66 as initiators. NPs were prepared by nanoprecipitation. Size, polydispersity, and zeta potential were measured by dynamic light scattering (DLS) and zetametry. (99m)Tc-SSS was prepared as previously described. Encapsulation efficacy was assessed by varying different parameters, such as encapsulation with preformed NPs or during their formation, influence of the solvent, and of the method to prepare the NPs. After decay, (99m)Tc-loaded NPs were also analyzed by DLS and zetametry. NPs' morphology was assessed by transmission electron microscopy. RESULTS: (99m)Tc-SSS was added during nanoprecipitation, using two different methods, to ensure good encapsulation. Radiolabeled NPs present increased diameters, with identical low polydispersity indexes and negative zeta potentials in comparison to non-radiolabeled NPs. CONCLUSION: A radiotracer was successfully encapsulated, but some further optimization is still needed. The next step will be to modify these radiolabeled NPs with a hepatotrope peptide, and to replace (99m)Tc with (188)Re for therapy. Our team is also working on drugs' encapsulation and grafting of a fluorescent probe. Combining these modalities is of interest for combined chemo-/radiotherapy, bimodal imaging, and/or theranostic approach.

Natural and synthetic poly(malic acid)-based derivates: a family of versatile biopolymers for the design of drug nanocarriers.

The field of specific drug delivery is an expanding research domain. Besides the use of liposomes formed from various lipids, natural and synthetic polymers have been developed to prepare more efficient drug delivery systems either under macromolecular prodrugs or under particulate nanovectors. To ameliorate the biocompatibility of such nanocarriers, degradable natural or synthetic polymers have attracted the interest of many researchers. In this context, poly(malic acid) (PMLA) extracted from microorganisms or synthesized from malic or aspartic acid was used to prepare water-soluble drug carriers or nanoparticles. Within this review, both the preparation and the applications of PMLA derivatives are described emphasizing the in vitro and in vivo assays. The results obtained by several groups highlight the interest of such polyesters in the field of drug delivery.