Conjugated poly(D,L-lactide-co-glycolide) for the preparation of in vivo detectable nanoparticles

Fluorescently Labeled PLGA Nanoparticles for Visualization In Vitro and In Vivo: The Importance of Dye Properties

Fluorescently labeled nanoparticles are widely used for evaluating their distribution in the biological environment. However, dye leakage can lead to misinterpretations of the nanoparticles' biodistribution. To better understand the interactions of dyes and nanoparticles and their biological environment, we explored PLGA nanoparticles labeled with four widely used dyes encapsulated (coumarin 6, rhodamine 123, DiI) or bound covalently to the polymer (Cy5.5.). The DiI label was stable in both aqueous and lipophilic environments, whereas the quick release of coumarin 6 was observed in model media containing albumin (42%) or liposomes (62%), which could be explained by the different affinity of these dyes to the polymer and lipophilic structures and which we also confirmed by computational modeling (log PDPPC/PLGA: DiI-2.3, Cou6-0.7). The importance of these factors was demonstrated by in vivo neuroimaging (ICON) of the rat retina using double-labeled Cy5.5/Cou6-nanoparticles: encapsulated Cou6 quickly leaked into the tissue, whereas the stably bound Cy.5.5 label remained associated with the vessels. This observation is a good example of the possible misinterpretation of imaging results because the coumarin 6 distribution creates the impression that nanoparticles effectively crossed the blood-retina barrier, whereas in fact no signal from the core material was found beyond the blood vessels.

Development of biodegradable polyesters based on a hydroxylated coumarin initiator towards fluorescent visible paclitaxel-loaded microspheres

In this work, we developed a facile end-functionalization method using hydroxylated coumarin to initiate the ring-opening polymerization of cyclic esters to synthesize a series of fluorescent biodegradable aliphatic polyesters with tailorable properties. The resulting fluorescent functionalized poly(l-lactide) (PLLA-COU), poly(ε-caprolactone) (PCL-COU) poly(δ-valerolactone) (PVL-COU) and poly(trimethylene carbonate) (PTMC-COU) were investigated to evaluate the dependence of fluorescence on the chemical structure and molecular weight of the materials. The differences in the electron withdrawing ability and the density of ester groups are responsible for the changes in the fluorescence quantum yield. Then, two representative biodegradable materials, namely, PLLA-COU and PCL-COU, were used to prepare fluorescent paclitaxel-loaded microspheres. During in vitro drug release, the release rate of the PCL-COU microspheres is dramatically faster than that of the PLLA-COU microspheres due to the difference in the material nature and their surface morphologies, possibly achieving a tunable degradation and release rate for the drug carriers. Fluorescent functionalized polyester microspheres can retain their fluorescence properties and emit bright blue light for fluorescence tracing during the degradation process. Biological evaluations showed that both fluorescent polyesters are devoid of any significant toxicity and have good biocompatibility. The results demonstrated that the obtained fluorescent polyesters are promising for use in traceable and controlled drug delivery with tunable drug release.

Mesenchymal stem cells loaded with paclitaxel-poly(lactic-co-glycolic acid) nanoparticles for glioma-targeting therapy

Background

Mesenchymal stem cells (MSCs) possess inherent tropism towards tumor cells, and so have attracted increased attention as targeted-therapy vehicles for glioma treatment.

Purpose

The objective of this study was to demonstrate the injection of MSCs loaded with paclitaxel (Ptx)-encapsulated poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles (NPs) for orthotopic glioma therapy in rats.

Methods

Ptx-PLGA NP-loaded MSC was obtained by incubating MSCs with Ptx-PLGA NPs. The drug transfer and cytotoxicity of Ptx-PLGA NP-loaded MSC against tumor cells were investigated in the transwell system. Biodistribution and antitumor activity was evaluated in the orthotopic glioma rats after contralateral injection.

Results

The optimal dose of MSC-loaded Ptx-PLGA NPs (1 pg/cell Ptx) had little effect on MSC-migration capacity, cell cycle, or multilineage-differentiation potential. Compared with Ptx-primed MSCs, Ptx-PLGA NP-primed MSCs had enhanced sustained Ptx release in the form of free Ptx and Ptx NPs. Ptx transfer from MSCs to glioma cells could induce tumor cell death in vitro. As for distribution in vivo, NP-loaded fluorescent MSCs were tracked throughout the tumor mass for 2 days after therapeutic injection. Survival was significantly longer after contralateral implantation of Ptx-PLGA NP-loaded MSCs than those injected with Ptx-primed MSCs or Ptx-PLGA NPs alone.

Conclusion

Based on timing and sufficient Ptx transfer from the MSCs to the tumor cells, Ptx-PLGA NP-loaded MSC is effective for glioma treatment. Incorporation of chemotherapeutic drug-loaded NPs into MSCs is a promising strategy for tumor-targeted therapy.

Nanoparticles-in-film for the combined vaginal delivery of anti-HIV microbicide drugs

Combining two or more antiretroviral drugs in one medical product is an interesting but challenging strategy for developing topical anti-HIV microbicides. We developed a new vaginal delivery system comprising the incorporation of nanoparticles (NPs) into a polymeric film base - NPs-in-film - and tested its ability to deliver tenofovir (TFV) and efavirenz (EFV). EFV-loaded poly(lactic-co-glycolic acid) NPs were incorporated alongside free TFV into fast dissolving films during film manufacturing. The delivery system was characterized for physicochemical properties, as well as genital distribution, local and systemic 24h pharmacokinetics (PK), and safety upon intravaginal administration to mice. NPs-in-film presented suitable technological, mechanical and cytotoxicity features for vaginal use. Retention of NPs in vivo was enhanced both in vaginal lavages and tissue when associated to film. PK data evidenced that vaginal drug levels rapidly decreased after administration but NPs-in-film were still able to enhance drug concentrations of EFV. Obtained values for area-under-the-curve for EFV were around one log10 higher than those for the free drugs in aqueous vehicle (phosphate buffered saline). Film alone also contributed to higher and more prolonged local drug levels as compared to the administration of TFV and EFV in aqueous vehicle. Systemic exposure to both drugs was low. NPs-in-film was found to be safe upon once daily vaginal administration to mice, with no significant genital histological changes or major alterations in cytokine/chemokine profiles being observed. Overall, the proposed NPs-in-film system seems to be an interesting delivery platform for developing combination vaginal anti-HIV microbicides.

Cholesterol-loaded nanoparticles ameliorate synaptic and cognitive function in Huntington's disease mice

Brain cholesterol biosynthesis and cholesterol levels are reduced in mouse models of Huntington's disease (HD), suggesting that locally synthesized, newly formed cholesterol is less available to neurons. This may be detrimental for neuronal function, especially given that locally synthesized cholesterol is implicated in synapse integrity and remodeling. Here, we used biodegradable and biocompatible polymeric nanoparticles (NPs) modified with glycopeptides (g7) and loaded with cholesterol (g7‐NPs‐Chol), which per se is not blood–brain barrier (BBB) permeable, to obtain high‐rate cholesterol delivery into the brain after intraperitoneal injection in HD mice. We report that g7‐NPs, in contrast to unmodified NPs, efficiently crossed the BBB and localized in glial and neuronal cells in different brain regions. We also found that repeated systemic delivery of g7‐NPs‐Chol rescued synaptic and cognitive dysfunction and partially improved global activity in HD mice. These results demonstrate that cholesterol supplementation to the HD brain reverses functional alterations associated with HD and highlight the potential of this new drug‐administration route to the diseased brain.

Nanoimaging: photophysical and pharmaceutical characterization of poly-lactide-co-glycolide nanoparticles engineered with quantum dots

Quantum dots (QDs) and polymeric nanoparticles (NPs) are considered good binomials for the development of multifunctional nanomedicines for multimodal imaging. Fluorescent imaging of QDs can monitor the behavior of QD-labeled NPs in both cells and animals with high temporal and spatial resolutions. The comprehension of polymer interaction with the metallic QD surface must be considered to achieve a complete chemicophysical characterization of these systems and to describe the QD optical properties to be used for their unequivocal identification in the tissue. In this study, by comparing two different synthetic procedures to obtain polymeric nanoparticles labeled with QDs, we investigated whether their optical properties may change according to the formulation methods, as a consequence of the different polymeric environments. Atomic force microscopy, transmission electron microscopy, confocal and fluorescence lifetime imaging microscopy characterization demonstrated that NPs modified with QDs after the formulation process (post-NPs-QDs) conserved the photophysical features of the QD probe. In contrast, by using a polymer modified with QDs to formulate NPs (pre-NPs-QDs), a significant quenching of QD fluorescence and a blueshift in its emission spectra were observed. Our results suggest that the packaging of QDs into the polymeric matrix causes a modification of the QD optical properties: these effects must be characterized in depth and carefully considered when developing nanosystems for imaging and biological applications.

pH-Triggered release from surface-modified poly(lactic-co-glycolic acid) nanoparticles

Nanoparticles (NP) of poly(lactic-co-glycolic acid) (PLGA) represent a promising biodegradable drug delivery system. We suggest here a two-step release system of PLGA nanoparticles with a pH-tunable polymeric shell, providing an initial pH-triggered step, releasing a membrane-toxic cationic compound. PLGA nanoparticles are coated by polyelectrolytes using the layer-by-layer self-assembly technique, employing poly(acrylic acid) (PAA) as a pH-sensitive component and poly(diallyldimethylammonium chloride) (PDADMAC) as the releasable polycation. The pH during multilayer deposition plays a major role and influences the titration curve of the layer system. The pH-tunability of PAA is intensively investigated with regard to the pH region, in which the particle system becomes uncharged. The isoelectric point can be shifted by employing suitable deposition pH values. The release is investigated by quantitative (1)H NMR, yielding a pH-dependent release curve. A release of PDADMAC is initiated by a decrease of the pH value. The released amount of polymer, as quantified by (1)H NMR analysis, clearly depends on the pH value and thus on the state of deprotonation of the pH-sensitive PAA layer. Subsequent incubation of the nanoparticles with high concentrations of sodium chloride shows no further release and thus demonstrates the pH-driven release to be quantitative.

Endocytosis of Nanomedicines: The Case of Glycopeptide Engineered PLGA Nanoparticles

The success of nanomedicine as a new strategy for drug delivery and targeting prompted the interest in developing approaches toward basic and clinical neuroscience. Despite enormous advances on brain research, central nervous system (CNS) disorders remain the world's leading cause of disability, in part due to the inability of the majority of drugs to reach the brain parenchyma. Many attempts to use nanomedicines as CNS drug delivery systems (DDS) were made; among the various non-invasive approaches, nanoparticulate carriers and, particularly, polymeric nanoparticles (NPs) seem to be the most interesting strategies. In particular, the ability of poly-lactide-co-glycolide NPs (PLGA-NPs) specifically engineered with a glycopeptide (g7), conferring to NPs' ability to cross the blood brain barrier (BBB) in rodents at a concentration of up to 10% of the injected dose, was demonstrated in previous studies using different routes of administrations. Most of the evidence on NP uptake mechanisms reported in the literature about intracellular pathways and processes of cell entry is based on in vitro studies. Therefore, beside the particular attention devoted to increasing the knowledge of the rate of in vivo BBB crossing of nanocarriers, the subsequent exocytosis in the brain compartments, their fate and trafficking in the brain surely represent major topics in this field.

Detection of PLGA-based nanoparticles at a single-cell level by synchrotron radiation FTIR spectromicroscopy and correlation with X-ray fluorescence microscopy

Poly-lactide-co-glycolide (PLGA) is one of the few polymers approved by the US Food and Drug Administration as a carrier for drug administration in humans; therefore, it is one of the most used materials in the formulation of polymeric nanoparticles (NPs) for therapeutic purposes. Because the cellular uptake of polymeric NPs is a hot topic in the nanomedicine field, the development of techniques able to ensure incontrovertible evidence of the presence of NPs in the cells plays a key role in gaining understanding of their therapeutic potential. On the strength of this premise, this article aims to evaluate the application of synchrotron radiation-based Fourier transform infrared spectroscopy (SR-FTIR) spectromicroscopy and SR X-ray fluorescence (SR-XRF) microscopy in the study of the in vitro interaction of PLGA NPs with cells. To reach this goal, we used PLGA NPs, sized around 200 nm and loaded with superparamagnetic iron oxide NPs (PLGA-IO-NPs; Fe₃O₄; size, 10-15 nm). After exposing human mesothelial (MeT5A) cells to PLGA-IO-NPs (0.1 mg/mL), the cells were analyzed after fixation both by SR-FTIR spectromicroscopy and SR-XRF microscopy setups. SR-FTIR-SM enabled the detection of PLGA NPs at single-cell level, allowing polymer detection inside the biological matrix by the characteristic band in the 1,700-2,000 cm(-1) region. The precise PLGA IR-signature (1,750 cm(-1) centered pick) also was clearly evident within an area of high amide density. SR-XRF microscopy performed on the same cells investigated under SR-FTIR microscopy allowed us to put in evidence the Fe presence in the cells and to emphasize the intracellular localization of the PLGA-IO-NPs. These findings suggest that SR-FTIR and SR-XRF techniques could be two valuable tools to follow the PLGA NPs' fate in in vitro studies on cell cultures.

Polymeric materials for theranostic applications

Nanotechnology has continuously contributed to the fast development of diagnostic and therapeutic agents. Theranostic nanomedicine has encompassed the ongoing efforts on concurrent molecular imaging of biomarkers, delivery of therapeutic agents, and monitoring of therapy response. Among these formulations, polymer-based theranostic agents hold great promise for the construction of multifunctional agents for translational medicine. In this article, we reviewed the state-of-the-art polymeric nanoparticles, from preparation to application, as potential theranostic agents for diagnosis and therapy. We summarized several major polymer formulas, including polymeric conjugate complexes, nanospheres, micelles, and dendrimers for integrated molecular imaging and therapeutic applications.

Novel multi-biotin grafted poly(lactic acid) and its self-assembling nanoparticles capable of binding to streptavidin

Targeted drug delivery requires novel biodegradable, specific binding systems with longer circulation time. The aim of this study was to prepare biotinylated poly(lactic acid) (PLA) nanoparticles (NPs) which can meet regular requirements as well conjugate more biotins in the polymer to provide better binding with streptavidin. A biotin-graft-PLA was synthesized based on previously published biodegradable poly(ethylene glycol) (PEG)-graft-PLA, with one polymer molecule containing three PEG molecules. Newly synthesized biotin-graft-PLA had three biotins per polymer molecule, higher than the previous biotinylated PLA (≤1 biotin per polymer molecule). A PEG with a much lower molecular weight (MW ~1900) than the previous biotinylated PLA (PEG MW ≥ 3800), and thus more biocompatible, was used which supplied good nonspecific protein-resistant property compatible to PEG-graft-PLA, suggesting its possible longer stay in the bloodstream. Biotin-graft-PLA specifically bound to streptavidin and self-assembled into NPs, during which naproxen, a model small molecule (MW 230 Da) and hydrophobic drug, was encapsulated (encapsulation efficiency 51.88%). The naproxen-loaded NPs with particle size and zeta potential of 175 nm and −27.35 mV realized controlled release within 170 hours, comparable to previous studies. The biotin-graft-PLA NPs adhered approximately two-fold more on streptavidin film and on biotin film via a streptavidin arm both in static and dynamic conditions compared with PEG-graft-PLA NPs, the proven nonspecific protein-resistant NPs. The specific binding of biotin-graft-PLA NPs with streptavidin and with biotin using streptavidin arm, as well as its entrapment and controlled release for naproxen, suggest potential applications in targeted drug delivery.

Intracellular drug delivery in Leishmania-infected macrophages: Evaluation of saponin-loaded PLGA nanoparticles

Drug delivery systems present an opportunity to potentiate the therapeutic effect of antileishmanial drugs. Colloidal carriers are rapidly cleared by the phagocytic cells of the reticuloendothelial system (RES), rendering them ideal vehicles for passive targeting of antileishmanials. This paper describes the development of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) for the antileishmanial saponin β-aescin. NPs were prepared using the combined emulsification solvent evaporation/salting-out technique. Confocal microscopy was used to visualise the internalisation and intracellular trafficking of fluorescein- and nile red-labelled PLGA NPs in J774A.1 macrophages infected with GFP-transfected Leishmania donovani. The in vitro activity of aescin and aescin-loaded NPs on L. infantum was determined in the axenic model as well as in the ex vivo model. The developed PLGA NPs were monodispersed with Z(ave)<300 nm, exhibited negative zeta potentials and had relatively high drug loadings ranging from 5.80 to 8.68% w/w PLGA. The fluorescent NPs were internalised by the macrophages and trafficked towards the lysosomes after 2 h in vitro incubation. Co-localisation of the NPs and the parasite was not shown. A two-fold increase in activity was observed in the ex vivo macrophage model by encapsulating β-aescin in PLGA NPs (IC(50), 0.48-0.76 µg/mL vs. 1.55 ± 0.32 µg/mL for the free drug).

Investigation on mechanisms of glycopeptide nanoparticles for drug delivery across the blood-brain barrier

AIM

Nanoneuroscience, based on the use polymeric nanoparticles (NPs), represents an emerging field of research for achieving an effective therapy for neurodegenerative diseases. In particular, poly-lactide-co-glycolide (PLGA) glyco-heptapetide-conjugated NPs (g7-NPs) were shown to be able to cross the blood-brain barrier (BBB). However, the in vivo mechanisms of the BBB crossing of this kind of NP has not been investigated until now. This article aimed to develop a deep understanding of the mechanism of BBB crossing of the modified NPs.

MATERIALS & METHODS

Loperamide and rhodamine-123 (model drugs unable to cross the BBB) were loaded into NPs, composed of a mixture of PLGA, differently modified with g7 or with a random sequence of the same aminoamids (random-g7). To study brain targeting of these model drugs, loaded NPs were administered via the tail vein in rats in order to perform both pharmacological studies and biodistribution analysis along with fluorescent, confocal and electron microscopy analysis, in order to achieve the NP BBB crossing mechanism. Computational analysis on the conformation of the g7- and random-g7-NPs of the NP surface was also developed.

RESULTS

Only loperamide delivered to the brain with g7-NPs created a high central analgesia, corresponding to the 14% of the injected dose, and data were confirmed by biodistribution studies. Electron photomicrographs showed the ability of g7-NPs in crossing the BBB as evidenced by several endocytotic vesicles and macropinocytotic processes. The computational analysis on g7 and random-g7 showed a different conformation (linear vs globular), thus suggesting a different interaction with the BBB.

CONCLUSION

Taken together, this evidence suggested that g7-NP BBB crossing is enabled by multiple pathways, mainly membrane-membrane interaction and macropinocytosis-like mechanisms. The results of the computational analysis showed the Biousian structure of the g7 peptide, in contrast to random-g7 peptide (globular conformation), suggesting that this difference is pivotal in explaining the BBB crossing and allowing us to hypothesize regarding the mechanism of BBB crossing by g7-NPs.

Fluorescent Labeling of Degradable Poly(Lactide-Co-Glycolide) for Cellular Nanoparticles Tracking in Living Cells

Fluorescent-labeled aliphatic polyesters are essential materials for in vitro and in vivo studies of the behavior of these biodegradable polymers in interaction with cells or in a body. In particular, the direct cellular localization of drug delivery systems based on these materials allows better understanding of the internalization mechanism and determination of the pharmacokinetics. Polylactide-co-glycolide (PLGA) is a rapidly degradable copolymer widely used in pharmaceutics and nanomedecine. It was prepared by ring-opening polymerization of lactide and glycolide in order to obtain a well-defined material to investigate conditions allowing the covalent linkage of a fluorescent dye (fluorescein) while preserving the macromolecular characteristics of the polymer. The success of the functionalization was ascertained by proton nuclear magnetic resonance (1H NMR), size-exclusion chromatography (SEC) and fluorescence spectroscopy.

NIR-labeled nanoparticles engineered for brain targeting: in vivo optical imaging application and fluorescent microscopy evidences

The presence of the blood-brain barrier (BBB) makes extremely difficult to develop efficacious strategies for targeting contrast agents and delivering drugs inside the Central Nervous System (CNS). To overcome this drawback, several kinds of CNS-targeted nanoparticles (NPs) have been developed. In particular, we proposed poly-lactide-co-glycolide (PLGA) NPs engineered with a simil-opioid glycopeptide (g7), which have already proved to be a promising tool for achieving a successful brain targeting after i.v. administration in rats. In order to obtain CNS-targeted NPs to use for in vivo imaging, we synthesized and administrated in mice PLGA NPs with double coverage: near-infrared (NIR) probe (DY-675) and g7. The optical imaging clearly showed a brain localization of these novel NPs. Thus, a novel kind of NIR-labeled NPs were obtained, providing a new, in vivo detectable nanotechnology tool. Besides, the confocal and fluorescence microscopy evidences allowed to further confirm the ability of g7 to promote not only the rat, but also the mouse BBB crossing.

A novel biomaterial for osteotropic drug nanocarriers: synthesis and biocompatibility evaluation of a PLGA–ALE conjugate

Background & aims: Osteotropic drug-delivery systems have been proposed as a means to provide drugs with affinity to bone tissues. Drugs or proteins have been linked chemically to bone-seeking agents, such as bisphosphonates (BPs); alternatively, drug-loaded nanoparticles have been used to target specific tissues, such as tumor areas. In our current research, these approaches were merged by synthesizing a novel bone-seeking polymer conjugate, from which targetable nanoparticles can be produced. Materials & methods: An amino-BP, alendronate (ALE) was bound covalently to a biodegradable polymer, poly(lactic-co-glycolide) (PLGA), containing a free end carboxylic group. Blood compatibility and cytotoxicity were assessed in vitro. Results & discussion: By a classical solvent-evaporation method, nanoparticles with a mean size of 200–300 nm were prepared from the conjugate; sterilization was achieved by γ-irradiation, confirming their potential as injectable drug nanocarriers. Owing to the presence of the BP residue, PLGA–ALE nanoparticles were adsorbed onto hydroxyapatite to a higher extent than pure PLGA nanoparticles. The PLGA–ALE conjugate did not induce either hemolysis or alterations of the plasmatic phase of coagulation, or cytotoxic effects on endothelial cells and trabecular osteoblasts. Conclusion: The prepared conjugate represents a novel biomaterial that is able to provide nanoparticles, which can be further loaded with drugs, such as anticancer agents, and addressed to osteolytic or other bone diseases.

Engineering biodegradable polyester particles with specific drug targeting and drug release properties

Poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) microspheres and nanoparticles remain the focus of intensive research effort directed to the controlled release and in vivo localization of drugs. In recent years engineering approaches have been devised to create novel micro- and nano-particles which provide greater control over the drug release profile and present opportunities for drug targeting at the tissue and cellular levels. This has been possible with better understanding and manipulation of the fabrication and degradation processes, particularly emulsion-solvent extraction, and conjugation of polyesters with ligands or other polymers before or after particle formation. As a result, particle surface and internal porosity have been designed to meet criteria-facilitating passive targeting (e.g., for pulmonary delivery), modification of the drug release profile (e.g., attenuation of the burst release) and active targeting via ligand binding to specific cell receptors. It is now possible to envisage adventurous applications for polyester microparticles beyond their inherent role as biodegradable, controlled drug delivery vehicles. These may include drug delivery vehicles for the treatment of cerebral disease and tumor targeting, and co-delivery of drugs in a pulsatile and/or time-delayed fashion.

Targeting the central nervous system: In vivo experiments with peptide-derivatized nanoparticles loaded with Loperamide and Rhodamine-123

Polymeric nanoparticles (Np) represent one of the most innovative non-invasive approaches for the drug delivery to the central nervous system (CNS). It is known that the ability of the Np to cross the Blood Brain Barrier (BBB), thus allowing the drugs to exert their pharmacological activity in the central nervous district, is linked to their surface characteristics. Recently it was shown that the biocompatible polyester poly(d,l-lactide-co-glycolide) (PLGA) derivatized with the peptide H(2)N-Gly-l-Phe-d-Thr-Gly-l-Phe-l-Leu-l-Ser(O-beta-d-Glucose)-CONH(2) [g7] was a useful starting material for the preparation of Np (g7-Np); moreover, fluorescent studies showed that these Np were able to cross the BBB. In this research, g-7 Np were loaded with Loperamide in order to assess their ability as drug carriers for CNS, and with Rhodamine-123, in order to qualitatively determine their biodistribution in different brain macro-areas. A pharmacological evidence is given that g7-Np are able to cross the BBB, ensuring, for the first time, a sustained release of the embedded drug, and that these Np are able to reach all the brain areas here examined. The ability to enter the CNS appears to be linked to the sequence of the peptidic moiety present on their surface.

Peptide-derivatized biodegradable nanoparticles able to cross the blood-brain barrier

Injectable nanoparticulate drug carriers (Np) able to cross the blood-brain barrier (BBB) have important potential applications for the treatment of diseases that affect the central nervous system (CNS). With the aim to create a system able to address Np to the CNS, we synthesized conjugates between a biodegradable copolymer, poly(D,L-lactide-co-glycolide) (PLGA), and five short peptides, by means of an amidic linkage. These peptides, that are similar to synthetic opioid peptides, were synthesized in turn by means of Fmoc solid-phase peptide synthesis. The new five modified copolymers thus obtained turned out to be valuable starting material for the preparation of Np; these were made fluorescent, in order to allow their localization after their administration, by inclusion of a fluorescent probe. The Np thus prepared were characterized (morphology, size and z-potential) and were shown to possess the peptidic moieties on their surface, as evidenced by ESCA spectroscopy. Then, their ability to cross the BBB was assessed by the in vivo Rat Brain Perfusion Technique and, in one case, by means of a systemic administration (rat femoral vein injection). Fluorescent and confocal microscopy studies showed that while PLGA Np are unable to cross the BBB, for the first time these solid Np surface-modified with peptides were shown to be able to cross the BBB.