Novel composite core-shell nanoparticles as busulfan carriers

Biodegradable polymeric nanoparticles administered in the cerebrospinal fluid: Brain biodistribution, preferential internalization in microglia and implications for cell-selective drug release

Cell-selective drug release in the central nervous system (CNS) holds great promise for the treatment of many CNS disorders but it is still challenging. We previously demonstrated that polymeric nanoparticles (NPs) injected intra-parenchyma in the CNS can be internalized specifically in microglia/macrophages surrounding the injection site. Here, we explored NPs administration in the cerebrospinal fluid (CSF) to achieve a wider spreading and increased cell targeting throughout the CNS; we generated new NPs variants and studied the effect of modifying size and surface charge on NPs biodistribution and cellular uptake. Intra-cerebroventricular administration resulted in prevalent localization of the NPs in proximity to stem-cell niches, such as around the lateral ventricles, the subventricular zone and the rostral migratory stream. NPs internalization occurred preferentially in brain myeloid cells/microglia. We demonstrated that brain biodistribution and extent of internalization in microglia are influenced by NPs dimensions and can be improved by applying a transient disruption of the blood-brain barrier with mannitol, leading to NPs internalization in up to 25% of brain myeloid/microglia cells. A fraction of the targeted cells was positive for markers of proliferation or stained positive for stemness/progenitor-cell markers such as Nestin, c-kit, or NG2. Interestingly, through these newly formulated NPs we obtained controlled and selective release of drugs otherwise difficult to formulate (such as busulfan and etoposide) to the target cells, preventing unwanted side effects and the toxicity obtained by direct brain delivery of the not encapsulated drugs. Overall, these data provide proof of concept of the applicability of these novel NP-based drug formulations for achieving internalization not only in mature microglia but also possibly in more immature myeloid cells in the brain and pave the way for brain-restricted microglia-targeted drug delivery regimens.

A journey through the emergence of nanomedicines with poly(alkylcyanoacrylate) based nanoparticles

Starting in the late 1970s, the pioneering work of Patrick Couvreur gave birth to the first biodegradable nanoparticles composed of a biodegradable synthetic polymer. These nanoparticles, made of poly(alkylcyanoacrylate) (PACA), were the first synthetic polymer-based nanoparticulate drug carriers undergoing a phase III clinical trial so far. Analyzing the journey from the birth of PACA nanoparticles to their clinical evaluation, this paper highlights their remarkable adaptability to bypass various drug delivery challenges found on the way. At present, PACA nanoparticles include a wide range of nanoparticles that can associate drugs of different chemical nature and can be administered in vivo by different routes. The most recent technologies giving the nanoparticles customised functions could also be implemented on this family of nanoparticles. Through different examples, this paper discusses the seminal role of the PACA nanoparticles' family in the development of nanomedicines.

Liposomal Formulations for an Efficient Encapsulation of Epigallocatechin-3-gallate: An in- Silico/Experimental Approach

As a part of research project aimed to optimize antioxidant delivery, here we studied the influence of both salts and lipid matrix composition on the interaction of epigallocatechin-3-gallate (EGCG) with bilayer leaflets. Thus, we combined in silico and experimental methods to study the ability of neutral and anionic vesicles to encapsulate EGCG in the presence of Ca²⁺ and Mg²⁺ divalent salts. Experimental and in silico results show a very high correlation, thus confirming the efficiency of the developed methodology. In particular, we found out that the presence of calcium ions hinders the insertion of EGCG in the liposome bilayer in both neutral and anionic systems. On the contrary, the presence of MgCl₂ improves the insertion degree of EGCG molecules respect to the liposomes without divalent salts. The best and most efficient salt concentration is that corresponding to a 5:1 molar ratio between Mg²⁺ and EGCG, in both neutral and anionic vesicles. Concerning the lipid matrix composition, the anionic one results in better promotion of the catechin insertion within the bilayer since experimentally we achieved 100% EGCG encapsulation in the lipid carrier in the presence of a 5:1 molar ratio of magnesium. Thus, the combination of this anionic liposomal formulation with magnesium chloride, avoids time-consuming separation steps of unentrapped active principle and appears particularly suitable for EGCG delivery applications.

Renewable poly(δ-decalactone) based block copolymer micelles as drug delivery vehicle: in vitro and in vivo evaluation

Polymers from natural resources are attracting much attention in various fields including drug delivery as green alternatives to fossil fuel based polymers. In this quest, novel block copolymers based on renewable poly(δ-decalactone) (PDL) were evaluated for their drug delivery capabilities and compared with a fossil fuel based polymer i.e. methoxy-poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL). Using curcumin as a hydrophobic drug model, micelles of PDL block copolymers with different orientation i.e. AB (mPEG-b-PDL), ABA (PDL-b-PEG-b-PDL), ABC (mPEG-b-PDL-b-poly(pentadecalactone) and (mPEG-b-PCL) were prepared by nanoprecipitation method. The size, drug loading and curcumin stability studies results indicated that mPEG-b-PDL micelles was comparable to its counterpart mPEG-b-PCL micelles towards improved delivery of curcumin. Therefore, mixed micelles using these two copolymers were also evaluated to see any change in size, loading and drug release. Drug release studies proposed that sustained release can be obtained using poly(pentadecalactone) as crystalline core whereas rapid release can be achieved using amorphous PDL core. Further, mPEG-b-PDL micelles were found to be non-haemolytic, up to the concentration of 40 mg/mL. In vivo toxicity studies on rats advised low-toxic behaviour of these micelles up to 400 mg/kg dose, as evident by histopathological and biochemical analysis. In summary, it is anticipated that mPEG-b-PDL block copolymer micelles could serve as a renewable alternative for mPEG-b-PCL copolymers in drug delivery applications.

Biodistribution of biodegradable polymeric nano-carriers loaded with busulphan and designed for multimodal imaging

BACKGROUND

Multifunctional nanocarriers for controlled drug delivery, imaging of disease development and follow-up of treatment efficacy are promising novel tools for disease diagnosis and treatment. In the current investigation, we present a multifunctional theranostic nanocarrier system for anticancer drug delivery and molecular imaging. Superparamagnetic iron oxide nanoparticles (SPIONs) as an MRI contrast agent and busulphan as a model for lipophilic antineoplastic drugs were encapsulated into poly (ethylene glycol)-co-poly (caprolactone) (PEG-PCL) micelles via the emulsion-evaporation method, and PEG-PCL was labelled with VivoTag 680XL fluorochrome for in vivo fluorescence imaging.

RESULTS

Busulphan entrapment efficiency was 83% while the drug release showed a sustained pattern over 10 h. SPION loaded-PEG-PCL micelles showed contrast enhancement in T ₂ *-weighted MRI with high r ₂* relaxivity. In vitro cellular uptake of PEG-PCL micelles labeled with fluorescein in J774A cells was found to be time-dependent. The maximum uptake was observed after 24 h of incubation. The biodistribution of PEG-PCL micelles functionalized with VivoTag 680XL was investigated in Balb/c mice over 48 h using in vivo fluorescence imaging. The results of real-time live imaging were then confirmed by ex vivo organ imaging and histological examination. Generally, PEG-PCL micelles were highly distributed into the lungs during the first 4 h post intravenous administration, then redistributed and accumulated in liver and spleen until 48 h post administration. No pathological impairment was found in the major organs studied.

CONCLUSIONS

Thus, with loaded contrast agent and conjugated fluorochrome, PEG-PCL micelles as biodegradable and biocompatible nanocarriers are efficient multimodal imaging agents, offering high drug loading capacity, and sustained drug release. These might offer high treatment efficacy and real-time tracking of the drug delivery system in vivo, which is crucial for designing of an efficient drug delivery system.

Nanoparticles Based on Linear and Star-Shaped Poly(Ethylene Glycol)-Poly(ε-Caprolactone) Copolymers for the Delivery of Antitubulin Drug

PURPOSE

Biodegradable polymeric nanoparticles of different architectures based on polyethylene glycol-co-poly(ε-caprolactone) block copolymers have been loaded with noscapine (NOS) to study their effect on its anticancer activity. It was intended to use solubility of NOS in an acidic environment and ability of the nanoparticles to passively target drugs into cancer tissue to modify the NOS pharmacokinetic properties and reduce the requirement for frequent injections.

METHODS

Linear and star-shaped copolymers were synthetized and used to formulate NOS loaded nanoparticles. Cytotoxicity was performed using a sulforhodamine B method on MCF-7 cells, while biocompatibility was determined on rats followed by hematological and histopathological investigations.

RESULTS

Formulae with the smallest particle sizes and adequate entrapment efficiency revealed that NOS loaded nanoparticles showed higher extent of release at pH 4.5. Colloidal stability suggested that nanoparticles would be stable in blood when injected into the systemic circulation. Loaded nanoparticles had IC50 values lower than free drug. Hematological and histopathological studies showed no difference between treated and control groups. Pharmacokinetic analysis revealed that formulation P1 had a prolonged half-life and better bioavailability compared to drug solution.

CONCLUSIONS

Formulation of NOS into biodegradable polymeric nanoparticles has increased its efficacy and residence on cancer cells while passively avoiding normal body tissues. Graphical Abstract ᅟ.

Development and evaluation of nanoparticles based on mPEG-PLA for controlled delivery of vinpocetine: in vitro and in vivo studies

The aim of present study was to develop VIN-loaded mPEG-PLA nanoparticle systems. The VIN mPEG-PLA nanoparticles were prepared using an emulsion solvent evaporation method, and studied their particle size, morphology, encapsulation efficiency and drug-loading coefficient. Moreover, the nanoparticles were evaluated on the drug release behaviors in vitro and bioavailability in vivo. The results show that the spherical nanoparticles obtained were negatively charged with a zeta potential of about -23.4 mV and characterized ∼110 nm with a narrow size distribution. The encapsulation efficiency and drug loading of prepared NPs were 76.4 ± 6.3 and 9.2 ± 2.2% (n=5), respectively. The in vitro release showed that the percent of accumulated dissolution of VIN NPs in phosphate-buffered saline 6.8 over 24 h was <80%, which was almost 100% of VIN in commercial injections. The in vivo study indicated that systemic absorption of VIN was significantly enhanced by incorporating into mPEG-PLA NPs compared with VIN injection (2.87-fold in AUC_0-t). The results suggested that the form of VIN in mPEG-PLA NPs could enter the body circulation to perform sustained release in vitro and in vivo.

Antineoplastic busulfan encapsulated in a metal organic framework nanocarrier: first in vivo results

Nanoparticles of a mesoporous iron(iii) trimesate MIL-100 nanocarrier encapsulating high amounts of the challenging antineoplastic busulfan were administered to rats and compared with the commercial Busilvex®.

Supramolecular self-assembly of novel thermo-responsive double-hydrophilic and hydrophobic Y-shaped [MPEO-b-PEtOx-b-(PCL)2] terpolymers

Nonlinear amphiphilic block copolymer architectures with precisely controlled structures bring new challenges to biomedical materials research.

Multiple strategies to produce lipophilic nanoparticles leaving water-soluble poly(HPMA)

N-(2-Hydroxypropyl) methacrylamide (HPMA) is used to produce water-soluble polymers with non-immumogenic properties that can be used in drug delivery applications.

Improvement of pharmacokinetic and antitumor activity of layered double hydroxide nanoparticles by coating with PEGylated phospholipid membrane

Layered double hydroxide (LDH) has attracted considerable attention as a drug carrier. However, because of its poor in vivo behavior, polyethylene glycolylated (PEGylated) phospholipid must be used as a coformer to produce self-assembled core-shell nanoparticles. In the present study, we prepared a PEGylated phospholipid-coated LDH (PLDH) (PEG-PLDH) delivery system. The PEG-PLDH nanoparticles had an average size of 133.2 nm. Their core-shell structure was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. In vitro liposome-cell-association and cytotoxicity experiments demonstrated its ability to be internalized by cells. In vivo studies showed that PEGylated phospholipid membranes greatly reduced the blood clearance rate of LDH nanoparticles. PEG-PLDH nanoparticles demonstrated a good control of tumor growth and increased the survival rate of mice. These results suggest that PEG-PLDH nanoparticles can be a useful drug delivery system for cancer therapy.

Polymeric topology and composition constrained polyether-polyester micelles for directional antitumor drug delivery

Amphiphilic linear and dumbbell-shaped poly(ethylene glycol)-poly(lactide-co-glycolide) (PEG-PLGA) copolymers were simply synthesized by the ring-opening polymerization of lactide and glycolide using PEG or tetrahydroxyl-functionalized PEG as the macroinitiator and stannous octoate as the catalyst. The copolymers spontaneously self-assembled into spherical micelles in phosphate-buffered saline at pH 7.4. The self-assembly behavior was dependent on both the polymeric topology and composition. Doxorubicin (DOX), an anthracycline antitumor drug, was loaded into micelles through nanoprecipitation. The in vitro release behavior could be adjusted by regulating the topology or composition of the copolymer, or the pH of the release medium. The effective intracellular DOX release from DOX-loaded micelles was confirmed by confocal laser scanning microscopy and flow cytometry in vitro. DOX-loaded micelles displayed great cellular proliferation inhibition efficacies after incubation for 24, 48 or 72 h. The hemolysis ratio of DOX was significantly reduced by the presence of copolymer. These properties indicated that the micelles derived from linear or dumbbell-shaped copolymers were promising candidates as smart antitumor drug carriers for malignancy therapy.

Electrically conductive nanofibers with highly oriented structures and their potential application in skeletal muscle tissue engineering

Recent trends in scaffold design have focused on materials that can provide appropriate guidance cues for particular cell types to modulate cell behavior. In this study highly aligned and electrically conductive nanofibers that can simultaneously provide topographical and electrical cues for cells were developed. Thereafter their potential to serve as functional scaffolds for skeletal muscle tissue engineering was investigated. Well-ordered nanofibers, composed of polyaniline (PANi) and poly(ε-caprolactone) (PCL), were electrospun by introducing an external magnetic field in the collector region. Incorporation of PANi into PCL fibers significantly increased the electrical conductivity from a non-detectable level for the pure PCL fibers to 63.6±6.6mS cm(-1) for the fibers containing 3wt.% PANi (PCL/PANi-3). To investigate the synergistic effects of topographical and electrical cues using the electrospun scaffolds on skeletal myoblast differentiation, mouse C2C12 myoblasts were cultured on random PCL (R-PCL), aligned PCL (A-PCL), random PCL/PANi-3 (R-PCL/PANi) and aligned PCL/PANi-3 (A-PCL/PANi) nanofibers. Our results showed that the aligned nanofibers (A-PCL and A-PCL/PANi) could guide myoblast orientation and promote myotube formation (i.e. approximately 40% and 80% increases in myotube numbers) compared with R-PCL scaffolds. In addition, electrically conductive A-PCL/PANi nanofibers further enhanced myotube maturation (i.e. approximately 30% and 23% or 15% and 18% increases in the fusion and maturation indices) compared with non-conductive A-PCL scaffolds or R-PCL/PANi. These results demonstrated that a combined effect of both guidance cues was more effective than an individual cue, suggesting a potential use of A-PCL/PANi nanofibers for skeletal muscle regeneration.

Improvement of in vivo efficacy of recombinant human erythropoietin by encapsulation in PEG-PLA micelle

To improve the pharmacokinetics and stability of recombinant human erythropoietin (rhEPO), rhEPO was successfully formulated into poly(ethylene glycol)–poly(d,l-lactide) (PEG–PLA) di-block copolymeric micelles at diameters ranging from 60 to 200 nm with narrow polydispersity indices (PDIs; PDI < 0.3) and trace amount of protein aggregation. The zeta potential of the spherical micelles was in the range of −3.78 to 4.65 mV and the highest encapsulation efficiency of rhEPO in the PEG–PLA micelles was about 80%. In vitro release profiles indicated that the stability of rhEPO in the micelles was improved significantly and only a trace amount of aggregate was found. Pharmacokinetic studies in rats showed highly enhanced plasma retention time of the rhEPO-loaded PEG-PLA micelles in comparison with the native rhEPO group. Increased hemoglobin concentrations were also found in the rat study. Native polyacrylamide gel electrophoresis results demonstrated that rhEPO was successfully encapsulated into the micelles, which was stable in phosphate buffered saline with different pHs and concentrations of NaCl. Therefore, PEG–PLA micelles can be a potential protein drug delivery system.

In vitro evaluation of anticancer nanomedicines based on doxorubicin and amphiphilic Y-shaped copolymers

Four monomethoxy poly(ethylene glycol)-poly(L-lactide-co-glycolide)₂ (mPEG-P( LA-co-GA)₂) copolymers were synthesized by ring-opening polymerization of L-lactide and glycolide with double hydroxyl functionalized mPEG (mPEG-(OH)₂) as macroinitiator and stannous octoate as catalyst. The copolymers self-assembled into nanoscale micellar/vesicular aggregations in phosphate buffer at pH 7.4. Doxorubicin (DOX), an anthracycline anticancer drug, was loaded into the micellar/vesicular nanoparticles, yielding micellar/vesicular nanomedicines. The in vitro release behaviors could be adjusted by content of hydrophobic polyester and pH of the release medium. In vitro cell experiments showed that the intracellular DOX release could be adjusted by content of P(LA-co-GA), and the nanomedicines displayed effective proliferation inhibition against Henrietta Lacks’s cells with different culture times. Hemolysis tests indicated that the copolymers were hemocompatible, and the presence of copolymers could reduce the hemolysis ratio of DOX significantly. These results suggested that the novel anticancer nanomedicines based on DOX and amphiphilic Y-shaped copolymers were attractive candidates as tumor tissular and intracellular targeting drug delivery systems in vivo, with enhanced stability during circulation and accelerated drug release at the target sites.

Efficient delivery of antitumor drug to the nuclei of tumor cells by amphiphilic biodegradable poly(L-aspartic acid-co-lactic acid)/DPPE co-polymer nanoparticles

The use of biodegradable polymeric nanoparticles (NPs) for controlled drug delivery has shown significant therapeutic potential. Polyaspartic acid and polylactic acid are the most intensively studied biodegradable polymers. In the present study, novel amphiphilic biodegradable co-polymer NPs, poly(L-aspartic acid-co-lactic acid) with 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) (poly(AA-co-LA)/DPPE) is synthesized and subsequently used to encapsulate an antitumor drug doxorubicin (DOX). The formulation parameters of the NPs are optimized to improve encapsulation efficiency. The resulting drug-loaded NPs possess better size homogeneity (polydispersity) and exhibit pH-responsive drug release profiles. Cellular viability assays indicate that the poly(AA-co-LA)/DPPE NPs did not induce cell death, whereas doxorubicin encapsulated NPs were cytotoxic to various types of tumor cells. In addition, the free NPs could not enter the cell nuclei after internalized in tumor cells. The DOX-loaded NPs exhibit efficient intracellular delivery in tumor cells with co-localization in lysosome and delay entering into the nucleus, which suggests a time- and pH-dependent drug release profile within cells. When applied to deliver chemotherapeutics to a mouse xenograft model of human lung adenocarcinoma, DOX-loaded NPs have a comparable antitumor activity with free DOX, and greatly reduce systemic toxicity and mortality. The delivery of cytotoxic drugs directly to the nucleus specifically within tumor cells is of great interest. These results demonstrate the feasibility of the application of the amphiphilic polyaspartic acid derivative, poly(AA-co-LA)/DPPE, as a nanocarrier for cell nuclear delivery of potent antitumor drugs.

Porous metal organic framework nanoparticles to address the challenges related to busulfan encapsulation

Busulfan is an alkylating agent widely used in chemotherapy, but with severe side effects. Many attempts have been made to entrap busulfan in nanocarriers to avoid liver accumulation and to protect it against rapid degradation in aqueous media. However, poor loadings (≤5 wt%) and fast release were generally obtained due to the low affinity of busulfan towards the nanocarriers. Moreover, drug crystallization often occurred during nanoparticle preparation. To circumvent these drawbacks, metal organic framework (MOF) nanoparticles, based on crystalline porous iron (III) carboxylates, have shown an unprecedented loading (up to 25 wt%) of busulfan. This was attributed to the high porosity of nanoMOFs as well as to their hydrophilic–hydrophobic internal microenvironment well adapted to the amphiphilic character of busulfan. NanoMOFs formulations have kept busulfan in molecular form, preventing its crystallization and degradation. Indeed, busulfan was released intact, as proved by the maintenance of its pharmacological activity.

Rayleigh theory of ultrasound scattering applied to liquid-filled contrast nanoparticles

We present a novel modified theory based upon Rayleigh scattering of ultrasound from composite nanoparticles with a liquid core and solid shell. We derive closed form solutions to the scattering cross-section and have applied this model to an ultrasound contrast agent consisting of a liquid-filled core (perfluorooctyl bromide, PFOB) encapsulated by a polymer shell (poly-caprolactone, PCL). Sensitivity analysis was performed to predict the dependence of the scattering cross-section upon material and dimensional parameters. A rapid increase in the scattering cross-section was achieved by increasing the compressibility of the core, validating the incorporation of high compressibility PFOB; the compressibility of the shell had little impact on the overall scattering cross-section although a more compressible shell is desirable. Changes in the density of the shell and the core result in predicted local minima in the scattering cross-section, approximately corresponding to the PFOB-PCL contrast agent considered; hence, incorporation of a lower shell density could potentially significantly improve the scattering cross-section. A 50% reduction in shell thickness relative to external radius increased the predicted scattering cross-section by 50%. Although it has often been considered that the shell has a negative effect on the echogeneity due to its low compressibility, we have shown that it can potentially play an important role in the echogeneity of the contrast agent. The challenge for the future is to identify suitable shell and core materials that meet the predicted characteristics in order to achieve optimal echogenity.

Positively-charged, porous, polysaccharide nanoparticles loaded with anionic molecules behave as 'stealth' cationic nanocarriers

PURPOSE

Stealth nanoparticles are generally obtained after modifying their surface with hydrophilic polymers, such as PEG. In this study, we analysed the effect of a phospholipid (DG) or protein (BSA) inclusion in porous cationic polysaccharide (NP(+)) on their physico-chemical structure and the effect on complement activation.

METHODS

NP(+)s were characterised in terms of size, zeta potential (zeta) and static light scattering (SLS). Complement consumption was assessed in normal human serum (NHS) by measuring the residual haemolytic capacity of the complement system.

RESULTS

DG loading did not change their size or zeta, whereas progressive BSA loading lightly decreased their zeta. An electrophoretic mobility analysis study showed the presence of two differently-charged sublayers at the NP(+) surface which are not affected by DG loading. Complement system activation, studied via a CH50 test, was suppressed by DG or BSA loading. We also demonstrated that NP(+)s could be loaded by a polyanionic molecule, such as BSA, after their preliminary filling by a hydrophobic molecule, such as DG.

CONCLUSION

These nanoparticles are able to absorb large amounts of phospholipids or proteins without change in their size or zeta potential. Complement studies showed that stealth behaviour is observed when they are loaded and saturated either with anionic phospholipid or proteins.

Novel self-assembled core-shell nanoparticles based on crystalline amorphous moieties of aliphatic copolyesters for efficient controlled drug release

Poly(propylene succinate-co-caprolactone) copolymers [P(PSu-co-CL)] with different epsilon-caprolactone (epsilon-CL) to propylene succcinate (PSu) monomer ratios were synthesized using ring opening polymerization. These polymers consisted of crystalline poly(epsilon-caprolactone) (PCL) and amorphous poly(propylene succinate) (PPSu) moieties, as shown by WAXD. In vitro biocompatibility studies showed that these copolyesters are biocompatible. Drug-loaded nanoparticles, using tibolone as a model drug, were prepared by the solvent evaporation method. Nanoparticle size ranged between 150 and 190 nm and decreased with increasing propylene succinate (PSu) ratio in the copolymers. Nanoparticle yield, encapsulation efficiency, and drug loading increased with increasing PSu ratio. Scanning Electron Microscopy (SEM) revealed that the prepared nanoparticles had a spherical shape and Transmission Electron Microscopy (TEM) showed that they were self-assembled in core-shell structures. Amorphous PPSu and crystalline PCL comprised the core and shell, respectively. The drug is mainly located into the amorphous core in the form of nanocrystals. Drug release studies showed that complete release of the drug from the nanoparticles occurs over a period of 50 h. The release rate is greatly influenced by the copolymer composition, nanoparticle size, and encapsulation efficiency. Among the main advantages of the nanoparticles produced in this study is the absence of burst effect during drug release.

Analytical characterization of chitosan nanoparticles for peptide drug delivery applications

Chitosan-cyclodextrin hybrid nanoparticles (NPs) were obtained by the ionic gelation process in the presence of glutathione (GSH), chosen as a model drug. NPs were characterized by means of transmission electron microscopy and zeta-potential measurements. Furthermore, a detailed X-ray photoelectron spectroscopy study was carried out in both conventional and depth-profile modes. The combination of controlled ion-erosion experiments and a scrupulous curve-fitting approach allowed for the first time the quantitative study of the GSH in-depth distribution in the NPs. NPs were proven to efficiently encapsulate GSH in their inner cores, thus showing promising perspectives as drug carriers.

Freeze-Drying of Composite Core-Shell Nanoparticles

The effects of four sugars (glucose, saccharose, maltose, trehalose) and one surfactant (Poloxamer 188), on the freeze-drying of poly(isobutylcyanoacrylate) (PIBCA), poly(epsilon-caprolactone)-poly(ethylene glycol) (PCL-PEG), and novel core (mainly PIBCA)-shell (principally PEG) composite nanoparticles (CNP) obtained by co-precipitation were investigated. The efficiency of the additives against the adverse effect of freeze-drying on the redispersibility of the nanoparticles was evaluated, based on the visual appearance of the nanoparticle suspensions (Tyndall effect and aggregation), and on the determination of the mean diameter ratio of the nanoparticles before and after freeze-drying. The results indicated that the addition of both sugars and surfactant was essential for the good redispersion of freeze-dried nanoparticles displaying hydrophobic (PIBCA) or hydrophilic (PCL-PEG and CNP) surfaces.

Novel method of doxorubicin-SPION reversible association for magnetic drug targeting

A new method of reversible association of doxorubicin (DOX) to superparamagnetic iron oxide nanoparticles (SPION) is developed for magnetically targeted chemotherapy. The efficacy of this approach is evaluated in terms of drug loading, delivery kinetics and cytotoxicity in vitro. Aqueous suspensions of SPION (ferrofluids) were prepared by coprecipitation of ferric and ferrous chlorides in alkaline medium followed by surface oxidation by ferric nitrate and surface treatment with citrate ions. The ferrofluids were loaded with DOX using a pre-formed DOX-Fe(2+) complex. The resulting drug loading was as high as 14% (w/w). This value exceeds the maximal loading known from literature up today. The release of DOX from the nanoparticles is strongly pH-dependent: at pH 7.4 the amount of drug released attains a plateau of approximately 85% after 1h, whereas at pH 4.0 the release is almost immediate. At both pH, the released drug is iron-free. The in vitro cytotoxicity of the DOX-loaded SPION on the MCF-7 breast cancer cell line is similar to that of DOX in solution or even higher, at low-drug concentrations. The present study demonstrates the potential of the novel method of pH-sensitive DOX-SPION association to design novel magnetic nanovectors for chemotherapy.

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.