Non-covalent strategies to functionalize polymeric nanoparticles with NGR peptides for targeting breast cancer.

Surface functionalization of nanoparticles (NPs) with tumor-targeting peptides is an emerging approach with a huge potential to translate in the clinic and ameliorate the efficacy of nano-oncologicals. One major challenge is to find straightforward strategies for anchoring peptides on the surface of biodegradable NPs and ensuring their correct exposure and orientation to bind the target receptor. Here, we propose a non-covalent strategy to functionalize polyester aminic NPs based on the formation of either electrostatic or lipophilic interactions between NPs and the peptide modified with an anchoring moiety. We selected an iNGRt peptide containing a CendR motif (CRNGR) targeting neuropilin receptor 1 (NRP-1), which is upregulated in several cancers. iNGRt was linked with either a short poly(glutamic acid) chain (polyE) or a palmitoyl chain (Palm) and used to functionalize the surface of NPs made of a diamine poly(ε-caprolactone). iNGRt-PolyE was adsorbed on preformed cationic NPs through electrostatic interaction, whereas iNGRt-Palm was integrated into the forming NPs through interactions. In both cases, peptides were strongly associated with NPs of ∼100 nm, low polydispersity indexes, and positive zeta potential values. NPs entered MDA-MB231 breast cancer cells overexpressing NRP-1 via receptor-mediated endocytosis and showed a different cell localization depending on the mode of peptide anchoring. When loaded with the lipophilic anticancer drug docetaxel (DTX), NPs functionalized with the iNGRt-Palm variant exerted a time- and dose-dependent cytotoxicity similar to DTX in MDA-MB-231 cells but were less toxic than DTX toward control MRC-5 human fibroblasts, not expressing NRP-1. In a heterotopic mouse model of triple negative breast cancer, iNGRt-Palm NPs were tolerated better than free DTX and demonstrated superior anticancer activity and survival compared to both free DTX and NPs without peptide functionalization. We foresee that the functionalization strategy with palmitoylated peptides proposed here can be extended to other biodegradable NPs and peptide sequences designed for therapeutic or targeting purposes.

Biodegradable nanoparticles combining cancer cell targeting and anti-angiogenic activity for synergistic chemotherapy in epithelial cancer.

A biodegradable engineered nanoplatform combining anti-angiogenic activity and targeting of cancer cells to improve the anticancer activity of docetaxel (DTX) is here proposed. Indeed, we have developed biodegradable nanoparticles (NPs) of poly(ethylene glycol)-poly(ε-caprolactone), exposing on the surface both folate motifs (Fol) for recognition in cells overexpressing Folate receptor-α (FRα) and the anti-angiogenic hexapeptide aFLT1. NPs showed a size around 100 nm, the exposure of 60% of Fol moieties on the surface, and the ability to entrap DTX and sustain its release with time. NPs were stable in simulated biological fluids and slightly interacted with Fetal Bovine serum, especially in the formulation decorated with Fol and aFLT1. The presence of Fol on NPs did not impair the anti-angiogenic activity of aFLT1, as assessed by in vitro tube formation assay in HUVEC endothelial cells. In both 2D and 3D KB cell cultures in vitro, the cytotoxicity of DTX loaded in NPs was not significantly affected by Fol/aFLT1 double decoration compared to free DTX. Remarkably, NPs distributed differently in 3D multicellular spheroids of FRα-positive KB cancer cells depending on the type of ligand displayed on the surface. In particular, NPs unmodified on the surface were randomly distributed in the spheroid, whereas the presence of Fol promoted the accumulation in the outer rims of the spheroid. Finally, NPs with Fol and aFLT1 gave a uniform distribution throughout the spheroid structure. When tested in zebrafish embryos xenografted with KB cells, NPs displaying Fol/aFLT1 reduced DTX systemic toxicity and inhibited the growth of the tumor mass and associated vasculature synergistically. Overall, nanotechnology offers excellent ground for combining therapeutic concepts in cancer, paving the way to novel multifunctional nanopharmaceuticals decorated with bioactive elements that can significantly improve therapeutic outcomes.

PEGylated cationic nanoassemblies based on triblock copolymers to combine siRNA therapeutics with anticancer drugs.

Nowadays, the clinical administration of siRNA therapeutics is still challenging due to the need of safe and efficient delivery carriers. In this context, biodegradable and amphiphilic triblock copolymers (ABC) containing amine-based cationic segments could be a powerful tool for siRNA delivery. Herein, we propose a range of poly(ethylene glycol) (PEG)-poly(2-dimethyl(aminoethyl) methacrylate) (pDMAEMA)-polycaprolactone (PCL) copolymers with different lengths of the blocks and hydrophilic/lipophilic balance to deliver siRNA alone or in association with a conventional anticancer drug. mPEG-pDMAEMA-PCL copolymers were synthesized by a combination of techniques and characterized by NMR analysis, Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Copolymers were then employed to prepare NPs through nanoprecipitation. NPs based on copolymers with long PCL chains (SSL-NPs and LLL-NPs) showed the best colloidal properties and a highly stable core-shell structure with a better orientation of the PEG fringe on the surface. Concerning siRNA delivery, SSL-NPs based on copolymers with short PEG and pDMAEMA chains showed optimized ability to complex and then deliver siRNA at the cell level. The strong interaction between the nucleic acid and the cationic pDMAEMA blocks of NPs was then confirmed by release studies that showed a sustained release of siRNA within 48 h. The transfection efficiency of NPs was assessed in human melanoma cells. NPs were complexed with a therapeutic siRNA against TUBB3 (TUB-siRNA). We observed the best results with SSL-NPs, probably due to the higher preserved buffer capacity of the pDMAEMA blocks. Finally, in order to give a proof of concept of a possible application in the combined chemo/gene-therapy of cancer, SSL-NPs complexed with TUB-siRNA were loaded with docetaxel (DTX) and then cytotoxicity was evaluated in the same cell line. The co-delivery of TUB-siRNA into NPs appeared to strongly potentiate the anti-proliferative activity of DTX, thus highlighting the combinatory activity of the NPs.

Semi-Crystalline Hydrophobic Polyamidoamines: A New Family of Technological Materials?

The hitherto known polyamidoamines (PAAs) are not suitable as structural materials because they are usually water-soluble or swellable in water. This paper deals with the synthesis and characterization of semi-crystalline hydrophobic PAAs (H-PAAs) by combining different bis-sec-amines with bis-acrylamides obtained from C6-C12 bis-prim-amines. H-PAAs were initially obtained in a solution of benzyl alcohol, a solvent suitable for both monomers and polymers. Their number average molecular weights, M¯n, which were determined with 1H-NMR by evaluating the percentage of their terminal units, varied from 6000 to >10,000. The solubility, thermal properties, ignitability and water resistance of H-PAAs were determined. They were soluble in organic solvents, semi-crystalline and thermally stable. The most promising ones were also prepared using a bulk process, which has never been previously reported for PAA synthesis. In the form of films, these H-PAAs were apparently unaffected by water. The films underwent tensile and wettability tests. They showed similar Young moduli (260-263 MPa), whereas the maximum stress and the stress at break depended on the number of methylene groups of the starting bis-acrylamides. Their wettability was somewhat higher than that of common Nylons. Interestingly, none of the H-PAAs considered, either as films or powders, ignited after prolonged exposure to a methane flame.

Alginate/human elastin-like polypeptide composite films with antioxidant properties for potential wound healing application.

In this contribution we describe the preparation and characterization of a series of cross-linked films based on the combination of an elastin-derived biomimetic polypeptide (Human Elastin-Like Polypeptide, HELP) with alginate (ALG) to obtain a composite with enhanced properties. ALG/HELP composite films loaded with the hydrophobic natural antioxidant curcumin were prepared by solvent casting method followed by the cross-linking with calcium chloride. The compatibility between the two components as well as the final properties was evaluated. The micro-morphological study of films showed a homogeneous structure, but the film tensile strength decrease with HELP content and elongation at break was adversely affected by biopolymer addition. Spectroscopic and thermal analyses confirmed an interaction between ALG and HELP which also causes a modification in swelling kinetics and faster degradation. Moreover, the study of curcumin release showed a controlled delivery up to 10 days with a faster release rate in the presence of HELP. Human Dermal Fibroblasts (hDF) were used to test the in vitro cytocompatibility. The antioxidant activity correlated to the increase of HELP content suggested the applicability of these composites to develop smart biomaterials. Overall, these features indicated how this composite material has considerable potential as customizable platforms for various biomedical applications.

Zein Beta-Cyclodextrin Micropowders for Iron Bisglycinate Delivery.

Given the limited number of materials available to design delivery platforms for nutrients, the rational combination of raw materials already approved as food ingredients and their processing through nano-micro technology can offer a unique tool for innovation. Here, we propose a nano-in-micro strategy to produce powders based on the hydrophobic protein zein, useful for the oral delivery of a hydrophilic iron source (iron bisglycinate) in anaemic patients. Iron-loaded powders were prepared through a two-step strategy consisting in the formation of a zein pseudolatex followed by a spray-drying step. To extend the manipulation space for zein and entrap iron bisglycinate, ß-cyclodextrin (ßCD) was selected as helping excipient. Addition of ßCD allowed iron loading in the pseudolatex and greatly increased product yields after the drying process as compared to zein alone. Iron-loaded micro-sized powders were characterised by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to elucidate the role of ßCD as a compatibilizer for the zein-iron system. Remarkably, micropowders released only 20% of FeBIS in a simulated gastric fluid, whereas release in a simulated intestinal fluid was almost completed in 7 h. In summary, ßCD association to zein is a novel strategy to expand applications in the oral delivery of iron bisglycinate and, prospectively, to micronutrient chelates.

Surface Exposure of PEG and Amines on Biodegradable Nanoparticles as a Strategy to Tune Their Interaction with Protein-Rich Biological Media.

Nanoparticles (NPs) based on amphiphilic block copolymers of polyethylene glycol (PEG) and biodegradable polyesters are of particular current interest in drug nanodelivery due to their easily manipulated properties. The interaction of these NPs with biological environments is highly influenced by shell features, which drive biological identity after administration. To widen the strategies available for tuning particle surface chemistry, here we developed a panel of amine-bearing PEGylated NPs with a poly(ε-caprolactone) (PCL) core for the delivery of lipophilic drugs, and investigated the impact of NP modifications on their interaction with abundant circulating proteins (human serum albumin-HSA-and mucin), as well as their transport through biological barriers (artificial mucus-AM, extracellular matrix-ECM). We prepared NPs based on a diamino-terminated PCL (amine-NPs) and its mixture with PEG-PCL copolymers (amine/PEG-NPs) at different PEG molecular weights by nanoprecipitation, as well as corresponding NPs of PEG-PCL (PEG-NPs). The presence of an amine-bearing polymer resulted in NPs with a net positive charge and a zeta potential dependent on the length of PEG in the copolymer. Amine/PEG-NPs had a larger fixed aqueous layer thickness as compared to PEG-NPs, suggesting that PEG conformation is affected by the presence of positive charges. In general, amine-bearing NPs promptly interacted with the dysopsonic protein HSA, due to electrostatic interactions, and lose stability, thereby undergoing time-related aggregation. On the other hand, amine/PEG-NPs interaction with mucin induced switching to a negative surface charge but did not alter the quality of the dispersion. The transport kinetics of NPs through a layer of artificial mucus and tumor extracellular matrix was studied by means of fluorescent NPs based upon FRET. Amine/PEG-NPs did not cross the ECM, but they were promptly transported through the AM, with swifter transport noted at increasing MWs of PEG in the copolymer. Finally, we demonstrated that all the different NP types developed in this study are internalized by human monocytes and, despite the positive charge, they did not induce a measurable inflammatory effect. In conclusion, we showed that the concurrent presence of both PEG and amine groups on NP surface is a promising strategy for directing their interaction with body compartments. While PEG-NPs are confirmed for their capacity to cross ECM-like compartments, amine/PEG-NPs are revealed as a powerful platform to widen the arsenal of nanotools available for overcoming mucus-covered epithelia.

Biodegradable nanoparticles exposing a short anti-FLT1 peptide as antiangiogenic platform to complement docetaxel anticancer activity.

Inhibition of tumor angiogenesis is considered as a valuable clinical strategy to treat some tumors, although benefits in term of progression-free and overall survival have been modest. Recent findings have pushed toward the use of antiangiogenic drugs in combination with chemotherapy regimens to potentiate therapeutic outcome. Herein, we propose a novel type of biodegradable antiangiogenic core-shell polymeric nanoparticles (NPs) for the delivery of poorly water-soluble chemotherapeutics. An amphiphilic diblock copolymer of poly(ethyleneglycol)-poly(ε-caprolactone) (PEG-PCL) was conjugated with an anti-FLT1 hexapeptide (aFLT1) at -OH PEG end, mixed in appropriate ratios with a monomethoxy-PEG-PCL and nanoprecipitated to form core-shell aFLT1-bearing NPs (DBLaFLT1). DBLaFLT1 were <100 nm, exposed aFLT1 on the surface and showed a higher thickness of the external hydrophilic shell as compared to NPs that do not bear aFLT1 (DBL). Very interestingly, DBLaFLT1 showed an antiangiogenic activity in the human umbilical endothelial cells (HUVEC) tube formation assay three-fold higher than an equivalent dose of free aFLT1. To provide a proof-of-concept of DBLaFLT1 potential in the delivery of conventional chemotherapeutics, docetaxel (DTX) was selected as model drug. DBLaFLT1 entrapped DTX with high efficiency and sustained its release along time in simulated biological conditions. At a non-cytotoxic dose, DTX-loaded DBLaFLT1 almost completely abolished tube formation in HUVEC while inhibition of DTX loaded DBL was significantly lower. The cytotoxicity of DTX-loaded NPs in HUVEC and triple negative breast cancer cells (MDA-MB-231) was not significantly different from that of the free drug in a wide range of concentrations and up to 72 h. Studies carried out in MDA-MB-231 cells implanted in chicken embryo chorioallantoic membranes (CAMs) evidenced an antiangiogenic activity of DTX-loaded DBLaFLT1 higher as compared with that of both DTX-loaded DBL and free DTX. While cancer cell migration from the tumor site was unaffected, the anticancer activity of DTX-loaded NPs was higher than that of free DTX and maximized for DTX-DBLaFLT1. In perspective, these results suggest that the delivery approach proposed here can be applied to other lipophilic chemotherapeutics devoid of relevant antiangiogenic properties to improve the final therapeutic response.

Macroporous alginate foams crosslinked with strontium for bone tissue engineering.

Nowadays, the need of novel strategies to repair and regenerate bone defects in the field of biomedical applications has increased. Novel approaches include the design of natural bioactive scaffolds mimicking bone tissue. These bioactive scaffolds have to possess biophysical properties suitable to address biological response towards newly bone tissue formation. In particular, scaffold porosity and pore size play a pivotal role in cell migration, adhesion and proliferation, thus increasing cell-material surface interaction and osteogenic signals transmission. Here we propose the development of macroporous alginate foams (MAFs) with porous and well interconnected structure, useful to enhance growth and osteogenic differentiation of human Mesenchymal Stem Cells (hMSCs). Moreover, in this study we report a new method for MAFs fabrication based on the combination of internal gelation technique with gas foaming. Strontium was employed in combination with calcium as cross-linking agent for the alginate chains and as enhancer of the osteogenic differentiation. The influence of strontium ions on the gelation kinetics, physical properties and degradation in physiological medium of MAFs was investigated. Our results suggest that the combination of internal gelation technique with gas foaming followed by freeze-drying is an easy and straightforward procedure to prepare alginate foams with high porosity and interconnectivity, able to support cell infiltration. Finally, biological assays showed how scaffolds with high strontium content are able to support cell growth and differentiation in long times by promoting osteogenic marker expression.

Biodegradable nanoparticles bearing amine groups as a strategy to alter surface features, biological identity and accumulation in a lung metastasis model.

Polymer-based nanoparticles (NPs) with a cationic charge have emerged recently as a potent nanotool due to their unique ability to penetrate deeply inside tumor tissue and to interact preferentially with the plasma membrane of cancer cells. In this paper, we propose a general strategy to obtain biodegradable cationic NPs of poly(ε-caprolactone) (PCL) based on an amine terminated PCL (NH2-PCL4.2k) or its mixture with monomethoxypoly(ethylene glycol)-PCL (mPEG1k-PCL4k). Positively-charged NPs were obtained, switching to net negative values through adsorption of low molecular weight hyaluronan. NPs exposing both amine and PEG groups on the surface showed a larger fixed aqueous layer thickness as compared to fully PEGylated NPs, suggesting that PEG conformation/localization is affected by the presence of amino groups. The stability of the positively-charged NPs was affected by the presence of ions, while interaction with the human plasma protein pool indicated time-dependent protein corona formation imparting an overall negative charge. NP-induced haemolysis was low, while cytotoxicity against A549 and Calu-3 lung cancer cell lines was cell-specific as well as dose and time-dependent. Finally, the presence of amino groups greatly changed the in vivo biodistribution of the NPs in tumor-bearing mice (lung colonization of B16F10 cancer cells) allowing the amine/PEGylated NPs to accumulate mainly at the target organ. Overall, this study demonstrates that NPs with a mixed amine/PEGylated surface exhibit a peculiar biological identity that alters their interaction with the bioenvironment and are thus worthy of further investigation in the delivery of chemotherapeutics.

Correction: Biodegradable nanoparticles bearing amine groups as a strategy to alter surface features, biological identity and accumulation in a lung metastasis model.

Correction for 'Biodegradable nanoparticles bearing amine groups as a strategy to alter surface features, biological identity and accumulation in a lung metastasis model' by Diletta Esposito et al., J. Mater. Chem. B, 2018, 6, 5922-5930.

Shedding light on surface exposition of poly(ethylene glycol) and folate targeting units on nanoparticles of poly(ε-caprolactone) diblock copolymers: Beyond a paradigm.

Polymeric nanoparticles (NPs) of poly(ε-caprolactone) (PCL) covered with a hydrophilic poly(ethylene glycol) (PEG) shell are usually prepared from diblock PEG-PCL copolymers through different techniques. Furthermore PEG, NPs can be decorated with targeting ligands to accumulate in specific cell lines. However, the density and conformation of PEG on the surface and its impact on the exposition of small targeting ligands has been poorly considered so far although this has a huge impact on biological behaviour. Here, we focus on PEG-PCL NPs and their folate-targeted version to encourage accumulation in cancer cells overexpressing folate receptor α. NPs were prepared with mixtures of PEG-PCL with different PEG length (short 1.0kDa, long 2.0kDa,) and a folate-functionalized PEG-PCL (PEG 1.5kDa) by the widely employed solvent displacement method. In depth characterization of NPs surface by 1H NMR, fluorescence and photon correlation spectroscopy evidenced a PEGylation extent below 7% with PEG in a mushroom conformation and the presence of folate more exposed to water pool in the case of copolymer with short PEG. NPs with short PEG adsorbed HSA forming a soft corona without aggregating. Although limited, PEGylation overall reduced NPs uptake in human macrophages. Uptake of NPs exposing folate prepared with short PEG was higher in KB cells (FR+) than in A549 (FR-), occurred via FR-receptor and involved lipid rafts-dependent endocytosis. In conclusion, the present results demonstrate that PEG length critically affects protein interaction and folate exposition with a logical impact on receptor-mediated cell uptake. Our study highlights that the too simplistic view suggesting that PEG-PCL gives PEG-coated NPs needs to be re-examined in the light of actual surface properties, which should always be considered case-by-case.

Alginate hydrogels coated with chitosan for wound dressing.

In this work, a coating of chitosan onto alginate hydrogels was realized using the water-soluble hydrochloride form of chitosan (CH-Cl), with the dual purpose of imparting antibacterial activity and delaying the release of hydrophilic molecules from the alginate matrix. Alginate hydrogels with different calcium contents were prepared by the internal setting method and coated by immersion in a CH-Cl solution. Structural analysis by cryo-scanning electron microscopy was carried out to highlight morphological alterations due to the coating layer. Tests in vitro with human mesenchymal stromal cells (MSC) were assessed to check the absence of toxicity of CH-Cl. Swelling, stability in physiological solution and release characteristics using rhodamine B as the hydrophilic model drug were compared to those of relative uncoated hydrogels. Finally, antibacterial activity against Escherichia coli was tested. Results show that alginate hydrogels coated with chitosan hydrochloride described here can be proposed as a novel medicated dressing by associating intrinsic antimicrobial activity with improved sustained release characteristics.

Novel zinc alginate hydrogels prepared by internal setting method with intrinsic antibacterial activity.

In this paper, a controlled gelation of alginate was performed for the first time using ZnCO3 and GDL. Uniform and transparent gels were obtained and investigated as potential wound dressings. Homogeneity, water content, swelling capability, water evaporation rate, stability in normal saline solution, mechanical properties and antibacterial activity were assessed as a function of zinc concentration. Gelation rate increased at increasing zinc content, while a decrease in water uptake and an improvement of stability were found. Release of zinc in physiological environments showed that concentration of zinc released in solution lies below the cytotoxicity level. Hydrogels showed antimicrobial activity against Escherichia coli. The hydrogel with highest zinc content was stabilized with calcium by immersion in a calcium chloride solution. The resulting hydrogel preserved homogeneity and antibacterial activity. Furthermore, it showed even an improvement of stability and mechanical properties, which makes it suitable as long-lasting wound dressing.

Functionalized PCL/HA nanocomposites as microporous membranes for bone regeneration.

In the present work, microporous membranes based on poly(ε-caprolactone) (PCL) and PCL functionalized with amine (PCL-DMAEA) or anhydride groups (PCL-MAGMA) were realized by solvent-non solvent phase inversion and proposed for use in Guided Tissue Regeneration (GTR). Nanowhiskers of hydroxyapatite (HA) were also incorporated in the polymer matrix to realize nanocomposite membranes. Scanning Electron Microscopy (SEM) showed improved interfacial adhesion with HA for functionalized polymers, and highlighted substantial differences in the porosity. A relationship between the developed porous structure of the membrane and the chemical nature of grafted groups was proposed. Compared to virgin PCL, hydrophilicity increases for functionalized PCL, while the addition of HA influences significantly the hydrophilic characteristics only in the case of virgin polymer. A significant increase of in vitro degradation rate was found for PCL-MAGMA based membranes, and at lower extent of PCL-DMAEA membranes. The novel materials were investigated regarding their potential as support for cell growth in bone repair using multipotent mesenchymal stromal cells (MSC) as a model. MSC plated onto the various membranes were analyzed in terms of adhesion, proliferation and osteogenic capacity that resulted to be related to chemical as well as porous structure. In particular, PCL-DMAEA and the relative nanocomposite membranes are the most promising in terms of cell-biomaterial interactions.

Synthesis of chitosan-PEO hydrogels via mesylation and regioselective Cu(I)-catalyzed cycloaddition.

In this work, a well-defined hydrogel was developed by coupling chitosan with PEO through "click chemistry". Azide functionalities were introduced onto chitosan, through mesylation of C-6 hydroxyl groups, and reacted with a di-alkyne PEO by a regioselective Cu(I)-catalyzed cycloaddition. This synthetic approach allowed us to obtain a hydrogel with a controlled crosslinking degree. In fact, the extent of coupling is strictly dependent on the amount of azido groups on chitosan, which in turn can be easily modulated. The obtained hydrogel, with a crosslinking degree of around 90%, showed interesting swelling properties. With respect to chitosan hydrogels reported in literature, a considerably higher equilibrium uptake was reached (940%). The possibility to control the crosslinking degree of hydrogel and its capability to rapidly absorb high amounts of water make this material suitable for several applications, such as controlled drug release and wound healing.

Crosslinker effects on functional properties of alginate/N-succinylchitosan based hydrogels.

In this paper, physico-chemical, mechanical and antimicrobial properties of hydrogels based on alginate/N-succinylchitosan blends crosslinked by calcium or zinc ions containing cellulose microfibers were investigated and discussed. With respect to plain alginate hydrogels, the addition of N-succinylchitosan significantly improved properties such as swelling degree and stability in saline solution. The water vapour transmission rate confirmed that all the hydrogels were able to assure a moist wound environment. Morphological analysis showed a good embedding of fibres within the zinc crosslinked hydrogels. In addition, zinc-crosslinked hydrogels evidenced antimicrobial activity against two common skin pathogenic bacteria, Staphylococcus aureus and Escherichia coli. Cytotoxicity assays proved that the amount of zinc released is slightly over the toxic level. Overall, the characteristics of the zinc-crosslinked hydrogels showed their potential interest as materials for wound dressing.

Development of innovative biopolymers and related composites for bone tissue regeneration: study of their interaction with human osteoprogenitor cells.

PURPOSE: In the framework of a project aiming to improve the properties of poly(ε-caprolactone) (PCL)-based devices, we prepared novel composites and tested their in vitro biocompatibility and osteogenic capacity on human mesenchymal stromal cells (MSC) from bone marrow. METHODS: We prepared two functionalized derivatives, PCL-g-MAGMA and PCL-g-DMAEA, by insertion of anhydride groups by radical grafting of maleic anhydride (MA) and glycidyl-methacrylate (GMA) molecules, and by insertion of N-(dimethylamino)ethylacrylate (DMAEA) of tertiary amines groups, respectively. In addition, in order to improve the osteoconductive properties of the materials, we also prepared the corresponding composites containing the mineral component of bone, namely hydroxyapatite (HA). Mesenchymal stromal cells (MSC) derived from bone marrow were prepared, plated onto a number of discs obtained from these functionalized derivatives and tested in terms of adhesion and vitality (by MTT test and SEM observation), and the expression of alkaline phosphatase, the early marker of osteoblastic phenotype. RESULTS: The biological in vitro assessment of the functionalized materials, PCL-g-MAGMA and PCL-g-DMAEA, appeared promising only in part, in particular the cells exhibited very poor adhesion to PCL-g-MAGMA. On the contrary, the related composites, PCL-g-MAGMA-HA and PCL-g-DMAEA-HA clearly showed that the addition of HA greatly ameliorated the cell-material interaction. In particular, a surprisingly increased response characterized PCL-g-MAGMA-HA, either in terms of adhesion and vitality or in terms of alkaline phosphatase activity. CONCLUSIONS: Altogether these studies showed that the addition of HA nanowhiskers resulted for all basic materials, in particular PCL-g-MAGMA, in improved cell adhesion and performance.