ABSTRACT

A simple and efficient way to synthesize peptide-containing silicone materials is described. Silicone oils containing a chosen ratio of bioactive peptide sequences were prepared by acid-catalyzed copolymerization of dichlorodimethylsilane, hybrid dichloromethyl peptidosilane and either Si-vinyl or Si-H functionalized monomers. Functionalized silicone oils were first obtained and then after hydrosilylation cross-linking, bioactive PDMS based materials were straightforward obtained. The introduction of an antibacterial peptide yields PDMS materials showing an interesting activity against Staphylococcus Aureus. In the same way, RGD ligands-containing PDMS demonstrated improved cell adhesion properties. This generic method was fully compatible with the stability of peptides and thus opened the way to the synthesis of a wide range of biologically active silicones.

ABSTRACT

New synthetic textiles with physical and/or biological properties are increasingly used in medical applications. While a simple textile coating is usually carried out to obtain biological properties, covalent grafting should be considered for long-term applications. Herein, we have developed a new hybrid bioactive nylon whose synthesis involves a peptide sequence with a diacyl derivative. Numerous types of peptide-nylons were prepared by varying the molar percentage (0.1 %, 1 % and 10%) and orientation of the peptide in the polymer backbone. Nylons incorporating antibacterial peptides significantly inhibited S. aureus proliferation whereas nylons functionalized with cell-adhesive peptide enhanced the proliferation of L929 fibroblast. These results show that the incorporation of the peptides directly into the nylon skeleton is efficient and provides biological properties that suggest new ways of functionalizing biomedical textiles.

ABSTRACT

The need for bioactive dressings increases with the population aging and the prevalence of chronic diseases. In contrast, there are very few dressings on the market which are designed to display a chosen bioactivity. In this context, we investigated the surface-functionalization of silicone wound dressing with bioactive peptides. One of the challenges was to avoid multistep grafting reactions involving catalysts, solvents or toxic reagents, which are not suitable for the fabrication of medical devices at an industrial scale. In the other hand, a covalent bonding was necessary to avoid the loss of the biological effect by progressive removal of the peptide in biological fluids generated by the wound. To solve these limitations, we developed a strategy allowing an easy and direct functionalization of silicone. This strategy relies on hybrid silylated bioactive peptides, which chemoselectively react with plasma-activated silicone surfaces. We synthesized three hybrid peptides with wound healing properties, which were grafted on commercially available silicone dressings Cerederm® and Mepitel®. Grafted dressings were evaluated in vitro and enabled a quicker scare recovery and extracellular matrix deposition with human dermal fibroblasts. These results were confirmed by in vivo studies showing an enhanced wound-healing of the pig skin. By this simple method, we transformed inert dressing into bioactive dressing which showed properties of wound healing.

ABSTRACT

We have recently reported on a new class of silicone-peptide biopolymers obtained by polymerization of di-functionalized chlorodimethylsilyl hybrid peptides. Herein we describe a related strategy based on dichloromethylsilane-derived peptides, which yields novel polymers with a polysiloxane backbone, comparable to a silicone bearing pendent peptide chains. Interestingly, polymerization is chemoselective towards amino acids side-chains, proceeds in a single step in very mild conditions (neutral pH, water, room temperature). As potential application, a cationic sequence was polymerized and used an antibacterial coating.

ABSTRACT

A novel synthetic method to synthesize hydroxyapatite​/poly (D,​L) lactic acid biocomposite is presented in this study by mixing only the precursors hydroxyapatite and (D,​L) LA monomer without adding neither solvent nor catalyst.  Three compns. were successfully synthesized with the wt. ratios of 1​/1, 1​/3, and 3​/5 (hydroxyapatite​/(D,​L) lactic acid)​, and the grafting efficiency of poly (D,​L) lactic acid on hydroxyapatite surface reaches up to 84 %.  SEM and Fourier transform IR spectroscopy showed that the hydroxyapatite particles were successfully incorporated into the poly (D,​L) lactic acid polymer and X ray diffraction anal. showed that hydroxyapatite preserved its crystallinity after poly (D,​L) lactic acid grafting.  Differential scanning calorimetry shows that Tg of hydroxyapatite​/poly (D,​L) lactic acid composite is less than Tg of pure poly (D,​L) lactic acid, which facilitates the shaping of the composite obtained.  The addn. of poly (D,​L) lactic acid improves the adsorption properties of hydroxyapatite for fibronectin extracellular matrix protein.  Furthermore, the presence of poly (D,​L) lactic acid on hydroxyapatite surface coated with fibronectin enhanced pre-​osteoblast STRO-​1 adhesion and cell spreading.  These results show the promising potential of hydroxyapatite​/poly (D,​L) lactic acid composite as a bone substitute material for orthopedic applications and bone tissue engineering.

ABSTRACT

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.

ABSTRACT

With the aim to develop biomaterials for temporary medical devices, a series of novel reducible and/or degradable elastomers has been prepared from PLA‐b‐PEG‐b‐PLA copolymers photo‐crosslinked with diallyl sulfide or pentaerythritol tetrakis(3‐mercaptopropionate). Thermal and mechanical properties, including elastic limit and Young modulus, are assessed. Degradation is then evaluated under standard hydrolytic conditions. Reducibility of a selected elastomer is then illustrated using 2‐mercaptoethanol or glutathione as reducing agents. The redox‐sensitivity of the selected elastomer and the possibility to modulate the degradability are shown. Considering drug‐eluting elastomeric devices applications, anti‐inflammatory drug ibuprofen loading is illustrated with the two simplest elastomer formulations. A rapid or slow linear release is observed as a function of the low or high molecular weight of the triblock pre‐polymers. Finally, the cytocompatibility of the degradable elastomers is assessed with regard to their potential to favor or inhibit L929 murine fibroblasts proliferation as a function of the hydrophilicity/hydrophobicity of the triblock copolymers.

ABSTRACT

Novel biodegradable networks have been prepared by combination of post-polymerization modification of poly(e-caprolactone) and thiol-yne photo cross-linking. In a first step, a novel multifunctional poly(e-caprolactone) bearing propargyl groups (PCL-yne, 8 mol% substitution degree) was obtained in a rapid one-pot reaction and at a multigram scale. In a second step, PCL-yne and mixtures of PCL and PCL-yne were cross-linked via photoradical thiol-yne reaction in the presence of pentaerythritol tetrakis(3-mercaptopropionate) and various photoinitiators. The thermal properties and stabilities of the obtained networks have been evaluated before assessment of their mechanical properties. Finally, biocompatibility studies are reported with evaluation of the proliferation of L929 fibroblasts on the materials.

ABSTRACT

Internal biliary stenting during biliary reconstruction in liver transplantation decrease anastomotic biliary complications. Implantation of a resorbable internal biliary stent (RIBS) is interesting since it would avoid an ablation gesture. The objective of present work was to evaluate adequacy of selected PLA-b-PEG-b-PLA copolymers for RIBS aimed to secure biliary anastomose during healing and prevent complications, such as bile leak and stricture. The kinetics of degradation and mechanical properties of a RIBS prototype were evaluated with respect to the main bile duct stenting requirements in liver transplantation. For this purpose, RIBS degradation under biliary mimicking solution versus standard phosphate buffer control solution was discussed. Morphological changes, mass loss, water uptake, molecular weight, permeability, pH variations, and mechanical properties were examined over time. The permeability and mechanical properties were evaluated under simulated biliary conditions to explore the usefulness of a PLA-b-PEG-b-PLA RIBS to secure biliary anastomosis. Results showed no pH influence on the kinetics of degradation, with degradable RIBS remaining impermeable for at least 8 weeks, and keeping its mechanical properties for 10 weeks. Complete degradation is reached at 6 months. PLA-b-PEG-b-PLA RIBS have the required in vitro degradation characteristics to secure biliary anastomosis in liver transplantation and envision in vivo applications

ABSTRACT

The implantation of an internal biliary stent (IBS) during liver transplantation has recently been shown to reduce biliary complications. To avoid a potentially morbid ablation procedure, we developed a resorbable and radiopaque internal biliary stent (RIBS). We studied the mechanical and radiological properties of RIBS upon in vivo implantation in rats and we evaluated RIBS implantability in human anatomical specimens.

For this purpose, a blend of PLA₅₀-PEG-PLA₅₀ triblock copolymer, used as a polymer matrix, and of X-ray-visible triiodobenzoate-poly(e-caprolactone) copolymer (PCL-TIB), as a radiopaque additive, was used to design X-ray-visible RIBS. Samples were implanted in the peritoneal cavity of rats. The radiological, chemical, and biomechanical properties were evaluated during degradation. Further histological studies were carried out to evaluate the degradation and compatibility of the RIBS. A human cadaver implantability study was also performed.

The in vivo results revealed a decline in the RIBS mechanical properties within 3 months, whereas clear and stable X-ray visualization of the RIBS was possible for up to 6 months. Histological analyses confirmed compatibility and resorption of the RIBS, with a limited inflammatory response. The RIBS could be successfully implanted in human anatomic specimens. The results reported in this study will allow the development of trackable and degradable IBS to reduce biliary complications after liver transplantation.

ABSTRACT

Biliary diseases are the third most common cause of surgical digestive disease. There is a close relationship between the mechanical performance of the bile duct and its physiological function. Data of biomechanical properties of human main bile duct are scarce in literature. Furthermore, mechanical properties of soft tissues are affected by these preservation procedures. The aim of the present work was, on the one hand, to observe the microstructure of the human bile duct by means of histological analysis, on the other hand, to characterize the mechanical behavior and describe the impact of different preservation processes. A mechanical study in a controlled environment consisting of cyclic tests was made. The results of the mechanical tests are discussed and explained using the micro-structural observations. The results show an influence of the loading direction, which is representative of an anisotropic behavior. A strong hysteresis due to the viscoelastic properties of soft tissues was also observed. Embalming and freezing preservation methods had an impact on the biomechanical properties of human main bile duct, with fiber network deterioration. That may further provide a useful quantitative baseline for anatomical and surgical training using embalming and freezing.

ABSTRACT

PLA-b-PEG-b-PLA is a biodegradable triblock copolymer that presents both the mechanical properties of PLA and the hydrophilicity of PEG. In this paper, physical and mechanical properties of PLA-b-PEG-b-PLA are studied during in vitro degradation. The degradation process leads to a mass loss, a decrease of number average molecular weight and an increase of dispersity index. Mechanical experiments are made in a specific experimental set-up designed to create an environment close to in vivo conditions. The viscoelastic behaviour of the material is studied during the degradation. Finally, the mechanical behaviour is modelled with a linear viscoelastic model. A degradation variable is defined and included in the model to describe the hydrolytic degradation. This variable is linked to physical parameters of the macromolecular polymer network. The model allows us to describe weak deformations but become less accurate for larger deformations. The abilities and limits of the model are discussed.

ABSTRACT

Modification of the biodegradable and renewable poly(lactide) (PLA) to provide functional aliphatic polyesters is highly desirable to meet applications requirements. In this context, the objective of this work was to evaluate the possibility to use free-radical substitution as a simple and non-degrading method to yield the desired functional PLA. Halogenation of PLA was carried out in solution and various conditions of reaction have been evaluated. Halogenated PLAs were characterized by 1H NMR spectroscopy and size exclusion chromatography (SEC) to evaluate the substitution ratios and to check the non-degrading character of the radical modification. Furthermore, reactions on model compounds as well as MALDI-TOF analyses have been performed to elucidate the involved mechanism. The combined results proved the free-radical halogenation of PLA in solution to be regioselective with only the w-halogenated PLA being obtained without main-chain substitution.

ABSTRACT

Modification of the biodegradable and renewable poly(lactide) (PLA) to provide functional aliphatic polyesters is highly desirable to meet applications requirements. In this context, the objective of this work was to evaluate the possibility to use free-radical substitution as a simple and non-degrading method to yield the desired functional PLA. Halogenation of PLA was carried out in solution and various conditions of reaction have been evaluated. Halogenated PLAs were characterized by 1H NMR spectroscopy and size exclusion chromatography (SEC) to evaluate the substitution ratios and to check the non-degrading character of the radical modification. Furthermore, reactions on model compounds as well as MALDI-TOF analyses have been performed to elucidate the involved mechanism. The combined results proved the free-radical halogenation of PLA in solution to be regioselective with only the w-halogenated PLA being obtained without main-chain substitution.

ABSTRACT

Polymer-based drug delivery systems may significantly improve cancer therapy. We developed amphiphilic poly(e-caprolactone)-graft-(poly-N-(2-hydroxypropyl) methacrylamide) copolymers (PCL-graft-pHPMA) with tunable amphiphilicity intended for efficient dual delivery via simultaneous encapsulation of hydrophobic drug, Bcl-2 inhibitor ABT-199, and pH-sensitive conjugation of other  chemotherapeutics, doxorubicin, to desired sites, e.g. tumors. Using controlled RAFT polymerization and click chemistry well-defined PCL-graft-pHPMA of diverse M_w and physical properties were prepared. By simple dissolution they self-assembled into highly stable micelles with D_h ≈ 25 nm and low critical micelle concentration (around 5 μg mL^-1). The total drug payload reached 17 wt % while maintaining system solubility. The micelles exhibited long-term stability in buffers, while they were cleaved in the presence of lipase, thus proving degradation and drug release after uptake to lysosomes of cancer cells with minimal drug leakage during blood circulation. PCL-graft-pHPMA micelles may serve as a long-circulating drug depo for effective dual therapy of diverse malignancies.

ABSTRACT

We developed a new simplified method for the synthesis of well-defined linear, diblock, or starlike N-(2-hydroxypropyl)methacrylamide (HPMA)-based polymer drug carriers using controlled reversible addition–fragmentation chain transfer polymerization. The prepared monodispersed polymers are after the drug attachment intended for enhanced anticancer therapy. This new approach significantly reduces the number of required synthetic steps and minimizes the consumption of organic solvents during the synthesis. As a result, highly defined linear, diblock, and starlike copolymers designed for pH-triggered drug activation/release in tumor tissue were formed in sufficient amounts for further physicochemical and biological studies. Within the synthesis, we also developed a new procedure for the selective deprotection of tert-butoxycarbonyl hydrazide and amine groups on hydrophilic HPMA copolymers, including the one-pot removal of polymer end groups. We studied and described in detail the kinetics and efficacy of the deprotection reaction. We believe the simplified synthetic approach facilitates the preparation of polymer conjugates bound by the pH-sensitive hydrazone bond and their application in tumor treatment.

ABSTRACT

The development of flexible drug delivery systems that can be tuned as a function of the drug to be delivered and of the target disease is crucial in modern medicine. For this aim, novel amphiphilic poly(ε-caprolactone)-g-poly(ethylene glycol) (PCL-g-PEG) copolymers with well-controlled design were synthesized by thiol–yne photochemistry. The grafting density and the copolymer amphiphilicity were easily controlled via the reaction parameters: concentration, reaction time, PEG length and the molar ratio between PCL and PEG or the photoinitiator in the reaction mixture. The self-assembling behavior of the copolymers was studied and a correlation between the composition of PCL-g-PEG and the nanoaggregate diameter sizes (28 to 73 nm) and critical aggregation concentrations (1.1 to 4.3 mg L⁻¹) was found. The influence of copolymer amphiphilicity on the drug loading was evaluated with various drugs including anticancer drugs (paclitaxel, ABT-199), drugs to overcome multidrug resistance in cancer cells (curcumin, elacridar), an anti-inflammatory drug (dexamethasone) and an antibacterial drug (clofazimine). Finally, the influence of amphiphilicity on curcumin release and toxicity towards MCF-7 cancer cell lines was studied. The impact of the grafting density, PEG length and the overall EG/CL ratio is discussed in detail. Curcumin loaded PCL-g-PEG with lower EG/CL ratios and shorter PEG chains showed higher toxicity compared to their more hydrophilic counterparts.

ABSTRACT

A simple method for the synthesis of a family of poly(ɛ-caprolactone)-g-polyethylene glycol (PCL-g-PEG) copolymers of controlled amphiphilicity and their use to generate nanospheres or micelles are reported. PCL-g-PEG with various compositions are prepared from a single strategy relying on a combination of post-polymerization modification and subsequent thiol-yne photografting. Alkyne-functional PCL (PCL-yne) are first obtained by anionic activation and reaction with propargyl bromide to yield PCL-yne with 8% alkyne groups. PEG-thiol is then reacted on PCL-yne under UV activation to yield the targeted graft copolymer by thiol-yne photoaddition. The advantage of the approach is that control over the composition is easily achieved yielding to amphiphilic graft copolymers with ethylene glycol/ caprolactone (EG/CL) ratios ranging from 0.1 to 1.3. Starting from this single strategy, it was therefore possible to obtain nanospheres (DH~55 nm) or micelles (DH~30 nm) by copolymers self-assembly depending on the ratio EG/CL. The potential of the PCL-g-PEG micelles as drug carrier was finally evaluated with curcumin that was efficiently encapsulated, protected and released over 80 days. Interestingly it was found that drug encapsulation efficiency and drug loading were higher for PCL-g-PEG copolymers compared to block PCL-b-PEG.