Multilayered Polyurethane/Poly(vinyl alcohol) Nanofibrous Mats for Local Topotecan Delivery as a Potential Retinoblastoma Treatment.

Local chemotherapy using polymer drug delivery systems has the potential to treat some cancers, including intraocular retinoblastoma, which is difficult to treat with systemically delivered drugs. Well-designed carriers can provide the required drug concentration at the target site over a prolonged time, reduce the overall drug dose needed, and suppress severe side effects. Herein, nanofibrous carriers of the anticancer agent topotecan (TPT) with a multilayered structure composed of a TPT-loaded inner layer of poly(vinyl alcohol) (PVA) and outer covering layers of polyurethane (PUR) are proposed. Scanning electron microscopy showed homogeneous incorporation of TPT into the PVA nanofibers. HPLC-FLD proved the good loading efficiency of TPT (≥85%) with a content of the pharmacologically active lactone TPT of more than 97%. In vitro release experiments demonstrated that the PUR cover layers effectively reduced the initial burst release of hydrophilic TPT. In a 3-round experiment with human retinoblastoma cells (Y-79), TPT showed prolonged release from the sandwich-structured nanofibers compared with that from a PVA monolayer, with significantly enhanced cytotoxic effects as a result of an increase in the PUR layer thickness. The presented PUR-PVA/TPT-PUR nanofibers appear to be promising carriers of active TPT lactone that could be useful for local cancer therapy.

The Role of Cryotherapy in Vitreous Concentrations of Topotecan Delivered by Episcleral Hydrogel Implant.

Transscleral diffusion delivery of chemotherapy is a promising way to reach the vitreal seeds of retinoblastoma, the most common intraocular malignancy in childhood. In this in vivo study, the delivery of topotecan via lens-shaped, bi-layered hydrogel implants was combined with transconjunctival cryotherapy to assess whether cryotherapy leads to higher concentrations of topotecan in the vitreous. The study included 18 New Zealand albino rabbits; nine rabbits received a topotecan-loaded implant episclerally and another nine rabbits received transconjunctival cryotherapy superotemporally 2 weeks before implant administration. Median vitreous total topotecan exposures (area under the curve, AUC) were 455 ng·h/mL for the cryotherapy group and 281 ng·h/mL for the non-cryotherapy group, and were significantly higher in the cryotherapy group, similar to maximum levels. Median plasma AUC were 50 ng·h/mL and 34 ng·h/mL for the cryotherapy and non-cryotherapy groups, respectively, with no statistically significant differences between them. In both groups, AUC values in the vitreous were significantly higher than in plasma, with plasma exposure at only approximately 11-12% of the level of vitreous exposure. The results confirmed the important role of the choroidal vessels in the pharmacokinetics of topotecan during transscleral administration and showed a positive effect of cryotherapy on intravitreal penetration, resulting in a significantly higher total exposure in the vitreous.

Hydrogel implants for transscleral diffusion delivery of topotecan: In vivo proof of concept in a rabbit eye model.

Treatment of retinoblastoma (Rb) has greatly improved in recent years in terms of survival and eye salvage rates, using mainly intra-arterial or intravitreal chemotherapy. However, the treatment of vitreous tumor seeding still represents a challenge and it is of great interest to develop new strategies to deliver pharmacologically sufficient drug amounts to the vitreous humor. In the present work, we present a lens-shaped bi-layered hydrogel implant for delivery of topotecan (TPT) via transscleral diffusion. The implant consists of an inner TPT-loaded poly(2-hydroxyethyl methacrylate) (pHEMA) layer adjacent to the sclera and an outer covering poly(2-ethoxyethyl methacrylate) (pEOEMA) layer impermeable to TPT. TPT-loaded pHEMA samples exhibit long-lasting in vitro cytotoxicity against the Rb cell line Y79. In an in vivo experiment, pHEMA/pEOEMA implants are successfully surgically administered to the posterior segment of rabbit eyes. The determination of TPT pharmacokinetics demonstrates the attainment of promising levels of TPT (10 ng/ml) in vitreous humor 8 h after implant placement. The results from the pilot experiment constitute the proof of principle for the use of the proposed implants as a drug delivery system for the local treatment of intraocular diseases.

Biocompatible indocyanine green loaded PLA nanofibers for in situ antimicrobial photodynamic therapy.

Chronic wounds and their associated bacterial infections are major issues in modern health care systems. Therefore, antimicrobial resistance (AMR), treatment costs, and number of disability-adjusted life-years have gained more interest. Recently, photodynamic therapy emerged as an effective approach against resistant and naïve bacterial strains with a low probability of creating AMR. In this study, needleless electrospinning was used to produce an indocyanine green (ICG) loaded poly(d,l-lactide) nanofibrous mesh as a photoresponsive wound dressing. The non-woven mesh had a homogeneous nanofibrous structure and showed long-term hydrolytic stability at different pH values. The antimicrobial activity was tested against several bacterial strains, namely Staphylococcus saprophyticus subsp. bovis, Escherichia coli DH5 alpha, and Staphylococcus aureus subsp. aureus. Upon irradiation with a laser of a specific wavelength (λ = 810 nm), the bacterial viability was significantly reduced by 99.978% (3.66 log10), 99.699% (2.52 log10), and 99.977% (3.64 log10), respectively. The nanofibrous mesh showed good biocompatibility, which was confirmed by the proliferation of mouse fibroblasts (L929) on the surface and into deeper parts of the mesh. Furthermore, a favorable proangiogenic effect was observed in ovo using the chorioallantoic membrane assay. In general, it can be concluded that ICG loaded nanofibers as an innovative wound dressing represent a promising strategy against chronic wounds associated with skin infections.

Hydrogel implants for transscleral drug delivery for retinoblastoma treatment.

Retinoblastoma (Rb) is the most common primary malignant intraocular tumor in children which develops from the retinal stem cells. Systemic chemotherapy is the typical therapeutic treatment and though most children survive Rb, they often lose their vision, or the eye needs to be enucleated. Regarding to the pure availability of the target tumor by systemic chemotherapy, the local anticancer drug administration would be advantageous to increase the local drug concentration and minimize adverse side effects of chemotherapy. The present paper describes a new hydrogel implant enabled to deliver therapeutically active doses of low molecular weight hydrophilic antitumor drugs topotecan and vincristine. The hydrogel implant is proposed as bi-layered with an inner hydrophilic layer from 2-hydroxyethyl methacrylate (HEMA) serving as a reservoir of the chemotherapeutic agent and an outer hydrophobic layer from 2-ethoxyethyl methacrylate (EOEMA) acting as a barrier to protect the surrounding vascularized tissue against cytotoxicity of the delivered chemotherapeutics. The experiments with enucleated pig eyes demonstrated the ability of tested drugs to diffuse through sclera and reach the vitreous humor. HEMA-based hydrogels were examined in terms of sorption, release and transport properties, showing the possibility of adjusting the loading capacity and diffusion of the drugs by the degree of crosslinking. The EOEMA-based gels proved to be an inert for drug sorption and diffusion. A chorioallantoic membrane assay demonstrated excellent biocompatibility of unloaded hydrogels, and in vitro experiments confirmed significant cytotoxicity of drug-loaded hydrogels against a Rb cell line; 2 days for those topotecan-loaded and a minimum of 6 days for vincristine-loaded hydrogels. The bi-layered hydrogel implant can be considered promising for local administration of active agents to eye-globe for the treatment of Rb and also other ocular disorders.

Smart Macroporous IPN Hydrogels Responsive to pH, Temperature, and Ionic Strength: Synthesis, Characterization, and Evaluation of Controlled Release of Drugs.

Fast responsive macroporous interpenetrating polymer network (IPN) hydrogels were fabricated in this work by a sequential strategy, as follows: the first network, consisting of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEM) cross-linked with N,N'-methylenebisacrylamide (BAAm), was prepared at -18 °C, the second network consisting of poly(acrylamide) (PAAm) cross-linked with BAAm, being also generated by cryogelation technique. Both single network cryogels (SNC) and IPN cryogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and water uptake. The presence of weak polycation PDMAEM endows the SNCs and the IPNs cryogels with sensitivity at numerous external stimuli such as pH, temperature, ionic strength, electric field, among which the first three were investigated in this work. It was found that the initial concentration of monomers in both networks was the key factor in tailoring the properties of IPN cryogels such as swelling kinetics, equilibrium water content (EWC), phase transition temperature and the response at ionic strength. The pore size increased after the formation of the second network, the swelling kinetics in pure water being comparable with that of the SNC, phase transition temperature being situated in the range 35-36 °C for IPN cryogels. The water uptake at equilibrium (WUeq) abruptly increased at pH < 3.0 in the case of SNCs, whereas the response of IPN cryogels at the decrease of pH from 6.0 to 1.0 was strongly dependent on the gel structure, the values of WUeq being lower at a higher concentration of DMAEM in the first network, the monomer concentration in the second network being about 10 wt %. The pH response was very much diminished when the monomer concentration was high in both networks (15 wt % in the first network, and 21 wt % in the second network). The increase of the ionic strength from 0 up to 0.3 M NaCl led to the decrease of the WUeq, for all cryogels, the level of dehydration being higher and faster for the SNC than for the corresponding IPN cryogel. The release of diclofenac sodium (DS), as a model acidic drug, triggered by pH, temperature, and ionic strength from the IPN cryogels was evaluated. A pulsatile release of DS from the IPN cryogels was presented, with a slower release at 34 °C (below VPTT) and a faster release at 37 and 40 °C (above the VPTT).

Synthesis, characterization and drug release properties of 3D chitosan/clinoptilolite biocomposite cryogels.

Three-dimensional (3D) biocomposites based on chitosan (CS) and clinoptilolite (CPL) were prepared by cryogelation and their potential application as drug carriers was investigated. Variation of CPL content from 0 to 33wt.% allowed the formation of biocomposites with heterogeneous morphologies consisting of randomly distributed pores. The further increase of CPL content led to ordered porous architectures where parallel pore channels were observed. The CPL content had a strong influence on water uptake, as well as on the cumulative release of diclofenac sodium (DS) and indomethacin (IDM). It was demonstrated that the drug delivery preferentially takes place in phosphate buffer saline (pH 7.4) in comparison to simulated gastric fluid (pH 1.2), where only a reduced drug release was observed. The drug release mechanism dominating these systems is described as a pseudo-Fickian diffusion, but it changes to non-Fickian release when 33wt.% of CPL was entrapped into the CS matrix or when IDM was loaded into biocomposites.

Designing novel macroporous composite hydrogels based on methacrylic acid copolymers and chitosan and in vitro assessment of lysozyme controlled delivery.

Designing structure and morphology of macroporous hydrogels is crucial for their applications in controlled release systems of macromolecular drugs. Macroporous hydrogels, consisting of methacrylic acid (MAA) and either acryl amide (AAm) or 2-hydroxyethyl methacrylate (HEMA) (1st network), were prepared for this purpose by cryogelation (single network cryogels, SNCs). Macroporous interpenetrating polymer network (IPN) hydrogel composites were then prepared by a sequential strategy, the 2nd network consisting of chitosan (CS) cross-linked with poly(ethyleneglycol) diglycidyl ether (PEGDGE) being generated by the sorption of a CS and PEGDGE mixture in the 1st network followed by cross-linking. A strong difference in the behavior of SNCs and IPN hydrogel composites was found during the loading and release of lysozyme (LYS) used as macromolecular drug model. Thus, while the amount of LYS loaded on SNCs was higher than that loaded on the IPNs, the release of LYS from SNCs occurred at pH 2, when the ratio between MAA and AAm was 50:50, and only at pH 1 when the ratio between MAA and AAm was 70:30. The 2nd network led to the decrease of the pore size of the IPNs, mainly when the initial concentration of monomers was 10wt/v%, but the presence of CS facilitates the LYS release from IPNs, mainly at a concentration of monomer of 5wt/v%, and when HEMA was used as nonionic comonomer.

Spectroscopic Characterization of Azo Dyes Aggregation Induced by DABCO-Based Ionene Polymers and Dye Removal Efficiency as a Function of Ionene Structure.

The aggregation mode of three azo dyes, methyl orange (MO), ponceau SS (PSS), and direct blue 1 (DB1) induced by three 1,4-diazabicyclo[2.2.2]octane (DABCO)-based ionene polymers having different topologies (i.e., 1,2-ionene, 1,3-ionene, and 1,4-ionene) was investigated in this work. Metachromatic behavior of the dyes in the presence of ionenes, and the stability of the ionene/dye complex were discussed as a function of ionene structure. It was demonstrated that the association of the dye molecules with the ionenes and the metachromasy were strongly influenced by both the dye structure and the ionene topology. Thus, MO, having one -SO3Na group per molecule, was almost stoichiometrically bound to all ionenes regardless of their topology, showing also a metachromatic effect. In sharp contrast, the interaction of PSS and DB1 molecules with ionenes was strongly dependent on the polymer topology. It was found that PSS having two -SO3Na groups per molecule was preferentially bound onto both 1,2-ionene and 1,3-ionene, but DB1, having four -SO3Na groups per molecule and a more complex structure, was efficiently bound only onto 1,2-ionene. The dye removal efficiency with each ionene was evaluated in batch mode taking into account the affinity of ionenes for azo dyes. The experimental isotherms of the dye sorption were fitted with four isotherm models, i.e., Langmuir, Freundlich, Sips, and Dubinin-Radushkevich. It was found that the best fitting of the experimental data was given by the Langmuir, Sips, and Dubinin-Radushkevich isotherm models. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model, at 35 °C, was as follows: 985.71 mg MO/g 1,3-ionene, 483.71 mg PSS/g 1,3-ionene, 1010.49 mg PSS/g 1,2-ionene, and 976.7 mg DB1/g 1,2-ionene. Kinetic study of the dye removal indicated chemisorption as the main mechanism of sorption.

Efficient sorption of Cu(2+) by composite chelating sorbents based on potato starch-graft-polyamidoxime embedded in chitosan beads.

Ionic composites based on cross-linked chitosan (CS) as matrix and poly(amidoxime) grafted on potato starch (AOX) as entrapped chelating resin were prepared as beads, for the first time in this work, by two strategies: (1) thorough mixing of previously prepared AOX in the CS solution followed by the bead formation and (2) thorough mixing of the potato starch-g-poly(acrylonitrile) (PS-g-PAN) copolymer in the initial CS solution, followed by bead formation, the amidoximation of the nitrile groups taking place inside the beads. Ionotropic gelation in tripolyphosphate was used to obtain the composite beads, and in situ covalent cross-linking by epichlorohydrin was carried out to stabilize the beads in the acidic pH range. Fourier transform infrared spectroscopy and the swelling ratio values in the acidic pH range confirmed the influence of the synthesis strategy on the structure of the CS/AOX composites. Scanning electron microscopy was employed to reveal the morphology of the novel composites, both before and after their loading with Cu(2+). The binding capacity of Cu(2+) ions as a function of sorbent composition, synthesis strategy, pH, sorbent dose, contact time, initial concentration of Cu(2+), and temperature was examined in batch mode. The main difference between the composites prepared with the two strategies consisted of the higher sorption capacity and the much faster settlement of the equilibrium sorption for the composite prepared by the in situ amidoximation of PS-g-PAN. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Sips isotherms were applied to fit the sorption equilibrium data. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model at 25 °C was 133.15 mg Cu(2+)/g for the CS/AOX composite beads prepared with the first strategy and 238.14 mg Cu(2+)/g for the CS/AOX composite beads prepared with the second strategy, at the same AOX content. The pseudo-second order kinetic model well fitted the sorption kinetics data, supporting chemisorption as the mechanism of interaction between the chelating composites and the Cu(2+) ions. The CS/AOX composite sorbents could be reused up to five sorption/desorption cycles with no significant decrease in Cu(2+) sorption capacity.