Paclitaxel-polyurethane film for anti-cancer drug delivery: Film characterization and preliminary in vivo study

Towards the use of localised delivery strategies to counteract cancer therapy-induced cardiotoxicities

Cancer therapies have significantly improved cancer survival; however, these therapies can often result in undesired side effects to off target organs. Cardiac disease ranging from mild hypertension to heart failure can occur as a result of cancer therapies. This can warrant the discontinuation of cancer treatment in patients which can be detrimental, especially when the treatment is effective. There is an urgent need to mitigate cardiac disease that occurs as a result of cancer therapy. Delivery strategies such as the use of nanoparticles, hydrogels, and medical devices can be used to localise the treatment to the tumour and prevent off target side effects. This review summarises the advancements in localised delivery of anti-cancer therapies to tumours. It also examines the localised delivery of cardioprotectants to the heart for patients with systemic disease such as leukaemia where localised tumour delivery might not be an option.

Synthesis and characterization of PLGA-PEG-PLGA based thermosensitive polyurethane micelles for potential drug delivery

Polyurethane nanomicelle is a promising functional drug delivery system. In this work, the polyurethane (P3-PU) was synthesized from PLGA₁₂₀₀-PEG₁₄₅₀-PLGA₁₂₀₀ (P3, a thermosensitive and biodegradable triblock copolymer) and L-lysine ester diisocyanate (LDI). Then, reactive benzaldehyde was further imported to terminate P3-PU to obtain benzaldehyde modified polyurethane (P3-PUDA). The micelles, temperature-sensitive P3-PU nanomicelle and P3-PUDA nanomicelle, were systematically investigated, including the size, stability, temperature sensitivity, drug loading and release behavior, cytotoxic on human hepatocytes (L02), and inhibitory effect on human hepatocellular carcinoma cells (HepG2). The results show the thermosensitive behavior of the micelles can be adjusted by the terminal group. The polyurethane micelles with a uniform size between 20 nm and 30 nm showed excellent stability and good biocompatibility to L02 cells. Besides, in vitro experiments showed that Dox-loaded P3-PUDA micelles exhibited faster and higher release rate at 37 °C and better inhibitory effect on HepG2 than the Dox-loaded P3-PU micelles. Moreover, the achieved benzaldehyde modified polyurethanes also provides various possibilities to adjust further to enlarge its applications. Therefore, the polyurethane micelles will have great potential in the field of drug carriers.

Gemcitabine-incorporated polyurethane films for controlled release of an anticancer drug

Background

Local delivery of anti-cancer drugs through a stent is a very promising and anticipated treatment modality for patients who have obstructions in their gastrointestinal tract with malignant tumors. Anticancer drug release via stents, however, needs to be optimized with respect to drug delivery behavior for the stents to be effective for prolonged containment of tumor proliferation and stent re-obstruction. Local stent-based drug delivery has been tested using an effective anti-cancer drug, gemcitabine, but the release from the stent-coated polyurethane films is often too fast and the drug is depleted from the coated film virtually in a day.

Methods

To moderate the drug release from a polyurethane film, a gemcitabine-incorporated polyurethane film was enveloped with a pure polyurethane film, with no drug loading, and with a silicone film by solution casting after activation of the silicone film surface with plasma treatment.

Results

The pure polyurethane barrier film was effective; the interface of the two were indistinguishable on scanning electron microscopy, and the initial burst, i.e., the cumulative release in a day, decreased from 90 to 26%. The silicone film barrier, on the other hand, was defective as voids were seen using a scanning electron microscope, and micro-separation of the two layers was observed after the film was immersed in phosphate-buffered saline for 1 day during the in vitro drug release study.

Conclusions

Enveloping a gemcitabine-releasing polyurethane film with a homo-polymer barrier film was quite effective for moderating the initial burst of gemcitabine, thus, prolonging the release time of the drug. Enveloping the polyurethane film with a silicone film was also possible after plasma treatment of the silicone film surface, but the two films eventually separated in the aqueous environment. More studies are needed to tune the drug release behavior of gemcitabine from the stent covering film before attempting a clinical application of an anti-cancer drug releasing stent.

Antitumor effect of the paclitaxel-eluting membrane in a mouse model

Local treatment of primary bile duct cancer, which grows locally at the primary lesion and seldom metastasizes to distant sites, is challenging. The present study evaluated the antitumor effect, systemic toxicity, biodistribution and survival benefit of the paclitaxel-eluting polyurethane membrane in a tumor model. Membranes containing various amounts of paclitaxel (0, 100, 300, 600 and 1,200 µg/disc) were inserted beneath the tumor mass in mouse models. Tumor size and body weight of the tumor models were monitored for 26 days after insertion of the membrane. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay was performed in the tumor tissues. High-performance liquid chromatography was performed for evaluation of paclitaxel concentration in peripheral tissues. Tumor volumes on day 26 of membrane treatment were decreased in a dose-dependent manner. No significant difference in body weight was observed in the groups. A greater number of apoptotic cells were counted per high power field in tumor tissues following an increase of paclitaxel concentration. In the 1,200 µg-group, concentrations of paclitaxel were significantly higher in tumors compared with those of other tissues and serum. The paclitaxel-eluting membrane demonstrated a significant and dose-dependent antitumor activity, and did not exert systemic toxicity in the tumor model.

Biopolymers for Antitumor Implantable Drug Delivery Systems: Recent Advances and Future Outlook

In spite of remarkable improvements in cancer treatments and survivorship, cancer still remains as one of the major causes of death worldwide. Although current standards of care provide encouraging results, they still cause severe systemic toxicity and also fail in preventing recurrence of the disease. In order to address these issues, biomaterial-based implantable drug delivery systems (DDSs) have emerged as promising therapeutic platforms, which allow local administration of drugs directly to the tumor site. Owing to the unique properties of biopolymers, they have been used in a variety of ways to institute biodegradable implantable DDSs that exert precise spatiotemporal control over the release of therapeutic drug. Here, the most recent advances in biopolymer-based DDSs for suppressing tumor growth and preventing tumor recurrence are reviewed. Novel emerging biopolymers as well as cutting-edge polymeric microdevices deployed as implantable antitumor DDSs are discussed. Finally, a review of a new therapeutic modality within the field, which is based on implantable biopolymeric DDSs, is given.

Crystalline paclitaxel coated DES with bioactive protective layer development

Drug eluting stents (DES) based on polymeric-carriers currently lead the market, however, reports on clinical complications encourage the development of safer and more effective DES. We recently reported on carrier-free DES based on rapamycin crystalline coating as a potential therapeutic solution. Here, we report for the first time surface crystallization of paclitaxel (PT) onto metallic stents. The physicochemical principles of crystallization and key process parameters were extensively studied for fabrication of controllable and homogeneous crystalline coatings on stent scaffolds. Stents loaded with nearly 100μg PT were chosen as a potential therapeutic device with a multilayer coating of 4-7μm thickness. In vitro PT release from these coated stents shows constant release for at least 28days with 10% cumulatively released. The effect of fast dissolving top coating on the physical stability of the coated stent was determined. The top coating enhances the mechanical stability of the crystalline coating during deployment and expansion simulations. Also, incorporating PT in the protective top coating for developing bioactive top coating for multilayer controlled release purpose was intensively studied. This process has wide applications that can be further implemented for other drugs for effective local drug delivery from implantable medical devices.

Electrospun polyurethane/Eudragit ® L100-55 composite mats for the pH dependent release of paclitaxel on duodenal stent cover application

A nanofiber composite mat of PU and Eudragit(®) L100-55 was created using electrospinning process. The pH dependent release of paclitaxel was successfully done with the use of PU/EL100-55 nanocomposite mats as the controlling platform. The morphology of the nanofiber composites was surveyed using FESEM and ratios of the polymers affects the diameter of the nanofiber. Characterization of the nanofiber composite mat was done using FTIR, DSC-TGA method. The release rate of paclitaxel was determined and analyzed by in vitro drug release method. In order to mimic the condition of a human duodenum, the fibers were submersed on PBS of different pH levels (4.0, 6.0,) respectively, and then analyzed using high performance liquid chromatography (HPLC). Composite mats submersed in PBS with pH 4.0 showed lesser release profile compared to mats submersed in PBS with pH of 6.0. The composite mat has adequate mechanical properties and in vitro cell biocompatibility indicating that the material can be used for drug eluting stent cover application.

Polyurethane membrane with porous surface for controlled drug release in drug eluting stent

Background

Membrane covered drug eluting stents (DES) were prepared to prevent tumor ingrowth and to control drug release. Polyurethane (PU) is commonly used for DES coating material because of high tensile strength. The release of paclitaxel (PTX) may increase from porous PU membrane.

Results

Polyethylene glycol (PEG) was incorporated into PU membranes to form porous structure and control the release of hydrophobic anti-cancer drug such as PTX. The bare metal stents were coated with PEG incorporated PU and then, PEG was washed out to form porous structure. The crystallization of PTX was inhibited in porous PU membranes and the release of PTX from porous PU membranes was approximately 8.6% more extended over 19 days.

Conclusions

The enhanced release of PTX from porous PU membranes may increase the patency for the DES covering materials.

Controllable drug release of electrospun thermoresponsive poly(N-isopropylacrylamide)/poly(2-acrylamido-2- methylpropanesulfonic acid) nanofibers

Electrospinning micro- and nanofibers are being increasingly investigated for drug delivery. The components and their stimuli-responsive properties of fibers are important factors influencing the drug release behavior. The aim of this study is to fabricate thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm)/poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) nanofibers by single-spinneret electrospinning technique. The electrospun nanofibers are used as a drug carrier by cospinning with nifedipine (NIF), and the release behaviors of NIF from the thermoresponsive nanofibers can be controlled by the response of nanofibers with temperature. The morphology of the nanofibers and its composites with NIF was determined by scanning electron microscopy (SEM). The hydrogen bond interactions between PNIPAAm/PAMPS and the water-insoluble drug of NIF were introduced and confirmed by Fourier-transform infrared spectroscopy and energy dispersive spectrometer. The thermoresponsive properties of nanofibers were investigated by contact angle (CA) measurements. The release behaviors of NIF from the PNIPAAm/PAMPS nanofibers were observed by SEM and demonstrated by UV-vis spectroscopy. It was found that uniform fibers of NIF and PNIPAAm/PAMPS could be fabricated without particles on the surface. The release of NIF from nanofibers could be controlled effectively by the changes of hydrogen bonds between PNIPAAm/PAMPS and NIF, and by adjusting temperatures of the thermoresponsive nanofibers.