Micro-/Nano-Particles-Loaded Electrospun Hierarchical Polymeric Fibers For Cancer Therapy And Diagnosis

Cancer is one of the world’s most devastating diseases affecting human health. An ideal strategy to deal with cancer, is early diagnosis and timely treatment. However huge challenges still exit. On the one hand, as so far, systemic chemotherapy along with surgical resection or radiotherapy is still the primary mean for cancer therapy, which accompanied with severe toxicity in healthy tissues or even death. Nanocarrier-based drug delivery systems (such as polymeric micelles), developed in recent years, may solve these problem in some degree. But the modest increase in tumor accumulation in practice, still limit the therapeutic effect of these nanocarriers, due to numerous barriers en route from the injection site to the target cells. On the other hand, techniques of early cancer diagnosis for now, such as detection of circulating tumor cells (CTCs), are still restricted by the poor accuracy, low efficiency and high cost. Reasons for these problems can be the lack of enough knowledge of tumor biomarkers and the materials for capturing these biomarkers are underdeveloped.So based on the previous researches by the other scientists, efforts has been made to strike some of these problems with material science in this dissertation. The eletrospun nanofibers and micro/nano particle carriers were combined together to develop the novel implantable antitumor device and substrate with the ability of non-specific capturing CTCs.For the cancer therapy, first, in the chapter 2, the polymeric micelles and electrospun nanofibers were combined to precisely control the release of multiple drugs. The multi-drug delivery system (Cur-Ms/Dox-nanofibers) is achieved, first, by the fabrication of hydrophobic curcumin encapsulated micelles (Cur-Ms) assembled from biodegradable mPEG-PCL copolymer, and second, by the blending of the micelle powder with hydrophilic doxorubicin (Dox) in polyvinyl alcohol solution, followed by simply electrospinning this combination. Results of scanning electron microscopy (SEM) and confocal laser sacanning microscopy (CLSM) demonstrate the successful encapsulation of micelles into electrospun nanofibers. From the CLSM images, it’s easy to find that Dox is dispersed uniformly in fiber matrix, while the Cur-Ms aggregates distribute discontinuously along the fiber axis. The successful release of micelles fixed in the fiber matrix were also proved and the structures of the release micelles are almost the same with the original ones. Then, in vitro drug release study were carried out and the results show that the release behavior of the two different drugs were time-programmed as following pattern:the hydrophilic drug distributed in the water-soluble fiber matrix was released with the dissolving of the matrix, simultaneously, the loaded micelles containing hydrophobic drug within fiber matrix were also liberated, later, most of the hydrophobic drug encapsulated into the released micelles was gradually released. In vitro tumor cell inhibition assay indicates that the delivery system possesses great potential in inhibiting growth of cancer cells.Next, for in vivo anti-cancer effect study of the micelles-loaded nanofibers in the future work, the micelles-loaded nanofiber system has been optimized in the Chapter 3. A coaxial electrospinning has been employed to fabricate the implantable active-targeting micelle-in-nanofiber device with a core-shell structure in which Dox-loaded active-targeting micelles mixed with PVA were encapsulated in the core region and genipin cross-linked gelatin formed the outer shell. Transmission electron microscopy (TEM) were performed to confirm the core-shell structure of these electrospun nanofibers. CLSM results indicate that micelles were successfully embedded in the core-shell nanofibers. The release of micelles were proved by dissolving the micelles-loaded nanofibers in water and the results also show that the release micelles are almost the same with the original ones in shape and diameter. Then the in vitro drug release study and in vitro degradation of micelles-loaded coaxial nanofibers showed that encapsulation of Dox-loaded micelles into core-shell nanofibers can prolong the release period of Dox, which is owing to that, after micelles were entrapped in nanofibers, the leaking of the encapsulated drug from the micelles can be limited by the matrix in the core of nanofibers and the cross-linked outer shells of the nanofibers, which act as a barrier and restricts the disassembly of micelles immobilized in the nanofiber matrix. In vitro antitumor activity assay indicates that these delivery system possesses great potential in the inhibition of cancer cells.Based on the work of Chapter 3, in vivo antitumor effect of micelles-loaded coaxial nanofibers has been investigated furtherly. These nanofibers were implanted into 4T1 tumor-bearing nude mice or Balb/c mice subcutaneously near the tumors. In vivo and ex vivo Dox fluorescence imaging and in vivo drug biodistribution study showed that these implantable nanofiber devices (especially the active-targeting micelle-in-nanofiber device) has the ability of ensuring therapeutic drug levels at the tumor site for extended periods of time while maintaining low systemic drug exposure to the normal tissue. The targeting micelles functionalized with folate, were also enhanced the targeting effect and contribute to the enrichment of the drug in the tumor. At last, the variation in tumor volume, body weight, survival rate and histological analysis also demonstrate that the localized drug delivery system of the implantable micelle-in-nanofiber device possesses a high therapeutic efficacy against tumors and a low toxicity to the body, which is owing to the avoid of the drug loss caused by the reticuloendothelial system (RES), the reduce of drug enrichment in non-tumor site and the continuously release of drug-loaed micelles.In the last Chapter (Chapter 5), a new beaded electrospun nanofibers for non-specific capturing of CTCs was developed. Firstly, monodispersed polydopamine sub-micrometer spheres (PDA SMSs) with varying diameters were prepared by adjusting the molar ratio of ammonia to dopamine hydrochloride during polymerization of dopamine. Later, the necklace-like hierarchical PDA SMSs/alginate composite nanofibers were fabricated successfully by using electrospinning and optimizing the weight ratio of PDA SMSs and fiber matrix. Then, The results of cancer cell capture experiments have shown that our PDA SMSs/alginate composite nanofibers, especially the one containing 270 nm PDA SMSs, have a considerable potential in capturing rare circulating tumor cells. At last, the CLSM and SEM images revealed that an enough strong interaction occurred between the captured cells and the composite nanofibers, which may be owing to the enhanced topographical interaction resulting from complex surface of composite nanofibers and the contribution to improve the cell adhesion by polydopamine.