Στην παρούσα εργασία διερευνήθηκε περαιτέρω η δυνατότητα ανάπτυξης νανοσωματιδίων ελεγχόμενης χορήγησης και (παθητικής) στόχευσης σισπλατίνας με βάση τα PLGAmPEG συμπολυμερή. Αρχικά μελετήθηκε η επίδραση των συνθηκών παρασκευής στο μέγεθος των λαμβανομένων νανοσωματιδίων και στην φόρτωση και την ενκαψακίωση της σισπλατίνας σε PLGA(40)mPEG(5) νανοσωματίδια. Στη συνέχεια έγινε μελέτη της αντικαρκινικής δραστικότητας νανοσωματιδίων φορτωμένων με σισπλατίνη, τριών διαφορετικών πολυμερικών συστάσεων PLGA(7)mPEG(5) PLGA(31)mPEG(5) και PLGA(57)mPEG(5), έναντι LNCaP καρκινικών κυττάρων προστάτη και σύγκριση αυτής με την δραστικότητα του ελεύθερου φαρμάκου απέναντι στην ίδια καρκινική σειρά. / In the present work was investigated further the possibility of growth of nanoparticles with PLGAmPEG copolymers. Initially it was studied the effect of preparation conditions in the size of the nanoparticles and in the loading and the encapsulation of cisplatin in PLGA(40)mPEG(5) nanoparticles. Afterwards we studied the anticancer efficacy of cisplatin loaded nanoparticles , of three different polymeric constitution PLGA(7)mPEG (5), PLGA(31)mPEG(5) and PLGA(57)mPEG(5), opposite of LNCaP cancer cells and comparison of this with the efficacy of the free medicine towards the same cancer cells.

Cisplatin is an effective chemotheraputic agent for head and neck squamous cell carcinoma particularly in conjunction with radiation therapy. Unfortunately, its cytotoxic profile and associated systemic side effects limit its clinical efficacy. A localized delivery system was developed for cisplatin by processing calcium polyphosphate (CPP) in a multistep gelling protocol, with the goal of limiting its systemic toxicity and enhancing its overall clinical applicability. In addition, a novel method for processing the material was examined utilizing cold isostatic pressure (CIP) to allow for miniaturization of the system into an implantable device. The integration of cisplatin into the matrix was examined for efficient and dose dependent loading via dissolution of the final product and measurement of platinum concentrations by inductively coupled plasma optical emission spectrometry (ICP-OES). Drug release was measured in vitro by placing the CPP-cisplatin matrix into TRIS buffer solution while measuring the platinum concentration at given intervals from 0.5 hours to 14 days. The cytotoxicity of the cisplatin against L1210 cells was examined using an MTT assay following a 12-hour elution. The material demonstrated a predictable and dose dependent loading of cisplatin, although the release of the drug showed variability exemplified by a more pronounced burst release with aging of the stock CPP glass particulate. The CPP/cisplatin matrix exhibited cytotoxic effects after processing. This work suggests that further evaluation of this material as a matrix for cisplatin delivery should be undertaken in an attempt to normalize release, maximize the concentration within the system and further optimize the bead format in order to improve the potential for clinical usage.

Background: Many well-known pharmacologic agents have been shown to have toxic effects to the cochleo-vestibular system. Examples of such ototoxic agents include cisplatin and aminoglycoside antibiotics. Ototoxicity monitoring consists of a comprehensive pattern of audiological assessments designed to detect the onset of any hearing loss. Three main methods have emerged over the past decade, and include the basic audiological assessment, extended high frequency (EHF) audiometry, and otoacoustic emission (OAE) measurement. These measures can be used separately or in combination, depending on clinical purpose and patient considerations. It is suggested by the American Academy of Audiology Position Statement and Clinical Practice Guidelines: Ototoxicity Monitoring, that baseline testing be done in a fairly comprehensive manner, including pure-tone thresholds in both the conventional- and extended high frequency ranges, tympanometry, speech audiometry, and the testing of OAEs (AAA, 2009). Anecdotal evidence suggests that New Zealand Audiologists do not currently follow a national ototoxicity monitoring protocol. Therefore the main aim of this study was to explore the current status of ototoxicity monitoring within New Zealand. Hypothesis: It was hypothesized that hospital based Audiology departments across New Zealand each followed their own internal ototoxicity monitoring protocol based, to a large extent, on the guidelines proposed by the American Academy of Audiology and by the American Speech-Language-Hearing Association. Method: Through the use of a Telephone Interview Questionnaire, 16 charge Audiologists were interviewed to establish their current state of knowledge regarding ototoxicity monitoring at 16 out of 20 district health boards in New Zealand. Enquiries about the current systems and procedures in place at their departments together with any suggestions and recommendations to improve on these systems were made. Results: This study found that only 9 of the 16 DHBs interviewed currently follow an ototoxicity monitoring protocol. Furthermore, other than initially hypothesized the origin of the protocols followed by the remaining 7 departments were reported to have ranged from independently developed protocols to historically adopted protocols. One department implemented an adapted version of a protocol by Fausti et al. (Ear and Hearing 1999; 20(6):497-505). This diversity in origin however, does confirm our initial suspicion that no universal and standardized monitoring protocol is currently being followed by Audiologists working in the public health sector of New Zealand.

Cisplatin (CDDP; cis-diamminedichloroplatinum) resistance presents a major impediment in the treatment of several gynecologic solid tumors, including ovarian and cervical tumors. p53, a critical regulator of cellular apoptosis, is a determinant of CDDP sensitivity. In our study, we have observed that the dysregulation of p53 regulators, checkpoint kinase 1 (Chk1) and protein phosphatase magnesium-dependent 1 (PPM1D), significantly reduced CDDP responsiveness in human cancer cells. Isogenic wt-p53 CDDP-sensitive (OV2008) and -resistant (C13*) cervical cancer cells, and isogenic wt-p53 CDDP-sensitive (A2780s) and p53 mutant resistant (A2780cp) ovarian cancer cells, along with CDDP-resistant ovarian cancer cell lines (OCC-1 and OVCAR-3, mutant p53; SKOV-3, p53 null) were used to elucidate the mechanisms of p53 regulation in human gynecologic cancer cells. We have complemented our study with a xenograft model (A2780s) and a tissue microarray of human ovarian tumors to validate our in vitro observations. We have demonstrated that CDDP differentially regulated the p53 activator Chk1 in sensitive and resistant cancer cells; it enhances Chk1 activation in sensitive but not resistant cells. This differential regulation also extended to PPM1D, whereby CDDP enhanced PPM1D content in resistant but not sensitive cells. PPM1D knockdown sensitized resistant cells to CDDP, which was associated with up-regulation of Chk1 and p53 activations, while PPM1D over-expression had the opposite effect. We have also shown that CDDP sensitivity in response to PPM1D down-regulation was p53-dependent. Moreover, CDDP promotes PPM1D nuclear localization in resistant cells and nuclear exclusion in sensitive cells and xenograft tumors. Enhanced PPM1D expression in human ovarian tumors is significantly associated with tumor aggression. Dysregulation of the oncogene Akt has been implicated in a variety of human malignancies, including ovarian cancer. We have demonstrated that Akt regulates PPM1D stability, since activated Akt over-expression in sensitive cells rescued PPM1D from CDDP-induced proteasomal degradation and Akt down-regulation in resistant cells lead to PPM1D de-stabilization and down-regulation. We have shown for the first time that PPM1D is downstream of Akt through which it can modulate CDDP sensitivity in human cancer cells. These findings extend the current knowledge on the molecular basis of CDDP resistance in gynecological cancers and may help in developing effective therapeutic strategies.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available online.

Zugl.: Bonn, Univ., Diss., 2007

Thesis (Ph.D)--University of Wollongong, 2003. / Typescript. Includes bibliographical references: leaf 210-234.

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2007. / Vita. Briscoe Library received only one copy of this dissertation. It is shelved in the Archives for safekeeping. Includes bibliographical references.