Construction And Applications Of Polyacrylamide-based Hydrogel Dosimeters

Ionizing radiation has been extensively used in medical diagnosis and treatments.It is of significance to measure the dose of ionizing radiation,which can not only improve the accuracy and safety of radiotherapy,but give a clue to radiation protection.Hydrogels have shown numerous applications in the medical fields(e.g.,dosimeters)due to(but not limited to)their excellent tissue equivalence as well as biocompatibility.In this thesis,we constructed a series of polyacrylamide(PAAm)hydrogel-based dosimeters for the measurement of the dose of ionizing radiation.Specifically,in the Chapter 2,AAm and acrylic acid(AAc)monomers were copolymerized in the presence of a cationic polyelectrolyte polydimethyldiallylammonium chloride(PDADMAC),generating a non-covalently crosslinked poly(AAm-co-AAc)/PDAMAC(or PAAD)hydrogel.The PAAD hydrogel was shown excellent mechanical performance,adhesion and biocompatibility.The effect of AAl concentration,positive and negative ion concentration and ratio on the mechanical properties and fatigue resistance of PAAD hydrogels was studied.Our PAAD hydrogel was able to bond with a variety of substrates,including rubbers,plastics,glass,metals and porcine skin(mimic human skin).Furthermore,we introduced a thermoluminescence dosimeter(TLD)into PAAD hydrogel to construct a PAAm hydrogel-TLD composite to measure the dose of ionizing radiation.It was found that such composite dosimeters well retained the capability of the dose measurement as a result of TLD,More importantly,we built a TLD array on the PAAm hydrogel for locally measure ionizing radiation doses on a macroscopic skin-mimic surface.In the Chapter 3,we prepared poly(AAm-co-N-(3-aminopropyl)methac rylamide)(poly(AAm-co-APMA)or PAA)hydrogel particles by inverse emulsion polymerization.Subsequently,the PAA hydrogel was coupled with fluorescent molecule aminophenylfluorescein(APF),aiming to measure ionizing radiation doses.The PAA/APF(or PAAA)hydrogel featured a hydrodynamic diameter of about 40 nm.After exposure to ionzing radition,PAAA hydrogel emitted green fluorescence at 515 nm under 488 nm excitation,and the fluorescence intensity was shown good linear in response to ionizing radiation doses in the range 0?20 Gy.Furthermore,the PAAA hydrogel was shown the lowest detection limitation of 0.5 Gy,and an error<5%as well as good thermal(4?50 ?)and time(20 days)stability.Finally,the PAAA hydrogel was embedded with 2 wt%agarose to construct a novel PAAA-agarose film.Such film featured good dose linearity and thus proved feasible in the plane dose measurement in clinical radiotherapy.In the Chapter 4,the ionizing radiation-sensitive fluorescent dye coumarin-3-carboxylic acid(CCA)and ionizing radiation-insensitive fluorescent dye 5(6)carboxytetramethylrhodamine(TAMRA)was covalently linked to the matrix of PAAm-based nanogel to obtain a ratiometric fluorescent nanogel.It was found that the fluorescence intensity at 450 nm increased linearly as the dose of ionizing radiation increased;whereas the fluorescence intensity at 580 nm retained constant under ionizing radiation.The fluorescence ratio of 450 nm to 580 nm I450/I580 linearly increased with increasing ionizing radiation dose in both low dose region(0?2 Gy)and high dose region(0?20 Gy).Furthermore,the error of the measurement is less than 4.3%and the dose information can be well maintained for a long period or in a temperature range of 4?50?.By virtue of its low cytotoxicity,we introduced the hydrogel into A549 cell for intracellular dose measurements.As visually,intracellular fluorescence signal varied as a function of ionizing radiation dose.