18-Synthesis and characterization of conjugated polymers nanoparticles with potential application in the study of biological systems

RAMIRO SPADA; LAURA HERNANDEZ; GABRIELA PORCAL; LUIS IBARRA; LORENA MACOR; LUCAS BELLOMO; FRANCO BELLOMO; RODRIGO PONZIO; CARLOS CHESTA; RODRIGO PALACIOS

SANTIAGO DE CHILE

Simposio; 25th I-APS Meeting, Santiago Chile; 2016

Conjugated polymer nanoparticles (CPNPs) have excellent photophysical and biological properties that make them suitable for biomedical applications such as photosensitizers in photodynamic therapy (PDT), fluorescent cell markers or probes. Some of these properties are: high absorption cross section in the UV-visible range, high quantum yields of emission and production of reactive oxygen species, good biocompatibility, stability and photostability in aqueous media. In this work, we synthesized and characterized CPNPs of Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) with interesting photophysical properties. Organic dopants were incorporated into the CPNPs (on its surface or though its volume) in order to improve the ability to generate O2(1Δg) and to explore in detail intra-particle energy transfer processes. The ability of platinum octaethylporphyrin (PtOEP) doped and undoped CPNPs to photosensitize the production single oxygen (O2(1Δg)) was explored using anthracene-9,10-dipropionic acid (ADPA), a well know O2(1Δg) chemical trap. The results indicate that PtOEP doping produces an increase in O2(1Δg) generation and that the sensing ability of ADPA is affected by pH. Using time-resolved and steady state fluorescence quenching we explored the ability of CPNPs to bind ionic and neutral organic dyes on its surface. These experiments were performed in the presence and absence of polyethylen glycol (PEG) which acts as a nanoparticle surface modifier blocking dye binding. Finally, in order to improve our understanding of intra-particle energy transfer processes in de presence and absence of dye dopants, we developed computer models based on Monte-Carlo type simulations. In these simulations dopant molecules act as acceptors via a Forster type energy transfer mechanism. Comparison of simulated and experimental results allowed us to validate the model and to extract important parameters associated with F8BT such as the exciton diffusion length.