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Deteção de traços moleculares de triclosan em meios líquidos complexos
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Resumo(s)
O triclosan (TCS) é um agente antibacteriano utilizado em produtos farmacêuticos e de hi-
giene pessoal (PPCP), cada vez mais recorrente em reservas de água, o que representa riscos
para a saúde pública. Torna-se essencial o desenvolvimento de métodos de deteção de TCS
para monitorização. Devido às propriedades lipofílicas do TCS, o objetivo desta tese consis-
tiu na criação de um sensor baseado em filmes ultrafinos de lípidos, capaz de detetar quan-
tidades vestigiais de TCS em meios aquosos complexos. Para concretizar este objetivo, este
trabalho foi dividido em duas partes: Na primeira, estudou-se a interação da molécula de
TCS com uma bicamada lipídica de
1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine
(POPC) utilizando simulação de Dinâmica Molecular (MD). Verificou-se a fácil inserção da
molécula de TCS na bicamada, preferencialmente entre 9 e 11 Å. O estudo do ângulo de
inserção indicou liberdade de rotação, evitando orientações em que os cloros mais periféri-
cos se alinhavam em paralelo com a normal da bicamada. Na segunda parte, desenvolve-
ram-se sensores baseados em filmes lipídicos e analisaram-se as suas características elétricas
em função da concentração de TCS em água da torneira. Suportes sólidos com elétrodos
interdigitados de ouro, revestidos por filmes finos preparados por camada-por-camada uti-
lizando o polieletrólito hidrocloreto de polialilamina (PAH) e o fosfolípido
1,2-Dipalmitoyl-
sn-glycero-3-phosphoglycerol (DPPG), detetaram TCS em amostras de água da torneira do-
pada utilizando espectroscopia de impedância como método de deteção. O LOD do sensor
foi de 4.23 × 10⁻11 M e detetou-se deriva devido à possível degradação dos filmes. Os dados
foram analisados por método de análise de componentes principais (PCA), que demonstra-
ram a capacidade de distinguir claramente as amostras com diferentes concentrações de
TCS num intervalo linear de 10-12 a 10-5 M. O PCA feito a partir dos valores de ângulo de fase
e módulo de impedância, apresentou uma sensibilidade de 3.51 ± 0.21, sendo possível cal-
cular a concentração de TCS em função de F1 através da calibração 𝐶 = 10𝐹1/3.51. Estes
resultados permitem concluir que filmes lipídicos apresentam elevado potencial para o de-
senvolvimento de uma língua eletrónica que permita detetar TCS em água
Triclosan (TCS) is an antibacterial agent used in pharmaceutical and personal care products (PPCPs), increasingly detected in water reservoirs, which poses a risk to public health. The development of detection methods for TCS is therefore essential for environmental moni- toring. Given the lipophilic properties of TCS, this thesis aimed to develop a sensor based on ultrathin lipid films capable of detecting trace amounts of TCS in complex aqueous media. To this end, the work was divided into two parts. In the first one, the interaction of TCS with a lipid bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was studied us- ing Molecular Dynamics (MD) simulations. The results showed that the TCS molecule readily inserts into the bilayer, preferentially between 9 and 11 Å. The insertion angle analysis indi- cated rotational freedom, avoiding orientations in which the peripheral chlorines aligned parallel to the bilayer normal. In the second part, sensors based on lipid films were developed and their electrical characteristics evaluated as a function of TCS concentration in tap water. Solid supports with gold interdigitated electrodes coated with thin films prepared by a layer- by-layer method using the polyelectrolyte poly(allylamine hydrochloride) (PAH) and the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) detected TCS in spiked tap water samples using impedance spectroscopy as the detection method. The sensor ex- hibited a limit of detection (LOD) of 4.23 × 10⁻11 M and showed signal drift, possibly due to film degradation. The data were analyzed by principal component analysis (PCA), which demonstrated the ability to clearly distinguish samples with different TCS concentrations in the linear range of 10-12 to 10-5 M. PCA based on phase angle and impedance magnitude values yielded a sensitivity of 3.51 ± 0.21, enabling calculation of TCS concentration as a function of F1 through the calibration 𝐶 = 10𝐹1/3.51. These results demonstrate the poten- tial of lipid films for the development of an electronic tongue to detect TCS in water.
Triclosan (TCS) is an antibacterial agent used in pharmaceutical and personal care products (PPCPs), increasingly detected in water reservoirs, which poses a risk to public health. The development of detection methods for TCS is therefore essential for environmental moni- toring. Given the lipophilic properties of TCS, this thesis aimed to develop a sensor based on ultrathin lipid films capable of detecting trace amounts of TCS in complex aqueous media. To this end, the work was divided into two parts. In the first one, the interaction of TCS with a lipid bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was studied us- ing Molecular Dynamics (MD) simulations. The results showed that the TCS molecule readily inserts into the bilayer, preferentially between 9 and 11 Å. The insertion angle analysis indi- cated rotational freedom, avoiding orientations in which the peripheral chlorines aligned parallel to the bilayer normal. In the second part, sensors based on lipid films were developed and their electrical characteristics evaluated as a function of TCS concentration in tap water. Solid supports with gold interdigitated electrodes coated with thin films prepared by a layer- by-layer method using the polyelectrolyte poly(allylamine hydrochloride) (PAH) and the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) detected TCS in spiked tap water samples using impedance spectroscopy as the detection method. The sensor ex- hibited a limit of detection (LOD) of 4.23 × 10⁻11 M and showed signal drift, possibly due to film degradation. The data were analyzed by principal component analysis (PCA), which demonstrated the ability to clearly distinguish samples with different TCS concentrations in the linear range of 10-12 to 10-5 M. PCA based on phase angle and impedance magnitude values yielded a sensitivity of 3.51 ± 0.21, enabling calculation of TCS concentration as a function of F1 through the calibration 𝐶 = 10𝐹1/3.51. These results demonstrate the poten- tial of lipid films for the development of an electronic tongue to detect TCS in water.
Descrição
Palavras-chave
Triclosan sensor lipossoma filmes ultrafinos camada-por-camada espectroscopia de impedância