Edith I. Yslas

Polyaniline nanofibers: Acute toxicity and teratogenic effect on Rhinella arenarum embryos

The fate and effect of nanomaterials in the environment is of paramount importance towards the technological application of the materials. This work shows the ecotoxicological potential of polyaniline (PANI) nanofibers in the larvae Rhinella arenarum by means of AMPHITOX test. Acute toxicity of PANI nanofibers towards embryos of the common South American toad R. arenarum (Anura: bufonidae) was evaluated in the premetamorphosis (stage 25) larvae. The exposure of R. arenarum larvae to at dose of 150, 250 and 400 mg L(-1) resulted in 100% viability within 96 h exposure. The embryos at 2-4 blastomers stage (early life stage teratogenic test) revealed that embryos were not killed and no teratogenic effects were observed when embryos were incubated with PANI nanofibers (150 and 250 mg L(-1)), while only a growth retardation of embryos was induced at levels of 250 mg PANI nanofibers L(-1). On the other hand, at 400 mg L(-1) concentration, a reduction in the body length of larvae and tail malformation was observed. This results suggest that a concentration-dependent toxicity is operative, typified by phenotypes that had abnormal body axes. The presence of PANI nanofibers in gut contents and its excretion by larval stages of R. arenarum was confirmed by UV-visible spectroscopy.

Assessment of polyaniline nanoparticles toxicity and teratogenicity in aquatic environment using Rhinella arenarum model.

With the rapid growth of nanotechnology and the applications of nanoparticles, environmental exposure to these particles is increasing. However, their impact in human and environmental health is not well studied. Anurans, with life stage comprising embryos, tadpoles and adults, have an extremely permeable skin which makes them excellent indicators of environmental health. This study evaluated the acute toxicity effects of polyaniline nanoparticles (PANI-Np) in different dispersant on embryos and larvae of Rhinella arenarum. The results showed that LC50 of PANI-Np dispersed in polyvinylpyrrolidone (PVP) were 1,500 mg/L, while LC50 by PANI-Np dispersed in PVP+PNIPAM (polyN-isopropylacrilamide) showed a highest toxicity (1,170 mg/L). The embryo teratogenicity increased with increasing exposure concentration in both kinds of PANI-Np although in PANI-Np1, there is an increased teratogenic effect associated with the polymer stabilizer PVP.

Hybrid biomaterials based on calcium carbonate and polyaniline nanoparticles for application in photothermal therapy

Inorganic materials contain remarkable properties for drug delivery, such as a large surface area and nanoporous structure. Among these materials, CaCO3 microparticles (CMPs) exhibit a high encapsulation efficiency and solubility in acidic media. The extracellular pH of tumor neoplastic tissue is significantly lower than the extracellular pH of normal tissue facilitating the release of drug-encapsulating CMPs in this area. Conducting polyaniline (PANI) absorbs light energy and transforms it into localized heat to produce cell death. This work aimed to generate hybrid CMPs loaded with PANI for photothermal therapy (PTT). The hybrid nanomaterial was synthesized with CaCO3 and carboxymethyl cellulose in a simple, reproducible manner. The CMP-PANI-Cys particles were developed for the first time and represent a novel type of hybrid biomaterial. Resultant nanoparticles were characterized utilizing scanning electron microscopy, dynamic light scattering, zeta potential, UV-vis, FTIR and Raman spectroscopy. In vitro HeLa cells in dark and irradiated conditions showed that CMP-PANI-Cys and PANI-Cys are nontoxic at the assayed concentrations. Hybrid biomaterials displayed high efficiency for potential PTT compared with PANI-Cys. In summary, hierarchical hybrid biomaterials composed of CMPs and PANI-Cys combined with near infrared irradiation represents a useful alternative in PTT.

Cysteine modified polyaniline films improve biocompatibility for two cell lines

This work focuses on one of the most exciting application areas of conjugated conducting polymers, which is cell culture and tissue engineering. To improve the biocompatibility of conducting polymers we present an easy method that involves the modification of the polymer backbone using l-cysteine. In this publication, we show the synthesis of polyaniline (PANI) films supported onto Polyethylene terephthalate (PET) films, and modified using cysteine (PANI-Cys) in order to generate a biocompatible substrate for cell culture. The PANI-Cys films are characterized by Fourier Transform infrared and UV-visible spectroscopy. The changes in the hydrophilicity of the polymer films after and before the modification were tested using contact angle measurements. After modification the contact angle changes from 86°±1 to 90°±1, suggesting a more hydrophylic surface. The adhesion properties of LM2 and HaCaT cell lines on the surface of PANI-Cys films in comparison with tissue culture plastic (TCP) are studied. The PANI-Cys film shows better biocompatibility than PANI film for both cell lines. The cell morphologies on the TCP and PANI-Cys film were examined by florescence and Atomic Force Microscopy (AFM). Microscopic observations show normal cellular behavior when PANI-Cys is used as a substrate of both cell lines (HaCaT and LM2) as when they are cultured on TCP. The ability of these PANI-Cys films to support cell attachment and growth indicates their potential use as biocompatible surfaces and in tissue engineering.

Pharmacokinetic, toxicological and phototherapeutic studies of phthalocyanine ZnPcCF3

Photodynamic therapy (PDT) is an alternative modality for cancer therapy. It induces neoplasic cells death through photoachievable sensitizers. The aim of this work was to evaluate the pharmacokinetic, toxic and phototherapeutic effects of the phthalocyanine ZnPcCF(3) in a Balb/c mice tumor model. Biodistribution studies were carried out by intraperitoneal injection of 0.2mg/kg ZnPcCF(3). Histological studies and serum biochemical parameters were used to evaluate hepatic and renal toxicity and functionality. After tumor irradiation (210J/cm(2)), an analysis of tumor necrosis degree was used to evaluate the phototherapeutic effects. It was measured at 1, 2, 3 and 4 days after PDT. Vital staining was performed by intraperitoneal injection of 0.35ml 1% Evans Blue solution. Six hours later, tumors were excised and examined. The unstained area was attributed to necrotic tissue, whereas the stained area showed tissue with preserved blood supply. ZnPcCF(3) was accumulated in spleen, liver and duodenum. It suggests that ZnPcCF(3) is eliminated from the body via bile-gut. The phthalocyanine was not found in brain, therefore, it would not cross the blood-brain barrier, thus toxicity risk in the central nervous system is not probable. Moreover, ZnPcCF(3) does not accumulate in skin, it would eliminate cutaneous photosensitizing risks. The dose of 0.2mg/kg ZnPcCF(3) resulted in a low acute toxicity with revertible damages, which indicates that this dose can be used for PDT. The tumor death was of 89% 4 days after PDT. It indicates that ZnPcCF(3) would be effective in PDT.

Easy way to fabricate nanostructures on a reactive polymer surface.

The fabrication of advanced architectures in poly(glycidylmethacrylate-co-styrene) (PGMA-S) copolymers using direct laser interference patterning (DLIP) and its selective functionalization is reported. The structure features depend mainly on the laser energy used and on the styrene content in the copolymer. The topography, measured by electronic scanning microscopy, show regular and ordered arrays for the polystyrene (PS) and for the copolymers PGMA-S. The surface PS homopolymer is ablated at the position of maximum light fluence (constructive interference), while in the copolymers the surfaces swell up at the regions with maximal fluence. The styrene units are shown to absorb the laser energy giving photothermally ablated regions or promoting the chemical decomposition of acrylate units or polymer segments. In that way, DLIP provides a unique way to produce regularly ordered structures protruding or depressing from the polymer surface without altering to a large extent the chemical nature of the material. In addition, it is shown, using fluorescence microscopy, that amine-polyethylenglycol-CdSe quantum dots (NH(2)-PEG-QDs) could be spatially localized by reaction with patterned surfaces of PGMA-S. In that way, it is proven that a patterned and chemically reactive surface can be created using DLIP of PGMA-S.

Promotion of photodynamic therapy-induced death: Laboratory experimental methodology

Photodynamic therapy, a cancer treatment using a photosensitizer and visible light, has been shown to induce apoptosis or necrosis. In the present paper we recommend the use of a phthalocyanine derivative in an experimental class with the purpose of introducing students to photodynamic treatment of cultured cells, morphological observation of cell death, and viability assays. We consider that this activity might help students trained previously in tissue culture handling to experience a richer way of learning concepts and techniques.

Physiological parameters and biodistribution of 5,10,15,20-tetra (4-methoxyphenyl) porphyrin in rats.

Physiological parameters on hepatic and renal functionality and biodistribution, accumulation and elimination, in different organs of the 5,10,15,20-tetra (4-methoxyphenyl) porphyrin (TMP) were determined in Wistar rats. The transport of TMP by low-density (LDL) and high-density lipoproteins (HDL) was also investigated. The photosensitizer is accumulated in the spleen, where its concentration is significantly increased 21 d post-injection; it also accumulates in the liver and in a lower proportion, in the duodenum, and poorly in brain and muscle. The urine and serum biochemical parameters reached normal values both in control and treated groups. The glomerular filtrate rate was not affected by the TMP treatment in any of the studied times. These results would indicate that the sensitizer does not modify the renal glomerular function. TMP is mainly eliminated from the organism via the bile-gut pathway. Considering the total amount of porphyrin bound to both lipoproteins (LDL and HDL) in comparison with the total value of the TMP in serum, it can be inferred that a large amount of the agent is transported by lipoproteins in the plasma. This study proves information about the behavior of TMP in vivo under dark conditions. The results can be used to design photodynamic treatments using this porphyrin model as the sensitizer.