Madeira Chemistry Research Centre

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Publications

Physicochemical properties and cell viability of shrimp chitosan films as affected by film casting solvents. I-potential use as wound dressing

Publication . Eulálio, Hugo Yves C.; Vieira, Mariana; Fideles, Thiago B.; Tomás, Helena; Silva, Suédina M. L.; Peniche, Carlos A.; Fook, Marcus Vinícius L.

: Chitosan solubility in aqueous organic acids has been widely investigated. However, most of the previous works have been done with plasticized chitosan films and using acetic acid as the film casting solvent. In addition, the properties of these films varied among studies, since they are influenced by different factors such as the chitin source used to produce chitosan, the processing variables involved in the conversion of chitin into chitosan, chitosan properties, types of acids used to dissolve chitosan, types and amounts of plasticizers and the film preparation method. Therefore, this work aimed to prepare chitosan films by the solvent casting method, using chitosan derived from Litopenaeus vannamei shrimp shell waste, and five different organic acids (acetic, lactic, maleic, tartaric, and citric acids) without plasticizer, in order to evaluate the effect of organic acid type and chitosan source on physicochemical properties, degradation and cytotoxicity of these chitosan films. The goal was to select the best suited casting solvent to develop wound dressing from shrimp chitosan films. Shrimp chitosan films were analyzed in terms of their qualitative assessment, thickness, water vapor permeability (WVP), water vapor transmission rate (WVTR), wettability, tensile properties, degradation in phosphate buffered saline (PBS) and cytotoxicity towards human fibroblasts using the resazurin reduction method. Regardless of the acid type employed in film preparation, all films were transparent and slightly yellowish, presented homogeneous surfaces, and the thickness was compatible with the epidermis thickness. However, only the ones prepared with maleic acid presented adequate characteristics of WVP, WVTR, wettability, degradability, cytotoxicity and good tensile properties for future application as a wound dressing material. The findings of this study contributed not only to select the best suited casting solvent to develop chitosan films for wound dressing but also to normalize a solubilization protocol for chitosan, derived from Litopenaeus vannamei shrimp shell waste, which can be used in the pharmaceutical industry.

2020Journal article

Open access

Cyclotriphosphazene-based derivatives for antibacterial Applications: an update on recent advances

Publication . Su, Xiqi; Wang, Le; Xie, JingHua; Liu, XiaoHui; Tomás, Helena

As a phosphorus scaffold, hexachlorocyclotriphosphazene (HCCP) is widely used for the synthesis of varieties of derivatives, including metal-binding complexes and several unique organometallic compounds, which exhibit potential catalytic, flame retardant and bio logical activities. Some metal-binding HCCP derivatives have shown antibacterial activities as free ligands and metal complexes. These derivatives can also serve as building blocks for the formation of antibacterial metal-containing polymers. This mini-review is focused on the de sign and development of HCCP derivatives as potential antibacterial agents with representa tive examples as well as antibacterial mechanisms from recent years

2021Journal article

Open access

A novel and simpler alkaline hydrolysis methodology for extraction of ferulic acid from brewer’s spent grain and its (partial) purification through adsorption in a synthetic resin

Publication . Ideia, Pedro; Sousa-Ferreira, Ivo; Castilho, Paula C.

This work aims to develop simpler methodologies of extracting ferulic acid (FA) from brewer’s spent grain (BSG). BSG is produced by brewing companies at high amounts all over the year and does not possess a direct application. Thus, its use as raw material for extraction of bioactive compounds has gained attention in the last years. FA has different interesting applications in cosmetics, food industry, and pharmaceutics. Several studies aim for its extraction from BSG by various methods, namely alkaline hydrolysis. In the present work, we suggest the use of autoclave to process higher amounts of BSG in a lab scale. A simplification of the regular post-hydrolysis procedures is also proposed to decrease the number of experimental steps and energy costs and to simultaneously increase the extraction yield (up to 470 mg of FA per 100 g of BSG). The adsorption of extracted FA in a synthetic resin is suggested as a partial purification method.

2020Journal article

Open access

Engineered Neutral Phosphorous Dendrimers Protect Mouse Cortical Neurons and Brain Organoids from Excitotoxic Death

Publication . Posadas, Inmaculada; Romero-Castillo, Laura; Ronca, Rosa-Anna; Karpus, Andrii; Mignani, Serge; Majoral, Jean-Pierre; Muñoz-Fernández, Mariángeles; Ceña, Valentin

Nanoparticles are playing an increasing role in biomedical applications. Excitotoxicity plays a significant role in the pathophysiology of neurodegenerative diseases, such as Alzheimer’s or Parkinson’s disease. Glutamate ionotropic receptors, mainly those activated by N-methyl-D aspartate (NMDA), play a key role in excitotoxic death by increasing intraneuronal calcium levels; triggering mitochondrial potential collapse; increasing free radicals; activating caspases 3, 9, and 12; and inducing endoplasmic reticulum stress. Neutral phosphorous dendrimers, acting intracellularly, have neuroprotective actions by interfering with NMDA-mediated excitotoxic mechanisms in rat cortical neurons. In addition, phosphorous dendrimers can access neurons inside human brain organoids, complex tridimensional structures that replicate a significant number of properties of the human brain, to interfere with NMDA-induced mechanisms of neuronal death. Phosphorous dendrimers are one of the few nanoparticles able to gain access to the inside of neurons, both in primary cultures and in brain organoids, and to exert pharmacological actions by themselves.

2022Journal article

Open access

Functionalized Nitroimidazole Scaffold Construction and Their Pharmaceutical Applications: A 1950–2021 Comprehensive Overview

Publication . Gupta, Ria; Sharma, Sumit; Singh, Rohit; Vishwakarma, Ram A.; Mignani, Serge; Singh, Parvinder Pal

Nitroimidazole represents one of the most essential and unique scaffolds in drug discovery since its discovery in the 1950s. It was K. Maeda in Japan who reported in 1953 the first nitroimidazole as a natural product from Nocardia mesenterica with antibacterial activity, which was later identified as Azomycin 1 (2-nitroimidazole) and remained in focus until now. This natural antibiotic was the starting point for synthesizing numerous analogs and regio-isomers, leading to several life-saving drugs and clinical candidates against a number of diseases, including infections (bacterial, viral, parasitic) and cancers, as well as imaging agents in medicine/diagnosis. In the present decade, the nitroimidazole scaffold has again been given two life-saving drugs (Delamanid and Pretomanid) used to treat MDR (multi-drug resistant) tuberculosis. Keeping in view the highly successful track-record of the nitroimidazole scaffold in providing breakthrough therapeutic drugs, this comprehensive review focuses explicitly on presenting the activity profile and synthetic chemistry of functionalized nitroimidazole (2-, 4- and 5-nitroimidazoles as well as the fused nitroimidazoles) based drugs and leads published from 1950 to 2021. The present review also presents the miscellaneous examples in each class. In addition, the mutagenic profile of nitroimidazole-based drugs and leads and derivatives is also discussed.

2022Journal article

Open access