The blue crab (Callinectes sapidus, Rathbun 1896) has become a significant source of raw materials in biotechnology and nanotechnology due to the biomaterials present in its shell. Natural polymers such as chitin and chitosan, derived from the crab's shell, are particularly noteworthy for their environmentally friendly and biologically compatible properties. These biopolymers provide an innovative alternative in the synthesis of quantum dots (QDs). Quantum dots are favored in various applications, including biomedical imaging, environmental sensors, and energy storage, due to their superior optoelectronic properties. Chitosan obtained from blue crab shells acts as both a stabilizer and a coating agent in the green synthesis of quantum dots. This process minimizes the use of toxic chemicals, thus promoting environmental sustainability. Moreover, the antimicrobial and biodegradable properties of chitosan enhance its usability in biomedical applications. For instance, biocompatible carbon-based quantum dots have shown promising results in cancer diagnostics and drug delivery systems. The synthesis of quantum dots using biomaterials is more cost-effective and environmentally friendly compared to traditional methods. Furthermore, utilizing blue crab shells as a waste material contributes to both marine ecosystem preservation and the circular economy. These synthesis methods are reported to create a significant paradigm shift in the field of sustainable technology development. In conclusion, the synthesis of quantum dots using biomaterials derived from blue crabs has the potential to reduce environmental impacts while serving advanced technological applications. This approach significantly contributes to the development of biotechnological innovations and sustainable development goals.

The objective of this study was to develop and characterize a pH indicator based on chitosan (C) and starch (S) including anthocyanins from eggplant to indicate food quality changes through the detection of changes in the pH of packaged food products. Anthocyanins were extracted with solvents including ethanol and water (7:3, V:V) (EgP-E) and water (EgP-W) in acidic pH. The pH indicator films were obtained incorporating anthocyanin as 1.5 g extract/100 g film solution. The optical, mechanical and water vapor permeability properties were used to characterize the pH indicator films. The total monomeric anthocyanin content and phenolic content of extract solutions were also determined. Color variations of pH indicator films were measured by a colorimeter after immersion in different pH buffers (pH 2.0–10.0). Initially, dried C films and S based films were observed in a violet color and a magenta color, respectively. C and S films with anthocyanins showed color variations from pink (in acidic pH) to bluish-green (in neutral pH) and to violet (in basic pH) in different pH values. The water vapor permeability of films with anthocyanins was higher than films without anthocyanins. Additionally, C and S based films including anthocyanins extracted with water showed better permeability values. C:EgP-W and S:EgP-W films presented higher elasticity values when compared with films including ethanolic extracts (p