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Nanotechnology is one of the most relevant scientific areas today due to its multiple applications in fields such as medicine, environmental remediation, information technology and energy conversion. This importance has led to the need to advance in the development of environmentally sustainable and safe nanomaterials by incorporating the principles of green chemistry during their synthesis and in their applications. However, this qualitative framework of thought does not offer minimum criteria for the use of the term “green”, and therefore, this adjective is commonly used to refer to bio-based or nanotechnological processes without taking into account their net ecological impact. In this context, environmental sustainability metrics can be applied to nanotechnology to compare, optimize and quantify the environmental sustainability of synthesis procedures. This review provides an overview of green chemistry and its application in nanotechnology, but also an analysis of the use of green chemistry principles in the development of bio-based nanobiotechnology and nanosynthesis, with special emphasis on the use of sustainability's metrics for the quantitative analysis of nanomaterial synthesis protocols. These include: Atom Economy, E-factor, Process Mass Intensity, Energy Intensity, and Life Cycle Analysis.

The understanding of progressive advances in the development of intelligent systems based on biocompatible, biodegradable, and renewable resources and their applications in important fields, such as medical, pharmaceutical, agricultural, and industrial, have increased attention in the use of cellulose for obtaining stimuli-responsive materials. Within the smart polymer systems, one of the most relevant is hydrogels, which are materials with important characteristics of water absorption, elasticity, and multifunctionality. These materials have been developed from several renewable sources such as chitin, starch, and cellulose; in particular, cellulose and cellulose by-products have allowed the designing of hydrogels with a wide range of functionalities and applications. Of interest for us, hydrogels are capable of experiencing a response as a result of changes in their environment or external stimuli, which can be chemical or/and physical, for example, pH, temperature, ionic strength, and electromagnetic fields, among others. Initially, in this chapter, physical-chemical properties and the importance of cellulose as a polymeric material will be described, emphasizing its use for obtaining stimuli-responsive hydrogels and their applications, in particular, in the biomedical field. In this way, their properties, the obtaining routes, and characterization methods of stimuli-responsive cellulose-based hydrogels (CBHG), from physical to chemical, are analyzed and described. Finally, significant applications of stimuli-responsive, CBHGs in drug-controlled release and tissue engineering are shown and discussed.