## 1 Introduction  
Polysaccharides are a cheap, sustainable and renewable group of commonly available organic compounds. They are considered as attractive resources for obtaining several novel biodegradable materials, attractive for medicine, chemical and pharmaceutical industries or food technology. Natural polysaccharides are enjoying a growing interest for their spreading fields of potential applications [1]. For their chemical structure, polysaccharides can be readily modified by involving physical, physicochemical, chemical and enzymatic methods. Numerous studies confirm the bioactivity of polysaccharides, providing their applications in clinical practice, nutrition and dietetics [2]. Depending on their origin, polysaccharides exhibit antioxidative, immunomodulating, anti-inflammatory, antiviral (among others, HIV), antimutagenic, cancerostatic and anticlotting properties [3, 4, 5]. Sodium alginate is a linear polymer composed of D-mannuronic and L-guluronic acid blocks. It has been approved by the US Food and Drug Administration (FDA) for human use in certain biomedical applications [6]. As a polysaccharide hydrogel, it finds various applications in industry, for example, in biodegradable plastic packaging materials [7], medicine and biotechnology [8]. It is non-toxic, biodegradable, biocompatible and has a far lower cost than many other biopolymers. It is also renewable [9]. Recent studies recognized the applicability of various polysaccharides in the synthesis of inorganic nanoparticles [10; 11; 12]. Polysaccharides act as reducers and stabilizers--matrices, providing the formation of nanoparticles uniform in size and satisfying, in this manner, requirements for their practical applications [13]. Nanoparticles immobilized within such matrices exhibit all the demanded properties: functionality, barrier properties, transparency and other interesting features. Nanocomposites with such nanoparticles are biodegradable and environmentally benign. Thus, they enjoy numerous potential applications, such as in prophylaxis, therapy and agricultural production [14]. The most suitable polysaccharides in developing nanoparticles are: starch, cellulose, alignates, pectins, xanthan gum, cyclodext, chitosan [15], heparin [16], furcellaran [17] and hyaluronic acid [18; 19; 20]. The mechanical properties of the polysaccharide materials can be improved with some additives such as hydrophobic materials and plasticizers [21; 22]. Inorganic compounds are alternative additives [23; 24]. Some papers announce the use of graphene oxide for this purpose [25; 26; 27]. Graphene and its derivatives are monolayer carbon materials. Their unique bidimensional structure offers a large surface, adsorbing nucleic bases and aromatic compounds involving \(\pi\)-\(\pi\) interactions. Epoxy, hydroxyl and carboxylic groups facilitate their conjugation with biomolecules [28]. [PERSON] [29] has presented a novel nanohybrid of hyaluronic acid and graphene oxide for a device sensitive to pH changes of drug carriers. This hybrid successfully liberated cancerostatic doxorubicin. Recent studies have also investigated the antibacterial effect of graphene oxide occurring due to its interactions with bacterial cell membranes [30; 31; 32]. As with other nanoparticles, graphene exhibits a tendency to aggregation via the van der Waals interaction between graphene layers. This behavior limits graphene applications. The aggregation can be inhibited when metal nanoparticles are deposited on the graphene surface. Metal nanoparticles introduced onto the surface of the graphene prevent the aggregation and provide good photoconductivity and catalytic properties of the graphene/metal nanocomposites [33; 34]. The good conductivity, strong ultraviolet-visible absorption ability and catalytic activity of silver nanoparticles are the reason for their popularity in many fields, such as electronic devices, biomarkers and antibacterial agents [35].