## 1 Introduction  
Poly(Ethylene Terephthalate) (PET), due to its physicochemical and technical attributes (high uniformity, mechanical strength, permeability to gases, transparency and resistance against UV and chemicals), presents a multifunctional polymer [1; 2; 3] widely engaged in various applications ranging from a production of containers and packaging [4], through textiles [5; 6; 7; 8], the health care polymeric materials [9; 10; 11; 12] and concrete components [13] to flexible electronic device applications [14]. However, the lack of antibacterial properties with unsatisfactory biocompatibility and functionality of PET frequently limits its use in some industrial and medical fields, especially in biomedical device and filtration membrane applications [15]. Moreover, due to its own porosity PET is conducive to microbial adhesion and subsequent bacteria colonization [16]. Therefore, for improvement of antimicrobial properties PET was subjected to several surface modification technologies [17; 18], the majority based on functionalization [19; 20], grafting [21; 22; 23; 24; 25; 26; 27; 28], surface topography modification [29; 30; 31; 32; 33], coating [34; 35; 36; 37] and their combinations [38; 39; 40]. Of substantial importance in the field of antimicrobial PET are its composites, equipped with antibacterial organic additivities (mainly chitosan and antibiotics [21; 22; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50]). Thus, antimicrobial hybrids of PET-organic biocides can be represented by PET-Chitosan [21; 22; 41], PET-Chitosan/hyaluronic acid [42; 43; 44], PET-Antibiotics (e.g., rifampicin [45]; cephalospororin [46]; gentamicin [47], tetracycline [48]; chlorhexidine [49] or daptomycin [50]). Because of increasing demand for effective antimicrobials combating bacterial cross-infections and infectious diseases [51], metals and salts deposited over polymers became a valuable alternative to traditional antibiotics [52; 53; 54; 55; 56; 57; 58; 59]. In hybrids PET-inorganic bactericides representative are: PET-Ag nanoparticles [60; 61; 62; 63; 64; 65; 66; 67], PET-silver salts [68; 69], PET-TiO\({}_{2}\)[70; 71; 72; 73], PET-Zn/ZnO\({}_{2}\)[74; 75; 76; 77] and/or PET-Au [78]. In the set of PET-metal hybrids only a few PET-Cu hybrids have been reported [79; 80; 81; 82]. Between various inorganic bactericides of medicinal interest growing attention is focusing on copper and its salts (over 5200 documents on antibacterial activity of copper abstracted by Scopus) [83], due to their low costs and easy preparation [84; 85; 86] as well as an antimicrobial efficiency [87; 88; 89; 90; 91; 92; 93; 94; 95; 96]. The antibacterial activity of the copper metallic surface is regarded to act by two supplemental mechanisms--surface-surface interaction of copper and bacteria (contact killing) [93] and/or surface oxidation of copper with the subsequent release of antibacterial cupric ions (e.g., [93; 94]). Polymer-copper composites have been formed by a number of various methods, [95; 96; 97; 98], including magnetic sputtering method: a simple and ecofriendly method, allowing deposition of the required amount of deposited metal in function of the time applied [99; 100; 101]. As a part of our research program directed on biologically active functionalized phosphonates [102; 103] and biofunctionalization of textile materials [104; 105; 106] we present the preparation and physico-chemical and biological properties of the PET-Cu polymer hybrid. The aim of this work was to modify the surface of the polyethylene terephthalate knitwear textile with copper, using the DC (Direct Current) magnetron sputtering method and fabrication of a new antimicrobial, multi-functional composite material. As far as pretreatment and finishing of textile fabrics are concerned, plasma technologies are currently increasingly replacing wet chemical processes. For instance, [PERSON] et al. [107] applied magnetron sputtering to modify the woven cotton fabrics with Cu.