## 1 Introduction  
The main purpose of periodontal treatment is to protect and regenerate diseased periodontal tissues. Another aim of such treatments is to stop chronic inflammatory processes destroying periodontal tissue and leading to pathological pocket formation. The basic method of periodontal infection treatment, referred to as scaling and root planning (SRP), relies on the elimination of subgingival bacterial deposits from the tooth surface by mechanical removal of the plaque [1,2]. However, this approach has limitations, mostly due to the inability of dental hand instruments to reach areasaffected by infection and due to the requirement for a highly skilled operator. As a result, SRP does not guarantee the elimination of anaerobic bacteria residing in the base of deep periodontal pockets as well as in the interstitial spaces, from where they are able to migrate into the tissues [2; 3]. The relationship between periodontal surgery treatment and sepsis caused by the dissemination of bacteria through the bloodstream is already well established [4; 5; 6; 7]. Therefore, to ensure efficient removal of pathogenic microorganisms from difficult-to-access sites, local antimicrobial therapy is applied [2; 8; 9]. Unfortunately, oral administration may lead to insufficient concentration of the drug within the periodontal pocket and to the rise of bacterial resistance against the compound [10]. Answering an urgent clinical demand, local drug-delivery devices have been developed to provide a high concentration of antimicrobial compound directly to the infected site. This minimizes systemic exposure to the drug [11; 12] and limits any potential adverse reactions [13]. Helpfully, due to its topography, a periodontal pocket may serve as a storage of an antimicrobial agent that can be released continually from the carrier, providing an anti-infectious measure in the proximity of the affected site [14]. Studies show that local use of metronidazoleole in the treatment of periodontal disease enhances the therapeutic effect of SRP but that the use of the metronidazoleole is associated with a lower risk of tissue damage, dental hypersensitivity, or colonization as a result of microbial migration from the interstitial spaces inaccessible to the surgeon [1; 8]. Thus, the choice of an appropriate carrier for drug delivery is of paramount importance to achieving a favorable outcome. Presently, a wide spectrum of carriers, both organic and inorganic, are employed for this purpose, with gelatin and cellulose (or its derivatives) being the most prominent examples. Gelatin is a natural protein obtained by partial hydrolysis of collagen. It possesses several beneficial features, including supporting cell proliferation and differentiation, and favorable physical-chemical attributes such as adhesiveness, plasticity, biocompatibility, biodegradability, water solubility, and the ability to form stable gels [15; 16; 17]. Gelatin-based matrices are currently used in tissue engineering as drug carriers (providing agents promoting bone regeneration) and as dressings in wound treatment. Gelatin/polymeric porous hydrogels are oxygen-permeable and have the ability to absorb tissue exudates and to create a moist environment, which is required for efficient tissue healing [18; 19]. Examples of cellulose-derived carriers include carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC), which are biodegradable, water-soluble cellulose ethers, displaying plasticizing muco-adhesive properties. To enhance the efficiency of carrier compounds, two or more polymers can be used as substrates and matrix properties can be adjusted to the desired parameters [20; 21; 22]. Mixtures of cellulose derivatives and natural polymers, i.e., gelatin, are used in dressings for the treatment of chronic wounds [23; 24; 25]. Moreover, freeze-drying of such gels, polymer dispersions, or their mixtures leads to the formation of dry dressings displaying a porous structure of a large surface area.