**1. Introduction**

One year ago, the coronavirus disease of 2019 (COVID-19) crisis forced us into confinement. The unexpected pandemic highlighted how infectious diseases can affect health and economies worldwide. As most countries slowly move toward recovery, considerable attention must be paid to the emergence of multi-resistant microorganisms. The fact that some infectious diseases can no longer be treated with antibiotics depicts an alarming issue in the health care sector [1]. This trend reinforces the need for improved measures to protect and save lives. The resistance to antimicrobial agents is due to the intensive and inappropriate use of antibiotics, self-drug addiction, hospital-acquired infections, unsafe disposal of hospital and biomedical wastes and the use of antibiotics in veterinary medicine [2].

**Citation:** Dridi, D.; Bouaziz, A.; Gargoubi, S.; Zouari, A.; B'chir, F.; Bartegi, A.; Majdoub, H.; Boudokhane, C. Enhanced Antibacterial Efficiency of Cellulosic Fibers: Microencapsulation and Green Grafting Strategies. *Coatings* **2021**, *11*, 980. https://doi.org/ 10.3390/coatings11080980

Received: 8 July 2021 Accepted: 12 August 2021 Published: 18 August 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

The demand for antimicrobial agents with high disinfection properties is on the rise. Effective and safe microbe-resistant materials are highly demanded to fight against the emergence of microbial contamination [3,4].

Plant-based antimicrobial substances are emerging as promising tools in the fight against multi-resistant pathogens, as reported by numerous recent studies [5]. Plants contain valuable components, such as glycosides, tannins, steroids, terpenoids, saponins, alkaloids, polyphenols, flavonoids, quinones and coumarins [6]. These substances are used as a defensive response to microorganisms, insects and herbivores [7].

Among the plant-derived products, essential oils are one of the most diverse classes of specialized metabolites that play an important role in the defense against microbial attacks [8]. Essential oils present a complex mixture of numerous volatile molecules with low molecular weight, including terpenoides, terpenes and other aliphatic and aromatic substances [9]. These constituents exhibit a broad spectrum of antimicrobial activities [10]. In addition, essential oils are biodegradable and safe for human health [11].

Increasing demand for effective and low-toxicity antimicrobial agents depicts essential oils as promising alternatives in a variety of domains [12]. Given the emergence of techniques such as microencapsulation and nanotechnology applications [13,14], the use of essential oils in the textile sector is emerging. These substances are used to impart either a pleasant smell or antimicrobial activity to the textile materials [13].

Microencapsulation and nano-finishing provide good efficacy for treated textiles. In comparison to conventional techniques, the large surface area of micro/nano particles ensures better affinity for textile substrates and leads to a successful and durable functionalization [15].

Despite numerous studies showing the antimicrobial action of essential oils when applied to textiles, the synergistic effect of these substances for textile applications has not been reported [16].

In the current work, we report an environmentally friendly finishing method to functionalize cotton fabric surfaces with antibacterial activity based on the synergic effect of two essential oils attached via a microencapsulation technique with citric acid as a binding agen<sup>t</sup> using the padding method.

#### **2. Materials and Methods**

## *2.1. Materials*

Essential oils were obtained from the bark of *Ceylon cinnamon* and cloves of *Syzygium aromaticum*, which were purchased from spice shops. Cinnamon and clove are commonly used spices which have been well recognized for their antimicrobial activities [17,18].

Chitosan (low molecular weight), acetic acid and NaOH were purchased from Sigma Aldrich (Sigma-Aldrich Chemie GmbH, Steinheim, Germany). Citric acid and Tween 20 (surfactant) were donated by the S2C Company (S2C, Sousse, Tunisia). The desized, bleached and mercerized woven cotton fabric used during the experiments was bought from the local market with a surface area of 280 <sup>g</sup>·m<sup>−</sup>2.
