Bacteriophages (phages) are obligate intracellular parasitic viruses that specifically infect bacteria. They are the most abundant and widely distributed biological entities on earth. Their ability to kill pathogenic bacteria has led to their utilization in various fields, including agriculture, food processing, packaging, and as therapeutics against bacterial infections. It is estimated that there are approximately 1031 phage particles in the biosphere. Phages exhibit diversity in terms of size, shape, complexity, and genomic content. Morphologically, they can be tailed, polyhedral (vesicular and envelope-like), filamentous (long filaments to short rods), or pleomorphic (including lemon, droplet, and ampule-shaped), and may possess lipid or lipoprotein envelopes [1]. The majority of the phages belong to the order Caudovirales, characterized by tailed phages with double-stranded DNA (dsDNA) and isometric capsids. Examples include coliphage lambda (Siphoviridae), T4 (Myoviridae), and T7 (Podoviridae), which infect Escherichia coli [2]. Phage genomes can consist of DNA or RNA, and they may be double- or single-stranded, with sizes ranging from less than ten kilobases to several hundred kilobases. Phages can follow lytic or lysogenic life cycles. Lytic phages infect the host bacteria by interacting with bacterial receptors, undergoing adsorption, injecting their genomes, replicating, producing new viral progeny, and ultimately releasing from the infected host bacterium [3]. Tailed dsDNA phages facilitate programmed host cell lysis through the action of two proteins: a holin and an endolysin. These proteins perforate the membrane and hydrolyze the cell wall peptidoglycan, respectively. In Gram-negative bacteria, an additional protein called spanins is involved in the lysis process.

In the era of antibiotic crisis, lytic phages and phage-derived proteins have emerged as viable alternatives to antimicrobials, primarily in response to the escalating antibiotic resistance crisis and the limited development of new antibiotics for antibacterial therapy [4]. The use of phages as antimicrobials offers several advantages, including their specificity towards bacterial species, often targeting particular strains, and their safety in relation to human eukaryotic cells [5]. The therapeutic potential of bacteriophages is notably narrow, effectively addressing infections while circumventing issues associated with antibiotic administration and preserving the beneficial microbiota [6]. Bacteriophages exhibit a narrow spectrum of activity, providing an advantage in preserving the beneficial human microbiome without adversely affecting non-pathogenic bacterial species. Bacteriophage and their products are considered non-self-antigens. Therefore, the administration of bacteriophage does not induce immunogenic responses in humans [6]. Moreover, due to the absence of specific receptors for bacteriophages on eukaryotic cells, these viruses were regarded as inert or non-reactive to animals and humans [7]. Bacteriophages that infect coliform bacteria, such as Escherichia coli, are called coliphages. Oral administration of T4-like coliphages, with broad host ranges targeting diarrhea-associated E. coli in mice, minimally impacted the normal E. coli gut flora [8]. Phages can persist in the human body for relatively prolonged periods (up to several days), eliminating the need for frequent administration. Their ability to propagate at the infection site after initial administration means that very few doses are sufficient. Pouillot et al. [9] demonstrated the therapeutic efficacy of a lytic phage, EC200pp, active against S242, a fatal neonatal meningitis E. coli O25:H4-ST131 multidrug-resistant clone that rescued 100 % of pups in a meningitis model with treatment at 1 and 7 h post-infection. However, delivering phages to the infection site without compromising efficacy is crucial. Very recently, Nicolas et al. [10] isolated and characterized a novel coliphage against antibiotic-resistant avian pathogenic E. coli (APEC), known for causing colibacillosis in poultry. Additionally, Kong et al. [11] isolated P762, a coliphage, from duck farm sewage, demonstrating activity against both Shiga-toxin-producing E. coli stereotypes O157 and non-O157, as well as APEC. Typically, phages are administered in buffers, creams, nanoemulsions, nanoparticles, or hydrogels. They can also be functionalized on various surfaces of polymers and used as wound dressing materials [12]. Among these, non-toxic hydrogels offer advantages in topical medical applications by maintaining moisture balance at wound sites. The sustainable topical delivery of phages to the wound site proves highly effective as a potent antibacterial agent.

Natural polymers, including collagen, cellulose, chitosan, alginate, and starch, are utilized in the fabrication of biomaterials for drug-delivery wound dressing patches [13]. These biopolymers are extensively investigated in pharmaceutical applications due to their attributes such as low toxicity, biodegradability, nonimmunogenicity, cytocompatibility, and biocompatibility [14]. Certain natural polysaccharides, including sodium alginate [15], chitosan [16], starch [17], cellulose [18], carrageenan [19], and other natural polymers like gelatin [20] serve as encapsulating polymers of rhizobacteria or probiotic bacteria. This encapsulation is employed for biocontrol purposes in managing plant pests and diseases, as well as for applications in human health. Furthermore, the byproducts resulting from the biological degradation of these biopolymers are non-toxic. Among these natural polymers, carrageenans, derived from marine resources, serve as a highly sustainable, cost-effective, eco-friendly, and renewable source. Carrageenans are linear, sulfated polygalactans found in the cell wall and intercellular matrices of certain edible marine red seaweeds [21]. Carrageenan-based hydrogels exhibit versatility in delivery systems and wound healing. Kalsoom Khan et al. [22] demonstrated the nontoxicity and biodegradability of carrageenan-based bionanocomposites containing ferrous oxide nanoparticles as a drug delivery tool in pharmaceutical applications. Recently, Rajan et al. [23] prepared a carrageenan hydrogel loaded with pluronic®F68/curcumin as a wound dressing material for chronic wounds. Nevertheless, there has been no attempt to immobilize bacteriophages in the natural marine polysaccharide carrageenan, nor to investigate the influence of carrageenan on the lytic activity and stability of bacteriophages. In our study, we isolated and characterized a lytic coliphage (vB_Eco2571-YU1) against the pathogenic bacterium Escherichia coli. Subsequently, we innovatively fabricated a hydrogel-based phage delivery system using the carrageenan, characterizing its mechanical properties, stability, and coliphage lytic activity for in vitro wound dressing applications.