## 1 Introduction  
Antimicrobial resistance (AMR) is a major threat that compromises the efficacy of antimicrobial drugs and thereby increases the prevalence of diseases in both developed and developing countries [1]. In recent studies, it has been estimated that AMR will be the leading cause of deaths for about 10 million people worldwide, annually, by 2050 [2]. Increasing AMR can be partly attributed to the unnecessary oral administration of drugs, especially in cases of prolonged therapy, which often continues for a long period of time. To address the AMR crisis, various strategies, including reduction of the excess use of antimicrobial drugs and optimisation of dosages and the duration of therapies are being studied [3]. Although these strategies are applicable, they are rather long-term approaches,and it will take time before a significant impact is seen against the rising cases of AMR. However, using a controlled and sustained drug delivery system of antimicrobials has been proposed as a promising strategy for the reduction of AMR [4,5]. This approach is about releasing the incorporated drugs in optimised concentrations at the targeted sites, minimising the need for frequent oral administration, which is one of the major contributors to AMR. In previous studies, various materials have been studied for the controlled release of drugs, and these include microcapsules, dendrimers, mesoporous silica, liposomes, organic micelles, quantum dots and biodegradable polymers [6, 7, 8]. However, these materials have various limitations, including uncontrolled degradation, low loading capacities and instability [9, 10]. Recently, the use of metal organic frameworks (MOFs) as an alternative platform for the controlled release of drugs has proven to be promising [11, 12]. MOFs are a class of hybrid crystalline materials formed from coordination bonds between metal ions crosslinked with organic linkers to form a two- or three- dimensional lattice with potential voids [13]. MOFs may contain micropores, which can be adjusted to various sizes with desired functional groups [14, 15, 16]. MOFs have therefore gained much attention due to their ultrahigh porosity, large surface area, thermal stability and high chemical selectivity, which makes them ideal for many applications, including chemical sensing, catalysis, supercapacitors and so on [17, 18, 19, 20, 21, 22]. Recently, MOFs have caught much attention as a vehicle for antimicrobial drug delivery mainly because of their ability to provide the controlled release of different antimicrobial drugs, which is sometimes coupled with the release of metal ions, such as Ag\({}^{+}\), Co\({}^{2+}\), Zn\({}^{2+}\) and organic linkers, to further enhance the antimicrobial effects of those systems [4, 23, 24, 25]. The ions and linkers released can act through various mechanisms. For example, some of these antimicrobial agents perforate the bacterial cell wall and interfere with the synthesis of the nucleic acids of the bacterial cell, thereby destroying the bacteria [26, 27]. However, some metal ions, like Ag\({}^{+}\) and Co\({}^{2+}\), can be toxic to human cells, hence limiting their applications in drug delivery [4, 28]. After considering this, a more biocompatible zinc-based MOF-5 has been chosen for drug delivery applications in this study, to avoid metal ion-based toxicity [5]. The chemical bonds between MOFs and the drugs include coordination bonds, hydrogen bonds and Van der Waals interactions [29, 30]. Additionally, the powder form of MOFs is a major limitation, especially in drug delivery applications, and hence, incorporating them into biodegradable polymers makes them easily applicable [31]. The instability of MOFs is another limitation, which can be attributed to the reversibility of the coordination bonds [32]. Biodegradable polymers, including poly-poly lactic-co-glycolic acid (PLGA) and polycaprolactone (PCL), have demonstrated the sufficient controlled release of drugs in previous studies [33, 34, 35]. These two polymers have varying degradability rates.