Nowadays, multi-drug resistant (MDR) bacteria pose a serious threat to people worldwide [[1], [2], [3], [4]] and very few antibiotics are available for the treatment of such infections. Beta-lactam antibiotics have been the cornerstone of the antibiotic treatment since the early 1940s [5]. Owing to their wide antibacterial spectrum and favourable safety profile, they remain the primary choice for treatment of severe infections worldwide. However, increasing resistance rates have challenged their widespread application in clinical practice. Rapid spread of β-lactamases in Gram-negative bacteria represents a genuine threat to successful treatment of both uncomplicated and serious infections [6,7]. To make matters worse, the research and development pipeline for new antibiotics has declined over recent decades, and novel treatment strategies have mostly yielded disappointing results in sepsis trials [8,9]. Given increasing resistance rates and the limited availability of new treatment options, clinical researchers have concentrated their efforts on optimising treatment with β-lactam antibiotics. This includes identifying patient populations at risk for underdosing and applying pharmacokinetic/pharmacodynamic (PK/PD) principles to define optimal dosing strategies. As a result, prolonged infusion of β-lactam antibiotics has been suggested as one of the dosing strategies to improve achievement of PK/PD targets and may improve patient outcomes, particularly in the intensive care unit (ICU) [10].

Meropenem and Cefepime (Fig. 1) are β-lactam antibiotics that belong to the carbapenem [11] and cephalosporin [12] groups, respectively. Cephalosporins are commonly used for mild and severe infections; they are effective against both gram-positive and gram-negative organisms. Carbapenems have a broad spectrum of application within the β-lactam antibiotics. Both groups of drugs are indicated for patients with severe infections caused by antibiotic-resistant bacteria [13].

The main problem with the use of these drugs is their low bioavailability, as the β-lactam ring undergoes degradation at body temperature, not being stable for more than 2–3 h in the body [14]. Given their short half-life (1.8–2.7 h for meropenem [15,16] and 1.9–2.1 h for Cefepime [17,18]), continuous infusions to the patient are necessary to maintain drug concentrations above the therapeutic level throughout treatment [[19], [20], [21]].

Nanotechnology offers a promising alternative to these problems through the use of nanocarriers [22] such as liposomes [23], nanoparticles [24], micelles [25], and carbon nanotubes [26]. In particular, carbon nanotubes (CNTs) can be defined as a sheet of graphene rolled into a hollow cylinder. They were first synthesized in the 1970s by Oberlin et al. [27] and in the 1990s by Ijima et al. [28] CNTs range in diameter from 0.4 to 5 nm and in length from a few nanometres to several micrometers. According to the number of layers, they can be classified as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) (see Fig. 1) [29,30]. Due to their properties, CNTs are used in a wide range of fields, including electronics, medicine, environmental applications, among others [31,32].

In relation to the medical applications, the interest of employing CNTs as drug nanocarriers stems from their large internal volume, capacity to immobilize many substances, exceptional functionalization potential, adsorption capabilities, biocompatibility and ability to cross biological barriers [33]. In fact, these carbon nanostructures have been used as nanocarriers in cancer treatment, theranostic applications, and the delivery of therapeutic molecules such as proteins [[34], [35], [36]], peptides [37], RNA, DNA [38], etc. Carbon nanotubes are superior drug carriers due to their stability, high drug-loading capacity, and easy functionalization. They enable targeted drug delivery, improving therapeutic efficacy and reducing side effects. Moreover, CNTs cross membranes without damaging cells, making them ideal for advanced drug delivery systems[[39], [40], [41]].

With this in mind, and aiming to enhance the stability of β-lactam antibiotics, this work investigates the encapsulation of Meropenem and Cefepime in single- and multi-walled carbon nanotubes. The equilibrium constants corresponding to the interaction of the β-lactam antibiotics to the carbon nanotubes have been estimated from encapsulation percentage data obtained at different CNT concentrations. Moreover, the characterization of the complexes CNT/β-lactam antibiotic was performed by DLS measurements. For the purpose of analysing the role of pristine CNTs as nanocarriers, the minimum inhibitory concentration (MIC) of the encapsulated drugs against the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium Staphylococcus aureus was determined by studying the growth of the microorganisms in the absence and presence of different amounts of the encapsulated antibiotics.