Additive manufacturing (AM), also known as three-dimensional printing (3DP), is an intriguing method that has been researched in the pharmaceutical field over the last decade. It is a manufacturing method based on the principle of digital design and successively adding the printing materials layer upon layer to fabricate a desired 3D product [1]. Various types of 3DP techniques, such as inkjet printing [2], binder jet printing [3], [4], fused deposition modeling (FDM) [5], [6], and semi-solid extrusion (SSE) 3DP [7], [8], [9], are at the forefront of research and development of novel pharmaceutical products and personalized medicines. They offer numerous advantages over traditional manufacturing methods, particularly in terms of tailoring dosage forms to individuals precisely by adjusting doses and product properties through changes in digital design and printing parameters. Modifications to the shapes, sizes, and porosity inside the structure can be more precisely controlled by adjusting the relevant model file in computer-aided design (CAD) software or adjusting the printing parameters (e.g., layer height, printing patterns, infill densities) in the 3D slicer and 3D printing host software. This simple way of modifying product geometries in the 3DP process enables the rapid creation of new customized and on-demand pharmaceutical products for each patient in a short period [10]. Thus far, some researchers have proposed studying the effect of geometry changes on the properties of developed products. For instance, Khaled et al. [11] discovered that the changes in the design of geometric shapes and internal structures considerably influenced the surface area and water absorption of the tablets, resulting in different drug release behaviors. In another study, Seoane-Viaño et al. [12] successfully fabricated three different sizes of 3D-printed tacrolimus suppositories using SSE 3DP and the precise specific doses of each size of developed suppositories were achieved in a single step process of changing the design templates in the CAD software.

Amongst all 3DP techniques, SSE 3DP, a subcategory of material extrusion 3DP, is regarded as the most promising approach for fabricating drug delivery systems that require high drug loading or contain thermo-sensitive drugs [13], [14]. The printing formulations prepared for SSE 3DP, also referred to as printing inks, were found to be in semi-solid (e.g., pastes or gels) or semi-molten forms, which are then extruded through a syringe-based print head under the pneumatic-based system or mechanical-based systems (piston-based system and screw-based system) to create the 3D object according to the design in modeling software [15]. Unlike other 3DP techniques, the distinctive aspect of this SSE 3DP is that there is no need for pre-processing manufacturing procedures (e.g., melt-extrusion of filaments in the FDM technique) or heating during the printing process [16]. On the other hand, this technique tends to increase the risk of 3D structures collapsing if used without suitable rheological properties of the printing inks. Thus, the rheological properties, flowability, and extrudability through the nozzle of the printing inks, as well as their ability to maintain the shapes of subsequent layers of 3D structures, are keystone parameters that must be taken into account during the formulation development in order for the printing inks to process well through SSE printing system [17].

Cellulose and its derivatives (e.g., hydroxypropyl methylcellulose (HPMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), and so on are the most commonly reported natural-based polymers in the previous literature related to pharmaceutical applications of 3DP technology [18]. Aside from the previously mentioned polymers, there are other interesting printable materials with few studies reporting on their potential for use as the base in formulating the inks for SSE 3DP in the regenerative medicine field and for other printing techniques in biomedical field [19], [20], [21]. One such polymer is carboxymethyl cellulose (CMC). However, to date, no studies have been undertaken to investigate the feasibility of using CMC to develop the drug delivery system via SSE 3DP.

In this study, CMC derived from durian rind wastes which had previously been synthesized and reported in the study of Rachtanapun et al. [22], was employed as the biopolymer base for preparing the printing inks. The overabundance amount of waste from durian, a popular tropical fruit that is widely consumed in the Thai domestic market and many Asian countries [23], raises concerns that waste may have accumulated excessively if there has been uncontrolled waste disposal or continuously increased rates of fruit consumption due to the rapid rise in global population and the strong economic growth of emerging countries year over year [24], [25]. Consequently, our research was conducted with the aims of enriching and sustainable reusing durian wastes as 3D printing material and then converting it into more value-added and innovative pharmaceutical products. For the first time, this study sought to assess the feasibility of using new source of CMC derived from durian rind wastes as a natural-based printing material in the fabrication of personalized oral films using SSE 3DP. Furthermore, the 3D-printed films were fabricated with different printing patterns and infill density by adjusting the printing parameters in 3D slicer and 3D printing host software to observe the influence of slicing parameter adjustments on the physicochemical, structural and drug release attributes of the 3D-printed films. This novel work would be advantageous to both agricultural and pharmaceutical industries as it provides numerous benefits, such as valorizing agro-food wastes, reducing wastes from 3D-printed synthesis polymers that are harmful to the environment and contradict the circular economy concept, leading to the production of novel eco-friendly and biodegradable pharmaceutical products, and simplifying the 3DP process for better application in real-life pharmaceutical practice.