3D Printing Technologies in Personalized

Three-dimensional printing (3DP) has been in existence for decades but has regained attention more recently due to the huge potential it holds to addressing several of the constraints associated with the current modality in therapeutic interventions. For example, conventionally manufactured dosage forms like tablets and capsules are regimented with a fit-for-all provision. Clinicians have limited options when gauging the required dose (based on the severity of the disease) from unit dose medicines like tablets or capsules. This situation is less acute with continuous dosage forms like syrups and suspensions. Limitations in calibrated dosing may poses constraints when prescribing/dispensing, which may lead to sub-therapeutic levels or potentially toxic blood levels in patients. When we take into account the fact that patients express various levels of metabolizing enzymes such as CYP 450 and hence respond differently to the same treatment scheme, the preceding scenario is all the more crucial. As a result, pharmacogenomics, which deals with the interplay between genetic variations in individuals and their responses to medication, is recognized as key to ensuring safety in therapeutics. Several researchers have devoted their attention to unlocking many genetic codes that play a crucial role in drug metabolism. The emerging 3D printing technology signifies a ground-breaking evolution in the production of medicines, transitioning from conventional technological methods to additive manufacturing. This advancement is particularly revolutionizing the pharmaceutical industry. For example, in hospital settings, 3D printing will facilitate the creation of personalized drug dosages, helping patients with specific medical needs. Similarly, in community pharmacies, this technology will enable on-demand drug production, ensuring medications are tailored to individual patients, thereby reducing wait times and enhancing treatment outcomes.

History

3D Printing posed as a possible platform for personalized medicine in the 1990s. There are major achievements in 3D printed medical device, FDA’s Center for Device and Radiological Health (CDRH) has reviewed and cleared 3DP medical devices.  The first 3D printing technique used in pharmaceutics was achieved by inkjet printing a binder solution onto a powder bed, binding therefore the particles together. 3D printing is more advanced in the fields of automobile, aerospace, biomedical and tissue engineering than in the pharmaceutical industry where it is in its initial phase. FDA encourages the development of advanced manufacturing technologies, including 3Dprinting, using risk-based approaches [1,7]

Pros and Cons of 3D Pharmaceutical Printing: 

The application of 3D printing in pharmaceuticals brings a range of benefits while also posing challenges, both of which play a crucial role in shaping its impact on drug [7,8]

development and patient care

One of the most significant transformative advantages of 3D printing in the pharmaceutical industry is the ability to customize medication. This technology enables the tailoring of drug combinations, release mechanisms, and dosages according to the specific requirements of each patient, thereby substantially improving treatment efficacy and adherence. In addition to facilitating customization, 3D printing enables the creation of intricate structures and geometries that cannot be achieved using conventional manufacturing techniques, thus facilitating the advancement of innovative medication delivery systems. Sophisticated drug release profiles, including staggered or delayed release, are made possible by these novel structures, which effectively optimize therapeutic outcomes while reducing adverse effects. [1] The research and development phases of the pharmaceutical industry can be accelerated due to the streamlined design and production of prototype medications made possible by the rapid prototyping capabilities of 3D printing . Furthermore, the utilization of 3D printing technology enables hospitals and pharmacies to produce medications on demand. This is particularly significant when it comes to the development of orphan pharmaceuticals or treatments for rare conditions, which are not feasible to produce on a large scale. On-site manufacturing serves the dual purpose of reducing costs and waste related to drug overproduction and storage, while also accommodating the development of personalized medications that may have limited shelf lives. In addition, the possibility to modify the dimensions, form, taste, or pigmentation of pharmaceutical substances renders [2] them attractive and simpler to ingest, thereby enhancing adherence, especially among susceptible categories, including children and geriatric patients .These unique properties make 3D printing a key player in advancing medication discovery and improving patient-centered care .The integration of 3D printing in pharmaceuticals, while innovative, presents a range of challenges that slow down its broader applications .Regulatory issues are a significant concern due to the personalized nature of 3D-printed drugs; each new formulation might necessitate a full approval process, which can be both costly and time-consuming . The initial costs for setting up 3D printing technology are also substantial, encompassing expensive equipment, specialized training, and ongoing expenses such as software updates and maintenance. In terms of scalability, 3D printing does not yet match the efficiency of traditional manufacturing methods for large-scale production, limiting its use to specialized drugs or niche markets. Another obstacle is the limited range of materials suitable for 3D printing, as many active pharmaceutical ingredients and excipients used in traditional manufacturing are not compatible with current 3D printing technologies. The relatively limited availability of excipients is the major obstacle for designing specialized dosage forms. Biodegradable, biocompatible, non-toxic, and stable excipients are essential for the wide application of 3D pharmaceutical printing. Furthermore, with the increase in the more complex structures of dosage forms, continuous updating of modelling software for its design and production is necessary. To avoid clogging or encourage consistency of the product, the control system, operating methods, and mechanical equipment must be updated and optimized. The efficacy of the printed products could also be influenced by physicochemical parameters, including the surface tension and viscosity of the adhesives, as well as the properties of the nozzle of the 3D printer. Furthermore, post-printing procedures such as drying methods, drying temperature, and drying time may influence the quality and appearance of the products. [6]

Principles of 3D Printing in Medicine

3D printing in medicine, also known as additive manufacturing, is a transformative technology that bridges the gap between digital medical imaging and physical reality. Its core principle is the creation of complex, patient-specific objects by depositing material layer-by-layer. [1]

1. The Workflow: From Image to Object

The primary principle of medical 3D printing is the digitization of anatomy. Unlike traditional manufacturing, which starts with a block of material (subtractive), 3D printing starts with nothing and adds material only where needed. [2]

1. Image Acquisition: High-resolution 3D data is captured using CT, MRI, or 3D ultrasound. The data is stored in DICOM (Digital Imaging and Communications in Medicine) format. [6]
2. Segmentation: Software is used to "isolate" specific tissues (e.g., a tumor or a specific bone) from the rest of the scan. [3–5]
3. CAD Conversion: The segmented data is converted into a 3D surface mesh, typically an STL file, which defines the geometry as a series of triangles. [7,8]
4. Slicing: The digital model is sliced into hundreds or thousands of horizontal layers. These layers become the "instructions" (G-code) for the printer. [1]
5. Printing: The printer follows these instructions to build the object from the bottom up. [2]

Advantages in medicine

• High precision and reproducibility
• Patient-specific customization
• Reduced material waste
• Rapid prototyping and production

3D Printing Technologies Used in Medicine (Methods in Detail)

1.1 Fused Deposition Modeling (FDM)

Fused Deposition Modeling (FDM), also known as Fused Filament Fabrication (FFF), is the most widely used 3D printing technology due to its cost-effectiveness and simplicity. In medicine, it serves as a critical tool for creating anatomical models, customized prosthetics, and even personalized drug delivery systems. [6]

1. The Core Mechanism

The fundamental principle of FDM is material extrusion. It operates like a highly precise, computer-controlled glue gun.

• Feedstock: The process begins with a solid thermoplastic filament (wound on a spool) being fed into the print head. [7,8]
• Melting: A "cold end" pulls the filament into a "hot end," where a heating element melts the plastic into a semi-liquid state. [1]
• Deposition: A motor pushes the molten material through a fine nozzle (typically in diameter) onto a build platform. [2]
• Solidification: As the plastic leaves the heated nozzle, it cools and hardens almost instantly, fusing to the layer beneath it through thermal bonding. [6]

2. Technical Parameters in Medicine

For medical applications, several technical factors must be tightly controlled to ensure safety and accuracy:

• Layer Height: Usually ranges from to. Smaller layers provide a smoother surface for surgical models but take longer to print. [7,8]
• Infill Density: The internal structure of the part. For a bone model, a” honeycomb" infill might be used to save material; for a functional prosthetic, density is required for strength. [1]
• Shell Thickness: The number of outer "walls." Thicker shells allow for post-processing like sanding or sterilization without compromising the part's integrity. [2]