Publications

BACKGROUND: Fused Deposition Modelling (FDM) 3D printing has received much interest as a fabrication method in the medical and pharmaceutical industry due to its accessibility and cost-effectiveness. A low-cost method to produce biocompatible and biodegradable filaments can improve the usability of FDM 3D printing for biomedical applications.

OBJECTIVES: The feasibility of producing low-cost filaments suitable for FDM 3D printing via single screw and twin-screw hot melt extrusion was explored.

METHODS: A single-screw extruder and a twin-screw extruder were used to produce biocompatible filaments composed of varying concentrations of polyethylene glycol (PEG) at 10%, 20%, 30% w/w and polylactic acid (PLA) 90%, 80% and 70% w/w, respectively. DSC, TGA and FTIR were employed to investigate the effect of PEG on the PLA filaments.

RESULTS: The presence of PEG lowered the processing temperature of the formulation compositions via melt-extrusion, making it suitable for pharmaceutical applications. The use of PEG can lower the melting point of the PLA polymer to 170°C, hence lowering the printing temperature. PEG can also improve the plasticity of the filaments, as the rupture strain of twin-screw extruded filaments increased up to 10-fold as compared to the commercial filaments. Advanced application of FTIR analysis confirmed the compatibility and miscibility of PEG with PLA.

CONCLUSION: Twin-screw extrusion is more effective in producing a polymeric mixture of filaments as the mixing is more homogenous. The PEG/PLA filament is suitable to be used in 3D printing of medical or pharmaceutical applications such as medical implants, drug delivery systems, or personalised tablets.

The effect of concentration, temperature, and the addition of graphene oxide (GO) nanosheets on the rheological and dielectric behavior of chitosan (CS) solutions, which influences the formation of the blend materials for various applications including 3D printing and packaging, was studied. Among tested acid solutions, the rheological behavior of 1% CS in acetic and lactic acid solutions was found to be similar, whereas the hydrochloric acid solution showed an abnormal drop in the dynamic moduli. Oscillatory rheology confirmed a distinct gel point for the CS solutions at below 10 °C. Both the G' and G″ of the solutions increased with the loading concentrations of GO between 0.5 and 1%, and it marginally dropped at the loading concentration of 2%, which is consistent with AFM observation. The steady-shear flow data fitted the Carreau model. Dielectric property measurement further confirmed that both the dielectric constant, ε' and the loss factor, ε″ for the CS in hydrochloric acid solutions behaved differently from others. Addition of GO significantly improved both ε' and ε″, indicating an improvement in the dielectric properties of CS/GO solutions. The dispersion of GO into the CS matrix was assessed by measuring XRD, FTIR, and microscopy of the film prepared from the solutions. Furthermore, the inclusion of GO into CS solution containing pluronic F127 (F127) base for potential 3D printing application showed positive results in terms of the printing accuracy and shape fidelity of the printed objects (films and scaffolds). The optimized composition with homogeneous particle distribution indicated that up to ∼50 mg/mL GO concentration (w/v of F127 base) was suitable to print both films and scaffolds for potential biomedical applications.

With the growing demand for personalized medicine and medical devices, the impact of on-demand triggerable (e.g., via magnetic fields) drug delivery systems increased significantly in recent years. The three-dimensional (3D) printing technology has already been applied in the development of personalized dosage forms because of its high-precision and accurate manufacturing ability. In this study, a novel magnetically triggerable drug delivery device composed of a magnetic polydimethylsiloxane (PDMS) sponge cylinder and a 3D printed reservoir was designed, fabricated and characterized. This system can realize a switch between "on" and "off" state easily through the application of different magnetic fields and from different directions. Active and repeatable control of the localized drug release could be achieved by the utilization of magnetic fields to this device due to the shrinking extent of the macro-porous magnetic sponge inside. The switching "on" state of drug-releasing could be realized by the magnetic bar contacted with the side part of the device because the times at which 50%, 80% and 90% (w/w) of the drug were dissolved are observed to be 20, 55 and 140 min, respectively. In contrast, the switching "off" state of drug-releasing could be realized by the magnetic bar placed at the bottom of the device as only 10% (w/w) of the drug could be released within 12 h. An anti-cancer substance, 5-fluorouracil (FLU), was used as the model drug to illustrate the drug release behaviour of the device under different strengths of magnetic fields applied. In vitro cell culture studies also demonstrated that the stronger the magnetic field applied, the higher the drug release from the deformed PDMS sponge cylinder and thus more obvious inhibition effects on Trex cell growth. All results confirmed that the device can provide a safe, long-term, triggerable and reutilizable way for localized disease treatment such as cancer.

This research demonstrates the use of fill density as an effective tool for controlling the drug release without changing the formulation composition. The merger of hot-melt extrusion (HME) with fused deposition modeling (FDM)-based 3-dimensional (3-D) printing processes over the last decade has directed pharmaceutical research towards the possibility of printing personalized medication. One key aspect of printing patient-specific dosage forms is controlling the release dynamics based on the patient's needs. The purpose of this research was to understand the impact of fill density and interrelate it with the release of a poorly water-soluble, weakly acidic, active pharmaceutical ingredient (API) from a hydroxypropyl methylcellulose acetate succinate (HPMC-AS) matrix, both mathematically and experimentally. Amorphous solid dispersions (ASDs) of ibuprofen with three grades of AquaSolveTM HPMC-AS (HG, MG, and LG) were developed using an HME process and evaluated using solid-state characterization techniques. Differential scanning calorimetry (DSC), powder X-ray diffraction (pXRD), and polarized light microscopy (PLM) confirmed the amorphous state of the drug in both polymeric filaments and 3D printed tablets. The suitability of the manufactured filaments for FDM processes was investigated using texture analysis (TA) which showed robust mechanical properties of the developed filament compositions. Using FDM, tablets with different fill densities (20-80%) and identical dimensions were printed for each polymer. In vitro pH shift dissolution studies revealed that the fill density has a significant impact (F(11, 24) = 15,271.147, p < 0.0001) and a strong negative correlation (r > -0.99; p < 0.0001) with the release performance, where 20% infill demonstrated the fastest and most complete release, whereas 80% infill depicted a more controlled release. The results obtained from this research can be used to develop a robust formulation strategy to control the drug release from 3D printed dosage forms as a function of fill density.

One of the main applications of bone graft materials is filling the gap after the surgical removal of bone cancer or tumors. Insufficient healing commonly leads to non-union fracture which could lead to cancer resurgence or infection. Emerging 3D printing of on-demand bone graft biomaterials can deliver personalized solutions with minimized risk of relapse and recurrence of cancer after bone removal surgery. This research aims to explore 3D printed calcium phosphate cement (CPC) based scaffolds as novel anti-cancer drug delivery systems to treat bone cancer. For the study, various 3D printed CPC based scaffolds (diameter 5 mm) with interconnected pores were utilized. Various optimized polymeric solutions containing a model anticancer drug 5-fluorouracil (5-FU) was used to homogenously coat the CPC scaffolds. Both hydrophilic Soluplus (SOL) and polyethylene glycol (PEG) and a combination of both were used to develop stable coating solutions. The surface morphology of the coated scaffolds, observed via SEM, revealed deposition of the polymeric solution represented by a semi-smooth surface as opposed to the blank scaffolds that showed a smoother surface. An advanced surface analysis conducted via confocal microscopy showed a homogenous distribution of the drug throughout the coated scaffolds. Solid-state analysis studied by applying differential scanning calorimetry (DSC) and X-ray diffraction (XRD) revealed semi-crystalline nature of the drug whereas mechanical analysis conducted via texture analysis showed no evidence in the change of the mechanical properties of the scaffolds after polymeric solutions were applied. The FTIR analysis revealed no major intermolecular interactions between 5-FU and the polymers used for coatings except for F2 where a potential nominal interaction was evidenced corresponding to higher Soluplus content in the formulation. In vitro dissolution studies showed that almost 100% of the drug released within 2 h for all scaffolds. Moreover, in vitro cell culture using two different cell lines (Hek293T-human kidney immortalized cell line and HeLa-human bone osteosarcoma epithelial cell line) showed significant inhibition of cell growth as a function of decreased numbers of cells after 5 days. It can be claimed that the developed 5-FU coated 3D printed scaffolds can successfully be used as bone graft materials to potentially treat bone cancer or bone neoplasm and for personalized medical solutions in the form of scaffolds for regenerative medicine or tissue engineering applications.

The present study explores the effect of melt binding of Soluplus® on in vitro release profiles of two hydrophilic drugs, metformin hydrochloride, and paracetamol. The melt viscosities of bulk polymer and physical mixtures with different concentrations of selected APIs were analyzed by using a rheometer. The rheological evaluation revealed both the suitable temperature range for melt extrusion process and drug-polymer extrudability. The effect of formulation and processing parameters (e.g. polymer/drug ratio, temperature, screw speed) on extrudability were evaluated in terms of torque and residence time analysis. The extrudates obtained via hot melt extrusion (HME) processing exhibited good flow and compressibility. Differential scanning calorimetry (DSC) and X-ray diffraction studies examined the change in glass transition temperature (Tg) and crystalline pattern of extruded formulations where all extruded formulations seemed to have retained their crystallinity. The thermogravimetric analysis determined the thermal stability (weight loss) as a function of operating temperature whereas scanning electron microscopy (SEM) showed agglomerated microstructure and rough surface with a porous network and void spaces. The tablets obtained after compression of milled extrudates showed excellent hardness with robust tablet characteristics. The in vitro release studies of individual batches performed in various USP recommended dissolution media (for paracetamol) showed the pH-independent release of the hydrophilic drugs from the polymer matrices.

The aim of this study was to develop and evaluate an optimized 3D bioprinting technology in order to fabricate novel scaffolds for the application of endothelial cell repair. Various biocompatible and biodegradable macroporous scaffolds (D = 10 mm) with interconnected pores (D =  500 µm) were fabricated using a commercially available 3D bioprinter (r3bEL mini, SE3D, USA). The resolution of the printing layers was set at  100 µm for all scaffolds. Various compositions of polylactic acid (PLA), polyethylene glycol (PEG) and pluronic F127 (F127) formulations were prepared and optimized to develop semi-solid viscous bioinks. Either dimethyloxalylglycine (DMOG) or erythroprotein (EPO) was used as a model drug and loaded in the viscous biocompatible ink formulations with a final concentration of 30% (w/w). The surface analysis of the bioinks via a spectroscopic analysis revealed a homogenous distribution of the forming materials throughout the surface, whereas SEM imaging of the scaffolds showed a smooth surface with homogenous macro-porous texture and precise pore size. The rheological and mechanical analyses showed optimum rheological and mechanical properties of each scaffold. As the drug, DMOG, is a HIF-1 inducer, its release from the scaffolds into PBS solution was measured indirectly using a bioassay for HIF-1α. This showed that the release of DMOG was sustained over 48 h. The release of DMOG was enough to cause a significant increase in HIF-1α levels in the bioassay, and when incubated with rat aortic endothelial cells (RAECs) for 2 h resulted in transcriptional activation of a HIF-1α target gene (VEGF). The optimum time for the increased expression of VEGF gene was approximately 30 min and was a 3-4-fold increase above baseline. This study provides a proof of concept, that a novel bioprinting platform can be exploited to develop biodegradable composite scaffolds for potential clinical applications in endothelial cell repair in cardiovascular disease (CVD), or in other conditions in which endothelial damage occurs.

The current study investigates the dissolution rate performance of amorphous solid solutions of a poorly water-soluble drug, efavirenz (EFV), in amorphous Soluplus® (SOL) and Kollidon® VA 64 (KVA64) polymeric systems. For the purpose of the study, various formulations with varying drug loadings of 30, 50, and 70% w/w were developed via hot-melt extrusion processing and adopting a Box-Behnken design of experiment (DoE) approach. The polymers were selected based on the Hansen solubility parameter calculation and the prediction of the possible drug-polymer miscibility. In DoE experiments, a Box-Behnken factorial design was conducted to evaluate the effect of independent variables such as Soluplus® ratio (A1), HME screw speed (A2), and processing temperature (A3), and Kollidon®VA64 ratio (B1), screw speed (B2), and processing temperature (B3) on responses such as solubility (X1 and Y1) and dissolution rate (X2 and Y2) for both ASS [EFV:SOL] and BSS [EFV:KVA64] systems. DSC and XRD data confirmed that bulk crystalline EFV transformed to amorphous form during the HME processing. Advanced chemical analyses conducted via 2D COSY NMR, FTIR chemical imaging, AFM analysis, and FTIR showed that EFV was homogenously dispersed in the respective polymer matrices. The maximum solubility and dissolution rate was observed in formulations containing 30% EFV with both SOL and KVA64 alone. This could be attributed to the maximum drug-polymer miscibility in the optimized formulations. The actual and predicted values of both responses were found precise and close to each other.

The current study explores the first case of the implementation of solution calorimetry (SolCal) in order to determine the amorphous content of crystalline benzoyl-methoxy-methylindol-acetic acid (BMA)-a model poorly soluble drug, in the amorphous granules prepared via single-step continuous twin-screw dry granulations (TSG). Amorphous magnesium aluminometasilicate (Neusilin®) (US2) was used as a novel inorganic carrier via a TwinLab 10 mm twin-screw extruder. The BMA/US2 blends were processed at 180 °C and varying drug: carrier ratios of 1:4, 1:2.5 and 1:1 (w/w). Physico-chemical characterisation conducted via SEM, DSC and XRPD showed amorphous state of the drug in all granulated formulations. Reverse optical microscopy revealed a meso-porous structure of US2 in which the drug particles are adsorbed and/or entrapped within the porous network of the carrier. This phenomenon can be the underlying reason for the increase of the amorphous content in the extruded granules. Solution calorimetry (SolCal) study revealed amorphous content of the drug in all formulations quite precisely, whereas the dynamic vapour sorption (DVS) analysis complemented the results from SolCal. Furthermore, an attempt has been made for the first time to interrelate the findings from the SolCal to that of the release of the drug from the amorphous granules. It can be concluded that SolCal can be used as a novel technique to precisely quantify and interrelate the amorphous content to its physico-chemical performances such as drug release from the granulated formulations processed via TSG.

Three-dimensional printing, also known as additive manufacturing, is a fabrication process whereby a 3D object is created layer-by-layer by depositing a feedstock material such as thermoplastic polymer. The 3D printing technology has been widely used for rapid prototyping and its interest as a fabrication method has grown significantly across many disciplines. The most common 3D printing technology is called the Fused Deposition Modelling (FDM) which utilises thermoplastic filaments as a starting material, then extrudes the material in sequential layers above its melting temperature to create a 3D object. These filaments can be fabricated using the Hot-Melt Extrusion (HME) technology. The advantage of using HME to manufacture polymer filaments for FDM printing is that a homogenous solid dispersion of two or more pharmaceutical excipients i.e., polymers can be made and a thermostable drug can even be introduced in the filament composition, which is otherwise impractical with any other techniques. By introducing HME techniques for 3D printing filament development can improve the bioavailability and solubility of drugs as well as sustain the drug release for a prolonged period of time. The latter is of particular interest when medical implants are considered via 3D printing. In recent years, there has been increasing interest in implementing a continuous manufacturing method on pharmaceutical products development and manufacture, in order to ensure high quality and efficacy with less batch-to-batch variations of the pharmaceutical products. The HME and FDM technology can be combined into one integrated continuous processing platform. This article reviews the working principle of Hot Melt Extrusion and Fused Deposition Modelling, and how these two technologies can be combined for the use of advanced pharmaceutical applications.