Impact of critical process parameters and critical material attributes on the critical quality attributes of liposomal formulations prepared using continuous processing.

Liposomes were one of the earliest drug delivery vehicles used for anti-cancer therapeutics and similarly, lipid-based nanoparticles have been used for abundance of applications as gene therapies. The methods to produce these particles have remained relatively unchanged until the recent emergence of continuous manufacturing. Continuous processing enables accelerated development of nanoparticle formulations while providing a scalable manufacturing solution. For this work a continuous processing platform for the production of lipid and polymeric-based nanoparticle formulations has been developed at the University of Connecticut. This research focuses on the formation of liposomes encompassing multiple design of experiments (DoEs) to identify functional relationships between critical process parameters (CPPs), critical material attributes (CMAs), and critical quality attributes (CQAs) for liposomal formulations produced using this continuous processing platform. Liposomes of various sizes and of low polydispersity index (PDI) were produced with different material attributes under various processing conditions. In general, lower mole percentages of cholesterol produced larger particles whereas the mole percent of phosphatidylglycerol did not seem to have a s impact on the size of the liposomes that were produced. The results showed that similarly sized liposomes could be produced with different processing conditions allowing for the flexibility to operate in regions most suitable for formulation components that may be sensitive to certain processing conditions. For example, if the target size of a formulation is 100 nm but the active pharmaceutical ingredient is sensitive to temperature, then the formulation can be manufactured at high (55 °C) or low (30 °C) depending on its characteristics. Additionally, the relationships between CMAs and CPPs were different from conventional liposomal manufacturing methods, allowing for more flexibility when using a continuous processing system. Models that can effectively predict the hydrodynamic diameter of monodispersed liposomes produced using continuous processing were developed. The models developed from the DoEs in this study may be useful for accelerated development of new lipid formulations as well as facilitate the translation from traditional manufacturing methods to continuous manufacturing for products already on the market.

Strategies for extended lifetime of implantable intraperitoneal insulin catheters.

Implantable insulin infusion systems using the intra-peritoneal route have dramatically changed the management of diabetes paving the way toward the realization of the potential "holy grail" of a fully implantable artificial pancreas. However, the wear duration of delivery catheters is compromised by the foreign body-mediated immune response. Both occlusion material present at the distal catheter tip end and fibrotic encapsulation surrounding the catheters influence the controlled and precise delivery of insulin, which eventually leads to the need for surgical intervention. The novel part of the current work is the investigation of the roles of implant physical properties (catheter size and tip configuration), as well as local inflammation control (through utilization of an anti-inflammatory agent) on the host fibrotic response using a previously developed animal model. The cellular and molecular response, the medication delivery efficacy as well as the ability to flush the catheters were examined and further compared among the different mitigation strategies. Reduction in catheter size as well as tuning the tip configuration from a cone shape to a round shape showed delayed host recognition and delayed propagation of the fibrotic response. However, the round shaped tips had an increased occurrence of lumen occlusion as a result of flow change. It became apparent that changing the physical properties of the catheters was not a long-term solution to catheter obstructions caused by the foreign body reaction. In comparison, control of the local inflammatory response through the use of an anti-inflammatory agent demonstrated a promising strategy for maintenance of catheter functionality without any type of obstructions. These finding will have a large impact toward the development of long-term use catheters for continuous intraperitoneal insulin infusion.

Root cause determination of intraperitoneal catheter obstructions: Insulin amyloid aggregates vs foreign body reaction.

Continuous intraperitoneal insulin infusion, from an implanted insulin pump connected to a catheter that delivers insulin directly to the peritoneal cavity has many clinical advantages for patients with Type 1 diabetes. However, the ongoing incidence of catheter obstructions remains a barrier to the widespread use of this therapy. To date, the root cause of these obstructions remains unknown. Here, a two-year clinical investigation was conducted, along with the development of an animal model to enable a mechanistic investigation into this issue. This novel animal model was able to mimic the catheter obstructions that occur in patients and, fortuitously, at an accelerated rate. This model allowed for independent assessment of each potential cause associated with catheter obstructions to help identify the root cause. Both macroscopic and microscopic analysis were conducted with regards to the onset and progression of catheter obstructions, along with monitoring of insulin delivery. Interestingly, although insulin aggregation occurs in insulin pumps and insulin aggregates were found in some catheter obstructions, insulin is unlikely to be the root cause, since obstructions also occurred in the control groups where only diluent (no insulin) was administered to the animals. Inflammatory cells, different phenotypes of fibroblasts, as well as collagen were observed in all obstructed catheters explanted from the patients and the animals. The presence of these cells and collagen is indicative of a typical foreign body reaction. In addition, the dynamic change in the fibroblasts with respect to morphology, phenotype, and spatial distribution suggests that tissue irritation-mediated epithelial to mesenchymal transition plays a role in catheter obstructions.

Artificial neural networks in tandem with molecular descriptors as predictive tools for continuous liposome manufacturing.

The current study utilized an artificial neural network (ANN) to generate computational models to achieve process optimization for a previously developed continuous liposome manufacturing system. The liposome formation was based on a continuous manufacturing system with a co-axial turbulent jet in a co-flow technology. The ethanol phase with lipids and aqueous phase resulted in liposomes of homogeneous sizes. The input features of the ANN included critical material attributes (CMAs) (e.g., hydrocarbon tail length, cholesterol percent, and buffer type) and critical process parameters (CPPs) (e.g., solvent temperature and flow rate), while the ANN outputs included critical quality attributes (CQAs) of liposomes (i.e., particle size and polydispersity index (PDI)). Two common ANN architectures, multiple-input-multiple-output (MIMO) models and multiple-input-single-output (MISO) models, were evaluated in this study, where the MISO outperformed MIMO with improved accuracy. Molecular descriptors, obtained from PaDEL-Descriptor software, were used to capture the physicochemical properties of the lipids and used in training of the ANN. The combination of CMAs, CPPs, and molecular descriptors as inputs to the MISO ANN model reduced the training and testing mean relative error. Additionally, a graphic user interface (GUI) was successfully developed to assist the end-user in performing interactive simulated risk analysis and visualizing model predictions.