(B-48) Application of dual-labeled nanoparticle system to evaluate nanoparticle fate in healthy and osteoarthritic joints

Introduction::
To combat osteoarthritis (OA), intra-articular drug delivery systems such as nanoparticles (NPs) are used to improve drug bioavailability, retention, and localization. Imaging modalities are required to track and evaluate how NPs behave in vivo, in terms of their retention, clearance, and biodistribution – NP fate. In vivo fluorescence system (IVIS) is the current standard to evaluate NP fate and is utilized by loading or conjugating a near-infrared fluorophores to NPs. This approach has certain limitations such as signal attenuation that can impede long-term quantitative assessment of NPs fate. To address these limitations, we had previously demonstrated the feasibility of an emerging imaging modality- magnetic particle imaging (MPI) to track NP fate in vivo in healthy joint. This was achieved by encapsulating superparamagnetic iron oxide (SPIONs) into NPs. MPI images superparamagnetic iron oxide nanoparticles (SPIONs), producing a three-dimensional quantitative image of SPIONs, circumventing fluorescence imaging limitations. The objective of this study focuses engineering a dual-labeled NPs with magnetic and fluorescence capabilities, and comparing NP fate between MPI and IVIS in healthy and OA-disease models




Materials and Methods:: Dual-labeled poly (lactic-co-glycolic acid) (PLGA) NPs were synthesized by modifying our previously established single-emulsion evaporation process. Briefly, the organic phase consists of PLGA dissolved in 1ml of 5mg/ml SPIONs in chloroform. The aqueous phase consists of polyvinyl alcohol and polyallylamine dissolved in phosphate buffered saline. The organic and aqueous phases were combined via probe sonication and stirred overnight. The next day fluorophore dye was then added to the NPs in suspension at a ratio of 10mg NP: 10ug dye and stirred for 2-3 hours in the dark. Following this, NPs were washed through a series of ultracentrifugation spins. Dual-labeled NPs were characterized in terms of their hydrodynamic size, charge, iron mass, fluorescence, and MPI signal intensity. Dual-labeled NPs were intra-articularly injected into healthy and two different OA-disease models 24hrs after OA initiation. For the disease models, OA was initiated surgically via anterior cruciate ligament transection (ACL-T) surgery or non-surgically through a non-invasive knee injury (NIKI) device. We then evaluated NP fate within 3 days or 14 days after OA initiation.

Results, Conclusions, and Discussions::
Dual-labeled NPs have physical properties that matched the desired size at and charge ranges at 160nm and 20mV based on our previous NPs system. We were to successfully engineer dual label- NPs with magnetic and fluorescence capacities. For the in vivo study, MPI and IVIS tracking demonstrated comparable properties in terms of NPs joint at day 3 retention between health, ACLT, and NIKI animal groups. In terms of joint biodistribution, there was no significant difference in NPs distribution patterns between animal groups based on IVIS tracking at day 3. For MPI tracking there was a significant difference between signal intensity of NPs distributed in femoral cartilage between NIKI and ACLT models. At day 14, NPs joint retention varied between IVIS and MPI, where the fluorescence signal was diminished at day 14, but magnetic signal was still present. Based on NP joint biodistribution, there was no signal difference between either animal group for both MPI and IVIS tracking. To advance targeted drug delivery for the joint, tools are needed to quantify the pharmacokinetics and biodistribution of drug carriers in the body in both preclinical and clinical studies. Based on our data, we were able to engineer dual-labeled NPs with imaging capabilities for MPI and IVIS, while maintaining ideal properties for targeting joint cartilage. Based on MPI tracking, we can track NP fate consistently on a longer timeline compared to IVIS tracking. Additionally, based on our preliminary data, NP fate did not vary difference between a surgical and non-surgical model of OA- specifically between NIKI and ACLT. This project is the first to apply dual-labeled NPs with MPI and IVIS tracking capabilities to assess if NP fate varies between OA animal models. This also represents the first steps towards leveraging MPI to understand how NPs delivery system and potential therapeutics are biodistributed, localized, and retained in the joint as OA progresses.




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