In vitro Quality Assessments of Perfluorocarbon Nanoemulsions for Near-infrared Fluorescence Imaging of Inflammation in Preclinical Models

Tracking macrophages by non-invasive molecular imaging can provide useful insights into the immunobiology of inflammatory disorders in preclinical disease models. Perfluorocarbon nanoemulsions (PFC-NEs) have been well documented in their ability to be taken up by macrophages through phagocytosis and serve as 19F magnetic resonance imaging (MRI) tracers of inflammation in vivo and ex vivo. Incorporation of near-infrared fluorescent (NIRF) dyes in PFC-NEs can help monitor the spatiotemporal distribution of macrophages in vivo during inflammatory processes, using NIRF imaging as a complementary methodology to MRI. Here, we discuss in depth how both colloidal and fluorescence stabilities of the PFC-NEs are essential for successful and reliable macrophage tracking in vivo and for their detection in excised tissues ex vivo by NIRF imaging. Furthermore, PFC-NE quality assures NIRF imaging reproducibility and reliability across preclinical studies, providing insights into inflammation progression and therapeutic response. Previous studies focused on assessments of colloidal property changes in response to stress and during storage as a means of quality control. We recently focused on the joint evaluation of both colloidal and fluorescence properties and their relationship to NIRF imaging outcomes. In this protocol, we summarize the key assessments of the fluorescent dye-labeled nanoemulsions, which include long-term particle size distribution monitoring as the measure of colloidal stability and monitoring of the fluorescence signal. Due to its simplicity and reproducibility, our protocols are easy to adopt for researchers to assess the quality of PFC-NEs for in vivo NIRF imaging applications.

Biomaterials for Protein Delivery: Opportunities and Challenges to Clinical Translation

The development of biomaterials for protein delivery is an emerging field that spans materials science, bioengineering, and medicine. In this review, we highlight the immense potential of protein-delivering biomaterials as therapeutic options and discuss the multifaceted challenges inherent to the field. We address current advancements and approaches in protein delivery that leverage stimuli-responsive materials, harness advanced fabrication techniques like 3D printing, and integrate nanotechnologies for greater targeting and improved stability, efficacy, and tolerability profiles. We also discuss the demand for highly complex delivery systems to maintain structural integrity and functionality of the protein payload. Finally, we discuss barriers to clinical translation, such as biocompatibility, immunogenicity, achieving reliable controlled release, efficient and targeted delivery, stability issues, scalability of production, and navigating the regulatory landscape for such materials. Overall, this review summarizes insights from a survey of the current literature and sheds light on the interplay between innovation and the practical implementation of biomaterials for protein delivery.

Theranostic nanoemulsions suppress macrophage-mediated acute inflammation in rats

In inflammatory diseases or following an injury, dysregulated inflammation is a common driver of pain and tissue damage. Macrophages are immune cells that contribute to the initiation, maintenance, and resolution of inflammation due to their phenotypic plasticity in response to signals from inflammatory microenvironments. Macrophages infiltrate and polarize toward a pro-inflammatory phenotype (M1-like), thereby increasing the severity of inflammation. Therefore, we aimed to suppress the pro-inflammatory activity of M1-like macrophages and decrease their infiltration at the site of inflammatory insult to resolve tissue inflammation. To achieve this, we developed a theranostic curcumin-loaded nanoemulsion platform that delivers a low dose of curcumin, a known anti-inflammatory phytochemical, to macrophages and allows in vivo tracking of macrophages by near-infrared fluorescence (NIRF) imaging technique. In vitro, we showed that curcumin-loaded nanoemulsion suppressed polarization of macrophages towards M1-like phenotype, consequently decreasing the release of pro-inflammatory cytokines and mediators like IL-6, IL-[Formula: see text] TNF-[Formula: see text], and nitric oxide (NO). Furthermore, curcumin-loaded nanoemulsion increased the level of IL-10, an anti-inflammatory cytokine, and protected macrophages against ferroptosis compared to drug-free nanoemulsion. In a rodent model of Complete Freund's adjuvant (CFA)-induced inflammation, we demonstrated that infiltrating macrophages sequestered curcumin-loaded nanoemulsion droplets and acted as cellular drug depots at the site of inflammation. This consequently decreased macrophage infiltration at the CFA-induced inflammation site in both sexes compared to drug-free nanoemulsion, as demonstrated by NIRF imaging, H&E staining, and immunofluorescence. Taken together, our results indicated that the anti-inflammatory efficacy of curcumin was significantly improved when directly delivered to pro-inflammatory macrophages via theranostic nanoemulsion. This work opens an avenue for exploring theranostic nanoemulsions as a platform for delivering natural anti-inflammatory products for immune modulation.