Skip to main content
2024 BMES Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.

Biomaterials

Biomaterials - Poster Session C

Poster M7 - Tuning High-Density Lipoprotein-Like Nanoparticle Composition Drives Function

Thursday, October 24, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  High-density lipoproteins (HDL) are natural nanoparticles that circulate in the blood stream and function to transport, uptake, and deliver cholesterol and other lipids (e.g., cholesteryl ester and triglycerides) to target cells. The HDL particles have potentially beneficial athero- and immuno-protective functions, which has resulted in attempts to synthesize and deliver reconstituted HDLs (rHDL) as therapies. One challenge, though, is that natural HDLs are a heterogeneous mixture of particles with different sizes, shapes, and compositions. This makes assigning specific structure-function relationships difficult. To better understand HDL structure-function and develop synthetic HDLs with enhanced therapeutic properties our group has developed a “template” approach for synthesizing spherical HDL-like nanoparticles (HDL NP) using inorganic (e.g., gold nanoparticle) or organic core (oc) materials. The core materials provide a size-restrictive substrate for the self-assembly of the HDL-associated protein, apolipoprotein A-I (apoA-I), and phospholipids to form HDL NPs with tunable physicochemical properties, which enables focused structure-function studies and comparisons to native HDLs. In this work we studied novel oc-HDL NP core composition and surface chemistry and the impact on specific HDL functions.

Materials and

Methods:  Two pairs of oc scaffolds were used to synthesize oc-HDL NPs, including: Pair 1) tetrastearyl pentaerythritol (PE-S4) and tetraoleyl pentaerythritol (PE-O4) and Pair 2) poly(ethylene glycol) sorbitol hexastearate (Sorb(PEG)1-S6) and poly(ethylene glycol) sorbitol hexaoleate (Sorb(PEG)1-O6). These cores vary in their number of carbon chains (N = 4 or 6) emanating from a common center and the degree of fatty acid tail saturation (N = 0 or N = 1). Furthermore, we explored the impact of phospholipid composition on oc-HDL NP synthesis and function by synthesizing PE-O4 nanoparticles with three different phospholipids [1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl phosphatidylcholine (DOPC), and 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS)]. The phospholipids differ regarding the degree of alkyl tail saturation (N = 0 or N = 1) and the charge of the headgroup (zwitterionic versus negative) at physiologic pH. A total of six oc-HDL NP constructs were synthesized using an emulsion-solvent evaporation method whereby the oc was combined with apo-A1 and the desired phospholipid: DPPC PE-S4, DPPC PE-O4, DPPC Sorb(PEG)1-S6, DPPC Sorb(PEG)1-O6, DOPC PE-O4, DOPS PE-O4. The oc-HDL NPs were characterized regarding size, charge, and shape using dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. The secondary structure of the apoA-I protein in oc-HDL NP was measured by circular dichroism (CD). The oc-HDL NP function was assessed by measuring in vitro cholesterol efflux capacity, anti-inflammatory function, and cholesteryl ester loading.

Results, Conclusions, and Discussions: DLS and zeta potential measurements revealed a relatively monodisperse population of 10 – 15 nm diameter and negatively charged oc-HDL NPs for all constructs. TEM showed roughly spherical morphology with measured sizes consistent with DLS. The α-helical content of apoA-I of the DPPC PE-S4 and DPPC PE-O4 most closely resembled native HDL2, while particles synthesized with sorbitol cores and unsaturated phospholipids (DOPC, DOPS) demonstrated increased percent α-helicity. The oc-HDL NPs synthesized with sorbitol cores and DOPS demonstrated greater cholesterol efflux capacity (one-way ANOVA, p < 0.05). Assays to measure the anti-inflammatory function of the oc-HDL NPs revealed DOPS PE-O4 possessed the greatest suppression of LPS-induced NF-κB and JNK signaling. As targeting SR-B1 has been shown to mediate anti-inflammatory functions of HDL, enhanced SR-B1 engagement due to the more negative zeta potential of this construct may underlie these findings. Regarding cholesteryl ester loading, DOPS PE-O4 demonstrated the highest loading, which may have implications for drug loading applications. In summary, our oc-HDL NP platform allowed us to tune oc-HDL NP surface and core composition to better understand structure-function relationships of spherical HDLs. Additionally, the DOPS PE-O4 oc-HDL NP has demonstrable functional benefits over the others, which make it a promising candidate for further in vitro and in vivo studies.

Acknowledgements (Optional):  Research reported in this abstract was supported by the Chemical Countermeasures Research Program (CCRP) executed by the National Institute of Allergy and Infectious Diseases (NIAID), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and the National Institutes of Health Office of the Director (NIH OD) (U54AR079795).