Protein Binding Affinity of Polymeric Nanoparticles as a Direct Indicator of Their Pharmacokinetics

Polymeric nanoparticles (NPs) are an important category of drug delivery systems, and their in vivo fate is closely associated with delivery efficacy. Analysis of the protein corona on the surface of NPs to understand the in vivo fate of different NPs has been shown to be reliable but complicated and time-consuming. In this work, we establish a simple approach for predicting the in vivo fate of polymeric NPs. We prepared a series of poly(ethylene glycol)-block-poly(d,l-lactide) (PEG-b-PLA) NPs with different protein binding behaviors by adjusting their PEG densities, which were determined by analyzing the serum protein adsorption. We further determined the protein binding affinity, denoted as the equilibrium association constant (K_A), to correlate with in vivo fate of NPs. The in vivo fate, including blood clearance and Kupffer cell uptake, was studied, and the maximum concentration (C_max), the area under the plasma concentration-time curve (AUC), and the mean residence time (MRT) were negatively linearly dependent, while Kupffer cell uptake was positively linearly dependent on K_A. Subsequently, we verified the reliability of the approach for in vivo fate prediction using poly(methoxyethyl ethylene phosphate)-block-poly(d,l-lactide) (PEEP-b-PLA) and poly(vinylpyrrolidone)-block-poly(d,l-lactide) (PVP-b-PLA) NPs, and the linear relationship between the K_A value and their PK parameters further suggests that the protein binding affinity of polymeric NPs can be a direct indicator of their pharmacokinetics.

Spherical Nucleic Acids with Tailored and Active Protein Coronae

Spherical nucleic acids (SNAs) are nanomaterials typically consisting of a nanoparticle core and a functional, dense, and highly oriented oligonucleotide shell with unusual biological properties that make them appealing for many applications, including sequence-specific gene silencing, mRNA quantification, and immunostimulation. When placed in biological fluids, SNAs readily interact with serum proteins, leading to the formation of ill-defined protein coronae on the surface, which can influence the targeting capabilities of the conjugate. In this work, SNAs were designed and synthesized with functional proteins, such as antibodies and serum albumin, deliberately adsorbed onto their surfaces. These particles exhibit increased resistance to protease degradation compared with native SNAs but still remain functional, as they can engage in hybridization with complementary oligonucleotides. SNAs with adsorbed targeting antibodies exhibit improved cellular selectivity within mixed cell populations. Similarly, SNAs coated with the dysopsonizing protein serum albumin show reduced macrophage uptake, providing a strategy for tailoring selective SNA delivery. Importantly, the protein coronae remain stable on the SNAs in human serum, exhibiting a less than 45% loss of protein through exchange after 12 h at 37 °C. Taken together, these results show that protein-SNA complexes and the method used to prepare them provide a new avenue for enhancing SNA stability, targeting, and biodistribution.

The Crown and the Scepter: Roles of the Protein Corona in Nanomedicine

Engineering nanomaterials are increasingly considered promising and powerful biomedical tools or devices for imaging, drug delivery, and cancer therapies, but few nanomaterials have been tested in clinical trials. This wide gap between bench discoveries and clinical application is mainly due to the limited understanding of the biological identity of nanomaterials. When they are exposed to the human body, nanoparticles inevitably interact with bodily fluids and thereby adsorb hundreds of biomolecules. A "biomolecular corona" forms on the surface of nanomaterials and confers a new biological identity for NPs, which determines the following biological events: cellular uptake, immune response, biodistribution, clearance, and toxicity. A deep and thorough understanding of the biological effects triggered by the protein corona in vivo will speed up their translation to the clinic. To date, nearly all studies have attempted to characterize the components of protein coronas depending on different physiochemical properties of NPs. Herein, recent advances are reviewed in order to better understand the impact of the biological effects of the nanoparticle-corona on nanomedicine applications. The recent development of the impact of protein corona formation on the pharmacokinetics of nanomedicines is also highlighted. Finally, the challenges and opportunities of nanomedicine toward future clinical applications are discussed.

IgA and IgM protein primarily drive plasma corona-induced adhesion reduction of PLGA nanoparticles in human blood flow

The high abundance of immunoglobulins (Igs) in the plasma protein corona on poly(lactic-co-glycolic) acid (PLGA)-based vascular-targeted carriers (VTCs) has previously been shown to reduce their adhesion to activated endothelial cells (aECs) in human blood flow. However, the relative role of individual Ig classes (e.g., IgG, IgA, and IgM) in causing adhesion reduction remains largely unknown. Here, we characterized the influence of specific Ig classes in prescribing the binding efficiency of PLGA nano-sized VTCs in blood flow. Specifically, we evaluated the flow adhesion to aECs of PLGA VTCs with systematic depletion of various Igs in their corona. Adhesion reduction was largely eliminated for PLGA VTCs when all Igs were removed from the corona. Furthermore, re-addition of IgA or IgM to the Igs-depleted corona reinstated the low adhesion of PLGA VTCs, as evidenced by ∼40-70% reduction relative to particles with an Igs-deficient corona. However, re-addition of a high concentration of IgG to the Igs-depleted corona did not cause significant adhesion reduction. Overall, the presented results reveal that PLGA VTC adhesion reduction in blood flows is primarily driven by high adsorption of IgA and IgM in the particle corona. Pre-coating of albumin on PLGA VTCs mitigated the extent of adhesion reduction in plasma for some donors but was largely ineffective in general. Overall, this work may shed light into effective control of protein corona composition, thereby enhancing VTC functionality in vivo for eventual clinical use.

Effect of anticoagulants on the protein corona-induced reduced drug carrier adhesion efficiency in human blood flow

Plasma proteins rapidly coat the surfaces of particulate drug carriers to form a protein corona upon their injection into the bloodstream. The high presence of immunoglobulins in the corona formed on poly(lactic-co-glycolic acid) (PLGA) vascular-targeted carrier (VTC) surfaces was recently shown to negatively impact their adhesion to activated endothelial cells (aECs) in vitro. Here, we characterized the influence of anticoagulants, or their absence, on the binding efficiency of VTCs of various materials via modulation of their protein corona. Specifically, we evaluated the adhesion of PLGA, poly(lactic acid) (PLA), polycaprolactone (PCL), silica, and polystyrene VTCs to aECs in heparinized, citrated, and non-anticoagulated (serum and whole) blood flows relative to buffer control. Particle adhesion is substantially reduced in non-anticoagulated blood flows regardless of the material type while only moderate to minimal reduction is observed for VTCs in anticoagulant-containing blood flow depending on the anticoagulant and material type. The substantial reduction in VTC adhesion in blood flows was linked to a high presence of immunoglobulin-sized proteins in the VTC corona via SDS-PAGE analysis. Of all the materials evaluated, PLGA was the most sensitive to plasma protein effects while PCL was the most resistant, suggesting particle hydrophobicity is a critical component of the observed negative plasma protein effects. Overall, this work demonstrates that anticoagulant positively alters the effect of plasma proteins in prescribing VTC adhesion to aECs in human blood flow, which has implication in the use of in vitro blood flow assays for functional evaluation of VTCs for in vivo use.

STATEMENT OF SIGNIFICANCE

This study addresses the impact of anticoagulant on altering the extent of the previously observed protein corona-induced adhesion reduction of vascular-targeted drug carriers in human blood flows. Specifically, serum blood flow (no anticoagulant) magnifies the negative effect of the plasma protein corona on drug carrier adhesion relative to citrated or heparinized blood flows. Overall, the results from this work suggest that serum better predicts targeted drug carrier adhesion efficiency in vivo compared to anticoagulant containing plasma. Furthermore, this study offers critical insight into the importance of how the choice of anticoagulant can greatly affect drug delivery-related processes in vitro.

Dendritic polyglycerol anions for the selective targeting of native and inflamed articular cartilage

Dye-conjugated polyanions show high affinities toward native and inflamed cartilage dependent on the anionic moiety and the condition of the tissue.