Saturation Transfer Difference NMR Spectroscopy for the Elucidation of Supramolecular Albumin–Polymer Interactions

Abstract

Albumin has consistently demonstrated its potential for enhancing the delivery of drugs and polymer–drug conjugates, binding via supramolecular forces within its multiple binding sites. Herein, we introduce saturation transfer difference (STD-NMR) as a method to identify the interactions between a polymer library and bovine serum albumin (BSA). With STD-NMR, the binding ability of polymers can be quickly screened by focusing on their individual structural features, making this technique more suitable for high throughput screening in comparison to traditional fluorescence studies.

Insights into the Gelation Mechanism of Metal-Coordinated Hydrogels by Paramagnetic NMR Spectroscopy and Molecular Dynamics

“…STD NMR is a well-established technique for investigating the dynamic binding of small molecules with a low-to-medium binding affinity to proteins . In soft matter, STD NMR has been used to study both gelator and solvent molecules, , with recent application for elucidation of supramolecular protein–polymer interactions …”

“…56 In soft matter, STD NMR has been used to study both gelator 8 and solvent molecules, 10,57 with recent application for elucidation of supramolecular protein−polymer interactions. 58 To monitor the interaction of CMC 1% w/v dispersions with residually protonated water (HDO, present in solution following the exchange of one of the deuterium atoms of D 2 O by a proton), we recorded a series of STD build-up curves with saturation time ranging from 1 to 20 s and from 0.1 to 8 s for CMC dispersions in the absence and in the presence of Fe 3+ ions, respectively (Figures 2a and S2). For the samples in the absence of metal ions, the long saturation time required to reach the STD signal plateau for HDO is dictated by the long T1 relaxation time characteristic of large molecules that slowly tumble in solution.…”

Development of an Albumin–Polymer Bioconjugate via Covalent Conjugation and Supramolecular Interactions

“…Directional shifts in the fluorescence maxima also divulge the change in polarity of the microenvironment of the Trp residues. The results obtained for SC 18 PMbPH are reiterated from a previous work 40 and shown in Figure 4a alongside Table S1 . In the quenching plot (Figure 4ai), a gradual decrease in fluorescence intensity was observed with increasing concentrations of the polymer added to BSA.…”

“…STD-NMR can provide information on whether other functional groups along the polymer aid or compete with the fatty acid endgroup for the albumin binding site by identifying multiple points of interaction between polymer and protein. 40 Combining conjugation of polymers via supramolecular forces with the covalent attachment of polymer opens the door to more complex architectures that provide new opportunities for combinatorial therapy and enhanced drug loading capacity. This possibility was recently explored by Liang and coworkers, who attached three different anticancer agents to a single molecule of the protein using a combination of different strategies.…”

“…The synthesis of the acyl block copolymer (SC 18 PMbPH) was previously reported. 40 To obtain the diacyl block copolymer, a RAFT agent bearing the endgroup (C 18 CPADB) was required. A large excess of stearic acid was imperative to obtain a high yield of the product with both fatty acid groups attached.…”