Elucidating the Molecular Structure of Hydrophobically Modified Polyethylenimine Nanoparticles and Its Potential Implications for DNA Binding

Abstract

The structural properties of the polyethylenimine (PEI) polymer are generally tuned and selectively modified to reinforce its potential in a broad spectrum of applied domains of medicine, healthcare, material design, sensing, and electronic optimization. The selective modification of the polymer brings about changes in its interfacial characteristics and behavior. The current work involves the synthesis of naphthalimide conjugated polyethylenimine organic nanoparticles (NPEI-ONPs). The interfacial molecular structure of NPEI-ONPs is explored in an aqueous medium at pH 7.4 using surface tensiometry and sum-frequency generation vibrational spectroscopy (SFG-VS). The hydrophobic functionalization rendered a concentration-dependent surface coverage of NPEI-ONPs, where the SFG-VS analysis exhibited the molecular rearrangement of its hydrophobic groups at the interface. The interaction of NPEI-ONPs with double-stranded DNA (dsDNA) is carried out to observe the relevance of the synthesized nanocomposites in the biomedical domain. The bulk-specific studies (i.e., thermal denaturation, viscometry, zeta (ζ) potential, and ATR-FTIR) reveal the condensation of dsDNA in the presence of NPEI-ONPs, making its structure more compact. The interface-sensitive SFG-VS showcased the impact of the dsDNA and NPEI-ONP interaction on the interfacial molecular behavior of NPEI-ONPs at the air–aqueous interface. Our results exhibit the potential of such hydrophobically functionalized ONPs as promising candidates for developing biomedical sealants, substrate coatings, and other biomedical domains.

Interfacial molecular structure of phosphazene-based polymer electrolyte at the air-aqueous interface using sum frequency generation vibrational spectroscopy

“…It is reflected in the decrease in the surface tension measurement of the aqueous solution as a function of MEEP concentration (figure S3, right y-axis). The observation ascribes towards the disruption and displacement of surface water molecule and it is slowly covered by the MEEP polymer molecules due to adsorption [52,53]. The variation in the surface tension values hint towards the occupancy of organic polymer molecules but fails to provide an indepth, molecular-level comprehension of the adsorbed groups present at the interfacial region.…”

“…We observed significant variations in the overall SFG intensity in the broad OH stretching region after introducing MEEP polymer compared to pristine water. The variations in the intensity profile in the broad OH-stretch region (3000-3600 cm −1 ) can be attributed to the ordering and relative hydrogen bonding strength of the water molecules at the air-aqueous interface [28,52,61]. Based on that, we have determined the overall oscillator strength of the OHstretch region by integrating the area against the MEEP concentrations, as displayed in figure 4(b).…”

“…Surface tension measurements on aqueous samples were systematically conducted using the Wilhelmy plate method on a Biolin Scientific KSV NIMA Langmuir-Blodget setup [51][52][53]. We employed a vertically suspended Pt plate as a probe medium.…”

“…The SFG signal intensity as a function of IR frequency provides the complete vibrational signature of the molecules present at the interfacial region. In our SFG setup, as shown in figure 2, a pulse mode-locked Nd:YAG laser (EKSPLA, PL2231-50) at 1064 nm with a pulse width of 30 ps and a repetition rate of 50 Hz has been used [51][52][53][54]. The visible beam of 532 nm is generated from the second harmonic generation unit.…”

Alkylated Sulfonium Modification of Low Molecular Weight Polyethylenimine to Form Lipopolymers as Gene Vectors

“…Hydrophobic modification can facilitate DNA compacting via additional hydrophobic interaction and increase the lipophilicity of polymer/DNA particles which could benefit the cell membrane interaction and cellular uptake. − Through modification, the charge density of PEI is reduced, and the cytotoxicity is changed. The essential features of the hydrophobic modification on PEI could be achieved by changing the length of the hydrophobic alkyl − or aryl fragments, by varying the modification degree, and by switching the linker between the charged backbone and the hydrophobic groups …”