Complexation With Human Serum Albumin Facilitates Sustained Release of Morin From Polylactic-Co-Glycolic Acid Nanoparticles

Understanding the interaction of proteins with nanoparticles has become an important area of research in biomedical and pharmaceutical fields. Morin is a flavonol which shows several properties including antioxidant, anticancer, and anti-inflammatory activities. However, the major limitation is its poor aqueous solubility. Therefore, morin-loaded polylactic-<i>co</i>-glycolic acid (PLGA) nanoparticles (MPNPs) were prepared to improve the solubility of morin. The resulting MPNPs were characterized by spectroscopic and microscopic techniques. The nanoparticles were spherical with an average size of 237 ± 17 nm. UV–visible, fluorescence, and circular dichroism (CD) spectroscopy were employed to study the interaction of the MPNPs with human serum albumin (HSA). Our study revealed that a static fluorescence quenching mechanism was involved in the interaction between HSA and MPNPs. Hydrophobic interactions also play an important role in stabilizing the HSA-MPNP complex. CD results suggest that there is an alteration of the secondary structure of HSA in the presence of MPNPs. MPNPs exhibit antioxidant properties which are supported by the DPPH assay. We have further checked the effect of HSA on the antioxidant property of morin and MPNPs. HSA binding with MPNPs was also found to influence the <i>in vitro</i> release property of morin from MPNPs wherein a delayed release response is observed

Glycation of human serum albumin alters its binding efficacy towards the dietary polyphenols: a comparative approach

<p>Diabetes is a major problem in the world. The proteins became modified during glycation after reacting with the reducing sugars (e.g. D-glucose) via non-enzymatic pathways. The glycated analogue of human serum albumin (HSA) has been characterized with the help of multi-spectroscopic methods. It has been observed that six glucose molecules can bind covalently to HSA under experimental condition. The binding affinity of the modified HSA towards the dietary polyphenols has been estimated using UV–vis and fluorescence spectroscopic techniques. The binding constant values of the ligands were found to decrease after the modification of HSA.</p> <p>The binding affinities (<i>K</i>_<i>b</i>) of the polyphenols decreased towards human serum albumin after its structural modification with D-glucose. Highest percentage decrease in the binding is observed for quercetin among all the polyphenols.</p

Amino Acid-Based Polymer-Coated Silver Nanoparticles as Insulin Fibril Inhibitors

To explore the impact of polymer-coated silver nanoparticles (PC-AgNPs) on the extent of the insulin aggregation process, herein, we have synthesized three copolymers comprising poly(ethylene glycol) methyl ether methacrylate (PEGMA) and tert-butoxycarbonyl (Boc)-protected amino acid (alanine, leucine, and phenylalanine) containing methacrylate monomers, via reversible addition-fragmentation chain transfer (RAFT) polymerization. After deprotection of the Boc groups, the as-prepared water-soluble copolymers were coated on silver nanoparticles (Ag NPs), and the role of these NPs on insulin aggregation pathways was examined by multifarious spectroscopic and microscopic techniques. The extent of the inhibitory effect against the insulin fibrillation process was found to be related to the surface properties of the NPs, with the highest inhibitory effect detected for phenylalanine-based polymer-coated Ag NPs (PPhe-AgNPs). Using circular dichroism (CD) spectroscopy and Nile red (NR) fluorescence spectroscopy, we investigated the conformational changes and examined the role of hydrophobic interaction in inhibiting the aggregation properties of insulin upon treatment with PC-AgNPs. Furthermore, PC-AgNPs were also able to disintegrate the matured insulin fibrils and efficiently decreased the fibril-induced cytotoxicity, as confirmed by transmission electron microscopy (TEM) and the hemolysis study, respectively. Together, our findings established the novel amino acid-based PC-AgNPs as potent nanomaterials with 77–96% insulin fibril inhibition and marked disaggregation of matured insulin fibrils

Amyloid β‑Peptide Segment Conjugated Side-Chain Proline-Based Polymers as Potent Inhibitors in Lysozyme Amyloidosis

Developing effective amyloidosis inhibitors poses a significant challenge due to the dynamic nature of the protein structures, the complex interplay of interfaces in protein–protein interactions, and the irreversible nature of amyloid assembly. The interactions of amyloidogenic polypeptides with other peptides play a pivotal role in modulating amyloidosis and fibril formation. This study presents a novel approach for designing and synthesizing amyloid interaction surfaces using segments derived from the amyloid-promoting sequence of amyloid β-peptide [VF(Aβ(18–19)/FF(Aβ(19–20)/LVF(Aβ(17–19)/LVFF(Aβ(17–20)], where VF, FF, LVF and LVFF stands for valine phenylalanine dipeptide, phenylalanine phenylalanine dipeptide, leucine valine phenylalanine tripeptide and leucine valine phenylalanine phenylalanine tetrapeptide, respectively. These segments are conjugated with side-chain proline-based methacrylate polymers serving as potent lysozyme amyloidosis inhibitors and demonstrating reduced cytotoxicity of amyloid aggregations. Di-, tri-, and tetra-peptide conjugated chain transfer agents (CTAs) were synthesized and used for the reversible addition–fragmentation chain transfer polymerization of tert-butoxycarbonyl (Boc)-proline methacryloyloxyethyl ester (Boc-Pro-HEMA). Deprotection of Boc-groups from the side-chain proline pendants resulted in water-soluble polymers with defined peptide chain ends as peptide–polymer bioconjugates. Among them, the LVFF-conjugated polymer acted as a potent inhibitor with significantly suppressed lysozyme amyloidosis, a finding supported by comprehensive spectroscopic, microscopic, and computational analyses. These results unveil the synergistic effect between the segment-derived amyloid β-peptide and side-chain proline-based polymers, offering new prospects for targeting lysozyme amyloidosis

Modulating Insulin Aggregation with Charge Variable Cholic Acid-Derived Polymers

To understand the effect of cholic acid (CA)-based charge variable polymeric architectures on modulating the insulin aggregation process, herein, we have designed side-chain cholate-containing charge variable polymers. Three different types of copolymers from 2-(methacryloyloxy)­ethyl cholate with anionic or cationic or neutral units have been synthesized by reversible addition-fragmentation chain transfer polymerization. The effects of these copolymers on the insulin fibrillation process was studied by multiple biophysical approaches including different types of spectroscopic and microscopic analyses. Interestingly, the CA-based cationic polymer (CP-10) was observed to inhibit the insulin fibrillation process in a dose-dependent manner and to act as an effective anti-amyloidogenic agent. Corresponding anionic (AP-10) and neutral (NP-10) copolymers with cholate pendants remained insignificant in controlling the aggregation process. Tyrosine fluorescence assays and Nile red fluorescence measurements demonstrate the role of hydrophobic interaction to explain the inhibitory potencies of CP-10. Furthermore, circular dichroism spectroscopic measurements were carried out to explore the secondary structural changes of insulin fibrils in the presence of cationic polymers with and without cholate moieties. Isothermal titration calorimetry measurements revealed the involvement of electrostatic polar interaction between the CA-based cationic polymer and insulin at different stages of fibrillation. Overall, this work demonstrates the efficacy of the CA-based cationic polymer in controlling the insulin aggregation process and provides a novel dimension to the studies on protein aggregation

Nanoencapsulation as a Promising Platform for the Delivery of the Morin-Cu(II) Complex: Antibacterial and Anticancer Potential

Nanoencapsulation has emerged as a promising approach for the effective delivery of poorly aqueous soluble compounds. The current study focuses on the preparation of human serum albumin (HSA)-based nanoparticles (NPs) and poly lactic-co-glycolic acid (PLGA)-based nanoparticles for effective delivery of the morin-Cu­(II) complex. The NPs were analyzed based on different parameters such as particle size, surface charge, morphology, encapsulation efficiency, and in vitro release properties. The average particle sizes were found to be 214 ± 6 nm for Mor-Cu-HSA-NPs and 185 ± 7.5 nm for Mor-Cu-PLGA-NPs. The release of the morin-Cu­(II) complex from both the NPs (Mor-Cu-HSA-NPs and Mor-Cu-PLGA-NPs) followed a biphasic behavior, which comprises an early burst release followed by a sustained and controlled release. The resulting NPs also exhibit free radical scavenging activity confirmed by a standard antioxidant assay. The antibacterial activities of the NPs were investigated using a disk diffusion technique, and it was observed that both the NPs showed better antibacterial activity than morin and the morin-Cu­(II) complex. The anticancer activities of the prepared NPs were examined on MDA-MB-468 breast cancer cell lines using a cytotoxicity assay, and the mode of cell death was visualized using fluorescence microscopy. Our results revealed that NPs kill the cancer cells with greater efficiency than free morin and the morin-Cu­(II) complex. Thus, both HSA-based NPs and PLGA-based NPs can act as promising delivery systems for the morin-Cu­(II) complex and can be utilized for further biomedical applications