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1. Predicting protein function and orientation on a gold nanoparticle surface using a residue-based affinity scale

   https://doi.org/10.1038/s41467-022-34749-w  

   Xu, Joanna Xiuzhu ; Alom, Md. Siddik ; Yadav, Rahul ; Fitzkee, Nicholas C. ( November 2022 , Nature Communications)

   The orientation adopted by proteins on nanoparticle surfaces determines the nanoparticle’s bioactivity and its interactions with living systems. Here, we present a residue-based affinity scale for predicting protein orientation on citrate-gold nanoparticles (AuNPs). Competitive binding between protein variants accounts for thermodynamic and kinetic aspects of adsorption in this scale. For hydrophobic residues, the steric considerations dominate, whereas electrostatic interactions are critical for hydrophilic residues. The scale rationalizes the well-defined binding orientation of the small GB3 protein, and it subsequently predicts the orientation and active site accessibility of two enzymes on AuNPs. Additionally, our approach accounts for the AuNP-bound activity of five out of six additional enzymes from the literature. The model developed here enables high-throughput predictions of protein behavior on nanoparticles, and it enhances our understanding of protein orientation in the biomolecular corona, which should greatly enhance the performance and safety of nanomedicines used in vivo.
2. Microalgae Peptide-Stabilized Gold Nanoparticles as a Versatile Material for Biomedical Applications

   https://doi.org/10.3390/life12060831  

   Torres-Díaz, Marielys ; Abreu-Takemura, Caren ; Díaz-Vázquez, Liz M. ( June 2022 , Life)

   Microalgae peptides have many medical and industrial applications due to their functional properties. However, the rapid degradation of peptides not naturally present in biological samples represents a challenge. A strategy to increase microalgae peptide stability in biological samples is to use carriers to protect the active peptide and regulate its release. This study explores the use of gold nanoparticles (AuNPs) as carriers of the Chlorella microalgae peptide (VECYGPNRPQF). The potential of these peptide biomolecules as stabilizing agents to improve the colloidal stability of AuNPs in physiological environments is also discussed. Spectroscopic (UV-VIS, DLS) and Microscopic (TEM) analyses confirmed that the employed modification method produced spherical AuNPs by an average 15 nm diameter. Successful peptide capping of AuNPs was confirmed with TEM images and FTIR spectroscopy. The stability of the microalgae peptide increased when immobilized into the AuNPs surface, as confirmed by the observed thermal shifts in DSC and high zeta-potential values in the colloidal solution. By optimizing the synthesis of AuNPs and tracking the conferred chemical properties as AuNPs were modified with the peptide via various alternative methods, the synthesis of an effective peptide-based coating system for AuNPs and drug carriers was achieved. The microalgae peptide AuNPs showed lower ecotoxicitymore »and better viability than the regular AuNPs.« less
3. Understanding the Adsorption of Peptides and Proteins onto PEGylated Gold Nanoparticles

   https://doi.org/10.3390/molecules26195788  

   Perera, Yasiru Randika ; Xu, Joanna Xiuzhu ; Amarasekara, Dhanush L. ; Hughes, Alex C. ; Abbood, Ibraheem ; Fitzkee, Nicholas C. ( October 2021 , Molecules)

   Polyethylene glycol (PEG) surface conjugations are widely employed to render passivating properties to nanoparticles in biological applications. The benefits of surface passivation by PEG are reduced protein adsorption, diminished non-specific interactions, and improvement in pharmacokinetics. However, the limitations of PEG passivation remain an active area of research, and recent examples from the literature demonstrate how PEG passivation can fail. Here, we study the adsorption amount of biomolecules to PEGylated gold nanoparticles (AuNPs), focusing on how different protein properties influence binding. The AuNPs are PEGylated with three different sizes of conjugated PEG chains, and we examine interactions with proteins of different sizes, charges, and surface cysteine content. The experiments are carried out in vitro at physiologically relevant timescales to obtain the adsorption amounts and rates of each biomolecule on AuNP-PEGs of varying compositions. Our findings are relevant in understanding how protein size and the surface cysteine content affect binding, and our work reveals that cysteine residues can dramatically increase adsorption rates on PEGylated AuNPs. Moreover, shorter chain PEG molecules passivate the AuNP surface more effectively against all protein types.
4. Colloidal Gold Nanoparticles Induce Apoptosis in MCF-7 Human Breast Adenocarcinoma Cells

   Adewumi, H ; Carter, G ; Bhuiyan, S. ( December 2019 , Nano research applications)

   Nanoparticles have been widely used as remedies for disorders for a long time. They are 10-9 m specks of substances that can be found both naturally and synthesized in the laboratory with metal and nonmetal materials. In this study, gold nanoparticles (AuNPs) were synthesized using the citrate reduction method, and the 35 nm size of the nanoparticles was determined using a UV-Vis Spectrophotometer at 525 nm wavelength. The synthesized nanoparticles were further studied on MCF-7 breast cancer cells to understand how various genes are expressed in the induction of apoptosis in signal transduction pathways. The results obtained from the anticancer activity of the gold nanoparticles showed approximately 90% inhibition of cell growth after 72 hours of treatment. Western blot analysis demonstrated the downregulation of p44/42 MAPK (ERK1/2) protein due to gold nanoparticle treatment. Moreover, reverse transcription-polymerase chain reaction (RT-PCR) analysis of apoptotic genes revealed the upregulation of the p53 tumor suppressor gene, Bax, and caspase-9. The results assembled from this study further indicates that p44/42 MAPK, p53, caspase 9 and Bax play a major role in the mechanism of apoptosis in the MCF-7 breast cancer cells.
5. Modeling broadband cloaking using 3D nano-assembled plasmonic meta-structures

   https://doi.org/10.1364/OE.395840  

   Khan, Md. Imran ; Ghosh, Sayantani ; Baxter, Ryan ; Kim, Arnold D. ( July 2020 , Optics Express)

   The concept of “cloaking” an object is a very attractive one, especially in the visible (VIS) and near infra-red (NIR) regions of the electromagnetic spectrum, as that would reduce the visibility of an object to the eye. One possible route to achieving this goal is by leveraging the plasmonic property of metallic nanoparticles (NPs). We model and simulate light in the VIS and NIR scattered by a core of a homogeneous medium, covered by plasmonic cloak that is a spherical shell composed of gold nanoparticles (AuNPs). To consider realistic, scalable, and robust plasmonic cloaks that are comparable, or larger, in size to the wavelength, we introduce a multiscale simulation platform. This model uses the multiple scattering theory of Foldy and Lax to model interactions of light with AuNPs combined with the method of fundamental solutions to model interactions with the core. Numerical results of our simulations for the scattering cross-sections of core-shell composite indicate significant scattering suppression of up to 50% over a substantial portion of the desired spectral range (400 - 600 nm) for cores as large as 900 nm in diameter by a suitable combination of AuNP sizes and filling fractions of AuNPs in the shell.