Chem 8157

Professor Kokkoli’s talk is very interesting. Her goal is to design biomaterials which are targeted to the diseased cells. She use nanoparticle as carrier and functionalize the interface with polymer and peptides. Polymer is very hydrophobic which is used to keep protein in blood away from the nanoparticle. So the nanoparticle will not aggregate. The critical part of this work is to design the peptide which can bind the disease cell. The reason she use peptide is that peptide is much more promising here than protein because peptide has more active binding site, less worry about denaturation and can be control easily.
The result turns out promising. The peptide she uses, PR_b gives a much better result of specificity on disease cell than traditional RGD material. To further increase the specificity, she is planning to add aptamer to the nanoparitcle which can locate the cell more accurate. I wonder that could she replace peptide with aptamer since aptamer may have a better specificity?

I agree with Jing in regards to the clever nature and importance of Prof. Kokkoli's work.

In regards to the bioanalytical techniques that are needed to carry out her work, what techniques are needed? Which ones were mentioned?

Prof. Efie Kokkoli from Department of Chemical Engineering and Material Science in our University gave a presentation on Biomimetic Peptide-Amphiphiles for Receptor-Targeted Therapeutics yesterday. The main goal of this research is targeted drug delivery, including two steps: 1 the drugs are selectivity targeted to only the diseased cells; 2 the drugs are delivered inside the cells to the site of their pharmacological activity. The talk was focus on the first step. Based on literatures, there are acceptors of choice that can be recognized and specifically bond by a certain protein. Their design is the peptide, rather than the protein, which has two binding site to the acceptors of choice. It turns out that PR-b, the designed peptide, functionalized liposomes works very well and is promising for the targeted drug delivery. I’m not sure what the acceptor is. Is it specific for one type of cells? If it is, then we need to design different peptide for different cells we interested in. If it is not, how can we satisfy the selectivity targeting?

Regarding analytical methods...
Her group use NMR to probe the structure of the Peptide-amphiphiles and use some image methods to study how well that the nanoparticles functionalize with peptides they designed are selevtively target to the interested cells, for instance, TEM, AFM, Confocal Imaging.

Her group use NMR to probe the structure of the Peptide-amphiphiles and use some image methods to study how well that the nanoparticles functionalize with peptides they designed are selevtively target to the interested cells, for instance, TEM, AFM, Confocal Imaging.

Prof. Efie Kokkoli from Department of Chemical Engineering and Material Science in our University gave a presentation on Biomimetic Peptide-Amphiphiles for Receptor-Targeted Therapeutics yesterday. The main goal of this research is targeted drug delivery, including two steps: 1 the drugs are selectivity targeted to only the diseased cells; 2 the drugs are delivered inside the cells to the site of their pharmacological activity. The talk was focus on the first step. Based on literatures, there are acceptors of choice that can be recognized and specifically bond by a certain protein. Their design is the peptide, rather than the protein, which has two binding site to the acceptors of choice. It turns out that PR-b, the designed peptide, functionalized liposomes works very well and is promising for the targeted drug delivery. I’m not sure what the acceptor is. Is it specific for one type of cells? If it is, then we need to design different peptide for different cells we interested in. If it is not, how can we satisfy the selectivity targeting?

Professor Efie Kokkoli presented an interesting and promising seminar of designing functionalized nanoparticles in targeted therapeutics. Their group employs a lot of techniques and instruments to fulfill the interesting project by several parts. These include synthesis and characterization of nanoparticles (SEM); design, functionalization and selection of proper peptides or aptamers that have a high binding property and specificity to diseased cells. For the peptide part, they made the peptides and did sequence tests to see if they have the proper sequence required to do next substrate study, otherwise they go back to the sequence design. For the aptamer part, they can purchase the DNA library which is commercially available and carry out the SELEX (Systematic evolution of ligands by exponential enrichment) by CE or microfluidic devices [She did not explain what system they use for SELEX; they may be still be using column chromatography] The adhesion and specificity property studies involve the use fluorescence bioimaging techniques.

I have several concerns and questions about Professor Efie Kokkoli’s presentation. First, when she talked about the cell adhesion ability and specificity of the designed peptide, should the specificity go ahead of adhesion ability and why did she talk about adhesion first? Because the peptide should first recognize the receptor on the cell and then adhere to it, it’s a little difficult to understand the sequence in her presentation. Is that because they don’t know what kind of receptors the diseased cells secrete, so firstly test the adhesion, then study the specificity. Also, I am curious about in the future, how the drugs carried by the nanoparticles can be imported into the diseased cells and how the nanoparticles affect human body?

In response to Meng's question, some recent published works used the amphiphile polymers to form micelle-structured nanoparticles and simultaneously encapsulate drugs(always hydrophobic)into the hydrophobic core. Because these polymers are biodegradable, the drugs can be slowly released (the relased rate is based on which polymer you use) inside cancer cells and result in great cytotoxicity.

Reply to Li’s question, the receptor is α5β1 integrins. Prof. Kokkoli utilized the GRGDSP (primary binding site for α5β1 ) and PHSRN (secondary binding site for α5β1) sequences in the PR_b to target the abnormal cells that express α5β1 integrins. She mentioned the PR_b can target breast, colon, rectal and prostate cancer cells. If you are interested in her work, you can get more information from her publication (Kokkoli, E., Mardilovich, A., Wedekind, A., Rexeisen, E.L., Garg, A., and Craig, J.A. "Self-Assembly and Applications of Biomimetic and Bioactive Peptide-Amphiphiles", Soft Matter, 2006, 2 (12) 1015-1024).

For targeting selectivity, I think it is hard to find a molecule, peptide or protein to specifically target one cell type. There are a lot of different receptors on the cell membrane. However, one can find some abnormal cells that overexpress certain receptors and design specific targeting agents to bind these receptors. I think the targeting efficiency and selectivity are mainly based on the amount of receptors in different cells.

For Jing's question, I guess the peptide cannot be replaced with the DNA aptamers. The reason is the receptors on the membrane are proteins. Thus ligands have advantage over DNA aptamer to bind to the receptors. Many extracellular matrix proteins are able to regulate the cell adhesion, celll growth and receptor-ligand interactions.The diseased cells can be targeted according to the interactions between peptide and receptors. Since the active site of the receptors may include several types of peptides, it's better to have higher specificity. However I cannot figure out why adding aptamer to the nanoparticle can increase the specificity.

From the reference of Professor Kokkoli, the interactions between ligands and their receptors are measured directly without any labels. However, traditionally, the interactions are measured indirectly using secondary molecule or event(such as a fluorescent probe). I think this label-free measurement is a new technology to detect the interaction between ligands and receptors.

I find Dr. Kokkoli's research involving atomic force microscopy interesting. For such a prominent technique, it doesn't seem like it is in use as much as other techniques. Is this due to cost of the instrument or lack of important uses?