2-((E)-2-((E)-4-Chloro-5-(2-((E)-5-methoxy-3,3-dimethyl-1-(3-phenylpropyl)indolin-2-ylidene) ethylidene)-1,1-dimethyl-1,2,5,6-tetrahydropyridin-1-ium-3-yl)vinyl)-5-methoxy-3,3-dimethyl-1-(3-phenylpropyl)-3H-indol-1-ium

Round 1

Reviewer 1 Report

 

1. Regarding the statement:  The physicochemical parameters for ERB-60 were calculated using ChemAxon.  This should be experimentally derived as well.
2.  What is the proposed use of this new fluor.  It should be compared to references in that field.  For example, is this going to be used fto conjugate to antibodies in flow cytometry 
3. The NMR data showing the purity of the compound should be presented.  

Author Response

Responds to Reviewer 1 Comments:

1. Regarding the statement:  The physicochemical parameters for ERB-60 were calculated using ChemAxon.  This should be experimentally derived as well.

 

The use of chemAxon prior to the synthesis of molecular probe serves as a guiding principle to help us understand the physicochemical parameters of the synthesized dyes. Our experience with the use of this software have given us much information about fluorophores design and their optical and biodistribution properties. We therefore, use chemAxon to predict their physicochemical properties. Its outside the scope of this manuscript to experimentally determine properties like dipole moment, polarizability, molecular surface areas and the like. All these properties throughout literature are determined theoretical with the use of various algorithm or models to help predict possible molecular features. 

 

1.  What is the proposed use of this new fluor.  It should be compared to references in that field.  For example, is this going to be used to conjugate to antibodies in flow cytometry 

 

The overall goal in the designing and synthesizing of this newly fluorophore, ERB-60 is to use it as a contrast agent. However, as preliminary studies, we focused on the physicochemical, optical properties, and the computational behavior to understand how these features might affect the biodistribution as well as its imaging capabilities. Some of the greatest challenge in fluorescence imaging includes probes with improved molecular brightness and photostability. We therefore determined these properties in comparison to the FDA-approved contrast agents (ICG) and commercially available fluorophore (IR-786 iodide). As seen from our results, our newly fluorophore, ERB-60 tends to be brighter than ICG and more photostable than the IR-786 iodide. For full study and end goal, this compound will be modified with carboxylic moiety and conjugated to small targeting ligand to image tumors.

1. The NMR data showing the purity of the compound should be presented.  

NMR is already provided in the supplementary information document.

Reviewer 2 Report

The communication itself is very interesting and the synthetic route is quite engaging. this reviewer believe that more emphasis in characterization should be done. For example, mass spectrometry data should be provided, advanced NMR technique ( pulse and 2D) will give a conclusive data and elemental analysis should be considered. If  a good quality of crystal is suitable, X-Ray crystal diffraction, should be pursued. 

Author Response

Responds to Reviewer 2 Comments:

The communication itself is very interesting and the synthetic route is quite engaging. this reviewer believes that more emphasis in characterization should be done. For example, mass spectrometry data should be provided, advanced NMR technique (pulse and 2D) will give a conclusive data and elemental analysis should be considered. If a good quality of crystal is suitable, X-Ray crystal diffraction, should be pursued.

Thank you for your recommendation. Please note that we have provided the mass spectrum of ERB-60 and we have included such information in the characterization section of the compound as well as in the supplementary data. However, be aware that, there is no need for 2D or pulse NMR technique since this molecule is a very small molecule, which ¹H and ¹³C NMR only are enough to elucidate the final structure of the fluorophore.  From the NMR data provided in the supplementary information, one can easily determine the structure of the synthesized compound. In addition, the mass spectrum provided also adds to the identification of the new compound. With respect to X-Ray crystallographic, the goal of this manuscript does not require us to determine the geometry of this fluorophore in the solid state. Moreover, our institution does not have the required instrument for such analysis. Knowing the structure of this compound in their solid form does not add any meaningful information to the primary goal of this manuscript. Also, obtaining a good crystal from cyanine dyes is quite challenging. 

Round 2

Reviewer 1 Report

One sentence should be given as to the reason for developing the probes.  This will help the readers.  

If you want to say that the values were only theoretically derived, explicitly say this such that the authors are not looking for experimental data.  

I see the NMR data now.  Thank you

Reviewer 2 Report

Thanks for the explanation