Design, Fabrication, and Evaluation of Polyglycolic Acid Modules with Canals as Tissue Elements in Cellular-Assembly Technology

Round 1

Reviewer 1 Report

Dear authors, the work entitled “Design, fabrication, and evaluation of polyglycolic acid modules with canals as tissue elements in cellular assembly technology” represent a challenging approach in scaffold design for tissue engineering applications.

The idea is very promising since it should describe three possible cell construct modules. Anyway, different changes should improve the quality of the work.

Firstly, the authors declare that the modules (cylindrical, Raschig-ring, and transverse pore)were obtained via a modified SLS technology, but they should describe what this technological modification consists of, at least with a bibliographical reference.

As for biological assessment, was the choice of the Hep G2 cell line made in light of a possible application? If so, which one?

The authors should also better clarify the role of the Collagen Gel Culturing Kit, since it seems that the collagen kit should be adopted as a surface treatment and, in this context, Hep G2 cells should be in contact with collagen instead of the PGA fibres. As already shown in very nice works of Russo L. et al. (RSC advences, 2013; Carbohydrate research, 2015), covalent bonding of bioactive molecules at a material surface represents a valid strategy for material functionalization, since it may permit site-directed immobilization, avoiding stochastic biomolecule exposition on the surface. If the collagen should be viewed as the surface coating of the PGA fibres module, did the authors evaluate the stability of the coating, primarily at the interface?

On page 5 of 11, line 150, the authors should clarify if the experiment were performed or not in culture conditions (37°C, 5% CO₂).

Finally, it would be nice if the authors reported the results n terms of cell proliferation over time, with and without collagen gel culturing kit. In this context, figure 3c should be properly modified, giving it greater scientific prominence.

Confocal images should be improved in terms of quality and also cell morphology should be highlighted (avoiding background noise).

Author Response

Thank you so much for kindly helping review our manuscript and offering us many great constructive suggestions which we have closely followed to revise our paper.  

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

I would like to appreciate the authors involved in this research for adopting Additive manufacturing process for tissue engineering. However, there are lot of research have been accomplished in the same pattern, with different materials and structures. I would strongly recommend the authors to improve the experimental investigation based on selective laser sintering process parameters to attain an exact structure. Further, improvement is required on in-vitro study to prove those samples are biocompatability. 

The author requires amendments as mentioned below

1. The importance of selective laser sintering technology and PGA material is not described in detail in the introduction part. 
2. The properties of PGA material like density is not mentioned in the materials and methods. 
3. 2.2 characterization of PGA module section it is mentioned that the porosity of the module was determined. But the result based on porosity is very minimum  (line 200). Moreover, the cell attachment is mainly based on porosity level in the structure, which improves the cell growth attachment. The porosity level of all the samples are required either in terms of graphical or SEM image. 
4. Line 121, it is stated that "The microstructure of sintered PGA modules were evaluated by microscopy", but no where in the paper the SEM images are shown and discussed. If you have SEM images based on SLS processed samples list them and interpret their results with respect to porosity. Also, the SLS based SEM image will be useful to reveal the PGA powder particles melted and shapes. 
5. In figure 2.b, 3.b, 4.a and 4.b the scale of the image is not visible. mention the scale of the image in dark line and letters. without scale in the image it is invalid. 
6. SLS based parameters are not clearly mentioned. For example. laser scan speed plays an important role during fabrication process. To optimize the laser parameters, the scan speed is mandatory. list out the scan speed used in the table 1
7. Apparently, the laser parameters are trial and error method. Just wondering what type of laser is used and in the materials and methods the author mentioned the modified SLS. SLS specifications are required in the materials and methods columns.
8. why not the laser power is not used more than 7.29W? that may be give better results comparatively. Justifications requried.
9. section 3.2 evaluation of biodegradability. there is no valid tabular or graphical results shown. Justification required. 
10. SEM image of the cell growth is not shown any where in the paper. Justification required.

Author Response

Thank you so much for kindly helping review our manuscript and offering us many great constructive suggestions which we have closely followed to revise our paper.  

Please see the attachment.

Author Response File: Author Response.pdf