Overall, I am not sure that covalent linkages are leading to stiffer materials and slowed
curcumin release in your system. Isn’t it is just as easy to say that when PLA is added to
the fiber formulation, the curcumin release slows. This could just be due to increasing
the hydrophobicity of the material overall by adding PLA. The mechanical properties get
stiffer when PLA is added, could be due to the fact that PLA is a stiffer material than
gelatin.
Without some additional references for esterification occurring between PLA and gelatin
at 50 °C, it is hard to imagine it happening without more proof. Certain chemical
reactions need elevated temperatures to occur and esterification reactions between PLA
and gelatin will likely need to exceed 100 °C in order to occur. It is more likely and
simper that no cross linking is occurring and the resulting mechanical/release profiles
are just determined based on the combination of the material properties that you put
into the samples.
“(b) Cur (8.3 wt%):GL (30%): Gelatin (6.0 g) and curcumin (8.3 wt%) were dissolved in
20 mL of TFA”
Authors should use grams without parenthesis and put wt% in parenthesis. This is true
for all samples.
The revised text could be written:
“6.0 g of gelatin (30 wt.%) and X.X g of curcumin (8.3 wt.%) were dissolved…”
Also, once the authors have added the wt% of each chemical, then the naming system
for the sample could reflect the wt.% to make more sense of the figures. Specifically,
“Cur (8.3 wt%):GL:PLA (1:3)” is not particularly helpful, but the authors choose to use
“Cur:GL:PLA-I” instead (even less helpful). The same things can be said about the
naming of the other samples.
Page 9: “randomness properties”.
What are the authors referring to?
Page 11: “enhanced tensile properties were noticed”
What are the authors referring to?
Page 11: tensile discussion
The authors should include pure PLA into the stress/strain curve as it may explain the
trend towards a stiffer material when PLA is added (not covalent bonds forming between
curcumin, poly(lactic acid), and gelatin).
Page 21, Figure 1a.
As drawn the authors believe that the end groups of poly(lactic acid) (a secondary
alcohol and a carboxylic acid) react with gelatin to form an ester and an amide.
Additionally an alcohol from curcumin has formed an ester with gelatin. While the
solution is heated at 50 °C, it is highly unlikely that any of these reactions proceed at
this temperature without a catalyst. Rather, it is more likely that the resulting IR peaks
are just arising from intermolecular interactions rather than covalent linkages.
Page 21, Figure 1b.
Authors are missing an IR of pure gelatin. Without this graphed, the authors cannot
make any conclusions about the appearance of a new peak in the sample, without
showing all of the precursors.
Page 21, Figure 1c.
What does the read arrow mean? Is the figure just a zoom in?
Page 21: “(c) SEM image of Cur:GL:PLA-II aligned fiber scaffolds fabricated at 6,500
rpm in 30 seconds, respectively. Cur:GL:PLA-I and Cur:GL.PLA-II indicate Cur (8.3
wt%):GL:PLA (1:3) and Cur (8.3 wt%):GL:PLA (1:4), respectively. Scale bar = 100 μm
and 1 μm, respectively.”
The authors do not explain what the read arrow pointing to the second SEM image
refers to. Are the images of two different spun fiber samples? If so, why is there an
arrow?
Page 24: “Figure 4. DSC curves of pure curcumin, Cur:GL and Cur:GL:PLA (I and II).
Cur:GL indicates Cur (8.3 wt%):GL (30%); Cur:GL:PLA-I and Cur:GL.PLA-II indicate Cur
(8.3 wt%):GL:PLA (1:3) and Cur (8.3 wt%):GL:PLA (1:4), respectively.”
Graph has pure PLA, but is not described in the caption. Also the caption is overly
complicated, the authors could adopt the wt.% as suggested earlier and avoid redescribing what samples “Cur:GL:PLA-I and Cur:GL.PLA-II” are. The authors should
also add pure gelatin into the DSC as a comparison (and it is used as a control in Figure
5 anyway). Also where is gelatin’s endotherm?