Novel biodegradable polyurethanes reinforced with green nanofibers for applications in tissue engineering. Synthesis and characterization

Abstract

A new class of polyurethane (PU) biocomposites reinforced with green biocellulose nanofibers (BC) were designed and synthesized. These newly introduced non-cytotoxic and biodegradable composites were synthesized with different ratios of hard to soft segments of the linear, aliphatic hexamethylene diisocyanate (HDI) and polycaprolactone diol (PCL), respectively. The porosity was introduced in the polyurethane matrix using a combination of salt leaching and thermally induced phase separation (TIPS). BC contents were in the range of 0-15 % of the final PU by weight. FTIR spectra showed complete conversion of HDI through the disappearance of the isocyanate and imine characteristic bands (at 2260 cm À1 and 1635 cm À1 , respectively) and appearance of carbonyl group band in PU (at 1730 cm À1 ). The hard to soft segment (i.e., HDI:PCL) ratios in the final PU polymer were quantified from 1 H Nuclear Magnetic Resonance (NMR) spectra by comparing the proton peaks arising for CH 2 CO at 2.25 ppm or OCH 2 at 3.9 ppm to CH 2 N at 2.9 ppm. Results showed that the ratios in the final product were consistent with the amounts added initially during the synthesis. Scanning electron microscope (SEM) images showed that porosity (57-75 %) were formed (pore size in the range of 125-355 mm), with an increase in pore content with the decrease in HDI:PCL content.

Comment on ‘Novel biodegradable polyurethanes reinforced with green nanofibers for applications in tissue engineering. Synthesis and characterization’

“…I read this recent article with interest, specifically looking for the process of nanofiber handling and processing, which is key in determining whether to assign the terminology ‘green.’ However, this information is missing from the article. An investigation of biocellulose nanofibers studies cited in the article reveals the fact that those (References in Nakhoda and Dahman) are the corresponding author's own publications. None of these cited articles explain why the nanofibers are termed as ‘green.’…”

“…The best methodology for identification of product and process greenness is to apply the ‘12 Principles of Green Chemistry.’ Tools such as the iSUSTAIN™ Green Chemistry Index are beneficial in such studies. However, such studies were neither referred to nor conducted in the article in question . The biocellulose nanofiber preparation method is mentioned briefly in the article, yet it mentions the use of sulfuric acid and sodium hydroxide.…”

“…However, this information is missing from the article. An investigation of biocellulose nanofibers studies cited in the article reveals the fact that those (References [6][7][8][9][10][11][12]14] in Nakhoda and Dahman [1] ) are the corresponding author's own publications. None of these cited articles explain why the nanofibers are termed as 'green.…”

Response to “Comment on ‘Novel Biodegradable Polyurethanes Reinforced with Green Nanofibers for Applications in Tissue Engineering. Synthesis and Characterization’ ” by Swapnil Fegade

“…In a recent letter to the editor, the only concern that the author expressed was the “greenness” of the bacterial cellulose nanofibers (BCNF) as described in the article “Novel biodegradable polyurethane reinforced with green nanofibers for applications in tissue engineering. Synthesis and characterization.” According to this letter, using the term “green” was blind classification as long as the authors of the manuscript did not justify it by using tools such as the iSUSTAIN Green Chemistry Index. The letter stated that utilization of renewable feedstock is just one out of 12 principles for green chemistry.…”

“…Synthesis and characterization." [1] According to this letter, using the term "green" was blind classification as long as the authors of the manuscript did not justify it by using tools such as the iSUSTAIN Green Chemistry Index. The letter stated that utilization of renewable feedstock is just one out of 12 principles for green chemistry.…”