Resolving the Electrospinnability Zones and Diameter Prediction for the Electrospinning of the Gelatin/Water/Acetic Acid System

Abstract

The development of suitable biomimetic scaffolds is a fundamental requirement of tissue engineering. Although electrospinning has emerged as an effective method for producing such scaffolds of nanometer-sized fibers, the influence of solution characteristics on the morphology of the resulting nanofibers depends on each polymer solution system. In this study, gelatin nanofibers and microfibers were prepared via electrospinning using mixtures of water and acetic acid at different ratios as solvents. The viscosities of gelatin solutions before electrospinning were analyzed and two different behaviors were found as a function of the solvent composition, taking into account classic models of polymer science. A power law relationship between viscosity and gelatin concentration was found for each solvent system, and an empirical model including the influence of acetic acid was obtained for aqueous systems. Moreover, a ternary diagram considering gelatin, water, and acetic acid mass fractions was constructed as a tool to establish the electrospinnability domains in terms of fiber occurrence and morphology. Also, the isodiametric curves were defined in the fibers region. Finally, in order to correlate the diameter of electrospun nanofibers and the electrospinnability zones, the Berry number was used. However, as its only allows the range of electrospinnability to be established for a fixed solvent composition, a new dimensionless parameter (Bemod) was suggested to take into account all the acetic acid aqueous solutions as a single solvent.

Electrospinning of gelatin fibers using solutions with low acetic acid concentration: Effect of solvent composition on both diameter of electrospun fibers and cytotoxicity

“…On the contrary, other combinations were not suitable for electrospinning as they produced either very thick fibers [high acetic acid concentration and high gelatin concentration; Figure (i,m,q,r)] or did not produce fibers at all [low acetic acid concentration and low gelatin concentration; Figure (c,d,h)]. In the first case, the viscosity of the solution is very high due to the high amount of gelatin and the acetic acid is only able to partially solvate it, just allowing the electrospinning of very thick fibers or microfibers . In the second case, the solutions did not reach the necessary viscosity and polymer chain entanglement to be electrospun.…”

“…The samples prepared with a fixed gelatin concentration were analyzed by FTIR to determine the effect of acetic acid concentration on the chemical structure of the dissolved gelatin and of the electrospun fibers. Taking into account that a higher concentration of gelatin results in a higher effect of the acetic acid on the solution properties, it was decided to use the highest gelatin concentration (400 mg/mL) to maximize and improve the characterization of the structural changes in solution state. However, for the characterization of electrospun gelatin mats, a concentration of 300 mg/mL was chosen because of the better electrospinnability of the dope solutions.…”

“…However, because of their highly corrosive nature, these solvents may affect the original protein structure besides providing a potential cytotoxicity to the obtained scaffolds, as the presence of small amounts of residual solvent embedded on the electrospun fibers is almost unavoidable . This fact, combined with the high cost of these solvents, promoted the search of alternative systems to electrospin gelatin such as (i) the use of gelatin aqueous solution at high temperatures, (ii) blending gelatin with another biopolymer [e.g., sodium alginate, poly(ethylene oxide), poly(ε‐caprolactone), and polylactic acid], (iii) using solvent mixtures (acetic acid and ethyl acetate), and (iv) using carboxylic acids (formic acid or acetic acid).…”

Preparation of electrospun nanofibers from solutions of different gelatin types using a benign solvent mixture composed of water/PBS/ethanol

“…All those factors determine some important parameters such as the exact amino acid composition, the molecular weight distribution and the gel strength of each gelatin which are the key parameters controlling the viscosity of gelatin solutions. Because viscosity is one of the major parameters ruling electrospinnability, the aforementioned parameters are also decisive in the nanofiber production by this technique …”

Spinnability, Morphology and Mechanical Properties of Gelatins With Different Bloom Index

“…Researchers have electrospun gelatin by evaluating the type of solvent used (Choktaweesap et al, 2007;Song et al, 2008;Songchotikunpan et al, 2008;Zha et al, 2012;Erencia et al, 2014), the experimental parameters (Huang et al, 2004;Ki et al, 2005;okutan et al, 2014) and the type of gelatin hydrolysis, acid (type A) or basic (type B) (Ratanavaraporn et al, 2010). However, considering the variety of different gelatin molecular structures, few studies evaluate these properties.…”