In situ crosslinking of electrospun gelatin for improved fiber morphology retention and tunable degradation

Abstract

Electrospinning is a popular technique to fabricate tissue engineering scaffolds due to the exceptional tunability of the fiber morphology, which can be used to control the scaffold mechanical properties, degradation rate, and cell behavior. Recent work has focused on electrospinning natural polymers such as gelatin to improve the regeneration potential of these grafts. Gelatin scaffolds must be crosslinked to avoid rapid dissolution upon implantation with current crosslinking strategies requiring additional post-processing steps. Despite the strong dependence of scaffold properties on fiber morphology, there has been minimal emphasis on retaining the original fiber morphology of electrospun gelatin scaffolds after implantation. This work describes a method for in situ crosslinking of gelatin to produce electrospun fibers with improved fiber morphology retention after implantation. A double barrel syringe with an attached mixing head and a diisocyanate crosslinker were utilized to generate electrospun scaffolds that crosslink during the electrospinning process. These in situ crosslinked fiber meshes retained morphology after 1 week incubation in water at 37 1C; whereas, uncrosslinked meshes lost the fibrous morphology within 24 hours. Degree of crosslinking was quantified and relationships between the crosslinker ratio and enzymatic degradation rate were evaluated. The degradation rate decreased with increased crosslinker ratio, resulting in a highly tunable system. Additionally, tensile testing under simulated physiological conditions indicated that increased crosslinker ratios resulted in increases in initial modulus and tensile strength. Overall, this in situ crosslinking technique provides a method to crosslink gelatin during electrospinning and can be used to tune the degradation rate of resulting scaffolds while enabling improved fiber morphology retention after implantation.

Cell infiltrative hydrogel fibrous scaffolds for accelerated wound healing

“…Cut round samples of 2 cm diameter were incubated at 37°C with 1 mL 0.02 units collagenase mL −1 of DPBS for a month [36]. At pre-determined time points, the DPBS was removed and the samples were washed twice with distilled water, lyophilized, and weighed.…”

In Pursuit of Functional Electrospun Materials for Clinical Applications in Humans

“…Materials developed with these methods will have a spatial dependence on material properties orthogonal to the collecting substrate. Although a gradient of cross-linking density from the top to bottom layer of the fiber mat may be preferred for a desired degradation profile, a consistent cross-linking density can be achieved by using a double syringe pump with mixing head [94]. Another example of cross-linking during the electrospinning process is using photochemical crosslinking and positioning a UV lamp between the needle tip and collector so that the polymer cross-links while in flight to the collector [95].…”

Winner of the society for biomaterials student award in the Ph.D. category for the annual meeting of the society for biomaterials, april 11–14, 2018, Atlanta, GA: Development of a bimodal, in situ crosslinking method to achieve multifactor release from electrospun gelatin

“…8 Solutions were changed every 3 days. Electrospun specimens (40 3 10 3 0.2 mm 3 ) were placed into capped tubes containing 2 mL of PBS or 0.2 units/mL collagenase solution and incubated at 378C with shaking.…”

“…In particular, the delivery of growth factors and morphogens through scaffolds assists in recapitulating the spatial and temporal microenvironments presented by extracellular matrix in order to guide cellular attachment, migration, proliferation, and differentiation. [7][8][9][10] The relatively mild processing conditions of these gelatin matrices allows for their application in growth factor delivery without bioactivity loss. [3][4][5][6] Gelatin can be fabricated into a wide range of geometries, including microspheres, hydrogels, and electrospun meshes.…”

“…For example, Rujitanaroj et al demonstrated that glutaraldehyde vapor crosslinking could be utilized to control release of silver nanoparticles for antibacterial applications. 8 By crosslinking in situ, these systems enable direct control over fiber crosslinking and, in combination with the coelectrospinning method, enables the production of a single mesh containing fibers of different crosslinking chemistries and densities. 25,26 Del Gaudio et al reported that crosslinking gelatin meshes with 0.1 w/ v% versus 0.5 w/v% genipin solution reduced the burst release of VEGF from 80 to 50% in the first 24 h. 27 Although much of the research to date has focused on the delivery of single bioactive factors, the ability to deliver multiple factors with distinct kinetics has become a key area of current research.…”