Engineering of a smart drug-loaded ink for personalized wound patches

Chronic wounds (CWs) represent a major healthcare problem significantly affecting patient's quality of life. Despite the wide availability of commercial wound dressings, they are often ineffective in CW treatment due to the lack of patient personalization both in terms of in situ drug administration timing and shape. In this regard, this work aimed at overcoming such limiting issues by engineering a multifunctional ink with promising features for the fabrication of patient specific patches. More in detail, an amphiphilic poly(ether urethane) (PEU) (CHP407, Mn= 31kDa) was first synthesized by reacting Poloxamer 407, 1,6-diisocyanatohexane and 1,4-cyclohexanedimethanol. Then, CHP407 chains were functionalized with -COOH groups (P-CHP407) exploiting a green approach (i.e., plasma treatment with acrylic acid vapors) to provide the polymer with responsiveness to alkaline fluids. The success of the synthesis and the absence of plasma-induced degradation phenomena were proved by infrared (IR) spectroscopy, while exposed functional groups were quantified by Toluidine Blue O assay (4.7x1018±8.1x1017 -COOH groups/gpolymer). P-CHP407 hydrogels were loaded with Lactoferrin (LF) and studied as smart delivery carriers. First, the preservation of hydrogel thermo-responsiveness upon LF encapsulation was rheologically assessed, showing no remarkable differences in the sol-to-gel transition compared to the control. Then, released LF was quantified through the colorimetric bicinchoninic acid (BCA) assay, evidencing system capability to effectively tune payload release via a pH-controlled mechanism up to 7d. For instance, released LF amounts were quantified to be 5.6%±2.2%, 9.2%±0.98%, 11.3%±1% and 16.3%±1.7% after 24h of incubation against buffers at pH 5, 7, 9 and 11, respectively. Furthermore, ELISA tests performed on the same samples confirmed the obtained pH-controlled release profiles and proved the preservation of LF chemical integrity. Moreover, P-CHP407 hydrogels turned out to be cytocompatible according to the ISO 10993:5 regulation and able to support NIH-3T3 murine fibroblast proliferation as assessed through the 2D in vitro scratch test. Lastly, P-CHP407 hydrogels turned out to be easily printable under mild conditions. In view of hydrogel processing in the form of a patient-personalized wound dressing, another PEU (DHP407) differing for the chain extender (i.e., N-Boc diethanolamine) was also synthesized and functionalized with photo-sensitive moieties aiming at developing a smart ink able to permanently keep the shape upon extrusion and Vis light irradiation. To this purpose, DHP407 was first subjected to an acidic treatment to expose -NH groups (1.2x1019±2.2x1018 units/gpolymer as quantified through Orange II sodium salt colorimetric assay), later exploited to graft acrylate groups (PA-DHP407) through a water-based chemistry. IR spectroscopy proved the successful PEU synthesis, while acrylate moieties were quantified through Proton Nuclear Magnetic Resonance spectroscopy (5.8x1019 acrylates/gpolymer). Lastly, preliminary photorheological tests demonstrated the successful photocrosslinking through storage modulus increase upon system exposure to Vis light (60s, 80k Lux). Based on these results, the designed hydrogel showed promising features as smart drug-loaded ink for the fabrication of wound patches. PA-DHP407/P-CHP407 blend will be optimized in the future to couple thermo-, alkaline pH- and Vis light-responsiveness into a new potential constituent of patient personalized wound dressings