Periodic Reporting for period 1 - SNFWD (A pH-Responsive Bionanohybrid Nanofibrous Wound Dressing)
Berichtszeitraum: 2019-08-01 bis 2021-07-31
Importance for Society: Globally, chronic wounds e.g. diabetic ulcers impose a notable burden to patients and the health systems. In Europe, there are more than 55 million patients suffering from diabetes, thereof 8 million patients are vulnerable to developing a diabetic foot ulcer. As a consequence of inefficient treatment of such ulcers, up to 450,000 lower limb amputations take place that can cost as much as €2–2.5 billion. Yet, appropriate treatment strategies including use of wound dressings with high healing rate can prevent the undesired outcomes and alleviate such costs.
The targeted problem: To address the dynamic nature of wound healing, the wound care market is transitioning from classic protective barriers into advanced, active wound dressings, interacting with the wound by stimulating and managing cell migration and the sequence of healing events. In this regard, development of smart drug delivery wound dressings based on nanofibers, is a novel topic that could be of high importance due to the biomimicry and high surface area of such materials bringing about better dissolution rate and ease of incorporation of drugs. However, to industrially realize such systems, there are still some challenges. Of the most important challenges is fabrication approach of such systems, that must not lead to either a burst release or damage to the drug during the process.
Overall objectives: In this project, I dealt with this challenge and proposed a novel approach based on biomineralization for smart delivery of drug by a nanofibrous wound dressing. In this biomineralized nanofiber wound dressing, not only the nanofibrous structure and its biomimetic formulation and smart drug delivery facilitates interaction with live cells and manages the healing process, respectively, but also cheap and fast electrospinning process promise an industrially adaptable approach. Thus, this proposed research would be an important novel step towards introduction of nanofibrous drug delivery wound dressings to industry.
The targeted problem: To address the dynamic nature of wound healing, the wound care market is transitioning from classic protective barriers into advanced, active wound dressings, interacting with the wound by stimulating and managing cell migration and the sequence of healing events. In this regard, development of smart drug delivery wound dressings based on nanofibers, is a novel topic that could be of high importance due to the biomimicry and high surface area of such materials bringing about better dissolution rate and ease of incorporation of drugs. However, to industrially realize such systems, there are still some challenges. Of the most important challenges is fabrication approach of such systems, that must not lead to either a burst release or damage to the drug during the process.
Overall objectives: In this project, I dealt with this challenge and proposed a novel approach based on biomineralization for smart delivery of drug by a nanofibrous wound dressing. In this biomineralized nanofiber wound dressing, not only the nanofibrous structure and its biomimetic formulation and smart drug delivery facilitates interaction with live cells and manages the healing process, respectively, but also cheap and fast electrospinning process promise an industrially adaptable approach. Thus, this proposed research would be an important novel step towards introduction of nanofibrous drug delivery wound dressings to industry.
The project’s research topic was associated with the nanofibrous wound dressing materials, particularly the ones with antibacterial activity. Therefore, the project started with a reading phase and extraction of the required knowledge in relation with this class of wound dressings. The outcome of this primary phase was a review paper, entitled as “Antibacterial biohybrid nanofibers for wound dressings”, that was published in the renowned journal of Acta Biomaterialia (IF:7.242) (https://doi.org/10.1016/j.actbio.2020.02.022).
Preceded by the study phase, experiments were targeted at creation of a smart antibacterial nanofibrous wound dressing. For this purpose, polymer nanofibers were synthesized through electrospinning, biofunctionalized by incorporation/immobilization of a protein component and eventually surface decorated with a biomineral coating within the frame of the first work package, as mentioned in Annex 1. The biomineralization of the nanofibrous wound dressing took place by immersion of the biofunctionalized polymeric nanofibers in simulated body fluid (SBF). The biomineral surface layer could be later doped by beneficial elements such as Zn, that accelerate wound healing and improve angiogenesis, and could electrostatically hold negatively charged antibiotic drug molecules. The as-developed carrier coating is dissolved upon exposure to acidic liquids within the course of wound healing (pH shifts from alkaline to acidic), thereby releasing the drug into the wound milieu. Accordingly, bacterial infection of wound should be hindered by the release of ions such as Zn and Ca, wound is healed faster and vascularization occurs across the wound, leading to better therapeutic conditions for a chronic wound such as diabetic ulcer.
For this research, two polymeric systems were considered; 1) the synthetic, industrial, non-degradable polymer; polyacrylonitrile (PAN) dissolved in dimethylformamide (DMF; an organic solvent) for typical electrospinning to develop fibers; 2) the synthetic biodegradable polymer; polycaprolactone (PCL) dissolved in a benign solvent mixture of Acetic Acid (AA) and Formic Acid (FA), holding promise for a green (environmentally friendly) electrospinning. The first system enjoyed a biohybrid structure of polymer/protein with exposed semi-free protein ligands that could reduce cations (Ca2+) and form biominerals on the surface. While the second system comprised of a protein/polymer blend wherein protein could guarantee biomineralization and bioactivity and notably improve the mechanical properties of the nanofibrous dressing.
With respect to the first wound dressing material, PAN nanofibers were made through electrospinning, chemically functionalized (hydrolysed), biofunctionalized (by immobilization of Bovine Serum Albumin (BSA) on the surface) and eventually biomineralized.
The biomineralized PAN nanofibers showed an improved mechanical stability and offered higher cell viability for two important cells in the wound healing process, i.e. fibroblasts and keratinocytes. The results were published in Materials Science and Engineering C (IF: 5.88)(https://doi.org/10.1016/j.msec.2020.111248).
Regarding the second system, the BSA (protein)/PCL nanofibers containing 1 and 3 wt.% protein were made through green electrospinning based on non-hazardous (benign) solvents. The blend nanofibers were biocompatible and encouraged cell adhesion and growth of fibroblast cells. Moreover, they were notably mechanically stronger than their neat counterparts. Bioactivity of the nanofibers was reflected in extensive formation of biominerals on the surface. The promising results of this part of the research project will form the basis for another publication (in preparation).
Given the fact that the whole duration of the project from start (Aug. 1, 2019) to termination (July 1, 2020) took almost 11 months and due to the COVID-19 pandemic, lab access was limited and prohibited for almost 3 months, the latter stages of the research were left unaccomplished. Nevertheless, Zn doping of the biomineral layer and its loading with the antibiotic drug and testing of the drug and ion release behaviour under different pHs would be interesting and will be the focus of future studies.
Preceded by the study phase, experiments were targeted at creation of a smart antibacterial nanofibrous wound dressing. For this purpose, polymer nanofibers were synthesized through electrospinning, biofunctionalized by incorporation/immobilization of a protein component and eventually surface decorated with a biomineral coating within the frame of the first work package, as mentioned in Annex 1. The biomineralization of the nanofibrous wound dressing took place by immersion of the biofunctionalized polymeric nanofibers in simulated body fluid (SBF). The biomineral surface layer could be later doped by beneficial elements such as Zn, that accelerate wound healing and improve angiogenesis, and could electrostatically hold negatively charged antibiotic drug molecules. The as-developed carrier coating is dissolved upon exposure to acidic liquids within the course of wound healing (pH shifts from alkaline to acidic), thereby releasing the drug into the wound milieu. Accordingly, bacterial infection of wound should be hindered by the release of ions such as Zn and Ca, wound is healed faster and vascularization occurs across the wound, leading to better therapeutic conditions for a chronic wound such as diabetic ulcer.
For this research, two polymeric systems were considered; 1) the synthetic, industrial, non-degradable polymer; polyacrylonitrile (PAN) dissolved in dimethylformamide (DMF; an organic solvent) for typical electrospinning to develop fibers; 2) the synthetic biodegradable polymer; polycaprolactone (PCL) dissolved in a benign solvent mixture of Acetic Acid (AA) and Formic Acid (FA), holding promise for a green (environmentally friendly) electrospinning. The first system enjoyed a biohybrid structure of polymer/protein with exposed semi-free protein ligands that could reduce cations (Ca2+) and form biominerals on the surface. While the second system comprised of a protein/polymer blend wherein protein could guarantee biomineralization and bioactivity and notably improve the mechanical properties of the nanofibrous dressing.
With respect to the first wound dressing material, PAN nanofibers were made through electrospinning, chemically functionalized (hydrolysed), biofunctionalized (by immobilization of Bovine Serum Albumin (BSA) on the surface) and eventually biomineralized.
The biomineralized PAN nanofibers showed an improved mechanical stability and offered higher cell viability for two important cells in the wound healing process, i.e. fibroblasts and keratinocytes. The results were published in Materials Science and Engineering C (IF: 5.88)(https://doi.org/10.1016/j.msec.2020.111248).
Regarding the second system, the BSA (protein)/PCL nanofibers containing 1 and 3 wt.% protein were made through green electrospinning based on non-hazardous (benign) solvents. The blend nanofibers were biocompatible and encouraged cell adhesion and growth of fibroblast cells. Moreover, they were notably mechanically stronger than their neat counterparts. Bioactivity of the nanofibers was reflected in extensive formation of biominerals on the surface. The promising results of this part of the research project will form the basis for another publication (in preparation).
Given the fact that the whole duration of the project from start (Aug. 1, 2019) to termination (July 1, 2020) took almost 11 months and due to the COVID-19 pandemic, lab access was limited and prohibited for almost 3 months, the latter stages of the research were left unaccomplished. Nevertheless, Zn doping of the biomineral layer and its loading with the antibiotic drug and testing of the drug and ion release behaviour under different pHs would be interesting and will be the focus of future studies.
Synthetic polymers that can easily be processed through industrial production technologies are promising for development of temporary wound dressings. However, they need to be upgraded with respect to biocompatibility and bioactivity. PAN is a rarely studied material for biomedical applications, despite its various merits for industrialization and large scale production. In this project, PAN nanofiber mats were synthesized that could biomimic the natural extracellular matrix (ECM) topographically. Additionally, they were biofunctionalized and then biomineralized to enhance their cell responsiveness. The BSA protein used in this study for the sake of biofunctionalization was a commercial, inexpensive biomacromolecule. The biomineralized PAN nanofibers stimulated cellular activities and showed improved mechanical properties. Accordingly, a combination of cost-effective and straightforward processing and functionalization as well as optimum biological and mechanical characteristics hold great promise for further study and development of the system investigated here for wound dressing application.