The need is great for specialized skin tissues that can be used for wound healing and for replacement of skin damaged due to disease (e.g. diabetes caused ulcers) or injury (e.g. burns.) Though bioengineered skin research has been very active for over 40 years, available commercial products are still subject to rejection, infection and scarring, lack vascularization (blood vessels) and do not match the texture or color of the surrounding skin. The goal of this project is to address these limitations by developing a fully functional skin with minimal or no graft rejection, with wound healing capabilities, and that is individualized to match the texture, color and vascularization of the host tissue. Structure for the bioengineered skin will be provided by electrospun or 3D printed smart scaffolds consisting of polymers or composite hydrogels and bioinks (fluids that contain materials that provide the environment needed to support cell adhesion, proliferation and differentiation) that have been optimized for tissue generation and tested for antibacterial and antiviral activities. The optimized cell scaffolds, 3D printing methods, strategies and other technologies can be further refined to regenerate other organs (e.g. livers), thus establishing an exciting new research direction. The multidisciplinary expertise in nanobiotechnology, bioengineering, cell biology and immunology required for this project will provide invaluable opportunities for students involved in the research. Students will also benefit from the unique community of Alabama State University, a historically black university (HBCU) located in Central Alabama, and collaborative Universities and industry scientists and engineers. This setting, the Principal Investigator's strong commitment to undergraduate education and the project's appeal is expected to result in an increase in the number of minorities and women participating in the workforce in the region, state, and nation in STEM disciplines.
The goal of this project is to bioengineer fully functional skin tissues that can be used for wound healing and replacing skin damaged by disease or injury. Meritorious attributes include: no or minimal graft rejection, wound healing capabilities, antimicrobial protection, vascularization, and individualized texture and pigmentation that matches the host tissue. Key to the project's success is the development of smart scaffolds and bioinks into which growth factors, antimicrobials, nanoencapsulated DNA/cells, proangiogenic materials, decellularized ECM, etc. can be incorporated and skin models in which texture and pigmentation can be controlled. The Research Plan is organized under seven objectives. OBJECTIVE 1 is to develop novel biocompatible, cell and tissue specific, hydrogel materials and bioinks. Components to be designed and optimized include: synthetic polymer (PLA and PEG) scaffolds, composite hydrogels (collagen-chitosan and chitosan-alginate) scaffolds, electrospun composite (chilosan-pCL with PLGA-PGA nanofibers) scaffolds, gelatin-sodium alginate bioink, gelatin-fibrinogen-collagen bioink and decellularized ECM bioink (porcine cartilage and heart tissues). 3D scaffolds will be printed from the described hydrogels and bioinks, with further incorporation of various growth factors and ECM proteins. OBJECTIVE 2 is to produce smart infection resistant and genetically modified scaffolds and bioinks. Antibacterial/antiviral enhancement will be achieved by incorporation of encapsulated coated (silver PVP, gold, and silver) carbon nanotubes into the scaffolds and bioinks. A non-viral gene delivery system to enhance tissue generation will also be developed. OBJECTIVE 3 is to characterize the physical and chemical characteristics of the scaffolds and bioinks. Scaffold morphology will be analyzed using Scanning Electron, Transmission Electron and Atomic Force Microscopy (SEM, TEM and AFM). Functional groups in macromolecules will be determined using Fourier Transform Infrared Spectroscopy (FT-IR). The compression modulus will be determined using an INSTRON machine. The equilibrium swelling ratio will be measured using the conventional gravimeter method. Porosity will be measured using a displacement liquid that easily enters pores. OBJECTIVE 4 is optimization, development and characterization of skin tissues. Two layer skin tissues will be grown using fibroblasts (dermis) and keratinocytes (epidermis) and stem cells that can be differentiated into fibroblasts and keratinocytes as the skin grows to full thickness. Optimization of cell scaffolds will be assessed by determining seeding efficiency, cell proliferation, cell viability and cell attachment. Scaffolds and skin tissues will be analyzed histologically using SEM, TEM and AFM analyses, and mRNA expression levels of different skin compartment markers will be investigated using real-time PCR. OBJECTIVE 5 is to develop skin tissues with vascularization. Two approaches will be used: a) ex vivo development of vascularized skin by incorporating proangiogenic molecules in cell scaffolds prior to skin tissue development, and b) an in vivo approach that relies on dermal microvasculature cells to achieve vascularization post-skin tissue development. OBJECTIVE 6 is to develop skin tissues with melanotic features. Primary epidermal melanocytes will be cultured and used with fibroblasts and keratinocytes for 3D bioprinting of full thickness skin. Melanocyte morphology, proliferation, viability, melanin production and interactions with the fibroblasts and keratinocytes will be determined using technologies similar to those used in previous objectives. OBJECTIVE 7 is to assess the antimicrobial effects of skin tissues. The smart scaffolds with antimicrobial properties developed under Objective 2 will be used to develop human and mouse 3D skins that will be infected with skin bacteria, e.g. Staphylococcus aureus or Pseudomonas aeruginosa. Antimicrobial efficacy will be assessed by quantifying the post infection bacterial load (plate counting) and structural evaluation (ultrasound) of the infected skin.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.