Biomaterial applications in neural therapy and repair

Abstract

The use of biomaterials, such as hydrogels, as a scaffold to deliver cells and drugs is becoming increasingly common to treat neurological conditions, including stroke. With a limited intrinsic ability to regenerate after injury, innovative tissue engineering strategies have shown the potential of biomaterials in facilitating neural tissue regeneration and functional recovery. Using biomaterials can not only promote the survival and integration of transplanted cells in the existing circuitry, but also support controlled site specific delivery of therapeutic drugs. This review aims to provide the reader an understanding of the brain tissue microenvironment after injury, biomaterial criteria that support tissue repair, commonly used natural and synthetic biomaterials, benefits of incorporating cells and neurotrophic factors, as well as the potential of endogenous neurogenesis in repairing the injured brain.

Stroke Repair via Biomimicry of the Subventricular Zone

“…Although systemic, intravenous delivery methods can be non-invasive, they often lead to an accumulation of cells in clearing organs, including kidney and spleen, rather than the brain. Targeted intracerebral cell injection can be applied directly to the peri-infarct region; however, the multiple injections required to deliver adequate numbers of cells can cause further damage to the already injured tissue (Ghuman and Modo, 2016). With minimal damage to an already fragile environment, invasive approaches are unfavorable due to the threat of further disruption of tissue and the BBB.…”

“…These cells monitor the microenvironment by responding to injury through the secretion of cytokines and phagocytosing cellular debris at the site (Weinstein et al, 2010;Ghuman and Modo, 2016). Within minutes following stroke, the brain tissue surrounding the core contains activated microglia that accumulate within the lesioned cavity (Patel et al, 2013).…”

“…Photopolymerization processes, which are cross-linking reactions that occur with light exposure, are often used for hydrogel production; however, these reactions can lead to the formation of free-radicals that compromise cell survival. Polymers that can polymerize at physiological conditions, dependent on temperature or pH, avoid these potential toxic effects (Ghuman and Modo, 2016). Consideration of how biomaterials will interact with host tissue is critical to contribute to functional recovery of both the infarct area and surrounding tissues.…”

“…The successful use of biomaterials that recreate the SVZ native niche should support cell survival, proliferation, growth factor production, and protein secretion as necessary for appropriate cellular delivery and engraftment into the damaged area. Combining tissue engineering and cell transplantation advances can directly influence the differentiation and survival of neural progenitor and stem cells in vitro and in vivo (Ghuman and Modo, 2016).…”

“…Cell incorporation in combination with these materials calls for careful observation of cell-scaffold interactions, consequently allowing for control of cell processes, such as differentiation, morphological formation, and extension, to ultimately enhance connectivity in the ischemia area (Ghuman and Modo, 2016).…”