Biological cues

As described above, protein domains that provide discrete biological cues (e.g., cell binding) or mechanical properties (e.g., expansion or contraction with temperature changes) can be borrowed from nature and designed into synthetic polypeptides or joined with other polymers to provide bio-inspired function in new... 

Vertebrates possess three primary chemosensory systems gustation ( taste ), trigeminal, and olfaction ( smell ) but only one of these, the olfactory system, mediates responses to pheromones. Chemicals that stimulate the olfactory system are known as odorants and comprise one type of biological cue (any entity that stimulates a sensory system). Bouquets of odorants that can be discriminated as specific entities are termed odors. The olfactory system contains olfactory receptor neurons (ORNs) that comprise cranial nerve I and project directly to the forebrain. ORNs are now known to express only one to a few olfactory receptor proteins ( receptors ), which means that the chemoreceptive range of each neuron can be very narrow. The olfactory system also has several subcomponents including the vomeronasal organ, which is described below. 

In this regard, an important goal of tissue engineering for tissue repair is to utilize polymers as a means of controlling stem cells function and to affect their activity, in vitro and further in vivo, via physical, chemical, mechanical, and biological cues communicated from the polymer to the cells in order to obtain improved outcomes for tissue regeneration. ... 

It is evident that stem cells respond both to biological cues (e.g., growth factors) and to physical stimulus (e.g., shear stress, electric field and etc.). However, biological and physical cues are perceived as orthogonal in the sense that one is derived from physical forces or stresses while the other is proportional to a chemical concentration or gradient - two phenomena that should have limited, if any at all, interactions. While it is possible to induce conformation changes of... 

In order to culture cells in a 3D environment, a scaffold is required to provide both mechanical support as well as the biological cues found in the cells native environment. This role is played in vivo by the extracellular matrix (ECM), which is a mixture of structural proteins, glycosaminoglycans, and proteoglycans that surrounds the cells. The development of scaffolds for tissue engineering and 3D cell culture is therefore veiy heavily inspired by biology, since all scaffolds are essentially attempting to mimic the natural ECM, at least to some extent. 

The advantage of the naturally derived surfaces is their inherent biocompatibility. However, inconsistent purity arising from lot-to-lot variabihty and potential contamination of pathogens in cases where the material is obtained from a non-human source are disadvantages. On the other hand, synthetic materials are better to reproduce but they lack biological cues found in natural extracellular matrix. Therefore significant efforts have been made to search for polymer blend with functional groups that can be used to couple bioactive species on the surface. 

Biological cues, such as growth factors, hormones, ECMs, and small chemicals, can guide the pluripotency and differentiation direction of stem cell fate [32,33]. For many years, researchers have devoted substantial effort to identify the soluble factors that mimic the stem cell microenvironment. However, investigators have recently realized the potential importance of the physical cues of biomaterials that influence stem cells ... 

The cell-material interaction is a dynamic process which controls the cellular response and function (Rosso et al, 2004 Ruosiahti and Pierschbacher, 1987 Tamers et al., 2012 Tamers et al., 2012). The first phase of the process involves protein adsorption, which occurs on contact with body fluids and is influenced by the physicochemical characteristics of the material and its fabricated form. This is followed by the ceU-adhesion phase involving various biological molecules such as ECM, cell membrane, and cytoskeletal protein components. These interactions at the nanoscale modulate cellular responses in terms of migration, cell proliferation, and differentiation. Thus, considerable research efforts have been focused on development of nanomaterials with appropriate properties to enhance cell performance. The material properties in controlling the cell-material interactions can be broadly classified as physical, chemical, and biological cues (von der Mark et al., 2010). 

---