Role of polymers in microfluidic devices

Polymers are sustainable and renewable materials that are in high demand due to their excellent properties. Natural and synthetic polymers with high flexibility, good biocompatibility, good degradation rate, and stiffness are widely used for various applications, such as tissue engineering, drug delivery, and microfluidic chip fabrication. Indeed, recent advances in microfluidic technology allow the fabrication of polymeric matrix to construct microfluidic scaffolds for tissue engineering and to set up a well-controlled microenvironment for manipulating fluids and particles. In this review, polymers as materials for the fabrication of microfluidic chips have been highlighted. Successful models exploiting polymers in microfluidic devices to generate uniform particles as drug vehicles or artificial cells have been also discussed. Additionally, using polymers as bioink for 3D printing or as a matrix to functionalize the sensing surface in microfluidic devices has also been mentioned. The rapid progress made in the combination of polymers and microfluidics presents a low-cost, reproducible, and scalable approach for a promising future in the manufacturing of biomimetic scaffolds for tissue engineering

Binding enhancements of antibody functionalized natural and synthetic fibers

Development of low cost biosensing using convenient and environmentally benign materials is important for wide adoption and ultimately improved healthcare and sustainable development. Immobilized antibodies are often incorporated as an essential biorecognition element in point-of-care biosensors but these proteins are costly. We present a strategy of combining convenient and low-cost surface functionalization approaches for increasing the overall binding activity of antibody functionalized natural and synthetic fibers. We demonstrate a simple one-step in situ silica NP growth protocol for increasing the surface area available for functionalization on cotton and polyester fabrics as well as on nanoporous cellulose substrates. Comparing this effect with the widely adopted and low cost plant-based polyphenol coating to enhance antibody immobilization, we find that both approaches can similarly increase overall surface activity, and we illustrate conditions under which the two approaches can produce an additive effect. Furthermore, we introduce co-immobilization of antibodies with a sacrificial “steric helper” protein for further enhancing surface activities. In combination, several hundred percent higher activities compared to physical adsorption can be achieved while maintaining a low amount of antibodies used, thus paving a practical path towards low cost biosensing

Development of peptoid material for cell growth and differentiation

Previously held under moratorium from 7th June 2022 until 12th May 2023.Development of new systems that mimic the native cellular environment has emerged as one of the main strategies for tissue engineering and future biomedical applications. While nanoparticles (NPs) and nanotubes (NTs) positioned themselves as candidates of high potential in the field, more and more studies emphasize their size-related cytotoxicity, the difficulty of translating them from research laboratories into the clinic, and in conducting large-scale synthesis. Peptoids are peptide mimetics. The only difference from natural peptides is that the side chain is shifted from the backbone alpha carbon on the peptide to the nitrogen atom on the peptoid. This structural difference confers on peptoids several interesting properties such as biostability, and easy and economical synthesis. While the side chain shift deprives the peptoids from chiral centres and backbone secondary structure hydrogen bonding, the incorporation of specific side chains enables the folding of the peptoid chains into organised secondary structures such as nanosheets. This thesis presents the study of two different peptoid systems and their interaction with cells, namely peptoid nanosheets and a peptoid hydrogel. The aim was to create peptoid materials inspired by the mechanisms of extracellular matrix (ECM)-cell interaction to control stem cell growth and differentiation. In the first and major part of the thesis, we focused on the mechanical and biochemical properties. We wanted to mimic the mechanical interaction of the ECM that is displaying biologically relevant peptide ligands with cells. This was carried out by developing peptoid nanosheets (PNS) as a stiff and functionalizable platform and characterizing their effect on cells. Those PNS combine the following advantages: a structure close to the bilayer cell membrane, a peptidic nature and cell size similarity, stiff intrinsic mechanical strength, biocompatibility and the possibility of surface functionalisation with different types of ligands with high degree of control. In the second part, we wanted to capture the dynamic properties of the 3D environment provided by the ECM by beginning to develop a peptoid hydrogel that is capable of changing its mechanical stiffness upon exposure to a stimulus. This thesis describes not only the effect of the peptoid systems on MSCs but also the strategy and steps taken to develop a cell culture system capable of sustaining the integrity of both cells and PNS, as this is the first time the effect of peptoid systems on cells was studied. To summarise, peptoids are biostable, biocompatible and easy to synthesize, flexible to functionalise for developing biomimetics in the nano/micro scale. They have the potential to harness its advantages and at the same time evade the drawbacks of conventional nanomaterials used with biological systems.Development of new systems that mimic the native cellular environment has emerged as one of the main strategies for tissue engineering and future biomedical applications. While nanoparticles (NPs) and nanotubes (NTs) positioned themselves as candidates of high potential in the field, more and more studies emphasize their size-related cytotoxicity, the difficulty of translating them from research laboratories into the clinic, and in conducting large-scale synthesis. Peptoids are peptide mimetics. The only difference from natural peptides is that the side chain is shifted from the backbone alpha carbon on the peptide to the nitrogen atom on the peptoid. This structural difference confers on peptoids several interesting properties such as biostability, and easy and economical synthesis. While the side chain shift deprives the peptoids from chiral centres and backbone secondary structure hydrogen bonding, the incorporation of specific side chains enables the folding of the peptoid chains into organised secondary structures such as nanosheets. This thesis presents the study of two different peptoid systems and their interaction with cells, namely peptoid nanosheets and a peptoid hydrogel. The aim was to create peptoid materials inspired by the mechanisms of extracellular matrix (ECM)-cell interaction to control stem cell growth and differentiation. In the first and major part of the thesis, we focused on the mechanical and biochemical properties. We wanted to mimic the mechanical interaction of the ECM that is displaying biologically relevant peptide ligands with cells. This was carried out by developing peptoid nanosheets (PNS) as a stiff and functionalizable platform and characterizing their effect on cells. Those PNS combine the following advantages: a structure close to the bilayer cell membrane, a peptidic nature and cell size similarity, stiff intrinsic mechanical strength, biocompatibility and the possibility of surface functionalisation with different types of ligands with high degree of control. In the second part, we wanted to capture the dynamic properties of the 3D environment provided by the ECM by beginning to develop a peptoid hydrogel that is capable of changing its mechanical stiffness upon exposure to a stimulus. This thesis describes not only the effect of the peptoid systems on MSCs but also the strategy and steps taken to develop a cell culture system capable of sustaining the integrity of both cells and PNS, as this is the first time the effect of peptoid systems on cells was studied. To summarise, peptoids are biostable, biocompatible and easy to synthesize, flexible to functionalise for developing biomimetics in the nano/micro scale. They have the potential to harness its advantages and at the same time evade the drawbacks of conventional nanomaterials used with biological systems

Peptoid self-assembly : from minimal sequences to functional nano-assemblies and biomedical applications

This chapter provides a tutorial review on peptoid nano-assemblies and their biomedically relevant properties and applications. Peptoids are biomimetic molecules that differ from natural peptides only by a one-atom shift in the attachment position of the functional sidechain along the backbone. This minor change in chemical structure however enables major changes in molecular properties and synthetic protocol that can be very attractive for bioactive supramolecular nanotechnology. In the recent decade, peptoids have gained recognition in self-assembled and functional materials due to the sophistication of nano-assemblies demonstrated, the intrinsic bioactivity of specific sequences discovered, and the importance now placed on bioinspired materials. Indeed, there has been a diversity of inspirations for peptoid supramolecular chemistry, from peptide assembly and block copolymer polymersomes to crystallization and protein folding. Peptoid research is also greatly facilitated by the versatility of peptoid synthesis to enable systematic investigations of sidechain and sequence control for directing assembly of a wide range of nanostructures. These include nanofibers, nanotubes, nanosheets, micellar worms and nested vesicles, and this chapter emphasizes the links between sequence and assembled morphologies. Applications from biosensing to stimuli-responsive drug delivery are reviewed to illustrate the potential of peptoids in tailoring nano-assemblies for bioscience and biomedical applications. While the research from many groups which have been examined, some of our recent results in “minimal” assembling sequences as well as applications towards stem cell culture and antimicrobial lipopeptoids are also highlighted