Multifunctional and Spatially Controlled Bioconjugation to Melt Coextruded Nanofibers

Recent Advances and Challenges for Biological Materials in Micro/Nanocarrier Synthesis for Bone Infection and Tissue Engineering

Roughly 1.71 billion people worldwide suffer from large bone abnormalities, which are the primary cause of disability. Traditional bone grafting procedures have several drawbacks that impair their therapeutic efficacy and restrict their use in clinical settings. A great deal of work has been done to create fresh, more potent strategies. Under these circumstances, a crucial technique for the regeneration of major lesions has emerged: bone tissue engineering (BTE). BTE involves the use of biomaterials that can imitate the natural design of bone. To yet, no biological material has been able to fully meet the parameters of the perfect implantable material, even though several varieties have been created and investigated for bone regeneration. Against this backdrop, researchers have focused a great deal of interest over the past few years on the subject of nanotechnology and the use of nanostructures in regenerative medicine. The ability to create nanoengineered particles that can overcome the current constraints in regenerative strategies─such as decreased cell proliferation and differentiation, insufficient mechanical strength in biological materials, and insufficient production of extrinsic factors required for effective osteogenesis has revolutionized the field of bone and tissue engineering. The effects of nanoparticles on cell characteristics and the application of biological materials for bone regeneration are the main topics of our review, which summarizes the most recent in vitro and in vivo research on the application of nanotechnology in the context of BTE.

Engineered biomimetic micro/nano-materials for tissue regeneration

The incidence of tissue and organ damage caused by various diseases is increasing worldwide. Tissue engineering is a promising strategy of tackling this problem because of its potential to regenerate or replace damaged tissues and organs. The biochemical and biophysical cues of biomaterials can stimulate and induce biological activities such as cell adhesion, proliferation and differentiation, and ultimately achieve tissue repair and regeneration. Micro/nano materials are a special type of biomaterial that can mimic the microstructure of tissues on a microscopic scale due to its precise construction, further providing scaffolds with specific three-dimensional structures to guide the activities of cells. The study and application of biomimetic micro/nano-materials have greatly promoted the development of tissue engineering. This review aims to provide an overview of the different types of micro/nanomaterials, their preparation methods and their application in tissue regeneration.

Surface-Modified Melt Coextruded Nanofibers Enhance Blood Clotting In Vitro

Blood loss causes an estimated 1.9 million deaths per year globally, making new methods to stop bleeding and promote clot formation immediately following injury paramount. The fabrication of functional hemostatic materials has the potential to save countless lives by limiting bleeding and promoting clot formation following an injury. This work describes the melt manufacturing of poly(ε-caprolactone) nanofibers and their chemical functionalization to produce highly scalable materials with enhanced blood clotting properties. The nanofibers are manufactured using a high throughput melt coextrusion method. Once isolated, the nanofibers are functionalized with polymers that promote blood clotting through surface-initiated atom transfer radical polymerization. The functional nanofibers described herein speed up the coagulation cascade and produce more robust blood clots, allowing for the potential use of these functional nonwoven mats as advanced bandages.

Laser irradiation method to prepare polyethylene porous fiber membrane with ultrahigh xylene gas filtration capacity

In recent years, volatile organic compound (VOC) gases have caused potential harm to people's health. This study reveals the preparation of polyethylene porous fiber membrane with excellent low-concentration VOCs filtration performance via laser irradiation technology. A neodymium-doped yttrium aluminum garnet (Nd:YAG) pulsed laser beam was used to scan the laser-sensitive low-density polyethylene/carbon black (LDPE/CB) fibers prepared by nanolayer coextrusion in the air. The controllable thermal energy generated by laser irradiation makes the surface of the fiber membrane to produce a porous carbon layer in situ. Laser power and scanning speed are important parameters for controlling laser-induced carbonization. The results indicate that the rich "fluffy" carbon structures on the surface of the porous fiber membrane can efficiently adsorb xylene gas. This study can provide a positive reference for the large-scale preparation of polyolefin porous fiber membrane with VOCs filtration by simple and efficient laser irradiation method.

Postfabrication Tethering of Molecular Gradients on Aligned Nanofibers of Functional Poly(ε-caprolactone)s

Substrates with combinations of topographical and biochemical cues are highly useful for a number of fundamental biological investigations. Tethered molecular concentration gradients in particular are highly desired for a number of biomedical applications including cell migration. Herein, we report a versatile method for the fabrication of aligned nanofiber substrates with a tunable concentration gradient along the fiber direction. 4-Dibenzocyclooctynol (DIBO) was used as an initiator for the ring-opening copolymerization of ε-caprolactone (εCL) and allyl-functionalized ε-caprolactone (AεPCL), which yielded a well-defined polymer with orthogonal functional handles. These materials were fabricated into aligned nanofiber substrates via touch-spinning. Fibers were modified post-spinning with a concentration gradient of fluorescently labeled dye via a light activated thiol-ene reaction through a photomask. As a demonstration, the cell adhesive peptide RGD was chemically tethered to the fiber surface at a second functionalization site via strain-promoted azide-alkyne cycloaddition (SPAAC). This novel approach affords fabrication of dual functional nanofiber substrates.

Nanolayer coextrusion: An efficient and environmentally friendly micro/nanofiber fabrication technique

Researchers have developed many types of nanoscale materials with different properties. Among them, nanofibers have recently attracted increasing interest and attention due to their functional versatility and potential applications in diverse industries, including tapes, filtration, energy generation, and biomedical technologies. Nanolayer coextrusion, a novel polymer melt fiber processing technology, has gradually received attention due to its environmental friendliness, efficiency, simplicity and ability to be mass-produced. Compared with conventional techniques, nanolayer coextruded non-woven nanofibrous mats offer advantages such as a tunable fiber diameter, high porosity, high surface area to volume ratio, and the potential to manufacture composite nanofibers with different components to achieve desired structures and properties. Dozens of thermoplastic polymers have been coextruded for various applications, and the variety of polymers has gradually continued to increase. This review presents an overview of the nanolayer coextrusion technique and its promising advantages and potential applications. We discuss nanolayer coextrusion theory and the parameters (polymer and processing) that significantly affect the fiber morphology and properties. We focus on varied applications of nanolayer coextruded fibers in different fields and conclude by describing the future potential of this novel technology.

Poly(lactic-co-glycolic acid) devices: Production and applications for sustained protein delivery

Injectable or implantable poly(lactic-co-glycolic acid) (PLGA) devices for the sustained delivery of proteins have been widely studied and utilized to overcome the necessity of repeated administrations for therapeutic proteins due to poor pharmacokinetic profiles of macromolecular therapies. These devices can come in the form of microparticles, implants, or patches depending on the disease state and route of administration. Furthermore, the release rate can be tuned from weeks to months by controlling the polymer composition, geometry of the device, or introducing additives during device fabrication. Slow-release devices have become a very powerful tool for modern medicine. Production of these devices has initially focused on emulsion-based methods, relying on phase separation to encapsulate proteins within polymeric microparticles. Process parameters and the effect of additives have been thoroughly researched to ensure protein stability during device manufacturing and to control the release profile. Continuous fluidic production methods have also been utilized to create protein-laden PLGA devices through spray drying and electrospray production. Thermal processing of PLGA with solid proteins is an emerging production method that allows for continuous, high-throughput manufacturing of PLGA/protein devices. Overall, polymeric materials for protein delivery remain an emerging field of research for the creation of single administration treatments for a wide variety of disease. This review describes, in detail, methods to make PLGA devices, comparing traditional emulsion-based methods to emerging methods to fabricate protein-laden devices. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Peptide-Based Structures.

Facile Fabrication of CO2-Responsive Nanofibers from Photo-Cross-Linked Poly(pentafluorophenyl acrylate) Nanofibers

CO₂-responsive nanofibers were facilely prepared from photo-cross-linked poly(pentafluorophenyl acrylate) (PPFPA) nanofibers via "amine-active ester" chemical modification. Photo-cross-linked PPFPA nanofibers were modified with histamine under mild conditions to generate cross-linked poly(histamine acrylamide) (PHAAA) nanofibers featuring a CO₂ responsiveness. As expected, the prepared cross-linked PHAAA nanofibers can exhibit a CO₂-responsive behavior to induce a reversible transition from hydrophobic to hydrophilic upon alternating addition and removal of CO₂ on the surface of nanofibrous membranes. Based on this finding, we could demonstrate that cross-linked PHAAA nanofibers can be employed for reversible absorption and release of protein using bovine serum albumin (BSA) as a model.

A thiol probe for measuring unfolded protein load and proteostasis in cells

When proteostasis becomes unbalanced, unfolded proteins can accumulate and aggregate. Here we report that the dye, tetraphenylethene maleimide (TPE-MI) can be used to measure cellular unfolded protein load. TPE-MI fluorescence is activated upon labelling free cysteine thiols, normally buried in the core of globular proteins that are exposed upon unfolding. Crucially TPE-MI does not become fluorescent when conjugated to soluble glutathione. We find that TPE-MI fluorescence is enhanced upon reaction with cellular proteomes under conditions promoting accumulation of unfolded proteins. TPE-MI reactivity can be used to track which proteins expose more cysteine residues under stress through proteomic analysis. We show that TPE-MI can report imbalances in proteostasis in induced pluripotent stem cell models of Huntington disease, as well as cells transfected with mutant Huntington exon 1 before the formation of visible aggregates. TPE-MI also detects protein damage following dihydroartemisinin treatment of the malaria parasites Plasmodium falciparum. TPE-MI therefore holds promise as a tool to probe proteostasis mechanisms in disease.

Proteostasis is maintained through a number of molecular mechanisms, some of which function to protect the folded state of proteins. Here the authors demonstrate the use of TPE-MI in a fluorigenic dye assay for the quantitation of unfolded proteins that can be used to assess proteostasis on a cellular or proteome scale.

A General Strategy for Generating Gradients of Bioactive Proteins on Electrospun Nanofiber Mats by Masking with Bovine Serum Albumin

Electrospun nanofibers are widely used in tissue engineering owing to their capability to mimic the structures and architectures of various types of extracellular matrices. However, it has been difficult to incorporate a biochemical cue into the physical cue provided by the nanofibers. Here we report a simple and versatile method for generating gradients of bioactive proteins on nanofiber mats. We establish that the adsorption of bovine serum albumin (BSA) onto nanofibers is a time- and concentration-dependent process. By linearly increasing the volume of BSA solution introduced into a container, a gradient in BSA is readily generated across the length of a vertically oriented strip of nanofibers. Next, the bare regions uncovered by BSA can be filled with the bioactive protein of interest. In demonstrating the potential application, we examine the outgrowth of neurites from dorsal root ganglion (DRG) isolated from chick embryos and then seeded on aligned polycaprolactone nanofibers covered by nerve growth factor (NGF) with a uniform coverage or in a gradient. In the case of uniform coverage, the neurites extending from DRG show essentially the same length on either side of the DRG cell mass. For the sample with a gradient in NGF, the neurites extending along the gradient (i.e., increase of NGF concentration) were significantly longer than the neurites extending against the gradient.

Drawing in poly(ε-caprolactone) fibers: tuning mechanics, fiber dimensions and surface-modification density

This work describes the complex interplay between mechanical manipulation of coextruded fibers and the resulting photochemical yield of surface modification.

Fabrication of color changeable CO2 sensitive nanofibers

A CO₂ sensor was fabricated by attaching CO₂-sensitive spiropyran groups onto versatile photo-crosslinked poly(glycidyl methacrylate) (PGMA) precursor nanofibers via a nucleophilic ring-opening reaction.

Processing and surface modification of polymer nanofibers for biological scaffolds: a review

Polymeric fibrous constructs possess high surface area-to-volume ratios when compared with solid substrates and are quite commonly used as tissue engineering and cell growth scaffolds. An overview of important design and material considerations for fibrous scaffolds as well as an outline of both established and emerging solution- and melt-based fabrication techniques is provided. Innovative post-process surface modification avenues using "click" chemistry with both single and dual active cues as well as gradient cues, which maintain the fibrous structure are described. By combining process parameters with post-process surface modification, researchers have been able to selectively tune cellular response after seeding and culturing on fibrous constructs.

Protein and Bacterial Antifouling Behavior of Melt-Coextruded Nanofiber Mats

Antifouling surfaces are important for biomedical devices to prevent secondary infections and mitigate the effects of the foreign body response. Herein, we describe melt-coextruded poly(ε-caprolactone) (PCL) nanofiber mats grafted with antifouling polymers. Nonwoven PCL fiber mats are produced using a multilayered melt coextrusion process followed by high-pressure hydroentanglement to yield porous patches. The resulting fiber mats show submicrometer cross-sectional fiber dimensions and yield pore sizes that were nearly uniform, with a mean pore size of 1.6 ± 0.9 μm. Several antifouling polymers, including hydrophilic, zwitterionic, and amphipathic molecules, are grafted to the surface of the mats using a two-step procedure that includes photochemistry followed by the copper-catalyzed azide-alkyne cycloaddition reaction. Fiber mats are evaluated using separate adsorption tests for serum proteins and E. coli. The results indicate that poly(oligo(ethylene glycol) methyl ether methacrylate)-co-(trifluoroethyl methacrylate) (poly(OEGMEMA-co-TFEMA)) grafted mats exhibit approximately 85% less protein adhesion and 97% less E. coli adsorption when compared to unmodified PCL fibermats. In dynamic antifouling testing, the amphiphilic fluorous polymer surface shows the highest flux and highest rejection value of foulants. The work presented within has implications on the high-throughput production of antifouling microporous patches for medical applications.