The effect of acetylcholine-like biomimetic polymers on neuronal growth

Conventional and Nonconventional Sources of Exosomes-Isolation Methods and Influence on Their Downstream Biomedical Application

Despite extensive study of extracellular vesicles (EVs), specifically exosomes (EXs) as biomarkers, important modulators of physiological or pathological processes, or therapeutic agents, relatively little is known about nonconventional sources of EXs, such as invertebrate or plant EXs, and their uses. Likewise, there is no clear information on the overview of storage conditions and currently used isolation methods, including new ones, such as microfluidics, which fundamentally affect the characterization of EXs and their other biomedical applications. The purpose of this review is to briefly summarize conventional and nonconventional sources of EXs, storage conditions and typical isolation methods, widely used kits and new "smart" technologies with emphasis on the influence of isolation techniques on EX content, protein detection, RNA, mRNA and others. At the same time, attention is paid to a brief overview of the direction of biomedical application of EXs, especially in diagnostics, therapy, senescence and aging and, with regard to the current situation, in issues related to Covid-19.

Biomimetic modification of dual porosity poly(2-hydroxyethyl methacrylate) hydrogel scaffolds-porosity and stem cell growth evaluation

The macroporous synthetic poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels as 3D cellular scaffolds with specific internal morphology, so called dual pore size, were designed and studied. The morphological microstructure of hydrogels was characterized in the gel swollen state and the susceptibility of gels for stem cells was evaluated. The effect of specific chemical groups covalently bound in the hydrogel network by copolymerization on cell adhesion and growth, followed by effect of laminin coating were investigated. The evaluated gels contained either carboxyl groups of the methacrylic acid or quaternary ammonium groups brought by polymerizable ammonium salt or their combinations. The morphology of swollen gel was visualized using the laser scanning confocal microscopy. All hydrogels had very similar porous structures - their matrices contained large pores (up to 10² μm) surrounded with gel walls with small pores (10⁰ μm). The total pore volume in hydrogels swollen in buffer solution ranged between 69 and 86 vol%. Prior to the seeding of the mouse embryonal stem cells, the gels were coated with laminin. The hydrogel with quaternary ammonium groups (with or without laminin) stimulated the cell growth the most. The laminin coating lead to a significant and quaternary ammonium groups. The gel chemical modification influenced also the topology of cell coverage that ranged from individual cell clusters to well dispersed multi cellular structures. Findings in this study point out the laser scanning confocal microscopy as an irreplaceable method for a precise and quick assessment of the hydrogel morphology. In addition, these findings help to optimize the chemical composition of the hydrogel scaffold through the combination of chemical and biological factors leading to intensive cell attachment and proliferation.

Photo-controlled release of metal ions using triazoline-containing amphiphilic copolymers

Photo-controlled release of metal ions can be achieved by denitrogenation of triazoline from the micelles of amphiphilic copolymer, and has potential applications for biomedicines.

Quantum dots modified with quaternized poly(dimethylaminoethyl methacrylate) for selective recognition and killing of bacteria over mammalian cells

Copper-free click chemistry has been used to graft quaternized poly(dimethylaminoethyl methacrylate) (QPA) modified with azide to the quantum dots (QDs) derived with dibenzocyclooctynes (DBCO). The success of the quaternary ammonium polymer-modified QDs was confirmed by ultraviolet-visible spectrophotometry (UV-Vis), fluorescence spectroscopy, zeta (ζ) potential, size distribution, and transmission electron microscopy (TEM). The QPA-modified QDs exhibited properties of selective recognition and killing of bacteria. The novelty of this study lies in fact that the synthesis method of the antimicrobial QPA-modified QDs is simple. Moreover, from another standpoint, QPA-modified QDs simultaneously possess abilities of selective recognition and killing of bacteria over mammalian cells, which is very different from the currently designed multifunctional antimicrobial systems composed of complicated systematic compositions.

Multivalent Interactions between 2D Nanomaterials and Biointerfaces

2D nanomaterials, particularly graphene, offer many fascinating physicochemical properties that have generated exciting visions of future biological applications. In order to capitalize on the potential of 2D nanomaterials in this field, a full understanding of their interactions with biointerfaces is crucial. The uptake pathways, toxicity, long-term fate of 2D nanomaterials in biological systems, and their interactions with the living systems are fundamental questions that must be understood. Here, the latest progress is summarized, with a focus on pathogen, mammalian cell, and tissue interactions. The cellular uptake pathways of graphene derivatives will be discussed, along with health risks, and interactions with membranes-including bacteria and viruses-and the role of chemical structure and modifications. Other novel 2D nanomaterials with potential biomedical applications, such as transition-metal dichalcogenides, transition-metal oxide, and black phosphorus will be discussed at the end of this review.

Polymer Thin Films with Tunable Acetylcholine-like Functionality Enable Long-Term Culture of Primary Hippocampal Neurons

In vitro culture systems for primary neurons have served as useful tools for neuroscience research. However, conventional in vitro culture methods are still plagued by challenging problems with respect to applications to neurodegenerative disease models or neuron-based biosensors and neural chips, which commonly require long-term culture of neural cells. These impediments highlight the necessity of developing a platform capable of sustaining neural activity over months. Here, we designed a series of polymeric bilayers composed of poly(glycidyl methacrylate) (pGMA) and poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA), designated pGMA:pDMAEMA, using initiated chemical vapor deposition (iCVD). Harnessing the surface-growing characteristics of iCVD polymer films, we were able to precisely engraft acetylcholine-like functionalities (tertiary amine and quaternary ammonium) onto cell culture plates. Notably, pGD3, a pGMA:pDMAEMA preparation with the highest surface composition of quaternary ammonium, fostered the most rapid outgrowth of neural cells. Clear contrasts in neural growth and survival between pGD3 and poly-l-lysine (PLL)-coated surfaces became apparent after 30 days in vitro (DIV). Moreover, brain-derived neurotrophic factor level continuously accumulated in pGD3-cultured neurons, reaching a 3-fold increase at 50 DIV. Electrophysiological measurements at 30 DIV revealed that the pGD3 surface not only promoted healthy maturation of hippocampal neurons but also enhanced the function of hippocampal ionotropic glutamate receptors in response to synaptic glutamate release. Neurons cultured long-term on pGD3 also maintained their characteristic depolarization-induced Ca²⁺ influx functions. Furthermore, primary hippocampal neurons cultured on pGD3 showed long-term survival in a stable state up to 90 days-far longer than neurons on conventional PLL-coated surfaces. Taken together, our findings indicate that a polymer thin film with optimal acetylcholine-like functionality enables a long-term culture and survival of primary neurons.

Polyester with Pendent Acetylcholine-Mimicking Functionalities Promotes Neurite Growth

Successful regeneration of nerves can benefit from biomaterials that provide a supportive biochemical and mechanical environment while also degrading with controlled inflammation and minimal scar formation. Herein, we report a neuroactive polymer functionalized by covalent attachment of the neurotransmitter acetylcholine (Ach). The polymer was readily synthesized in two steps from poly(sebacoyl diglyceride) (PSeD), which previously demonstrated biocompatibility and biodegradation in vivo. Distinct from prior acetylcholine-biomimetic polymers, PSeD-Ach contains both quaternary ammonium and free acetyl moieties, closely resembling native acetylcholine structure. The polymer structure was confirmed via (1)H nuclear magnetic resonance and Fourier-transform infrared spectroscopy. Hydrophilicity, charge, and thermal properties of PSeD-Ach were determined by tensiometer, zetasizer, differential scanning calorimetry, and thermal gravimetric analysis, respectively. PC12 cells exhibited the greatest proliferation and neurite outgrowth on PSeD-Ach and laminin substrates, with no significant difference between these groups. PSeD-Ach yielded much longer neurite outgrowth than the control polymer containing ammonium but no the acetyl group, confirming the importance of the entire acetylcholine-like moiety. Furthermore, PSeD-Ach supports adhesion of primary rat dorsal root ganglions and subsequent neurite sprouting and extension. The sprouting rate is comparable to the best conditions from previous report. Our findings are significant in that they were obtained with acetylcholine-like functionalities in 100% repeating units, a condition shown to yield significant toxicity in prior publications. Moreover, PSeD-Ach exhibited favorable mechanical and degradation properties for nerve tissue engineering application. Humidified PSeD-Ach had an elastic modulus of 76.9 kPa, close to native neural tissue, and could well recover from cyclic dynamic compression. PSeD-Ach showed a gradual in vitro degradation under physiologic conditions with a mass loss of 60% within 4 weeks. Overall, this simple and versatile synthesis provides a useful tool to produce biomaterials for creating the appropriate stimulatory environment for nerve regeneration.

Click synthesis of quaternized poly(dimethylaminoethyl methacrylate) functionalized graphene oxide with improved antibacterial and antifouling ability

A quaternized poly(dimethylaminoethyl methacrylate) functionalized graphene oxide (GO-QPDMAEMA) was successfully prepared in this study via click chemistry. Alkyne-functionalized graphene oxide (GO-alkyne) was first synthesized through a two-step amidation reaction of GO-COOH. Meanwhile, azide-terminated poly(dimethylaminoethyl methacrylate) (PDMAEMA-N3) was prepared via the atom-transfer radical-polymerization of dimethylaminoethyl methacrylate (DMAEMA). Subsequently, PDMAEMA-N3 was grafted onto the GO-alkyne through click chemistry to obtain PDMAEMA modified graphene oxide (GO-PDMAEMA). Finally, the tertiary amino groups of GO-PDMAEMA were quaternized by ethyl bromide to provide a quaternized poly(dimethylaminoethyl methacrylate) functionalized graphene oxide (GO-QPDMAEMA). Various characterization techniques, including Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis spectrometry, ζ potential, Raman, contact angle analyses and field emission scanning electron microscope were used to ascertain the successful preparation of the quaternized GO-QPDMAEMA. Furthermore, antibacterial and antifouling activities of GO-QPDMAEMA were investigated via protein adsorption, as well as bacterial and cell adhesion studies. The results suggest that the GO-QPDMAEMA surface exhibited significant antibacterial and antifouling properties, compared with the GO-COOH and GO-PDMAEMA surfaces.

A visualized method for Cu2+ ion detection by self-assembling azide functionalized free graphene oxide using click chemistry

We report a visualized method for the detection of Cu²⁺ ions by self-assembling azide functionalized graphene oxide using click chemistry.

Dendritic Polyglycerol Sulfate Inhibits Microglial Activation and Reduces Hippocampal CA1 Dendritic Spine Morphology Deficits

Hyperactivity of microglia and loss of functional circuitry is a common feature of many neurological disorders including those induced or exacerbated by inflammation. Herein, we investigate the response of microglia and changes in hippocampal dendritic postsynaptic spines by dendritic polyglycerol sulfate (dPGS) treatment. Mouse microglia and organotypic hippocampal slices were exposed to dPGS and an inflammogen (lipopolysaccharides). Measurements of intracellular fluorescence and confocal microscopic analyses revealed that dPGS is avidly internalized by microglia but not CA1 pyramidal neurons. Concentration and time-dependent response studies consistently showed no obvious toxicity of dPGS. The adverse effects induced by proinflammogen LPS exposure were reduced and dendritic spine morphology was normalized with the addition of dPGS. This was accompanied by a significant reduction in nitrite and proinflammatory cytokines (TNF-α and IL-6) from hyperactive microglia suggesting normalized circuitry function with dPGS treatment. Collectively, these results suggest that dPGS acts anti-inflammatory, inhibits inflammation-induced degenerative changes in microglia phenotype and rescues dendritic spine morphology.

Fabrication of polymeric biomaterials: a strategy for tissue engineering and medical devices

Fabrication of biomaterials scaffolds using various methods and techniques is discussed, utilising biocompatible, biodegradable and stimuli-responsive polymers and their composites. This review covers the lithography and printing techniques, self-organisation and self-assembly methods for 3D structural scaffolds generation, and smart hydrogels, for tissue regeneration and medical devices.

Biomimetic choline-like graphene oxide composites for neurite sprouting and outgrowth

Neurodegenerative diseases or acute injuries of the nervous system always lead to neuron loss and neurite damage. Thus, the development of effective methods to repair these damaged neurons is necessary. The construction of biomimetic materials with specific physicochemical properties is a promising solution to induce neurite sprouting and guide the regenerating nerve. Herein, we present a simple method for constructing biomimetic graphene oxide (GO) composites by covalently bonding an acetylcholine-like unit (dimethylaminoethyl methacrylate, DMAEMA) or phosphorylcholine-like unit (2-methacryloyloxyethyl phosphorylcholine, MPC) onto GO surfaces to enhance neurite sprouting and outgrowth. The resulting GO composites were characterized by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV-vis spectrometry, scanning electron microscopy, and contact angle analyses. Primary rat hippocampal neurons were used to investigate nerve cell adhesion, spreading, and proliferation on these biomimetic GO composites. GO-DMAEMA and GO-MPC composites provide the desired biomimetic properties for superior biocompatibility without affecting cell viability. At 2 to 7 days after cell seeding was performed, the number of neurites and average neurite length on GO-DMAEMA and GO-MPC composites were significantly enhanced compared with the control GO. In addition, analysis of growth-associate protein-43 (GAP-43) by Western blot showed that GAP-43 expression was greatly improved in biomimetic GO composite groups compared to GO groups, which might promote neurite sprouting and outgrowth. All the results demonstrate the potential of DMAEMA- and MPC-modified GO composites as biomimetic materials for neural interfacing and provide basic information for future biomedical applications of graphene oxide.

Neural differentiation on synthetic scaffold materials

The potential of stem cells to differentiate into a variety of subgroups of neural cells makes stem cell differentiation and transplantation a promising candidate for neurodegenerative disorder therapies. However, selective differentiation of stem cells to neurons while preventing glial scar formation is a complex process. Mimicking the natural environment of neural tissue is pivotal, thus various synthetic materials have been developed for this purpose. The synthetic scaffolds can direct stem cells into a neural lineage by including extracellular factors that act on cell fate, which are mainly soluble signals, extracellular matrix proteins and physical factors (e.g. elasticity and topography). This article reviews synthetic materials developed for neural regeneration in terms of their extracellular matrix mimicking properties. Functionalization of synthetic materials by addition of bioactive chemical groups and adjustment of physical properties such as topography, electroactivity and elasticity are discussed.

Biomimetic polymer brushes containing tethered acetylcholine analogs for protein and hippocampal neuronal cell patterning

This paper describes a method to control neuronal cell adhesion and differentiation with both chemical and topographic cues by using a spatially defined polymer brush pattern. First, biomimetic methacrylate polymer brushes containing tethered neurotransmitter acetylcholine functionalities in the form of dimethylaminoethyl methacrylate or free hydroxyl-terminated poly(ethylene glycol) units were prepared using the "grown from" method through surface-initiated atom transfer radical polymerization reactions. The surface properties of the resulting brushes were thoroughly characterized with various techniques and hippocampal neuronal cell culture on the brush surfaces exhibit cell viability and differentiation comparable to, or even better than, those on commonly used poly-l-lysine coated glass coverslips. The polymer brushes were then patterned via UV photolithography techniques to provide specially designed surface features with different sizes (varying from 2 to 200 μm) and orientations (horizontal and vertical). Protein absorption experiments and hippocampal neuronal cell culture tests on the brush patterns showed that both protein and neurons can adhere to the patterns and therefore be guided by such patterns. These results also demonstrate that, because of their unique chemical composition and well-defined nature, the developed polymer brushes may find many potential applications in cell-material interactions studies and neural tissue engineering.

Synthesis of polyethylene glycol- and sulfobetaine-conjugated zwitterionic poly(L-lactide) and assay of its antifouling properties

A new antifouling polyester monomethoxy-poly(ethylene glycol)-b-poly(L-lactide)-b-poly(sulfobetaine methacrylate) (MPEG-PLA-PSBMA) was obtained by ring-opening polymerization of L-lactide, and subsequent click chemistry to graft the azide end-functionalized poly(sulfobetaine methacrylate) (polySBMA) moieties onto the alkyne end-functionalized MPEG-PLA (MPEG-PLA-alkyne). The chemical structure of the polymer was characterized using (1)H nuclear magnetic resonance and Fourier-transform infrared spectroscopy, and its physical properties (including molecular weight, glass transition temperature, and melting point) were determined using gel permeation chromatography and differential scanning calorimetry. To investigate its hydrophilicity and stability, as well as its antifouling properties, the polymer was also prepared as a surface coating on glass substrates. The wettability and stability of this polyester was examined by contact angle measurements. Furthermore, its antifouling properties were investigated via protein adsorption, cell adhesion studies, and bacterial attachment assays. The results suggest that the prepared zwitterionic polyester exhibits durable wettability and stability, as well as significant antifouling properties. The new zwitterionic polyester MPEG-PLA-PSBMA could be developed as a promising antifouling material with extensive biomedical applications.

The role of hydrogels with tethered acetylcholine functionality on the adhesion and viability of hippocampal neurons and glial cells

In neural tissue engineering, designing materials with the right chemical cues is crucial in providing a permissive microenvironment to encourage and guide neuronal cell attachment and differentiation. Modifying synthetic hydrogels with biologically active molecules has become an increasingly important route in this field to provide a successful biomaterial and cell interaction. This study presents a strategy of using the monomer 2-methacryloxyethyl trimethylammonium chloride (MAETAC) to provide tethered neurotransmitter acetylcholine-like functionality with a complete 2-acetoxy-N,N,N-trimethylethanaminium segment, thereby modifying the properties of commonly used, non-adhesive PEG-based hydrogels. The effect of the functional monomer concentration on the physical properties of the hydrogels was systematically studied, and the resulting hydrogels were also evaluated for mice hippocampal neural cell attachment and growth. Results from this study showed that MAETAC in the hydrogels promotes neuronal cell attachment and differentiation in a concentration-dependent manner, different proportions of MAETAC monomer in the reaction mixture produce hydrogels with different porous structures, swollen states, and mechanical strengths. Growth of mice hippocampal cells cultured on the hydrogels showed differences in number, length of processes and exhibited different survival rates. Our results indicate that chemical composition of the biomaterials is a key factor in neural cell attachment and growth, and integration of the appropriate amount of tethered neurotransmitter functionalities can be a simple and effective way to optimize existing biomaterials for neuronal tissue engineering applications.