Regulation of mitochondrial network architecture and function in mesenchymal stem cells by micropatterned surfaces.

Mitochondrial network architecture, which is closely related to mitochondrial function, is mechanically sensitive and regulated by multiple stimuli. However, the effects of microtopographic cues on mitochondria remain poorly defined. Herein, polycaprolactone (PCL) surfaces were used as models to investigate how micropatterns regulate mitochondrial network architecture and function in rat adipose-derived stem cells (rASCs). It was found that large pit (LP)-induced rASCs to form larger and more complex mitochondrial networks. Consistently, the expression of key genes related to mitochondrial dynamics revealed that mitochondrial fusion (MFN1 and MFN2) and midzone fission (DRP1 and MFF) were increased in rASCs on LP. In contrast, the middle pit (MP)-enhanced mitochondrial biogenesis, as evidenced by the larger mitochondrial area and higher expression of PGC-1. Both LP and MP promoted ATP production in rASCs. It is likely that LP increased ATP levels through modulating mitochondrial network architecture while MP stimulated mitochondria biogenesis to do so. Our study clarified the regulation of micropatterned surfaces on mitochondria, highlighting the potential of LP and MP as a simple platform to stimulate mitochondria and the subsequent cellular function of MSCs.

Suppression of LPS-activated inflammatory responses and chromosomal histone modifications in macrophages by micropattern-induced nuclear deformation.

Macrophages are important immune effector cells which participate various physiological and pathological conditions. Numerous studies have demonstrated the regulation of macrophage phenotype by micropatterns. It is well accepted that micropatterns affect cellular behaviors through changing cell shape and modulating the associated mechanical sensors on the plasma membrane and cytoskeleton. However, the role of nucleus, which serves as a critical physical sensing device, is often ignored. Herein, we found the nuclear deformation and the subsequently increased chromosomal histone methylation (H3K36me2) may contribute to the micropattern-induced suppression of macrophage inflammatory responses. Specifically, macrophages on micropatterned surfaces expressed lower levels of key inflammatory genes, compared with those on flat surfaces. Further investigation on macrophage nuclei showed that micropatterned surfaces cause shrinkage of nucleus volume and compaction of chromatin. Moreover, micropatterned surfaces elevated the methylation level of H3K36me2 in macrophages, while decreased the methylation level of H3K4me3. Our study provides new mechanistic insight into how micropatterns affect macrophage phenotype and highlights the importance of nuclear shape and chromatin histone modification in mediating micropattern-induced change in cell behaviors.

Degradation Adaptability Assessment of Semisolid Powder Molded Mg-Zn-Mn Alloys for Orthopedic Applications.

Semisolid powder molding was used to prepare the medical Mg-6Zn alloy; in order to further improve its degradation adaptability, 0.5 and 1 wt % Mn were added. Then, the effect of the forming temperature (540, 560, 580, and 600 °C) on the in vitro degradation behavior of the prepared Mg-6Zn-xMn (x = 0.5, 1 wt %) was analyzed, and the optimized alloy was obtained. Finally, the biocompatibility and in vivo degradation performance of the optimized and Mn-free alloys were evaluated. Importantly, single-photon emission tomographic imaging (SPECT/CT) was first applied to monitor the in vivo degradation process. The results show that the corrosion mechanism of the Mn-free alloy is microgalvanic corrosion control with corrosive pitting. After adding Mn, the in vitro degradation rate decreases by half (0.17 ± 0.01 mm/year) as the forming temperature increases to 600 °C, and Mg-6Zn-1Mn prepared at 600 °C is the optimized alloy. Mn addition improves the corrosion product film protection and discontinuous secondary phases, and thus, the corrosion mechanism is changed to corrosive pitting control. Additionally, semisolid powder molding is an easy method to prepare alloys with low average pore interconnectivity (<10%), which is helpful for slowing down the degradation rate. The Mn-containing alloy has better biocompatibility, with a cytotoxicity of grade 0-1, due to its lower degradation rate. The in vivo corrosion rate of the Mn-free alloy is 0.19 mm/year after 28 days of implantation, which was precisely detected by SPECT/CT in real-time. The long-term in vivo degradation adaptability of Mn-free and Mn-containing alloys was not correctly presented, which may be due to the unreasonable bone defect model causing implant displacement. However, both of these alloys cause no obvious inflammation and show good healing. In summary, semisolid powder molding is a potentially promising technique to prepare medical Mg alloys, and nuclear imaging is an effective in vivo degradation evaluation method.

[Study on Analytical Method of Leachable Substances of Allogeneic Products].

Products made from allogeneic tissue are largely used in clinical treatment due to its wide source compared with autologous tissue, causing less secondary trauma of patients and the good biocompatibility. Various organic solvents and other substances introduced in the production process of allogeneic products will leach down into the human through clinical treatment, thus bringing varying degrees of harm to patients. Therefore, it is very necessary to detect and control the leachables in such products. Based on the classification and summary of leachable substances existing in the allogeneic products, the preparation of extract and the establishment of the detection techniques for known and unknown leachable are briefly introduced in this study, in order to provide research method for the study of leachable substances of allogeneic products.

Fluorescent In Situ 3D Visualization of Dynamic Corrosion Processes of Magnesium Alloys.

Magnesium (Mg) alloys as implant materials with excellent biodegradation ability have promising clinical applications for tissue repair and restoration. Although the corrosion processes of Mg alloys in biophysiological media are closely related with their biodegradation ability, only limited methods have been developed for characterization of their corrosion processes, including electrochemical analysis, weight loss measurement, and hydrogen evolution analysis. Moreover, these methods suffer from drawbacks of poor spatiotemporal resolution, static observation, and tedious operation. To tackle these challenges, we herein developed a fluorescent probe PSPA for in situ 3D monitoring of the dynamic corrosion processes of Mg alloys on the basis of its selective turn-on detection ability toward magnesium hydroxide [Mg(OH)2], which is the main corrosion product of Mg alloys in biophysiological media. As far as we know, this is the first example of a fluorescent probe for the monitoring of corrosion processes of Mg alloys in biophysiological media. We believe this fluorescence analysis method with easy operation and high spatiotemporal resolution advantages will contribute greatly to the clinical applications of Mg alloy implants.

3D-printed bioactive ceramic scaffolds with biomimetic micro/nano-HAp surfaces mediated cell fate and promoted bone augmentation of the bone-implant interface in vivo.

Calcium phosphate bio-ceramics are osteo-conductive, but it remains a challenge to promote the induction of bone augmentation and capillary formation. The surface micro/nano-topography of materials can be recognized by cells and then the cell fate are mediated. Traditional regulation methods of carving surface structures on bio-ceramics employ mineral reagents and organic additives, which might introduce impurity phases and affect the biological results. In a previous study, a facile and novel method was utilized with ultrapure water as the unique reagent for hydrothermal treatment, and a uniform hydroxyapatite (HAp) surface layer was constructed on composite ceramics (ß-TCP/CaSiO3) in situ. Further combined with 3D printing technology, biomimetic hierarchical structure scaffolds were fabricated with interconnected porous composite ceramic scaffolds as the architecture and micro/nano-rod hybrid HAp as the surface layer. The obtained HAp surface layer favoured cell adhesion, alleviated the cytotoxicity of precursor scaffolds, and upregulated the cellular differentiation of mBMSCs and gene expression of HUVECs in vitro. In vivo studies showed that capillary formation, bone augmentation and new bone matrix formation were upregulated after the HAp surface layer was obtained, and the results confirmed that the fabricated biomimetic hierarchical structure scaffold could be an effective candidate for bone regeneration.

Electrical field induce mBMSCs differentiation to osteoblast via protein adsorption enhancement.

Electrical stimulation as a useful and simple method attracts a lot of attention due to its potential to influence cell behaviors. Reports on the change of cell interior structures and membrane under electrical field would be the possible mechanisms. However, changes in cell behavior caused by protein adsorption under different electric field has not been noticed and discussed yet. In this study, a composite hydrogel PDA-GO-PAAM with conductivity of 8.23 × 10-4 S/cm and has similar elastic modulus with pure PAAM was fabricated. It was found that BSA adsorption was higher on composite hydrogel，while electrical stimulation would further enhance BSA adsorption. Cell experiments revealed that electrical stimulation of mBMSCs insignificantly affect cell proliferation, and strongly promoted the expression of cell adhesion factors compared to the unstimulated control. Meanwhile, mBMSCs showed a spreading morphology on composite hydrogel and such spreading became even wider under the electrical stimulation. Under the effect of electrical stimulation, the larger the cell adhesion area was found on the hydrogel, the more the osteoblasts genotype and phenotype expression were, especially under the parameter of 1 V/cm and 1 h. Our results hence illustrate that electrical stimulation regulates osteogenic differentiation of mBMSCs via tuning cell adhesion and cell spreading mediated by protein adsorption.

Complete and rapid degradation of glyphosate with Fe3Ce1Ox catalyst for peroxymonosulfate activation at room temperature.

Glyphosate, a common broad-spectrum herbicide, is a serious environmental pollutant that causes a significant threat to humans. Hence, there is a pressing task to remove glyphosate from the environment. Here, we report an excellent Fe3Ce1Ox catalyst synthesized via the one-step co-precipitation method for activating peroxymonosulfate (PMS) to degrade glyphosate at 25 °C. As a result, glyphosate is completely degraded with a high degradation rate of 400 mg L-1·h-1, and the TOC and TN removals are 85.6% and 80.8%, respectively. As proven by systematic characterizations, the Fe-Ce synergistic effect plays a significant role in promoting PMS activation. The main reactive oxygen species for glyphosate oxidation are surface-bound SO4-· and ·OH, produced by activating PMS by electron transfer between Fe2+/Fe3+ and Ce3+/Ce4+ of Fe3Ce1Ox. In light of the products determined, the possible degradation process of glyphosate is also speculated: C-N and C-P bonds of glyphosate molecules are attacked to form aminomethylphosphonic acid (AMPA) and orthophosphate (PO43-) by surface-bound SO4-· and ·OH that continuously mineralize and dephosphorylate AMPA to generate small molecules and inorganic ions, such as H2O and PO43-. The results of this work suggest that Fe3Ce1Ox/PMS could provide a potential candidate for efficiently removing organic compounds containing nitrogen or phosphorus from wastewater.

Mechanistic insights into the adsorption and bioactivity of fibronectin on surfaces with varying chemistries by a combination of experimental strategies and molecular simulations.

Fibronectin (Fn) is significant to the performance of biomaterials, and the chemistry of biomaterial surface play important roles in Fn adsorption and subsequent cell behavior. However, the "molecular scale" mechanism is still unclear. Herein, we combined experimental strategies with molecular simulations to solve this problem. We prepared self-assembled monolayers with varying chemistries, i.e., SAMs-CH3, SAMs-NH2, SAMs-COOH and SAMs-OH, and characterized Fn adsorption and cell behaviors on them. Next, Monte Carlo method and all-atom molecular dynamics simulations were employed to reveal the orientation/conformation of Fn on surfaces. We found that SAMs-CH3 strongly adsorbed Fn via hydrophobic interactions, but show poor bioactivity as the low exposure of RGD/PHSRN motifs and the deformation of Fn. SAMs-NH2 and SAMs-COOH could adsorb Fn efficiently via vdW interactions, electrostatic interactions, hydrogen bonds and salt bridges. Fn exhibited excellent bioactivity for cell adhesion, proliferation and osteogenic differentiation as high exposure of bioactive motifs on SAMs-NH2, or as the activation of other inferior cell-binding motifs on SAMs-COOH. SAMs-OH showed poor Fn adsorption as the water film. However, the adsorbed Fn displayed non-negligible bioactivity due to high exposure of PHSRN motif and large degree of protein flexibility. We believe that the revealed mechanism presents great potential to rationally design Fn-activating biomaterials.

Controlling the adsorption of osteopontin for mediating cell behaviour by using self-assembled monolayers with varying surface chemistry.

Osteopontin (OPN) is an important protein for mediating cell behaviour on biomaterials. However, the interactions between the chemical groups on the biomaterial surface and OPN still need to be further clarified, which has restricted the application of OPN in biomaterial functionalization. In the present study, we developed different self-assembled monolayers (SAMs) with specific chemical groups, including SAMs-OH, SAMs-OEG, SAMs-COOH, SAMs-NH2, and SAMs-PO3H2, to study the behavior of OPN on these SAMs. The results showed that SAMs-NH2 could strongly adsorb OPN, and the amount of protein was highest on this material. Meanwhile, the lowest amount of OPN was present on SAMs-OEG. Interestingly, the unit-mass trend of bound OPN monoclonal antibodies (mAbs) on the SAMs was opposite to the OPN adsorption trend: lowest on SAMs-NH2 but highest on SAMs-OEG. In vitro cell assay results showed that mouse bone marrow mesenchymal stem cells (mBMSCs) on SAMs-COOH, SAMs-NH2, and SAMs-PO3H2 with pre-adsorbed OPN showed promoted behaviour, in terms of spreading, viability, and the expression levels of αv and ß3 genes, compared with the other two SAMs, demonstrating the higher bioactivity of the adsorbed OPN. We believe that our findings will have great potential for developing OPN-activated biomaterials.

Fusion peptide engineered "statically-versatile" titanium implant simultaneously enhancing anti-infection, vascularization and osseointegration.

Although antimicrobial titanium implants can prevent biomaterial-associated infection (BAI) in orthopedics, they display cytotoxicity and delayed osseointegration. Therefore, versatile implants are desirable for simultaneously inhibiting BAI and promoting osseointegration, especially "statically-versatile" ones with nonessential external stimulations for facilitating applications. Herein, we develop a "statically-versatile" titanium implant by immobilizing an innovative fusion peptide (FP) containing HHC36 antimicrobial sequence and QK angiogenic sequence via sodium borohydride reduction promoted Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC-SB), which shows higher immobilization efficiency than traditional CuAAC with sodium ascorbate reduction (CuAAC-SA). The FP-engineered implant exhibits over 96.8% antimicrobial activity against four types of clinical bacteria (S. aureus, E. coli, P. aeruginosa and methicillin-resistant S. aureus), being stronger than that modified with mixed peptides. This can be mechanistically attributed to the larger bacterial accessible surface area of HHC36 sequence. Notably, the implant can simultaneously enhance cellular proliferation, up-regulate expressions of angiogenesis-related genes/proteins (VEGF and VEGFR-2) of HUVECs and osteogenesis-related genes/proteins (ALP, COL-1, RUNX-2, OPN and OCN) of hBMSCs. In vivo assay with infection and non-infection bone-defect model reveals that the FP-engineered implant can kill 99.63% of S. aureus, and simultaneously promote vascularization and osseointegration. It is believed that this study presents an excellent strategy for developing "statically-versatile" orthopedic implants.

Cholecystokinin-8 attenuates methamphetamine-induced inflammatory activation of microglial cells through CCK2 receptor.

Methamphetamine (METH) exposure reportedly promotes microglial activation and pro-inflammatory cytokines secretion. Sustained inflammation in abusers of psychostimulant drugs further induces neural damage. Cholecystokinin-8 (CCK-8) is a gut-brain peptide which exerts a wide range of biological activities in the gastrointestinal tract and central nervous system. We previously found that pre-treatment with CCK-8 inhibited behavioural and histologic changes typically induced by repeated exposure to METH. Here, we aimed to estimate the effects of CCK-8 on METH-induced neuro-inflammation, which is markedly characterized by microglia activation and increased pro-inflammatory cytokines production in vivo and in vitro. Moreover, we assessed the subtypes of the CCK receptor mediating the regulatory effects of CCK-8, and the changes in the NF-κB signalling pathway. We found that CCK-8 inhibited METH-induced microglial activation and IL-6 and TNF-α generation in vivo and in vitro in a dose-dependent manner. Furthermore, co-treatment of CCK-8 with METH significantly attenuated the activation of the NF-κB signalling pathway by activating the CCK2 receptor subtype in N9 cells. In conclusion, our findings indicated the inhibitory effect of CCK-8 on METH-induced neuro-inflammation in vivo and in vitro, and suggested the underlying mechanism may involve the activation of the CCK2 receptor, which downregulated the NF-κB signalling pathway induced by METH stimulation.

Constructing a Sr2+-Substituted Surface Hydroxyapatite Hexagon-Like Microarray on 3D-Plotted Hydroxyapatite Scaffold to Regulate Osteogenic Differentiation.

Surface topography and chemical characteristics can regulate stem cell proliferation and differentiation, and decrease the bone-healing time. However, the synergetic function of the surface structure and chemical cues in bone-regeneration repair was rarely studied. Herein, a strontium ion (Sr2+)-substituted surface hydroxyapatite (HA) hexagon-like microarray was successfully constructed on 3D-plotted HA porous scaffold through hydrothermal reaction to generate topography and chemical dual cues. The crystal phase of the Sr2+-substituted surface microarray was HA, while the lattice constant of the Sr2+-substituted microarray increased with increasing Sr2+-substituted amount. Sr2+-substituted microarray could achieve the sustainable release of Sr2+, which could effectively promote osteogenic differentiation of human adipose-derived stem cells (ADSCs) even without osteogenic-induced media. Osteogenic characteristics were optimally enhanced using the higher Sr2+-substituted surface microarray (8Sr-HA). Sr2+-substituted microarray on the scaffold surface could future improve the osteogenic performance of HA porous scaffold. These results indicated that the Sr2+-substituted HA surface hexagon-like microarray on 3D-plotted HA scaffolds had promising biological performance for bone-regeneration repair scaffold.

Insight into vitronectin structural evolution on material surface chemistries: The mediation for cell adhesion.

Biomaterial surface chemistry engenders profound consequences on cell adhesion and the ultimate tissue response by adsorbing proteins from extracellular matrix, where vitronectin (Vn) is involved as one of the crucial mediator proteins. Deciphering the adsorption behaviors of Vn in molecular scale provides a useful account of how to design biomaterial surfaces. But the details of structural dynamics and consequential biological effect remain elusive. Herein, both experimental and computational approaches were applied to delineate the conformational and orientational evolution of Vn during adsorption onto self-assembled monolayers (SAMs) terminating with -COOH, -NH2, -CH3 and -OH. To unravel the interplay between cell binding and the charge and wettability of material surface, somatomedin-B (SMB) domain of Vn holding the RGD cell-binding motif was employed in molecular dynamics (MD) simulations, with orientation initialized by Monte Carlo (MC) method. Experimental evidences including protein adsorption, cell adhesion and integrin gene expressions were thoroughly investigated. The adsorption of Vn on different surface chemistries showed very complex profiles. Cell adhesion was enabled on all Vn-adsorbed surfaces but with distinct mechanisms mostly determined by conformational change induced reorientation. Higher amount of Vn was observed on negatively charged surface (COOH) and hydrophobic surface (CH3). However, advantageous orientations defined by RGD loop conditions were only obtained on the charged surfaces (COOH and NH2). Specifically, COOH surface straightened up the Vn molecules and accumulated them into a higher density, whereas CH3 surface squashed Vn and stacked them into higher density multilayer by tracking adsorption but with the RGD loops restrained. These findings may have a broad implication on the understanding of Vn functionality and would help develop new strategies for designing advanced biomaterials.

Cellulose Nanofiber/Carbon Nanotube Dual Network-Enabled Humidity Sensor with High Sensitivity and Durability.

Humidity sensors have been widely used for humidity monitoring in industrial fields, while the unsatisfactory flexibility, time consumption, and expensive integration process of conventional inorganic sensors significantly limit their application in wearable electronics. Using paper-based humidity sensors is considered a feasible method to overcome these drawbacks because of their good flexibility and roll-to-roll manufacturability, while they still face problems such as poor durability and low sensitivity. In this study, we report a high-performance paper-based humidity sensor based on a rationally designed bilayered structure consisting of a nanoporous cellulose nanofiber/carbon nanotube (CNF/CNT) sensitive layer and a microporous paper substrate. The vast number of hydrophilic hydroxyl groups on the surface of CNF and paper fibers enables fast water molecule exchange between the humidity-sensitive material and the external environment via hydrogen bonding, endowing the paper-based sensor with an excellent humidity responsive property. The obtained sensor displays a maximum response value of 65.0% (ΔI/I0) at 95% relative humidity. Furthermore, the mechanical interlocking structure formed between the CNF/CNT layer and the paper layer provides the sensor with strong interlayer adhesion. Benefiting from the unique structure, the sensor also exhibits outstanding bending (with a maximum curvature of 22.2 cm-1) and folding durability (up to 50 times). Finally, as a proof of concept, a simple humidity-measuring device is assembled, which demonstrates an excellent responsive property toward human breath and the change of air humidity, indicating a great potential of our paper-based humidity sensor toward practical applications.

Engineering natural matrices with black phosphorus nanosheets to generate multi-functional therapeutic nanocomposite hydrogels.

Natural polysaccharides and proteins have been widely explored for the preparation of hydrogel matrices due to their promising biocompatibility and biodegradability. However, it is challenging to achieve multiple functions of the hydrophilic matrix through convenient functionalization strategies. Herein we report the facile engineering of a natural matrix with black phosphorus (BP) nanosheets as building blocks to generate a therapeutic nanocomposite hydrogel (BP/Gel) with an array of promising features. BP nanosheets could reinforce the crosslinking networks and significantly promote their capabilities of mineralization. The BP/Gel nanocomposite hydrogel exhibits excellent near infrared (NIR) photothermal performance and good biocompatibility in vitro and in vivo. Upon NIR irradiation, the nanocomposite hydrogel demonstrates efficient photothermal antibacterial features. More remarkably, the BP nanosheet engineered hydrogel matrix is capable of promoting in vitro osteogenesis in the absence of osteoinductive factors, and in the meantime demonstrates significant newborn cranial bone tissue formation in a Sprague-Dawley rat model. These results demonstrate that BP nanosheets could endow the natural matrix with multiple functions including reinforced networks, photothermal performance, enhanced mineralization and bone regeneration, which provides a facile and highly efficient therapeutic strategy for bone tissue engineering.

Over-expression of CCK1 Receptor Reverse Morphine Dependence.

Studies demonstrated that cholecystokinin (CCK) system involved in morphine dependence and withdrawal. Our previous study showed that endogenous CCK system were up-regulated after chronic morphine exposure. Additionally, CCK1 receptor significantly blocked the inhibitory effect of exogenous CCK-8 on morphine dependence, but CCK2 receptor appears to be necessary for low concentrations of endogenous CCK to potentiate morphine dependence. Therefore, CCK1R and CCK2R function differently in chronic morphine dependence, but the mechanism is still unclear. In this study, HEK-293 cells co-transfected with µ-opioid receptors (HEK293-hMOR) and CCK1R or CCK2R were established. Cells were treated with 10 µM morphine for 6, 12, 16, 24 h and 100 µM naloxone precipitation for 15 min. cAMP overshoot was appeared at 12 h and was increased time dependently after morphine exposure in HEK293-hMOR cells. The cAMP overshoot did not appear in CCK1R-overexpressing HEK293-hMOR cells, while still appeared in CCK2R-overexpressing HEK293-hMOR cells. Over-expression of CCK1R reversed CREB and ERK1/2 activation in HEK293-hMOR cells exposed to morphine. Our study identifies over-expression of CCK1R significantly blocked morphine dependence, which was related with phosphorylation of CREB, and ERK1/2 signaling activation. While over-expression of CCK2R promoted morphine dependence, which was related with phosphorylation of CREB but not ERK1/2 signaling activation.

Role of Ninth Type-III Domain of Fibronectin in the Mediation of Cell-Binding Domain Adsorption on Surfaces with Different Chemistries.

The orientation and conformation of adhesive proteins after adsorption play a central role in cell-binding bioactivity. Fibronectin (Fn) holds two peptide sequences that favor cell adhesion: the Arg-Gly-Asp (RGD) loop on the tenth type-III domain (Fn-III10) and the Pro-His-Ser-Arg-Asn (PHSRN) synergy site on the ninth type-III domain (Fn-III9). Herein, adsorption of Fn fragments (Fn-III10 and Fn-III9-10) on self-assembled monolayers (SAMs) carrying various functional groups (-COOH, -NH2, -CH3, and -OH) was investigated by the Monte Carlo method and molecular dynamics simulation in order to understand its mediation effect on cell adhesion. The results demonstrated that Fn-III9 could enhance the stiffness of the Fn molecule and further fix the adsorption orientation. The RGD site of the Fn fragment appeared to be deactivated on hydrophobic surfaces (CH3-SAM) because of the binding of adjacent nonpolar residues on surfaces, whereas charged surfaces (COOH-SAM and NH2-SAM) and hydrophilic surfaces (OH-SAM) were conducive to the formation of cell-binding-favorable orientation for Fn fragments. The cell adhesion capability of Fn fragments was highly improved on positively charged surfaces (NH2-SAM) and hydrophilic surfaces because of the advantageous steric structure and orientation of both RGD and PHSRN sites. This work provides an insight into the interplay at the atomic scale between protein adsorption and surface chemistry for designing biologically responsive substrate surfaces.

A Rapidly Self-Healing Host-Guest Supramolecular Hydrogel with High Mechanical Strength and Excellent Biocompatibility.

It is still a challenge to achieve both excellent mechanical strength and biocompatibility in hydrogels. In this study, we exploited two interactions to form a novel biocompatible, slicing-resistant, and self-healing hydrogel. The first was molecular host-guest recognition between a host (isocyanatoethyl acrylate modified ß-cyclodextrin) and a guest (2-(2-(2-(2-(adamantyl-1-oxy)ethoxy)ethoxy)ethoxy)ethanol acrylate) to form "three-arm" host-guest supramolecules (HGSMs), and the second was covalent bonding between HGSMs (achieved by UV-initiated polymerization) to form strong cross-links in the hydrogel. The host-guest interaction enabled the hydrogel to rapidly self-heal. When it was cut, fresh surfaces were formed with dangling host and guest molecules (due to the breaking of host-guest recognition), which rapidly recognized each other again to heal the hydrogel by recombination of the cut surfaces. The smart hydrogels hold promise for use as biomaterials for soft-tissue repair.

The correlation between osteopontin adsorption and cell adhesion to mixed self-assembled monolayers of varying charges and wettability.

Osteopontin (OPN) is a key mediator of cell interactions with biomaterials. However, few studies have been dedicated to studying cell adhesion on OPN-adsorbed substrates with controlled charge and wettability. Here, amino-carboxyl (NH2/COOH) and hydroxyl-methyl (OH/CH3) mixed self-assembled monolayers (SAMs) of varying charges and wettability, respectively, were used as controllable model surfaces to study OPN adsorption and subsequent mesenchymal stem cell (MSC) adhesion. The amount of OPN adsorbed onto the NH2/COOH mixed SAMs appeared to monotonically depend on the surface charge, whereas only a moderately hydrophilic surface was conducive to OPN adsorption on OH/CH3 mixed SAMs. The results correlated well with cell spreading on OPN-coated surfaces in a serum-free medium culture. In addition, the OH/CH3 mixed SAMs with moderate wettability tended to promote ß1, ß3, αv and α5 integrins, indicating that wettability may guide cell adhesion by mediating the integrins signaling pathway. This work will have reference value for designing biologically responsive substrate surfaces.