Density Functional Theory Study of the Interaction of Arginine-Glycine-Aspartic Acid with Graphene, Defective Graphene, and Graphene Oxide

This study investigated the interaction between carbon nanostructures, including pristine graphene, defective graphene with monovacancy, graphene oxide (GO), and tripeptide arginine-glycine-aspartic acid (RGD), by density functional theory. The results from the adsorption energy analysis show that the strongest adsorption is observed when RGD is parallel to graphene surfaces, in which graphene interacts with all three functional groups of RGD, including NH₃⁺, COO^–, and guanidine. The interaction of NH₃⁺···π was stronger than that of guanidine–NH₂···π and COO^–···π. The vacancy improves the ability of graphene to attract RGD because of active dangling C atoms. GO has a stronger interaction with RGD than the pristine and defective graphene because of O-containing groups. The comparison of the GO model with the OH, epoxy, and mixed OH/epoxy groups reveals that various O-containing groups have distinguishing binding abilities with RGD. Water molecules strengthen the interactions between graphene and RGD, whereas they weaken the interaction between GO and RGD. The results provide useful guidance in designing optimal carbon nanomaterial surfaces with specific characteristics that could satisfy the demand for diverse applications of carbon nanomaterials in biomedical fields

High-Strength, Biomimetic Functional Chitosan-Based Hydrogels for Full-Thickness Osteochondral Defect Repair

Fabrication of a hydrogel scaffold for full-thickness osteochondral defect repair remains a grand challenge. Developing layered and multiphasic hydrogels to mimic the intrinsic hierarchical structure of the osteochondral unit is a promising strategy. Chitosan-based hydrogels are widely applied for biomedical applications. However, insufficient mechanical strength and lack of biological cues to restore damaged cartilage and subchondral tissue significantly hinder their application in osteochondral tissue engineering. In this study, a strong and tough, osteochondral-mimicking functional chitosan-based hydrogel (bilayer-gel) with an in situ mineralized, osteoconductive lower layer and a basic fibroblast growth factor (bFGF)-incorporated, chondrogenic inducing upper layer was developed. The obtained bilayer-gel showed a depth-dependent gradient pore structure and composition. The strong double crosslinked hydrogel network and the homogeneous deposition of hydroxyapatite nanoparticles (HAp) at the lower layer provided a compressive strength of up to 2.5 MPa and a compressive strain of up to 40%. In vitro study showed that the bilayer-gel facilitates both chondrogenic differentiation in the upper layer and osteogenic differentiation in the lower layer. In vivo implantation revealed that the bilayer-gel could simultaneously promote hyaline cartilage and subchondral bone formation, thus resulting in an improved osteochondral reconstruction outcome. The present bilayer-gel thus shows great potential for full-thickness osteochondral defect repair

Polydopamine Nanoparticles Modulating Stimuli-Responsive PNIPAM Hydrogels with Cell/Tissue Adhesiveness

Stimuli-responsive hydrogels can respond to stimuli by phase transformation or volume change and exhibit specific functions. Near-infrared (NIR)-responsive hydrogel is a type of stimuli-responsive hydrogel, which can be precisely controlled by altering the radiation intensity, exposure time of the light source, and irradiation sites. Here, polydopamine nanoparticles (PDA-NPs) were introduced into a poly­(<i>N</i>-isopropylacrylamide) (PNIPAM) network to fabricate a PDA-NPs/PNIPAM hydrogel with NIR responsibility, self-healing ability, and cell/tissue adhesiveness. After incorporation of PDA-NPs into the hydrogel, the PDA-NPs/PNIPAM hydrogel showed phase transitions and volume changes in response to NIR. Thus, the hydrogel can achieve triple response effects, including pulsatile drug release, NIR-driven actuation, and NIR-assisted healing. After coating PDA-NPs onto hydrogel surfaces, the hydrogel showed improved cell affinity, good tissue adhesiveness, and growth factor/protein immobilization ability because of reactive catechol groups on PDA-NPs. The tissue adhesion strength to porcine skin was as high as 90 KPa. <i>In vivo</i> full-skin defect experiments demonstrated that PDA-NPs coating on the hydrogel and an immobilized growth factor had a synergistic effect on accelerating wound healing. In summary, we combined thermosensitive PNIPAM and mussel-inspired PDA-NPs to form a NIR-responsive hydrogel, which may have potential applications for chemical and physical therapies

Effect of a combination of Rhizoma Coptidis alkaloids, Radix et Rhizoma Rhei polysaccharides, and Radix Scutellaria flavones (APF) on renal TGF-β1 and its receptor expression.

<p>(a-e) Immunohistochemistry of TGF-β1; (f) Quantitative analysis of immunohistochemical staining of TGF-β1; (g-h) Western blot analysis of TGF-β1 and α-SMA protein levels; (i-j) Real-time RCR analysis of TGF-β1 and TβRⅡmRNA levels. a: db/m, b: db/db, c: APF 300mg/kg, d: 600 mg/kg, e: metformin. Data are expressed as mean ±S.D., n = 3 for Western blot, and n = 5 for Immunohistochemistry and Real-time PCR, *p<0.05, **p<0.01 as compared with db/db group.</p

Effect of a combination of Rhizoma Coptidis alkaloids, Radix et Rhizoma Rhei polysaccharides, and Radix Scutellaria flavones (APF) on renal histopathology and ultrastructural pathology.

<p>(a-e) hematoxylin and eosin (HE) stain. (f-j) Periodic Acid Schiff (PAS) stain. Original magnification (a–j) × 400. (k-o) Electron microscopy (EM) analysis, Representative images of glomerular basement membrane thickening and mesangial matrix expansion, scale bars 2 μm, original magnification electron microscopy × 6000. (p) Ratio of the mesangial matrix area to total glomerular area (M/G) in PAS staining. Data are expressed as mean ± S.D., n = 10, **<i>p</i> < 0.01 as compared with db/db group.</p

Effect of a combination of Rhizoma Coptidis alkaloids, Radix et Rhizoma Rhei polysaccharides, and Radix Scutellaria flavones (APF) on renal fibrosis.

<p>(a-e) Masson’s modified trichrome histological (Masson); (p) Ratio of area with collagen accumulation to total glomerular area; (f-j) Immunohistochemistry of collagen I; (k-o) Immunohistochemistry of collagen IV. Original magnification (a–o) × 400; (q) Quantitative analysis of immunohistochemical staining of collagen I (Col I); (r) glomerular of collagen IV (Col IV); (s) interstitial of collagen IV (Col IV); (t-u) Real-time RCR analysis of collagen I and collagen IV mRNA levels. Data are expressed as mean ±S.D., n = 5, **p<0.01 as compared with db/db group.</p

Effect of a combination of Rhizoma Coptidis alkaloids, Radix et Rhizoma Rhei polysaccharides, and Radix Scutellaria flavones (APF) on renal histopathology and ultrastructural pathology.

<p>(a-e) hematoxylin and eosin (HE) stain. (f-j) Periodic Acid Schiff (PAS) stain. Original magnification (a–j) × 400. (k-o) Electron microscopy (EM) analysis, Representative images of glomerular basement membrane thickening and mesangial matrix expansion, scale bars 2 μm, original magnification electron microscopy × 6000. (p) Ratio of the mesangial matrix area to total glomerular area (M/G) in PAS staining. Data are expressed as mean ± S.D., n = 10, **<i>p</i> < 0.01 as compared with db/db group.</p

Electroactive Hydrogels with Photothermal/Photodynamic Effects for Effective Wound Healing Assisted by Polydopamine-Modified Graphene Oxide

Antibacterial hydrogel wound dressings have attracted considerable attention in recent years. However, bacterial infections can occur at any point during the wound-healing process. There is a demand for hydrogels that possess on-demand antibacterial and excellent wound repair properties. Herein, we report a near-infrared (NIR)-light-responsive indocyanine green (ICG)-loaded polydopamine (PDA)-mediated graphene oxide (PGO) and amorphous calcium phosphate (CaP)-incorporated poly(vinyl alcohol) (PVA) hydrogel using a mussel-inspired approach. PGO was reduced by PDA, which endowed the hydrogel with electroactivity and provided abundant sites for loading ICG. Amorphous CaP was formed in situ in the PVA hydrogel to enhance its mechanical properties and biocompatibility. Taking advantage of the high photothermal and photodynamic efficiency of ICG-PGO, the ICG-PGO-CaP-PVA hydrogel exhibited fascinating on-demand antibacterial activity through NIR light irradiation. Moreover, the thermally induced gel–sol conversion of PVA accelerated the release of Ca ions and allowed the hydrogel to adapt to irregular wounds. Meanwhile, PGO endows the hydrogel with conductivity and cell affinity, which facilitate endogenous electrical signal transfer to control cell behavior. In vitro and in vivo studies demonstrated that the ICG-PGO-CaP-PVA hydrogel exhibited a strong tissue repair activity under NIR light irradiation. This mussel-inspired strategy offers a novel way to design hydrogel dressings for wound healing

DFT Study of the Adsorption of Aspartic Acid on Pure, N-Doped, and Ca-Doped Rutile (110) Surfaces

Understanding the interaction mechanism between titanium oxide surfaces and proteins/peptides/amino acids is crucial to the success of Ti implants. Aspartic acid (abbreviated as Asp or D) is one of the most abundant amino acid in nature. In this study, Dmol3, a quantum mechanics first-principles density functional theory code, was employed to investigate the interaction of Asp with pure, nitrogen-doped, and calcium-doped rutile (R(110)) surfaces. The effect of water on the interaction was also studied. The adsorption energy analysis demonstrated that the strongest adsorption happened when both the amino and carboxyl groups of Asp approached the R(110) surfaces and formed a bidentate coordination to two surface Ti atoms. Hydrogen bonds from the H atoms of Asp and bridging-O atoms on the surface also contributed to the adsorption. Water hindered the Asp adsorption. N-doping and Ca-doping were not beneficial to Asp adsorption. The results imply that we may realize selective protein/peptide/amino acid adsorption on materials and determine the adsorption of specific biomolecules by an elaborately designed ion doping process. Our results could have potential impact on the design of effective material surface treatments for biomedical applications