Bacterial adhesion and biofilm formation are the primary causes of implant-associated infection, which is difficult to eliminate and may induce failure in dental implants. Chimeric peptides with both binding and antimicrobial motifs may provide a promising alternative to inhibit biofilm formation on titanium surfaces. In this study, chimeric peptides were designed by connecting an antimicrobial motif (JH8194: KRLFRRWQWRMKKY) with a binding motif (minTBP-1: RKLPDA) directly or via flexible/rigid linkers to modify Ti surfaces. We evaluated the binding behavior of peptides using quartz crystal microbalance (QCM) and atomic force microscopy (AFM) techniques and investigated the effect of the modification of titanium surfaces with these peptides on the bioactivity of Streptococcus gordonii (S. gordonii) and Streptococcus sanguis (S. sanguis). Compared with the flexible linker (GGGGS), the rigid linker (PAPAP) significantly increased the adsorption of the chimeric peptide on titanium surfaces (p < 0.05). Concentration-dependent adsorption is consistent with a single Langmuir model, whereas time-dependent adsorption is in line with a two-domain Langmuir model. Additionally, the chimeric peptide with the rigid linker exhibited more effective antimicrobial ability than the peptide with the flexible linker. This finding was ascribed to the ability of the rigid linker to separate functional domains and reduce their interference to the maximum extent. Consequently, the performance of chimeric peptides with specific titanium-binding motifs and antimicrobial motifs against bacteria can be optimized by the proper selection of linkers. This rational design of chimeric peptides provides a promising alternative to inhibit the formation of biofilms on titanium surfaces with the potential to prevent peri-implantitis and peri-implant mucositis.
Infections caused by pathogens colonization at wound sites in the process of bone healing are considered as one of the major reasons for the failure of guided bone regeneration (GBR). The objective of this study was to prepare a novel asymmetric collagen/chitosan GBR membrane containing minocycline-loaded chitosan nanoparticles. The morphologies of the membranes and nanoparticles were observed by SEM and TEM, respectively. The characterization and biocompatibility of the membranes was evaluated. The effect of the membrane on bone regeneration was assessed using the critical-size at cranial defect model. TEM images showed the spherical morphology of the nanoparticles. The results of SEM indicated that the asymmetric membrane contained a dense collagen layer and a loose chitosan layer. An in vitro experiment showed that the membrane can inhibit bacterial growth and promote osteoblasts and fibroblasts growth. The membrane showed the ability to promote angiogenesis and enhance bone regeneration in vivo. An asymmetric collagen/chitosan GBR membrane can be fabricated by loading minocycline encapsulated chitosan nanoparticles, and shows satisfactory biocompatibility and barrier function, which enhances bone regeneration. Therefore, this antibacterial GBR membrane is a promising therapeutic approach to prevent infection and guide bone regeneration.
Reprocessable acrylate vitrimer needs
to enhance its strength to
expand the application in photo-three-dimensional (photo-3D) printing.
However, the methods for improving mechanical properties by the addition
of nanofillers or a multifunctional resin into acrylate vitrimers
are inappropriate for photo-3D printing due to the low curing speed
of photopolymerization induced by weakening light transmittance or
reduction of dimensional accuracy caused by large shrinkage. At present,
we demonstrate a new strategy for developing a kind of mechanically
robust and reprocessable 3D printing thermosets by combining hydrogen
bonds and exchangeable β-hydroxyl esters into acrylate vitrimers.
To realize this purpose, diacrylate prepolymer containing β-hydroxyl
esters was first synthesized from glycidyl methacrylate and suberic
acid. Then, the resin formulations for 3D printing comprising the
synthesized diacrylate prepolymer together with acrylamide generate
exchanged β-hydroxyl ester and pendent amide in cross-linked
networks. Here, hydrogen bonds resulting from the amide group as sacrificial
bonds dissipate vast mechanical energy under an external load. With
the inclusion of 20 wt % acrylamide, the average tensile strength
and Young’s modulus are up to 40.1 and 871 MPa, which increased
by about 4.4 and 3.85 times, respectively. The network rearrangement
of cross-linked vitrimers can be achieved through the dynamic ester
exchange reactions with gradual disappearance of hydrogen bonds at
elevated temperatures, imparting reprocessability into the printed
structures. Various photo-3D printing or UV irradiation shapes were
successfully produced, and these dissolved in ethylene glycol could
be remolded again.
It is of greater significance to
develop amine-cured epoxy vitrimers
than conventional epoxy-carboxylic acid vitrimers because amines are
the most widely curing agents than carboxylic acids. Considering that
the reaction of amines with glycidyl esters can skillfully create
dynamic hydroxyl esters, so we synthesized aliphatic and aromatic
glycidyl esters and then cured them by amine-curing agents containing
disulfide bonds. Here, besides the generated hydroxyl esters, the
dynamic disulfide bonds are also integrated into the cross-linked
network to form dual dynamic vitrimers. The synthesized glycidyl esters
show very high-efficiency curing reactivity due to the lower activation
energy. The properties of dual dynamic vitrimers can be easily tuned
via the proportion of aromatic and aliphatic glycidyl esters to realize
the transition from the rubber state to glass state. Moreover, the
combinations of enhancement and toughening are achieved via the addition
of aromatic glycidyl esters into dual dynamic vitrimers without sacrificing
the curing activity and reprocessing property. Compared with single
dynamic vitrimers, the dual dynamic vitrimers exhibit excellent reprocessing
performances and unique rheological characteristics due to the exchange
reactions of transesterification and disulfide exchange at high temperatures,
which enables them to be reprocessed at 180 °C for only 5 min.
We utilized force tracing to directly record the endocytosis of single gold nanoparticles (Au NPs) with different sizes, revealing the size-dependent endocytosis dynamics and the crucial role of membrane cholesterol. The force, duration and velocity of Au NP invagination are accurately determined at the single-particle and microsecond level unprecedentedly.
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