The review introduces several methods for fabrication of robust peptide-based hydrogels and their biological applications in the fields of drug delivery and antitumor therapy, antimicrobial and wound healing materials, and 3D bioprinting and tissue engineering.

BackgroundDickeya zeae is the causal agent of maize and rice foot rot diseases, but recently it was also found to infect banana and cause severe losses in China. Strains from different sources showed significant diversity in nature, implying complicated evolution history and pathogenic mechanisms.ResultsD. zeae strains were isolated from soft rot banana plants and ornamental monocotyledonous Clivia miniata. Compared with D. zeae strain EC1 isolated from rice, clivia isolates did not show any antimicrobial activity, produced less extracellular enzymes, had a much narrow host ranges, but released higher amount of extracellular polysaccharides (EPS). In contrast, the banana isolates in general produced more extracellular enzymes and EPS than strain EC1. Furthermore, we provided evidence that the banana D. zeae isolate MS2 produces a new antibiotic/phytotoxin(s), which differs from the zeamine toxins produced by rice pathogen D. zeae strain EC1 genetically and in its antimicrobial potency.ConclusionsThe findings from this study expanded the natural host range of D. zeae and highlighted the genetic and phenotypic divergence of D. zeae strains. Conclusions can be drawn from a series of tests that at least two types of D. zeae strains could cause the soft rot disease of banana, with one producing antimicrobial compound while the other producing none, and the D. zeae clivia strains could only infect monocot hosts. D. zeae strains isolated from different sources have diverse virulence characteristics.Electronic supplementary materialThe online version of this article (10.1186/s12866-018-1300-y) contains supplementary material, which is available to authorized users.

Supramolecular hydrogels self-assembled from short peptides have shown great potential as biomimetic extracellular matrices with controllable properties designed at the molecular level. However, their weak mechanical strength still remains a big challenge for 3D bioprinting. Herein, two oppositely charged dipeptides are designed and used as bioinks in a ″layer-by-layer″ alternative bioprinting strategy. During printing, in situ gelation is achieved by electrostatic interactions between two dipeptides without additional cross-linking procedures. The binary hydrogels have tunable mechanical properties with elastic moduli ranging from 4 to 62 kPa and controllable biodegradability from days to weeks, which can ideally mimic the natural environment of a variety of cell types. It is demonstrated that the hydrogel scaffold enables the formation, growth, and natural release of HepaRG spheroids with sizes up to millimeters. This strategy may be suitable to develop a series of new bioink materials based on peptides and other supramolecular polymers for 3D bioprinting.

Dipeptide self-assembled hydrogels have potential biomedical applications because of their great biocompatibility, bioactivity, and tunable physicochemical properties, which can be modulated in the molecular level by design of amino acid sequences. Herein, a series of dipeptides (Fmoc-FL, -YL, -LL, and -YA) are designed to form shear-thinning hydrogels with self-healing and tunable mechanical properties by adjusting the synergetic effect of hydrophobic interactions (π-π stacking and hydrophobic effect) and hydrogen bonds of peptides through substitution of amino acid residues. The enhancement of hydrophobic interactions is a primary factor to promote mechanical rigidity of hydrogels, and strong hydrogen-bonding interactions between molecules contribute to the instantaneous self-healing property, which is supported by experimental studies (FTIR, CD, SEM, AFM, and rheology) and molecular dynamics simulations. The injectable dipeptide hydrogels were certified as an ideal endoscopic submucosal dissection filler to make operation convenient and secure in mice and living mini-pig’s experiments with a longer duration time, higher stiffness, and lower inflammatory response than commercial clinical fillers.

LbL-assembled tubes were employed for micro/nanoscale cargo transportation through the kinesin-microtubule system. Selectively modified with kinesins onto the inner tube walls through Ni-NTA complexes, these tubes can work as channels for microtubules. A motility assay shows the smooth movement of microtubules along the tube inner wall powered by the inside immobilized kinesins. It could be envisioned that cargoes with different sizes can be transported through these tubular channels with little outside interruption.