Well-defined star (co)polypeptides via a fast, efficient, and metal-free strategy

Polypeptides, especially star polypeptides, as a unique kind of biological macromolecules have broad applications in biomedical fields such as drug release, gene delivery, tissue engineering, and regenerative medicines due to their close structural similarity to naturally occurring peptides and proteins, biocompatibility, and amino acid functionality. However, the synthesis of star polypeptide mainly relies on the conventional primary amine-initiated ring-opening polymerization (ROP) of N-carboxyanhydrides (NCA) and suffers from low polymerization activity and limited controllability. This study proposes a fast, efficient and metal-free strategy to access star (co)polypeptides by combining the Michael reaction between acrylates and secondary aminoalcohols with the hydrogen-bonding organocatalytic ROP of NCA. This approach enables the preparation of a library of star (co)polypeptides with predesigned molecular weights, narrow molecular weight distributions, tunable arm number, and arm compositions. Importantly, this method exhibits high activity and selectivity at room temperature, making it both practical and versatile in synthesis applications.

Bone adhesive materials: From bench to bedside

Biodegradable bone adhesives represent a highly sought-after type of biomaterial which would enable replacement of traditional metallic devices for fixation of bone. However, these biomaterials should fulfil an extremely large number of requirements. As a consequence, bone-adhesive biomaterials which meet all of these requirements are not yet commercially available. Therefore, this comprehensive review provides an extensive overview of the development of bone adhesives from a translational perspective. First, the definition, classification, and chemistry of various types of bone adhesives are highlighted to provide a detailed overview of this emerging class of biomaterials. In this review we particularly focused studies which describe the use of materials that are capable of gluing two pieces of bone together within a time frame of minutes to days. Second, this review critically reflects on i) the experimental conditions of commonly employed adhesion tests to assess bone adhesion and ii) the current state-of-the-art regarding their preclinical and clinical applicability.

Synthesis and Hydrogelation of Star-Shaped Graft Copolypetides with Asymmetric Topology

To study the self-assembly and hydrogel formation of the star-shaped graft copolypeptides with asymmetric topology, star-shaped poly(_L-lysine) with various arm numbers were synthesized by using asymmetric polyglycerol dendrimers (PGDs) as the initiators and 1,1,3,3-tetramethylguanidine (TMG) as an activator for OH groups, followed by deprotection and grafting with indole or phenyl group on the side chain. The packing of the grafting moiety via non-covalent interactions not only facilitated the polypeptide segments to adopt more ordered conformations but also triggered the spontaneous hydrogelation. The hydrogelation ability was found to be correlated with polypeptide composition and topology. The star-shaped polypeptides with asymmetric topology exhibited poorer hydrogelation ability than those with symmetric topology due to the less efficient packing of the grafted moiety. The star-shaped polypeptides grafted with indole group on the side chain exhibited better hydrogelation ability than those grafted with phenyl group with the same arm number. This report demonstrated that the grafted moiety and polypeptide topology possessed the potential ability to modulate the polypeptide hydrogelation and hydrogel characteristics.

Study on hemostatic effect and mechanism of starch-based nano-microporous particles

The powdered hemostatic particles have broad application prospects in large open wounds, internal organ injuries and penetrating injuries of the body. In this study, nanoscale mescoporous and macroporous silica (MMSN), nanoscale mescoporous and macroporous bioactive glass (MBG), micron-scale cross-linked corn starch porous microspheres (CMS), MMSN@CMS and MBG@CMS starch-based nano-microporous particles were synthesized and their hemostatic effect and hemostatic mechanism were studied. The results showed that comparted with the single particle of CMS, the combination particles MBG@CMS and MMSN@CMS significantly increased the water absorption rate, activated both internal and external coagulation pathways, significantly shortened CBT, as well as the improved hemostatic effects in vitro. The immediately released Ca²⁺ from MBG@CMS in the blood to participate in the coagulation pathway, and MMSN@CMS activated platelets by concentrating blood coagulation factors, might be the main hemostatic mechanisms for the starch-based nano-microporous particles. Furthermore, the hemostatic efficacy of particles, both in the model of tail-amputation and liver injury in SD rats, showed the starch-based nano-microporous particles, especial MBG@CMS, could significantly reduce the weight of blood loss and shorten the bleeding time. Our research work stated that the starch-based nano-microporous particles MBG@CMS might be a hemostasis biomaterial with the potential applications for the emergency bleeding.

Tumor Noninvasive and Target Embolization Therapy Platform by Intravenous Injection Based on Acidic Microenvironment-Responsive Hyperbranched Poly(amino acid)s

Transcatheter arterial embolization (TAE) has been widely applied in treatments of unresectable or hypervascular tumors, but the procedure of TAE is complicated possibly brings inherent risks. Here, inspired by pH-responsive drug delivery systems, a new method of noninvasive and target embolization therapy by intravenous injection was developed. This method is based on a type of acidic microenvironment-responsive hyperbranched poly(amino acid) (HPTTG) to avoid using catheterization and real-time image guidance angiography, simplifying the procedure, elevating compliance and general applicability of embolization therapy. The pH value of the sol-to-gel phase transition with decreasing pH of HPTTG was controlled by adjusting the ratio of acidic amino acids in copolymers. The results of the tumor-bearing animal experiment indicate that the HPTTG have an excellent target and embolic ability; they accumulate the most at the tumor site in 8 h postinjection. Blood vessels of the tumors were occluded, and the tumors were inhibited and necrotized in about 20 days. Therefore, it is expected that HPTTG not only can be used as novel embolic materials for efficient noninvasive embolization therapy of many solid tumors but also can be used as a multifunctional platform for combined theranostics, for example, combination with controlled release, thermal ablation, multimodal imaging, synergistic therapy, etc.

Ring opening polymerization of α-amino acids: advances in synthesis, architecture and applications of polypeptides and their hybrids

This review provides a comprehensive overview of the latest advances in the synthesis, architectural design and biomedical applications of polypeptides and their hybrids.

Research status and development potential of composite hemostatic materials

Through the discussion of the coagulation mechanism of compositehemostatic materials, the future development potential of hemostatic materials is proposed.