An Inspection into Multifarious Ways to Synthesize Poly(Amino Acid)s

Engineered protein-based materials for tissue repair: A review

The human body may suffer multiple injuries and losses due to various external factors, such as tumors, diseases, traffic accidents, and war conflicts. Under such circumstances, engineered protein-based materials, as an innovative adjunctive material, can not only effectively promote the natural repair process of tissues, but also greatly circumvent the negative effects and complications that may be associated with conventional surgery. In this review, we first trace the definition and development of engineered protein-based materials and explain in detail their mechanism of action in promoting tissue repair. Subsequently, the advantages and disadvantages of various engineered protein-based materials in tissue repair are analyzed by comparison. In addition, the present review reveals in depth how material properties can be optimized by scientific means to meet different tissue repair needs. In addition, we present in detail specific application cases of engineered protein-based materials in the field of tissue repair. Finally, we summarize current challenges in engineered protein-based materials and provide an outlook for the future. This review not only provides theoretical support for the further exploration and development of engineered protein-based materials in the field of tissue repair, but also provides valuable references and inspiration for research in related fields.

3D-Printed Polymeric Biomaterials for Health Applications

3D printing, also known as additive manufacturing, holds immense potential for rapid prototyping and customized production of functional health-related devices. With advancements in polymer chemistry and biomedical engineering, polymeric biomaterials have become integral to 3D-printed biomedical applications. However, there still exists a bottleneck in the compatibility of polymeric biomaterials with different 3D printing methods, as well as intrinsic challenges such as limited printing resolution and rates. Therefore, this review aims to introduce the current state-of-the-art in 3D-printed functional polymeric health-related devices. It begins with an overview of the landscape of 3D printing techniques, followed by an examination of commonly used polymeric biomaterials. Subsequently, examples of 3D-printed biomedical devices are provided and classified into categories such as biosensors, bioactuators, soft robotics, energy storage systems, self-powered devices, and data science in bioplotting. The emphasis is on exploring the current capabilities of 3D printing in manufacturing polymeric biomaterials into desired geometries that facilitate device functionality and studying the reasons for material choice. Finally, an outlook with challenges and possible improvements in the near future is presented, projecting the contribution of general 3D printing and polymeric biomaterials in the field of healthcare.

Bioactive poly(amino acid)s for multi-modal cancer therapy

The interplay between the tumor cells and their microenvironments is as inseparable as the relationship between "seeds" and "soil." The tumor microenvironments (TMEs) exacerbate malignancy by enriching malignant cell subclones, generating extracellular matrices, and recruiting immunosuppressive cells, thereby diminishing the efficacy of clinical therapies. Modulating TMEs has emerged as a promising strategy to enhance cancer therapy. However, the existing drugs used in clinical settings do not target the TMEs specifically, underscoring the urgent need for advanced strategies. Bioactive materials present unique opportunities for modulating TMEs. Poly(amino acid)s with precisely controllable structures and properties offer exceptional characteristics, such as diverse structural units, excellent biosafety, ease of modification, sensitive biological responsiveness, and unique secondary structures. These attributes hold significant potential for the modulation of TMEs and clinical applications further. Consequently, developing bioactive poly(amino acid)s capable of modulating the TMEs by elucidating structure-activity relationships and mechanisms is a promising approach for innovative clinical oncology therapy. This review summarizes the recent progress of our research team in developing bioactive poly(amino acid)s for multi-modal tumor therapy. First, a brief overview of poly(amino acid) synthesis and their advantages as nanocarriers is provided. Subsequently, the pioneering research of our research group on synthesizing the biologically responsive, dynamically allosteric, and immunologically effective poly(amino acid)s are highlighted. These poly(amino acid)s are designed to enhance tumor therapy by modulating the intracellular, extracellular matrix, and stromal cell microenvironments. Finally, the future development of poly(amino acid)s is discussed. This review will guide and inspire the construction of bioactive poly(amino acid)s with promising clinical applications in cancer therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Peptide-Based Structures.

Facile Synthesis of High Molecular Weight Poly(ethylene glycol)-b-poly(amino acid)s by Relay Polymerization

Poly(amino acid)s (PAAs) are one kind of favorable biopolymer that can be used as a drug or gene carrier. However, conventional ring-opening polymerization of PAAs is slow and needs a strict anhydrous environment with an anhydrous reagent as well as the product without enough high molecular weight (Mn), which limits the expanding of PAAs' application. Herein, we took BLG-NCA as the monomer to quickly synthesize one kind of high Mn amphiphilic copolymer, poly(ethylene glycol)-b-poly(γ-benzyl-l-glutamic acid) (PEG-PBLG), by relay polymerization with a simple one-pot method within 3 h in mild conditions (open air, moisture insensitive). In the polymerization process, ring-opening polymerization-induced self-assembly in sodium bicarbonate aqueous solution first occurred to obtain low Mn PEG-PBLG seeds without purification. Then γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA) dichloromethane solution was added into PEG-PBLG seeds directly and stirred vigorously to form am emulsion; during this process, the amphiphilic PEG-PBLG seeds will anchor on the interface of DCM and water to ensure the concentration of α-helix rigid PBLG in DCM to maintain the following relay polymerization. Then, high Mn PEG-PBLG was obtained in mild conditions in one pot. We found that the α-helix rigid structure was essential for relay polymerization by studying the synthetic speed of amphiphilic copolymer with different secondary structures. MOE simulation results showed that PBLG and BLG-NCA tended to form a double hydrogen bond, which was beneficial to relay polymerization because of higher local concentrations that can produce more double hydrogen bonds. Our strategy can quickly obtain high Mn PEG-PBLG (224.9 KDa) within 3 h from PEG-NH2 and BLG-NCA in one pot and did not need an extra initiator. After deprotection, the poly(ethylene glycol)-b-poly(l-glutamate acid) (PEG-PGA) with high Mn as a second product can be used as an excellent antitumor drug carrier. The high Mn PEG-PGA can achieve an encapsulation rate of 86.7% and a drug loading rate of 47.3%, which is twice that of the low Mn PEG-PGA. As a result, the synthesis of PEG-PBLG by relay polymerization simplified the process of PEG-PAA polymerization and increased the Mn. In addition, this method opened a way to obtain other kinds of high Mn PEG-PBLG values in the future.

Self-Assembly of Poly(Amino Acid)s Mediated by Secondary Conformations

Self-assembly of block copolymers has recently drawn great attention due to its remarkable performance and wide variety of applications in biomedicine, biomaterials, microelectronics, photoelectric materials, catalysts, etc. Poly(amino acid)s (PAAs), formed by introducing synthetic amino acids into copolymer backbones, are able to fold into different secondary conformations when compared with traditional amphiphilic copolymers. Apart from changing the chemical composition and degree of polymerization of copolymers, the self-assembly behaviors of PAAs could be controlled by their secondary conformations, which are more flexible and adjustable for fine structure tailoring. In this article, we summarize the latest findings on the variables that influence secondary conformations, in particular the regulation of order-to-order conformational changes and the approaches used to manage the self-assembly behaviors of PAAs. These strategies include controlling pH, redox reactions, coordination, light, temperature, and so on. Hopefully, we can provide valuable perspectives that will be useful for the future development and use of synthetic PAAs.

Syntheses of Polypeptides and Their Biomedical Application for Anti-Tumor Drug Delivery

Polypeptides have attracted considerable attention in recent decades due to their inherent biodegradability and biocompatibility. This mini-review focuses on various ways to synthesize polypeptides, as well as on their biomedical applications as anti-tumor drug carriers over the past five years. Various approaches to preparing polypeptides are summarized, including solid phase peptide synthesis, recombinant DNA techniques, and the polymerization of activated amino acid monomers. More details on the polymerization of specifically activated amino acid monomers, such as amino acid N-carboxyanhydrides (NCAs), amino acid N-thiocarboxyanhydrides (NTAs), and N-phenoxycarbonyl amino acids (NPCs), are introduced. Some stimuli-responsive polypeptide-based drug delivery systems that can undergo different transitions, including stability, surface, and size transition, to realize a better anti-tumor effect, are elaborated upon. Finally, the challenges and opportunities in this field are briefly discussed.

Biodegradable Polysarcosine with Inserted Alanine Residues: Synthesis and Enzymolysis

Polysarcosine (PSar), a water-soluble polypeptoid, is gifted with biodegradability via the random ring-opening copolymerization of sarcosine- and alanine-N-thiocarboxyanhydrides catalyzed by acetic acid in controlled manners. Kinetic investigation reveals the copolymerization behavior of the two monomers. The random copolymers, named PaS, with high molecular weights between 5.3 and 43.6 kg/mol and tunable Ala molar fractions varying from 6 to 43% can be degraded by porcine pancreatic elastase within 50 days under mild conditions (pH = 8.0 at 37 °C). Both the biodegradation rate and water solubility of PaS depend on the content of Ala residues. PaS with Ala fractions below 43% are soluble in water, while the one with 43% Ala self-assembles in water into nanoparticles. Moreover, PaS are noncytotoxic at the concentration of 5 mg/mL. The biodegradability and biocompatibility endow the Ala-containing PSar with the potential to replace poly(ethylene glycol) as a protective shield in drug-delivery.

Micro- and Nanocapsules Based on Artificial Peptides

The encapsulation of active ingredients into solid capsules from biodegradable materials has received significant attention over the last decades. In this short review, we focus on the formation of micro- and nano-sized capsules and emulsions based on artificial peptides as a fully degradable material. It deals with various approaches for the preparation of peptide-based capsules as well as with their crucial properties such as size and stability. We categorize all preparation procedures into three basic approaches: self-assembly, polymerization and crosslinking, and layer-by-layer technology. This article is meant to offer a short overview over all successful methods suitable for obtaining access to these very promising carrier systems.

PiPo: random copolymers of C- with N-substituted glycines

This letter introduces a method to obtain PiPo by the copolymerization of N-phenyloxycarbonyl-amino acids initiated by primary amine. The obtained PiPo have adjustable solubility in water and organic solvents to assemble into nanoparticles.