Synthesis and characterization of a new family of cationic amino acid-based poly(ester amide)s and their biological properties

ROS-Responsive and Self-Tumor Curing Methionine Polymer Library Based Nanoparticles with Self-Accelerated Drug Release and Hydrophobicity/Hydrophilicity Switching Capability for Enhanced Cancer Therapy

The applications of amino acid-based polymers are impeded by their limited structure and functions. Herein, a small library of methionine-based polymers (Met-P) with programmed structure and reactive oxygen species (ROS)-responsive properties is developed for tumor therapy. The Met-P can self-assemble into sub-100 nm nanoparticles (NPs) and effectively load anticancer drugs (such as paclitaxel (PTX) (P@Met-P NPs)) via the nanoprecipitation method. The screened NPs with superior stability and high drug loading are further evaluated in vitro and in vivo. When encountering with ROS, the Met-P polymers will be oxidized and then switch from a hydrophobic to a hydrophilic state, triggering the rapid and self-accelerated release of PTX. The in vivo results indicated that the screened P@2Met10 NPs possessed significant anticancer performance and effectively alleviated the side effects of PTX. More interestingly, the blank 2Met10 NPs displayed an obvious self-tumor inhibiting efficacy. Furthermore, the other Met-P NPs (such as 2Met8, 4Met8, and 4Met10) are also found to exhibit varied self-anti-cancer capabilities. Overall, this ROS-responsive Met-P library is a rare anticancer platform with hydrophobic/hydrophilic switching, controlled drug release, and self-anticancer therapy capability.

Recent Advances of Poly(ester amide)s-Based Biomaterials

Biodegradable and biocompatible biomaterials have offered much more opportunities from an engineering standpoint for treating diseases and maintaining health. Poly(ester amide)s (PEAs), as an outstanding family among such biomaterials, have risen overwhelmingly in the past decades. These synthetic polymers have easily and widely available raw materials and a diversity of synthetic approaches, which have attracted considerable attention. More importantly, combining the superiorities of polyamides and polyesters, PEAs have emerged with better functions. They could have improved biodegradability, biocompatibility, and cell-material interactions. The PEAs derived from α-amino acids even allow the introduction of pendant sites for further modification or functionalization. Meanwhile, it is gradually recognized that the chemical structures are closely related to the physiochemical and biological properties of PEAs so that their properties can be precisely controlled. PEAs therefore become significant materials in the biomedical fields. This review will attempt to summarize the recent progress in the development of PEAs with respect to the preparation materials and methods, structure-property relationships along with their latest biomedical accomplishments, especially for drug delivery and tissue engineering.

Advances and impact of arginine-based materials in wound healing

In studies on wound-dressing materials, bioactive materials have been developed rapidly to accelerate wound healing. In recent years, scientists have studied arginine as a bioactive component due to its excellent biosafety, antimicrobial properties and therapeutic effects on wound healing. Surprisingly, arginine therapy is also used under specific pathological conditions, such as diabetes and trauma/hemorrhagic shock. Due to the broad utilization of arginine-assisted therapy, we present the unique properties of arginine for healing lesions of damaged tissue and examined multiple arginine-based systems for the application of wound healing. This review shows that arginine-based therapy can be separated in two categories: direct supplemental approaches of free arginine, and indirect approaches based on arginine derivatives in which modified arginine can be released after biodegradation. Using these two pathways, arginine-based therapy may prove to be a promising strategy in the development of wound curative treatments.

Progress in arginine-based gene delivery systems

Arginine based gene delivery systems with enhanced membrane penetration and lower cytotoxicity greatly enrich the gene vectors library and outline a new development direction of gene delivery.

Arginine based poly (ester amide)/ hyaluronic acid hybrid hydrogels for bone tissue Engineering

Bone transplantations are still facing many serious challenges, hydrogel as a new kind of artificial bone substitutes has developed into a promising bone scaffold material. However, it is still a challenge to combine bioactive agents and hydrogel matrix to promote osteoinductivity. Herein, we developed a novel bioactive hydrogel based on arginine-based unsaturated poly (ester amide) (Arg-UPEA) and methacrylated hyaluronic acid (HA-MA) via photo-crosslinking. As the results indicated, we found that the introduction of Arg-UPEA into HA-MA hydrogels could finely modulate their compressive modulus, swelling level and porous structure. Besides, among groups of different feed ratio, groups of 10 % and 15 % of Arg-UPEA content effectively enhanced osteogenic differentiation in osteoblasts when compared with HA-MA hydrogel. Furthermore, better bone regeneration and expression of osteogenesis-related factors in vivo also verified the Arg-UPEA/HA-MA hybrid hydrogels as a promising scaffold material for bone tissue engineering.

A light-facilitated drug delivery system from a pseudo-protein/hyaluronic acid nanocomplex with improved anti-tumor effects

Reduction-sensitive nanomedicine is a promising strategy to achieve controlled release of payloads in response to intracellular reductive milieu. However, endolysosomal sequestration of internalized carriers and insufficient redox potential in endolysosomes may delay the release of payloads and impact their therapeutic efficacy. Photochemical internalization (PCI), which takes advantage of light-induced endolysosomal rupture, is an effective technique for endosomal escape and cytosolic release of cargos. In this study, a biodegradable and reduction-sensitive nanocomplex was developed from arginine based poly(ester amide)s and hyaluronic acid (HA), and the PCI-photosensitizer AlPcS2a was conjugated to the surface of the nanocomplex (ArgPEA-ss-HA(AP)). This nanocomplex was used for the co-delivery of both PCI-photosensitizers and therapeutic agents to eliminate the biodistribution discrepancy resulting from the separated administration of free therapeutics. The PCI effect of the ArgPEA-ss-HA(AP) nanocomplex was validated in both monolayers and 3D spheroid models of MDA-MB-231 breast cancer cells. Synergism was detected between the PCI effect and doxorubicin-loaded nanocomplex in the inhibition of MDA-MB-231 cells. In addition, the ArgPEA-ss-HA(AP) nanocomplex also provided enhanced intratumoral penetration in 3D spheroids compared to free AlPcS2a. The in vivo results suggested that the conjugation of AlPCs2a in the nanocomplex enabled the consistent and preferential accumulation of both doxorubicin and AlPcS2a in tumor sites. A light-enhanced anti-tumor effect was observed for the doxorubicin-loaded nanocomplex at well-tolerable dosage. The ArgPEA-ss-HA(AP) nanocomplex, as a reduction-responsive delivery vehicle, can hold great potential to achieve spatio-temporally controllable anti-tumor effects.

Biodegradable amino acid-based poly(ester amine) with tunable immunomodulating properties and their in vitro and in vivo wound healing studies in diabetic rats' wounds

The objective of this study is to design a new family of biodegradable synthetic polymeric biomaterials for providing a tunable inhibition of macrophage's nitric oxide synthase (NOS) pathway. l-Arginine (Arg) is the common substrate for NOS and arginase. Both two metabolic pathways participate in the wound healing process. An impaired wound healing, such as diabetic or other chronic wounds is usually associated with an overproduction of NO by macrophages via the NOS pathway. In this study, a new family of l-nitroarginine (NOArg) based polyester amide (NOArg-PEA) and NOArg-Arg PEA copolymers (co-PEA) were designed and synthesized with different composition ratios. The NOArg-PEA and NOArg-Arg co-PEAs are biodegradable (more than 50% degradation in vitro in 4 days at 37 °C), biocompatible and did not activate the resting macrophage immune response per se. When classically activated or alternatively activated macrophages (CAM/AAM) were incubated with NOArg-PEA and NOArg-Arg co-PEAs, the treatments decreased the NO production of CAM, increased the arginase activity in both CAM and AAM, increased TGF-β1 production of CAM to various degrees and had no significant effect on TNF-α production. Diabetic rat models were used to evaluate the efficacy of NOArg-PEA and NOArg-Arg co-PEAs on wound healing. Diabetic rats treated with 2-NOArg-4 PEA, 2-NOArg-4-Arg-4 20/80, and 2-NOArg-4-Arg-4 50/50 biomaterials achieved 40%-80% faster-wound healing when compared with the control on day 7. The data from the histological and immunohistochemical analysis showed that the 2-NOArg-4-Arg-4 20/80 and 2-NOArg-4-Arg-4 50/50 treatments led to more AAM phenotypes (CD206) and arginase I production in wound tissue than the control during the first 7 days, i.e., suggesting pro-healing wound microenvironment with improved re-epithelialization of wound healing. A similar trend was retained until day 14. The 2-NOArg-4-Arg-4 20/80 and 2-NOArg-4-Arg-4 50/50 treatments also increased the collagen deposition and angiogenesis in the healing wound between day 7 and day 14. Both in vitro and in vivo data of this study showed that this new family of NOArg-Arg co-PEA biomaterials have the potential as viable alternatives for treating impaired wound healing, such as diabetic or other types of chronic wounds. STATEMENT OF SIGNIFICANCE: Diabetic or other chronic wounds is usually associated with an overproduction of NO and pro-inflammatory signals by macrophages. Arginine supplement or NOS inhibitors administration failed to achieve an expected improved wound healing because of the dynamic complexity of arginine catabolism, the difficulty in transition from pro-inflammatory to pro-healing, and the short-term efficacy. We designed and synthesized a new family of water-soluble and degradable nitroarginine-arginine polyester amides to rebalance NOS/arginase metabolism pathways of macrophages. They showed tunable immunomodulating properties in vitro. The in vivo studies were performed to evaluate their efficacy in accelerating the healing. These new biomaterials have the potential as viable alternatives for treating impaired wound healing. The general audience of Acta Biomaterialia should be interested in these findings.

Increased RNAi Efficacy in Spodoptera exigua via the Formulation of dsRNA With Guanylated Polymers

Lepidoptera comprise some of the most devastating herbivorous pest insects worldwide. One of the most promising novel pest control strategies is exploiting the RNA interference (RNAi) mechanism to target essential genes for knockdown and incite toxic effects in the target species without harming other organisms in the ecosystem. However, many insects are refractory to oral RNAi, often due to rapid degradation of ingested dsRNA in their digestive system. This is the case for many lepidopteran insects, including the beet armyworm Spodoptera exigua, which is characterized by a very alkaline gut environment (pH > 9.0) and a strong intestinal nucleolytic activity. In this research, guanidine-containing polymers were developed to protect dsRNA against nucleolytic degradation, specifically in high pH environments. First, their ability to protect dsRNA against nucleolytic degradation in gut juice of the beet armyworm S. exigua was investigated ex vivo. Polymers with high guanidine content provided a strong protection against nucleolytic degradation at pH 11, protecting the dsRNA for up to 30 h. Next, cellular uptake of the dsRNA and the polyplexes in lepidopteran CF203 midgut cells was investigated by confocal microscopy, showing that the polymer also enhanced cellular uptake of the dsRNA. Finally, in vivo feeding RNAi bioassays demonstrated that using these guanidine-containing polymer nanoparticles led to an increased RNAi efficiency in S. exigua. Targeting the essential gene chitin synthase B, we observed that the mortality increased to 53% in the polymer-protected dsRNA treatment compared to only 16% with the naked dsRNA and found that polymer-protected dsRNA completely halted the development of the caterpillars. These results show that using guanylated polymers as a formulation strategy can prevent degradation of dsRNA in the alkaline and strongly nucleolytic gut of lepidopteran insects. Furthermore, the polymer also enhances cellular uptake in lepidopteran midgut cells. This new delivery strategy could be of great use in further fundamental research in lepidopterans, using RNAi as a research tool, and could lead to future applications for RNAi-based pest control of lepidopteran insects.

Enhanced MHC-I antigen presentation from the delivery of ovalbumin by light-facilitated biodegradable poly(ester amide)s nanoparticles

The generation of CD8 T cells is crucial in adaptive immunity against cancer and many infectious diseases. Vaccines aimed to stimulate CD8 T cell response typically become ineffective because the antigens are subject to sequestration in endocytic compartments, instead of being delivered cytosolically for MHC-I processing and presentation. In this study, a nano-carrier (Arg-Phe-PEA(AP) nanoparticles) for ovalbumin (OVA) was developed from arginine- and phenylalanine-based poly(ester amide)s, which further formed an electrostatic complex with AlPcS2a, a typical photosensitizer for photochemical internalization (PCI) strategies. The nanocarrier significantly enhanced the internalization efficiency by dendritic cells of both OVA and AlPcS2a. The photochemical interruption of endocytic compartments by the AlPcS2a photosensitizer complexed in the nanocarrier enabled the light-facilitated endosomal escape of OVA. MHC-I presentation and CD8 T cell response were elicited by OVA-loaded Arg-Phe-PEA(AP) nanoparticles when light irradiation was applied at 660 nm. The light-facilitated delivery of OVA was dependent on the light dose and the concentration of the photosensitizer, both in vitro and in vivo. The optimized stimulation of MHC-I response demonstrated the potency of this light-facilitated nano-platform for CD8 T cell-inducing vaccination.

Biodegradable nanocomplex from hyaluronic acid and arginine based poly(ester amide)s as the delivery vehicles for improved photodynamic therapy of multidrug resistant tumor cells: An in vitro study of the performance of chlorin e6 photosensitizer

Photodynamic therapy (PDT), which enables the localized therapeutic effect by light irradiation, provides an alternative and complementary modality for the treatment of tumor. However, the aggregation of photosensitizers in acidic microenvironment of tumor and the non-targeted distribution of photosensitizers in normal tissues significantly affect the PDT efficiency. In this study, we developed a biodegradable nanocomplex HA-Arg-PEA from hyaluronic acid (HA) and arginine based poly(ester amide)s (Arg-PEA) as the nanocarrier for chlorin e6 (Ce6). HA enhanced the tumor-specific endocytosis mediated by the overexpression of CD44 receptor. Arg-PEA not only provide electrostatic interaction with HA to form self-assembled nanostructure, but also improve the monomerization of Ce6 at physiological pH as well as mildly acidic pH. The biodegradable characteristic of HA-Arg-PEA nanocomplex enabled the intracellular delivery of Ce6, in which its release and generation of singlet oxygen can be accelerated by enzymatic degradation of the carrier. The in vitro PDT efficiency of Ce6-loaded HA-Arg-PEA nanocomplex was examined in CD44 positive MDA-MB-435/MDR multidrug resistant melanoma cells. CD44-mediated uptake of Ce6-loaded HA-Arg-PEA nanocomplex significantly improved Ce6 level in MDA-MB-435/MDR cells within short incubation time, and the PDT efficiency in inhibiting multidrug resistant tumor cells was also enhanced at higher Ce6 concentrations. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1487-1499, 2017.

A Novel Pseudo-Protein-Based Biodegradable Nanomicellar Platform for the Delivery of Anticancer Drugs

Amino acid-based poly(ester amide)s are a new family of biodegradable polymers that exhibit "pseudo-protein" characteristics and the structural varieties of poly(ester amide)s make them hold great potential in multiple biomedical applications. In this study, a lysine-phenylalanine-based pseudo-protein is developed as the self-assembled nanomicellar carrier for efficient delivery of doxorubicin. The lysine moieties from the pseudo-protein provide available sites for further functionalization, and methylcoumarin is introduced for easy and photocontrollable crosslinking, to effectively improve the micellar stability in serum containing environment and against dilution. However, photocrosslinks do not bring in any barrier for the intracellular release of doxoubicin. Doxorubicin release is significantly accelerated by proteolytic enzyme, due to the biodegradability of pseudo-protein micelles. In addition, pseudo-protein delivery system exhibits unique interactions with HCT116 human colon cancer cells. Doxorubicin loaded in pseudo-protein micelles colocalizes with mitochondria and endolysosomes, while free doxorubicin is distributed only in the nuclei. Doxorubicin-loaded pseudo-protein micelles stimulate increased level of intracellular reactive oxygen species and mitochondrial damage. Free doxorubicin induces conditional apoptosis in HCT116 cells between 0.5× 10^-6 and 2 × 10^-6 m, while DOX loaded in pseudo-protein micelles induces apoptosis over a higher/broader concentration range (2 × 10^-6 -10 × 10^-6 m).

Folate-decorated arginine-based poly(ester urea urethane) nanoparticles as carriers for gambogic acid and effect on cancer cells

Gambogic acid (GA) exhibits a broad spectrum of anticancer activity and low chemotoxicity to normal tissues. However, poor aqueous solubility and sensitivity to hydrolysis make its pharmaceutical applications a challenge. Linear and branched Arg-based poly(ester urea urethane)s (Arg-PEUUs), folate (FA)-conjugated Arg PEUUs (FA-Arg-PEUUs), and their self-assembled nanoparticles (NPs) were designed, synthesized, and studied as the potential GA carriers for cancer treatment. The average diameters of linear or branched Arg-PEUU/FA-Arg-PEUU NPs were 98-267 nm. FA-Arg-PEUU NPs adhered onto and were internalized into HeLa and A549 cells, and showed no cytotoxicity. The GA loading efficiency in the NP carriers ranged from 40 to 98%, depending on the feed weight ratio of GA to Arg-PEUU and the Arg-PEUU polymer structure (i.e., linear vs. branched). The GA at 2 µg/mL concentration delivered by the FA-Arg-PEUU NP carriers had higher cytotoxicity and induced a higher apoptosis percentage against folate receptor (FR)-overexpressed HeLa or HCT116 than Arg-PEUU NPs. When compared to the free GA treatment, the GA loaded in the FA-Arg-PEUU NP carriers also led to significant loss of the mitochondrial membrane potential in a higher percentage of the cancer cell population and more DNA fragmentation. The GA loaded in FA-Arg-PEUU NP carriers at as low as 0.6 µg/mL GA concentration led to lower MMP-2 and MMP-9 activity of cancer cells compared to free GA, suggesting that GA-loaded Arg-PEUU NPs may have greater potential to reduce cancer cell invasion and metastasis than free GA. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 475-490, 2017.

Arginine-based polyester amide/polysaccharide hydrogels and their biological response

An advanced family of biodegradable cationic hybrid hydrogels was designed and fabricated from two precursors via a UV photocrosslinking in an aqueous medium: unsaturated arginine (Arg)-based functional poly(ester amide) (Arg-UPEA) and glycidyl methacrylate chitosan (GMA-chitosan). These Arg-UPEA/GMA-chitosan hybrid hydrogels were characterized in terms of their chemical structure, equilibrium swelling ratio (Qeq), compressive modulus, interior morphology and biodegradation properties. Lysozyme effectively accelerated the biodegradation of the hybrid hydrogels. The mixture of both precursors in an aqueous solution showed near non-cytotoxicity toward porcine aortic valve smooth muscle cells at total concentrations up to 6mgml(-1). The live/dead assay data showed that 3T3 fibroblasts were able to attach and grow on the hybrid hydrogel and pure GMA-chitosan hydrogel well. Arg-UPEA/GMA-chitosan hybrid hydrogels activated both TNF-α and NO production by RAW 264.7 macrophages, and the arginase activity was also elevated. The integration of the biodegradable Arg-UPEA into the GMA-chitosan can provide advantages in terms of elevated and balanced NO production and arginase activity that free Arg supplement could not achieve. The hybrid hydrogels may have potential application as a wound healing accelerator.