Biodegradable arginine-based poly(ester-amide)s as non-viral gene delivery reagents

Recent advances in the development of poly(ester amide)s-based carriers for drug delivery

Biodegradable and biocompatible biomaterials have several important applications in drug delivery. The biomaterial family known as poly(ester amide)s (PEAs) has garnered considerable interest because it exhibits the benefits of both polyester and polyamide, as well as production from readily available raw ingredients and sophisticated synthesis techniques. Specifically, α-amino acid-based PEAs (AA-PEAs) are promising carriers because of their structural flexibility, biocompatibility, and biodegradability. Herein, we summarize the latest applications of PEAs in drug delivery systems, including antitumor, gene therapy, and protein drugs, and discuss the prospects of drug delivery based on PEAs, which provides a reference for designing safe and efficient drug delivery carriers.

Progress in regulating inflammatory biomaterials for intervertebral disc regeneration

Intervertebral disc degeneration (IVDD) is rising worldwide and leading to significant health issues and financial strain for patients. Traditional treatments for IVDD can alleviate pain but do not reverse disease progression, and surgical removal of the damaged disc may be required for advanced disease. The inflammatory microenvironment is a key driver in the development of disc degeneration. Suitable anti-inflammatory substances are critical for controlling inflammation in IVDD. Several treatment options, including glucocorticoids, non-steroidal anti-inflammatory drugs, and biotherapy, are being studied for their potential to reduce inflammation. However, anti-inflammatories often have a short half-life when applied directly and are quickly excreted, thus limiting their therapeutic effects. Biomaterial-based platforms are being explored as anti-inflammation therapeutic strategies for IVDD treatment. This review introduces the pathophysiology of IVDD and discusses anti-inflammatory therapeutics and the components of these unique biomaterial platforms as comprehensive treatment systems. We discuss the strengths, shortcomings, and development prospects for various biomaterials platforms used to modulate the inflammatory microenvironment, thus providing guidance for future breakthroughs in IVDD treatment.

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.

Stimuli-Responsive Polymeric Nanosystems for Controlled Drug Delivery

Biocompatible nanosystems based on polymeric materials are promising drug delivery nanocarrier candidates for antitumor therapy. However, the efficacy is unsatisfying due to nonspecific accumulation and drug release of the nanoparticles in normal tissue. Recently, the nanosystems that can be triggered by tumor-specific stimuli have drawn great interest for drug delivery applications due to their controllable drug release properties. In this review, various polymers and external stimuli that can be employed to develop stimuli-responsive polymeric nanosystems are discussed, and finally, we delineate the challenges in designing this kind of Nanomedicine to improve the therapeutic efficacy.

Application of Non-Viral Vectors in Drug Delivery and Gene Therapy

Vectors and carriers play an indispensable role in gene therapy and drug delivery. Non-viral vectors are widely developed and applied in clinical practice due to their low immunogenicity, good biocompatibility, easy synthesis and modification, and low cost of production. This review summarized a variety of non-viral vectors and carriers including polymers, liposomes, gold nanoparticles, mesoporous silica nanoparticles and carbon nanotubes from the aspects of physicochemical characteristics, synthesis methods, functional modifications, and research applications. Notably, non-viral vectors can enhance the absorption of cargos, prolong the circulation time, improve therapeutic effects, and provide targeted delivery. Additional studies focused on recent innovation of novel synthesis techniques for vector materials. We also elaborated on the problems and future research directions in the development of non-viral vectors, which provided a theoretical basis for their broad applications.

Amino acid derived biopolymers: Recent advances and biomedical applications

Over the past few years, amino acids (AA) have emerged as promising biomaterials for the synthesis of functional polymers. Owing to the diversity of functional groups in amino acids, various polymerization methods may be used to make a wide range of well-defined functional amino-acid/peptide-based optically active polymers with varying polymer lengths, compositions, and designs. When incorporated with chirality and self-assembly, they offer a wide range of applications and are particularly appealing in the field of drug delivery, tissue engineering, and biosensing. There are several classes of these polymers that include polyamides (PA), polyesters (PE), poly(ester-amide)s (PEA)s, polyurethanes (PU)s, poly(depsipeptide)s (PDP)s, etc. They offer the ability to control functionality, conjugation, crosslinking, stimuli responsiveness, and tuneable mechanical/thermal properties. In this review, we present the recent advancements in the synthesis strategies for obtaining these amino acid-derived bio-macromolecules, their self-assembly properties, and the wealth of prevalent applications.

Genetic Delivery and Gene Therapy in Pulmonary Hypertension

Pulmonary hypertension (PH) is a progressive complex fatal disease of multiple etiologies. Hyperproliferation and resistance to apoptosis of vascular cells of intimal, medial, and adventitial layers of pulmonary vessels trigger excessive pulmonary vascular remodeling and vasoconstriction in the course of pulmonary arterial hypertension (PAH), a subgroup of PH. Multiple gene mutation/s or dysregulated gene expression contribute to the pathogenesis of PAH by endorsing the proliferation and promoting the resistance to apoptosis of pulmonary vascular cells. Given the vital role of these cells in PAH progression, the development of safe and efficient-gene therapeutic approaches that lead to restoration or down-regulation of gene expression, generally involved in the etiology of the disease is the need of the hour. Currently, none of the FDA-approved drugs provides a cure against PH, hence innovative tools may offer a novel treatment paradigm for this progressive and lethal disorder by silencing pathological genes, expressing therapeutic proteins, or through gene-editing applications. Here, we review the effectiveness and limitations of the presently available gene therapy approaches for PH. We provide a brief survey of commonly existing and currently applicable gene transfer methods for pulmonary vascular cells in vitro and describe some more recent developments for gene delivery existing in the field of PH in vivo.

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.

PEGylated Polyethylenimine Derivative-Mediated Local Delivery of the shSmad3 Inhibits Intimal Thickening after Vascular Injury

Intimal hyperplasia is a complex process which contributes to several clinical problems such as atherosclerosis and postangioplasty restenosis. Inhibition of Smad3 expression inhibits intimal thickening. Our previous study has modified biscarbamate cross-linked polyethylenimine derivative (PEI-Et) through PEGylation thus obtained polyethylene glycol-graft-polyethylenimine derivative (PEG-Et 1:1), which has lower cytotoxicity and higher gene transfection efficiency compared with PEI-Et. In this study, PEG-Et 1:1 was employed in Smad3 shRNA (shSmad3) delivery for preventing intimal hyperplasia after vascular injury. It was observed that PEG-Et 1:1 could condense shSmad3 gene into nanoparticles with particle size of 115–168 nm and zeta potential of 3–6 mV. PEG-Et 1:1 displayed remarkably lower cytotoxicity, higher transfection efficiency, and shRNA silencing efficiency than PEI-Et and PEI 25 kDa in vascular smooth muscle cells (VSMCs). Moreover, PEG-Et 1:1/shSmad3 polyplex treatment significantly inhibited collagen, matrix metalloproteinase 1 (MMP1), MMP2 and MMP9 expression, and upregulated tissue inhibitor of metalloproteinase 1 (TIMP1) expression both in vitro and in vivo. Furthermore, intravascular delivery of shSmad3 with PEG-Et 1:1 polyplex efficiently reduced Smad3 expression and inhibited intimal thickening 14 days after vascular injury. Ultimately, this study indicated that PEG-Et 1:1-mediated local delivery of shSmad3 is a promising strategy for preventing intimal thickening.

Poly(ester amide) particles for controlled delivery of celecoxib

Many potential pharmacological treatments for osteoarthritis can result in undesirable side effects due to the systemic administration of drugs, making the direct delivery of drugs to joints an attractive alternative. Poly(ester amide)s (PEAs) have been shown to exhibit promising properties for the development of particle-based intra-articular delivery vehicles. However, a limited range of PEA structures has been investigated. In this study, we prepared and characterized the properties of two different PEA particles composed of l-phenylalanine, sebacic acid, and either 1,4-butanediol or 1,8-octanediol (PBSe and POSe, respectively). The anti-inflammatory drug celecoxib (CXB) was encapsulated into the particles. Despite minor structural differences, PBSe and POSe exhibited different thermal and mechanical properties, and encapsulation of CXB influenced these properties. PBSe-CXB particles provided a slower release of drug in vitro relative to POSe-CXB. Toxicity studies showed that particles without drug exhibited low toxicity to ATDC5 and C2C12 cells, while the PBSe-CXB particles exhibited concentration-dependent toxicity. Host response to the particles was evaluated in an ovine model. No adverse effects were observed following intra-articular injection and it was observed that the particles diffused into the surrounding tissues. This work shows the importance of structural tuning in PEA delivery vehicles and demonstrates their potential for further development. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1235-1243, 2019.

Biomimetic Shells Endow Sub-50 nm Nanoparticles with Ultrahigh Paclitaxel Payloads for Specific and Robust Chemotherapy

Poor loading capacity and nonspecific tumor accumulation of current drug delivery system remain the critical challenges that prevent nanomedicine from maximizing therapeutic efficacy in cancer treatment. Herein, poly(ester amide) polymers composed of cationic and hydrophobic segments were formulated with a paclitaxel/human serum albumin (PTX/HSA) complex, as well as free PTX, to construct a core-shell nanoparticle (NP) platform with the interior simultaneously reserving PTX and PTX/HSA complex, while the exterior absorbing the PTX/HSA complex. Following systematic screening, the optimized NPs, namely, APP1i@e NPs, exhibited small particle size (43.95 nm), maximal PTX loading (42.23%), excellent dynamic stability (at least 1 week), and acid-triggered release. In vitro results showed that after being trafficked through caveolae-mediated endocytosis, APP1i@e NPs successfully escaped from endo-/lysosomes and then rapidly released cargos in the acidic cytosol, which continued to enhance cytotoxicity by mitochondrial control of apoptosis and suppression of microtubule dynamics. Longer circulation time and superior targeting efficiency post-intravenous injection confirmed that surface PEGylation imparted APP1i@e NPs with the ability to control their pharmacokinetics and biodistribution. The biomimetic shell design with HSA, which enlarged PTX stock and improved biosafety, made APP1i@e NPs more suitable for in vivo applications. Furthermore, in vivo safety and efficacy demonstrated that APP1i@e NPs effectively inhibited the growth of ovarian xenograft tumors, whereas significantly avoiding toxic issues associated with PTX. APP1i@e NPs with surface PEG coating and biomimetic HSA design, therefore, may provide a remarkable improvement in the therapeutic index of taxanes used in the clinic.

Arginine-based poly(ester amide) nanoparticle platform: From structure-property relationship to nucleic acid delivery

Many different types of polycations have been vigorously studied for nucleic acid delivery, but a systematical investigation of the structure-property relationships of polycations for nucleic acid delivery is still lacking. In this study, a new library of biodegradable and biocompatible arginine-based poly(ester amide) (Arg-PEA) biomaterials was designed and synthesized with a tunable structure for such a comprehensive structure-property research. Nanoparticle (NP) complexes were formed through the electrostatic interactions between the polycationic Arg-PEAs and anionic nucleic acids. The following structure effects of the Arg-PEAs on the transfection efficiency of nucleic acids were investigated: 1) the linker/spacer length (length effect and odd-even effect); 2) salt type of arginine; 3) the side chain; 4) chain stiffness; 5) molecular weight (MW). The data obtained revealed that a slight change in the Arg-PEA structure could finely tune its physicochemical property such as hydrophobicity, and this could subsequently affect the nanoparticle size and zeta potential, which, in turn, regulate the transfection efficiency and silencing outcomes. A further study of the Arg-PEA/CpG oligodeoxynucleotide NP complexes indicated that the polymer structure could precisily regulate the immune response of CpG, thus providing a new potential nano-immunotherapy strategy. The in vitro data have further confirmed that the Arg-PEA NPs showed a satisfactory delivery performance for a variety of nucleic acids. Therefore, the data from the current study provide comprehensive information about the Arg-PEA structure-transfection property relationship; the tunable property of the library of Arg-PEA biomaterials can be one of the promising candidates for nucleic acid delivery and other biomedical applications.

STATEMENT OF SIGNIFICANCE

Polycations have being intensive utilized for nucleic acid delivery. However, there has not been elucidated about the relationship between polycation's structure and the physicochemical properties/biological function. In this timely report, an arginine based poly(ester amide) (Arg-PEA) library was prepared with finely tunable structure to systematically investigate the structure-property relationships of polycations for nucleic acid delivery. The results revealed that slight change of Arg-PEA structure could finely tune the physicochemical property (such as hydrophobicity), which subsequently affect the size and zeta potential of Arg-PEA/nucleic acid nanoparticles(NPs), and finally regulate the resulting transfection or silencing outcomes. Further study of Arg-PEA/CpG NPs indicated that the polymer structure could precisely regulate immuno response of CpG, providing new potential nano-immunotherapy strategy. In vitro evaluations confirmed that the NPs showed satisfied delivery performance for a variety types of nucleic acids. Therefore, these studies provide comprehensive information of Arg-PEA structure-property relationship, and the tunable properties of Arg-PEAs make them promising candidates for nucleic acid delivery and other biomedical applications. Overall, we have shown enough significance and novelty in terms of nucleic acid delivery, biomaterials, pharmaceutical science and nanomedicine.

A comparison of plasmid DNA delivery efficiency and cytotoxicity of two cationic diblock polyoxazoline copolymers

Cationic polymers as non-viral gene delivery carriers are widely used because of their strong condensing properties and long-term safety, but acute cytotoxicity is a persistent challenge. In this study, two types of polyplexes were prepared by co-formulating plasmid DNA and two cationic diblock copolymers PABOXA₅-b-PMOXA₃₃-PA (primary amine) and PABOXA₅-b-PMOXA₃₃-TA (tertiary amine) to check their transfection efficacies in HeLa cells and HEK293T cells, respectively. The plasmid DNA/PABOXA₅-b-PMOXA₃₃-PA polyplex showed higher transfection efficacy compared to the plasmid DNA/PABOXA₅-b-PMOXA₃₃-TA polyplex under an N/P ratio of 40. Both polymers exhibited low toxicity, attributed to the shielding effect of a hydrophilic, noncharged block. Mechanistic insight into differential transfection efficiencies of the polymers were gained by visualization and comparison of the condensates via transmission electron and atomic force microscopy. The results provide information suited for further structure optimization of polymers that are aimed for targeted gene delivery.

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 biodegradable and biologically functional arginine-based poly(ester urea urethane) coating for Mg–Zn–Y–Nd alloy: enhancement in corrosion resistance and biocompatibility

Novel biodegradable and functional Arg-PEUU coating materials for MgZnYNd alloy stents may make drugs like sirolimus or paclitaxel unnecessary.

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.

Poly(ester amide)s with pendant azobenzenes: multi-responsive self-immolative moieties for modulating polymer assemblies

Polymer nanoassemblies containing pendant azobenzenes in their cores were prepared. Light-induced trans–cis isomerization of the azobenzenes increased the polarity of the assembly core, while reduction led to assembly degradation.

Poly(ester amide)s: recent insights into synthesis, stability and biomedical applications

Recent progress in polyesteramides, which are important polymers that can combine the properties of polyesters and polyamides, is described with a focus on synthesis and their application as biomaterials.

Cell penetrating peptide-based polyplexes shelled with polysaccharide to improve stability and gene transfection

Cell-penetrating peptides (CPP) have been widely developed as a strategy to enhance cell penetrating ability and transfection. In this work, octa-arginine modified dextran gene vector with pH-sensitivity was developed via host-guest interactions. α-Cyclodextrin was modified with octa-arginine (CDR), which had excellent cell penetrating ability. Dextran was selected as a backbone and modified with azobenzene as guest units by acid-labile imine bonds (Az-I-Dex). The supramolecular polymer CDR/Az-I-Dex with high a C/A molar ratio (molar ratio of CD on CDR to Az on Az-I-Dex) was unfavorable for DNA condensation. The dextran shell of CDR/Az-I-Dex/DNA polyplexes improved the stability under physiological conditions. However, once treated with acetate buffer (pH 5.4) for 3 h, large aggregates formed rapidly due to the cleavage of the dextran shell. As expected, the vector had cell viability of 80% even when the CDR concentration increased to 100 μg mL(-1). Moreover, due to the effective cellular uptake efficiency, CDR/Az-I-Dex/DNA polyplexes had 6-300 times higher transfection efficiency than CDR/DNA polyplexes. It was even higher than high molecular weight PLL-based polyplexes of HEK293 T cells. Importantly, chloroquine as an endosomal escape agent could not improve the transfection of CDR/Az-I-Dex/DNA polyplexes, which indicated that the CDR/Az-I-Dex supramolecular polymer had its own ability for endosomal escape. These results suggested that the CPP-based polyplexes shelled with polysaccharide can be promising non-viral gene delivery carriers.

A comparison of covalent and noncovalent strategies for paclitaxel release using poly(ester amide) graft copolymer micelles

Micelles formed from amphiphilic copolymers are promising for the delivery of drug molecules, potentially leading to enhanced properties and efficacies. Critical aspects of these systems include the use of biocompatible, biodegradable polymer backbones as well as the ability to control the incorporation of drugs and their release rates. In this work, a poly(ester amide)–poly(ethylene oxide) graft copolymer with paclitaxel conjugated via ester linkages was prepared and assembled into micelles. For comparison, micelles with physically encapsulated paclitaxel were also prepared. The release rates of these two systems were studied, and the micelles with covalently conjugated paclitaxel exhibited a prolonged release of the drug in comparison to the noncovalent system, which rapidly released the payload. In vitro studies suggested that the poly(ester amide)–poly(ethylene oxide) copolymers were nontoxic, whereas the toxicities of the drug-loaded micelles were dependent on their release rates. Overall, these systems are promising for further development as anticancer drug carriers.

A novel pseudo-protein-based biodegradable coating for magnesium substrates: in vitro corrosion phenomena and cytocompatibility

The goal of this study is to examine whether a member of the newly developed biodegradable pseudo-protein biomaterial family could provide a far better protection and performance than the popular hydrolytically degradable poly(glycolide-co-lactide) (PLGA) biomaterial on an experimental magnesium substrate as a model.

Brain-targeted delivery of trans-activating transcriptor-conjugated magnetic PLGA/lipid nanoparticles

Magnetic poly (D,L-lactide-co-glycolide) (PLGA)/lipid nanoparticles (MPLs) were fabricated from PLGA, L-α-phosphatidylethanolamine (DOPE), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-amino (polyethylene glycol) (DSPE-PEG-NH₂), and magnetic nanoparticles (NPs), and then conjugated to trans-activating transcriptor (TAT) peptide. The TAT-MPLs were designed to target the brain by magnetic guidance and TAT conjugation. The drugs hesperidin (HES), naringin (NAR), and glutathione (GSH) were encapsulated in MPLs with drug loading capacity (>10%) and drug encapsulation efficiency (>90%). The therapeutic efficacy of the drug-loaded TAT-MPLs in bEnd.3 cells was compared with that of drug-loaded MPLs. The cells accumulated higher levels of TAT-MPLs than MPLs. In addition, the accumulation of QD-loaded fluorescein isothiocyanate (FITC)-labeled TAT-MPLs in bEnd.3 cells was dose and time dependent. Our results show that TAT-conjugated MPLs may function as an effective drug delivery system that crosses the blood brain barrier to the brain.

Biomimetic L-aspartic acid-derived functional poly(ester amide)s for vascular tissue engineering

Functionalization of polymeric biomaterials permits the conjugation of cell signaling molecules capable of directing cell function. In this study, l-phenylalanine and l-aspartic acid were used to synthesize poly(ester amide)s (PEAs) with pendant carboxylic acid groups through an interfacial polycondensation approach. Human coronary artery smooth muscle cell (HCASMC) attachment, spreading and proliferation was observed on all PEA films. Vinculin expression at the cell periphery suggested that HCASMCs formed focal adhesions on the functional PEAs, while the absence of smooth muscle α-actin (SMαA) expression implied the cells adopted a proliferative phenotype. The PEAs were also electrospun to yield nanoscale three-dimensional (3-D) scaffolds with average fiber diameters ranging from 130 to 294nm. Immunoblotting studies suggested a potential increase in SMαA and calponin expression from HCASMCs cultured on 3-D fibrous scaffolds when compared to 2-D films. X-ray photoelectron spectroscopy and immunofluorescence demonstrated the conjugation of transforming growth factor-β1 to the surface of the functional PEA through the pendant carboxylic acid groups. Taken together, this study demonstrates that PEAs containing aspartic acid are viable biomaterials for further investigation in vascular tissue engineering.

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.

Synthesis, properties and applications of biodegradable polymers derived from diols and dicarboxylic acids: from polyesters to poly(ester amide)s

Poly(alkylene dicarboxylate)s constitute a family of biodegradable polymers with increasing interest for both commodity and speciality applications. Most of these polymers can be prepared from biobased diols and dicarboxylic acids such as 1,4-butanediol, succinic acid and carbohydrates. This review provides a current status report concerning synthesis, biodegradation and applications of a series of polymers that cover a wide range of properties, namely, materials from elastomeric to rigid characteristics that are suitable for applications such as hydrogels, soft tissue engineering, drug delivery systems and liquid crystals. Finally, the incorporation of aromatic units and α-amino acids is considered since stiffness of molecular chains and intermolecular interactions can be drastically changed. In fact, poly(ester amide)s derived from naturally occurring amino acids offer great possibilities as biodegradable materials for biomedical applications which are also extensively discussed.

Gold nanoparticles for nucleic acid delivery

Gold nanoparticles provide an attractive and applicable scaffold for delivery of nucleic acids. In this review, we focus on the use of covalent and noncovalent gold nanoparticle conjugates for applications in gene delivery and RNA-interference technologies. We also discuss challenges in nucleic acid delivery, including endosomal entrapment/escape and active delivery/presentation of nucleic acids in the cell.

Photodegradable poly(ester amide)s for indirect light-triggered release of paclitaxel

A photodegradable poly(ester amide) was developed. An amphiphilic graft copolymer derivative with paclitaxel conjugated via ester linkages formed micelles that released paclitaxel in response to UV light.

Cell compatible arginine containing cationic polymer: one-pot synthesis and preliminary biological assessment

Synthetic cationic polymers are of interest as both nonviral vectors for intracellular gene delivery and antimicrobial agents. For both applications synthetic polymers containing guanidine groups are of special interest since such kind of organic compounds/polymers show a high transfection potential along with antibacterial activity. It is important that the delocalization of the positive charge of the cationic group in guanidine significantly decreases the toxicity compared to the ammonium functionality. One of the most convenient ways for incorporating guanidine groups is the synthesis of polymers composed of the amino acid arginine (Arg) via either application of Arg-based monomers or chemical modification of polymers with derivatives of Arg. It is also important to have biodegradable cationic polymers that will be cleared from the body after their function as transfection or antimicrobial agent is fulfilled. This chapter deals with a two-step/one-pot synthesis of a new biodegradable cationic polymer-poly(ethylene malamide) containing L-arginine methyl ester covalently attached to the macrochains in β-position of the malamide residue via the α-amino group. The goal cationic polymer was synthesized by in situ interaction of arginine methyl ester dihydrochloride with intermediary poly(ethylene epoxy succinimide) formed by polycondensation of di-p-nitrophenyl-trans-epoxy succinate with ethylenediamine. The cell compatibility study with Chinese hamster ovary (CHO) and insect Schneider 2 cells (S2) within the concentration range of 0.02-500 mg/mL revealed that the new polymer is not cytotoxic. It formed nanocomplexes with pDNA (120-180 nm in size) at low polymer/DNA weight ratios (WR = 5-10). A preliminarily transfection efficiency of the Arg-containing new cationic polymer was assessed using CHO, S2, H5, and Sf9 cells.

Comprehensive study of DNA binding on iron (II,III) oxide nanoparticles with a positively charged polyamine three-dimensional coating

Iron (II,III) oxide Fe3O4 nanoparticles (25 and 50 nm NPs) are grafted with amine groups through silanization in order to generate a positively charged coating for binding negatively charged species including DNA molecules. The spatial nature of the coating changes from a 2-D-functionalized surface (monoamines) through a layer of amine oligomers (diethylenetriamine or DETA, about 1 nm in length) to a 3-D layer of polyamine (polyethyleneimine or PEI, thickness ≥3.5 nm). These Fe3O4-PEI NPs were prepared by binding short-chain PEI polymers to the iodopropyl groups grafted on the NP surface. In this work, the surface charge density, or zeta potential, of the nanoparticles is found not to be the only factor influencing the DNA binding capacity, which also seems not to be affected by their buffering capacity profile in the range of pH 4-10. This study also allows the investigation of this 3-D effect on the surface of a nanoparticle as opposed to conventional 2-D amine functionalization. The flexibility of the PEI coating, which consists of only 1, 2, and 3° amines, on the nanoparticle surface has a significant influence on the overall DNA binding capacity and the binding efficiency (or N/P ratio). These polyamine-functionalized nanoparticles can be used in the purification of biomolecules and the delivery of drugs and large biomolecules.

Arginine-based cationic liposomes for efficient in vitro plasmid DNA delivery with low cytotoxicity

Background

Currently available gene delivery vehicles have many limitations such as low gene delivery efficiency and high cytotoxicity. To overcome these drawbacks, we designed and synthesized two cationic lipids comprised of n-tetradecyl alcohol as the hydrophobic moiety, 3-hydrocarbon chain as the spacer, and different counterions (eg, hydrogen chloride [HCl] salt or trifluoroacetic acid [TFA] salt) in the arginine head group.

Methods

Cationic lipids were hydrated in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer to prepare cationic liposomes and characterized in terms of their size, zeta potential, phase transition temperature, and morphology. Lipoplexes were then prepared and characterized in terms of their size and zeta potential in the absence or presence of serum. The morphology of the lipoplexes was determined using transmission electron microscopy and atomic force microscopy. The gene delivery efficiency was evaluated in neuronal cells and HeLa cells and compared with that of lysine-based cationic assemblies and Lipofectamine™ 2000. The cytotoxicity level of the cationic lipids was investigated and compared with that of Lipofectamine™ 2000.

Results

We synthesized arginine-based cationic lipids having different counterions (ie, HCl-salt or TFA-salt) that formed cationic liposomes of around 100 nm in size. In the absence of serum, lipoplexes prepared from the arginine-based cationic liposomes and plasmid (p) DNA formed large aggregates and attained a positive zeta potential. However, in the presence of serum, the lipoplexes were smaller in size and negative in zeta potential. The morphology of the lipoplexes was vesicular. Arginine-based cationic liposomes with HCl-salt showed the highest transfection efficiency in PC-12 cells. However, arginine-based cationic liposomes with TFA salt showed the highest transfection efficiency in HeLa cells, regardless of the presence of serum, with very low associated cytotoxicity.

Conclusion

The gene delivery efficiency of amino acid-based cationic assemblies is influenced by the amino acids (ie, arginine or lysine) present as the hydrophilic head group and their associated counterions.