Improved Synthesis with High Yield and Increased Molecular Weight of Poly(α,β-malic acid) by Direct Polycondensation

Amino acid analogues provide multiple plausible pathways to prebiotic peptides

Prebiotic peptide synthesis has consistently been a prominent topic within the field of the origin of life. While research predominantly centres on the 20 classical amino acids, the synthesis process encounters significant thermodynamic barriers. Consequently, amino acid analogues are being explored as potential building blocks for prebiotic peptide synthesis. This review delves into the pathway of polypeptide formation, identifying specific amino acid analogues that might have existed on early Earth, potentially participating in peptide synthesis and chemical evolution. Moreover, considering the complexity and variability of the environment on early Earth, we propose the plausibility of coevolution between amino acids and their analogues.

Polymalic acid for translational nanomedicine

With rich carboxyl groups in the side chain, biodegradable polymalic acid (PMLA) is an ideal delivery platform for multifunctional purposes, including imaging diagnosis and targeting therapy. This polymeric material can be obtained via chemical synthesis, or biological production where L-malic acids are polymerized in the presence of PMLA synthetase inside a variety of microorganisms. Fermentative methods have been employed to produce PMLAs from biological sources, and analytical assessments have been established to characterize this natural biopolymer. Further functionalized, PMLA serves as a versatile carrier of pharmaceutically active molecules at nano scale. In this review, we first delineate biosynthesis of PMLA in different microorganisms and compare with its chemical synthesis. We then introduce the biodegradation mechanism PMLA, its upscaled bioproduction together with characterization. After discussing advantages and disadvantages of PMLA as a suitable delivery carrier, and strategies used to functionalize PMLA for disease diagnosis and therapy, we finally summarize the current challenges in the biomedical applications of PMLA and envisage the future role of PMLA in clinical nanomedicine.

The biosynthesis of polymalic acid (PMLA) and its biotechnical high-grade production from microorganisms compared with the chemical synthesis of PMLA

The physicochemical and biological characteristics of PMLA and its derivatives

How PMLA’s general chemical characteristics can be used to generate various macromolecular compounds for pharmaceutical delivery

The concepts of biological and clinical targeting exemplified by PMLA-based drugs and imaging agents and their biodistribution and biodegradability

An evaluation of the mechanisms that generate preclinical antitumor efficacy and the translational potential for clinical imaging

Valorization of a Pyrolytic Aqueous Condensate and Its Main Components for L-Malic Acid Production with Aspergillus oryzae DSM 1863

Pyrolytic aqueous condensate (PAC) might serve as a cost-effective substrate for microbial malic acid production, as it is an unused side stream of the fast pyrolysis of lignocellulosic biomass that contains acetol and acetate as potential carbon sources. In the present study, shake flask cultures were performed to evaluate the suitability of acetol and its combination with acetate as substrates for growth and L-malate production with the filamentous fungus Aspergillus oryzae. Acetol concentrations of up to 40 g/L were shown to be utilized for fungal growth. In combination with acetate, co-metabolization of both substrates for biomass and malate formation was observed, although the maximum tolerated acetol concentration decreased to 20 g/L. Furthermore, malate production on PAC detoxified by a combination of rotary evaporation, overliming and activated carbon treatment was studied. In shake flasks, cultivation using 100% PAC resulted in the production of 3.37 ± 0.61 g/L malate, which was considerably improved by pH adjustment up to 9.77 ± 0.55 g/L. A successful scale-up to 0.5-L bioreactors was conducted, achieving comparable yields and productivities to the shake flask cultures. Accordingly, fungal malate production using PAC was successfully demonstrated, paving the way for a bio-based production of the acid.

Improved Synthesis of a Novel Biodegradable Tunable Micellar Polymer Based on Partially Hydrogenated Poly(β-malic Acid-co-benzyl Malate)

Poly(benzyl malate) (PBM), together with its derivatives, have been studied as nanocarriers for biomedical applications due to their superior biocompatibility and biodegradability. The acquisition of PBM is primarily from chemical routes, which could offer polymer-controlled molecular weight and a unique controllable morphology. Nowadays, the frequently used synthesis from L-aspartic acid gives an overall yield of 4.5%. In this work, a novel synthesis route with malic acid as the initiator was successfully designed and optimized, increasing the reaction yield up to 31.2%. Furthermore, a crystalline form of PBM (PBM-2) that polymerized from high optical purity benzyl-β-malolactonate (MLABn) was discovered during the optimization process. X-ray diffraction (XRD) patterns revealed that the crystalline PBM-2 had obvious diffraction peaks, demonstrating that its internal atoms were arranged in a more orderly manner and were different from the amorphous PBM-1 prepared from the racemic MLABn. The differential scanning calorimetry (DSC) curves and thermogravimetric curves elucidated the diverse thermal behaviors between PBM-1 and PBM-2. The degradation curves and scanning electron microscopy (SEM) images further demonstrated the biodegradability of PBM, which have different crystal structures. The hardness of PBM-2 implied the potential application in bone regeneration, while it resulted in the reduction of solubility when compared with PBM-1, which made it difficult to be dissolved and hydrogenated. The solution was therefore heated up to 75 °C to achieve benzyl deprotection, and a series of partially hydrogenated PBM was sequent prepared. Their optimal hydrogenation rates were screened to determine the optimal conditions for the formation of micelles suitable for drug-carrier applications. In summary, the synthesis route from malic acid facilitated the production of PBM for a shorter time and with a higher yield. The biodegradability, biosafety, mechanical properties, and adjustable hydrogenation widen the application of PBM with tunable properties as drug carriers.

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.

Pyrazinoic acid-Poly(malic acid) biodegradable nanoconjugate for efficient intracellular delivery

Tuberculosis is an infectious disease affecting mostly lungs, that is still considered a health global problem as it causes millions of deaths worldwide. Current treatment is effective but associated with severe adverse effects due to the high doses of each anti-tuberculosis drug daily administrated by oral therapy. For the first time, a pyrazinoic acid (PA) biodegradable nanoconjugate was synthesized and developed for pulmonary administration in an attempt to reduce the administered doses by achieving a high drug payload and controlled release at the target site. The conjugate was synthesized by coupling pyrazinoic acid on carboxylic groups of poly(malic acid), which is a biodegradable and biocompatible polymer, and posteriorly self-assembled into nanoconjugates. Characterization confirmed the formation of nanometric, spherical and negatively charged pyrazinoic acid nanoconjugate (NC-PA). NC-PA was stable for 60 days at 4 and 37°C and able to deliver PA in a sustained release manner over time. On macrophages, they exhibited no cell toxicity for a wide range of concentrations (from 1 to 100 µg/mL), demonstrating the safety of NC-PA. In addition, the nanoconjugate was efficiently taken up by RAW 264.7 cells over 6 hours reaching a maximum value after 3 hours of incubation. In conclusion, innovative nanoconjugates are a promising alternative to deliver drugs directly to the lungs and contributing to improving tuberculosis therapy.

Development and benefit evaluation of fermentation strategies for poly(malic acid) production from malt syrup by Aureobasidium melanogenum GXZ-6

Malt syrup, as a low-cost substrate without any pretreatment, was proved to be able to replace maltose for ploymalic acid (PMA) production by Aureobasidium melanogenum GXZ-6. The PMA titer of 55.53 ± 1.72 g/L was obtained by batch fermentation in a 10-L fermentor with addition of malate, citrate and sodium malonate. Then, a higher PMA titer of 124.07 ± 2.28 g/L was obtained in fed-batch fermentation, which increased by 123.43% than that from batch fermentation. Moreover, repeated-batch fermentation with three batches gave a PMA titer of 64.06 g/L on average with a higher yield of 0.81 g/g and productivity of 0.56 g/L·h. Fermentation process and economics analysis were performed by SuperPro Designer for a 2000 metric tons plant. Results showed that PMA production cost was as low as $ 1.716/kg by fed-batch fermentation, which provides an economical strategy for large-scale PMA production.

Polycondensation of a Perylene Bisimide Derivative and L-Malic Acid as Water-Soluble Conjugates for Fluorescent Labeling of Live Mammalian Cells

Based on simple mixing and polymerization of a hydroxyl-containing derivative of perylene bisimide (PBI) and l-malic acid, here, we demonstrate a new type of dye-polymer conjugate, PBI-poly(α,β-malic acid) (PBI–PMA). Benefiting from the excellent water-solubility of weak polyanionic PMA structure and the high fluorescence of PBI, the PBI-PMA conjugates readily dissolve in water, displaying strong pH-dependent fluorescence with the highest intensity at pH 6. Due to the excellent biocompatibility of PMA, those conjugates showed low cytotoxicity on L929 cells. Using L929 and HeLa cells, we also confirmed that the PBI-PMA-labeled cells display intense fluorescence. Overall, the PBI-PMA conjugate demonstrates high potential as a cell labeling agent with its synthesis ease, good solubility in aqueous medium, low cytotoxicity, and high fluorescence.

The crystallization behaviors and mechanical properties of poly(l-lactic acid)/magnesium oxide nanoparticle composites

Nanocomposites of biodegradable PLLA and magnesium oxide composite (PLLA/MgO-NPs) and surface modified magnesium oxide composite (PLLA/m-MgO-NPs) were prepared using a solution casting method.

Silica@zirconia@poly(malic acid) nanoparticles: promising nanocarriers for theranostic applications

Nanocarriers designed, synthesized and characterized for the targeted delivery of diagnostic and therapeutic ^99mTc to folate-overexpressing tumors.

Cytocompatibility of novel extracellular matrix protein analogs of biodegradable polyester polymers derived from α-hydroxy amino acids

One of the challenges in regenerative medicine is the development of novel biodegradable materials to build scaffolds that will support multiple cell types for tissue engineering. Here we describe the preparation, characterization, and cytocompatibility of homo- and hetero-polyesters of α-hydroxy amino acid derivatives with or without lactic acid conjugation. The polymers were prepared by a direct condensation method and characterized using gel permeation chromatography, (1)H-nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, optical activity, and solubility. The surface charge of the polymers was evaluated using zeta potential measurements. The polymers were coated onto glass cover slips followed by characterization using nano-surface profiler, thin film reflectometry, and atomic force microscopy (AFM). Their interaction with endothelial and neuronal cells was assessed using adhesion, proliferation, and differentiation assays. Of the characterized polymers, Poly-HOVal-LA, but not Poly-(D)HOPhe, significantly augmented nerve growth factor (NGF)-induced neuronal differentiation of the PC12 pheochromcytoma cells. In contrast, Poly-HOLeu increased by 20% the adhesion of endothelial cells, but did not affect PC12 cell differentiation. NGF-induced Erk1/2 phosphorylation in PC12 cells grown on the different polymers was similar to the effect observed for cells cultured on collagen type I. While no significant association could be established between charge and the differentiative/proliferative properties of the polymers, AFM analysis indicated augmentation of NGF-induced neuronal differentiation on smooth polymer surfaces. We conclude that overall selective cytocompatibility and bioactivity might render α-hydroxy amino acid polymers useful as extracellular matrix-mimicking materials for tissue engineering.

Benzyl β-malolactonate polymers: a long story with recent advances

Benzyl β-malolactonate (MLABe) and its corresponding poly(benzyl β-malolactonate) (PMLABe) homopolymers and copolymers of the poly(hydroxyalkanoate) (PHA) family.

Surface functionalization of superparamagnetic nanoparticles for the development of highly efficient magnetic resonance probe for macrophages

In vivo magnetic resonance imaging (MRI) tracking of macrophages plays an important role in monitoring and understanding numerous human diseases with high macrophage activity. In this work, superparamagnetic iron oxide nanoparticles (SPIONs) of ∼12 nm were surface-functionalized with poly(DL-lactic acid-co-malic acid) copolymer (PLMA) via a nanoprecipitation method. The r(1), r(2) and r(2) /r(1) values of the PLMA-SPIONs obtained at a magnetic field of 3 T were 0.38, 196 and 516 mM(-1) s(-1) , respectively. The high r(2)/r(1) ratio can be expected to provide enhanced MR contrast. The PLMA-SPIONs were readily taken in by macrophages and the high iron uptake was confirmed via Prussian Blue staining and quantified by inductively coupled plasma mass spectrometry (ICP-MS). No significant cytotoxicity was found even at a high nanoparticle loading of 67.7 pg Fe per cell. A linear relationship between R(2) and R2* values and the number of PLMA-SPIONs labeled cells was observed in vitro. As a result of the significantly higher R2* than R(2) effects, an in vitro detection threshold of about 2820 labeled cells was achieved with short labeling time and low nanoparticle concentration using a clinical 3 T MRI scanner. Thus, the PLMA-SPIONs can be potentially useful as magnetic resonance probes for targeting and tracking macrophages.