Monodisperse Polyaspartic Acid Derivative Microspheres for Potential Tumor Embolization Therapy

Polyaspartic acid derivatives are a well-known kind of polypeptide with good biocompatibility and biodegradability, and thus have been widely used as biomedical materials, including drug-loaded nano-scale micelles or macroscopic hydrogels. In this work, for the first time, monodisperse polyaspartic acid derivative microspheres with diameter ranging from 120 to 350 µm for potential tumor embolization therapy are successfully prepared by single emulsion droplet microfluidic technique. The obtained microsphere shows fast cationic anticancer drug doxorubicin hydrochloride loading kinetics with high loading capacity, which is much better than those of the commercial ones. Additionally, drug release behaviors of the drug-loaded microspheres with different diameters in different media are also studied and discussed in detail. These results provide some new insights for the preparation and potential application of polyaspartic acid derivative-based monodisperse microspheres, especially for their potential application as embolic agent.

Sustainable Soil Additives for Water and Micronutrient Supply: Swelling and Chelating Properties of Polyaspartic Acid Hydrogels Utilizing Newly Developed Crosslinkers

Drought and water shortage are serious problems in many arid and semi-arid regions. This problem is getting worse and even continues in temperate climatic regions due to climate change. To address this problem, the use of biodegradable hydrogels is increasingly important for the application as water-retaining additives in soil. Furthermore, efficient (micro-)nutrient supply can be provided by the use of tailored hydrogels. Biodegradable polyaspartic acid (PASP) hydrogels with different available (1,6-hexamethylene diamine (HMD) and L-lysine (LYS)) and newly developed crosslinkers based on diesters of glycine (GLY) and (di-)ethylene glycol (DEG and EG, respectively) were synthesized and characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) and regarding their swelling properties (kinetic, absorbency under load (AUL)) as well as biodegradability of PASP hydrogel. Copper (II) and zinc (II), respectively, were loaded as micronutrients in two different approaches: in situ with crosslinking and subsequent loading of prepared hydrogels. The results showed successful syntheses of di-glycine-ester-based crosslinkers. Hydrogels with good water-absorbing properties were formed. Moreover, the developed crosslinking agents in combination with the specific reaction conditions resulted in higher water absorbency with increased crosslinker content used in synthesis (10% vs. 20%). The prepared hydrogels are candidates for water-storing soil additives due to the biodegradability of PASP, which is shown in an exemple. The incorporation of Cu(II) and Zn(II) ions can provide these micronutrients for plant growth.

Liquid Transmission Electron Microscopy for Probing Collagen Biomineralization

Collagen biomineralization is fundamental to hard tissue assembly. While studied extensively, collagen mineralization processes are not fully understood, with the majority of theories derived from electron microscopy (EM) under static, dehydrated, or frozen conditions, unlike the liquid phase environment where mineralization occurs. Herein, novel liquid transmission EM (TEM) strategies are presented, in which collagen mineralization was explored in liquid for the first time via TEM. Custom thin-film enclosures were employed to visualize the mineralization of reconstituted collagen fibrils in a calcium phosphate and polyaspartic acid solution to promote intrafibrillar mineralization. TEM highlighted that at early time points precursor mineral particles attached to collagen and progressed to crystalline mineral platelets aligned with fibrils at later time points. This aligns with observations from other techniques and validates the liquid TEM approach. This work provides a new liquid imaging approach for exploring collagen biomineralization, advancing toward understanding disease pathogenesis and remineralization strategies for hard tissues.

Defect Regulation of Efficient Dion-Jacobson Quasi-2D Perovskite Solar Cells via a Polyaspartic Acid Interlayer

Interfacial modification is a promising strategy to fabricate highly efficient perovskite solar cells (PSCs). Nevertheless, research studies about optimization for the performance of Dion-Jacobson (DJ)-phase quasi-2D PSCs by underlying surface modification are rarely reported. The relevant influence of interfacial modification on defect regulation in the bulk and at the interface for PSCs is still unexplored. Herein, an interlayer of polyaspartic acid (PASP) was introduced at the interface of a hole transporting layer and a perovskite absorber to regulate both the film quality and interface property for BDA-based DJ quasi-2D PSCs (n = 5). The PASP interlayer suppressed the charge recombination, restricted the interfacial charge accumulation, and promoted the charge transport in devices and therefore improved the power conversion efficiency of PSCs from 15.03 to 17.34%. Moreover, through device simulation, it was concluded that the increase of open-circuit voltage (Voc) was mainly attributed to the suppression of interface defects, while the increase of short-circuit current (Jsc) was ascribed to the restriction of interface defects and perovskite bulk defects. The improvement of both Voc and Jsc originated from the passivation of shallow defect states. The present work provides a promising route for the fabrication of efficient quasi-2D PSCs and enriches the fundamental understanding of defect regulation on photovoltaic performance.

Three novel Actinoplanes species isolated by using polyaspartic acid as a water-retaining agent for the enrichment in situ

Three novel actinomycete strains, designated TRM66264-DLM^T, TRM88002^T and TRM88003^T, were isolated by using polyaspartic acid as a water-retaining agent for the enrichment in situ. The 16S rRNA gene sequence and phylogenetic analyses of three strains indicated that they belonged to the genus Actinoplanes. The phylogenetically closest strains of TRM66264-DLM^T, TRM88002^T and TRM88003^T were Actinoplanes bogorensis LIPI11-2-Ac043^T (98.4 %), Actinoplanes abujensis A4029^T (98.0 %) and Actinoplanes ferrugineus IFO15555^T (98.1 %), respectively. The major polar lipids of strains TRM66264-DLM^T and TRM88002^T were phosphatidylethanolamine and disphosphatidylglycerol, while strain TRM88003^T only had phosphatidylethanolamine. The predominant menaquinones of strain TRM66264-DLM^T were identified as MK-9(H₄) and MK-9 (H₆). Strains TRM88002^T and TRM88003^T had MK-9(H₄). The cell-wall peptidoglycan of three strains contained meso-diaminopimelic acid. The whole-cell sugars of strain TRM66264-DLM^T were identified as arabinose, glucose, galactose and xylose. Strains TRM88002^T and TRM88003^T mainly had arabinose and glucose. The DNA G+C content of strains TRM66264-DLM^T, TRM88002^T and TRM88003^T were 70.48, 70.46 and 70.64 mol%, respectively. Genotypic and phenotypic analysis confirmed that all three strains sre new members of the genus Acinoplanes. Therefore, it is proposed that strains TRM66264-DLM^T, TRM88002^T and TRM88003^T represent three novel species of the genus Actinoplanes, for which the names Actinoplanes polyasparticus sp. nov. (type strain TRM66264-DLM^T=CCTCC AA 2021015^T=LMG 32389^T), Actinoplanes hotanensis sp. nov. (type strain TRM88002^T=CCTCC AA 2021036^T=LMG 32621^T) and Actinoplanes aksuensis sp. nov. (type strain TRM88003^T=CCTCC AA 2021037 ^T=LMG 32622^T) are proposed.

Effects of molecular weight of polyaspartic acid on nitrogen use efficiency and crop yield

BACKGROUND

In the past decades, ever-increasing fertilizer use has led to a continuous increase in agricultural output. However, serious waste of resources occurs because of the low utilization of fertilizers. Polyaspartic acid (PASP) is a biodegradable polymer that can be used as a fertilizer synergist in agricultural production to improve the nutrient utilization capacity of plants. For polymers, the molecular weight (MW) often affects their effectiveness. However, little information is available on the effects of PASP MW in agriculture, especially on nitrogen leaching and plant element uptake.

RESULTS

This work was conducted to identify the effect of PASPs with three different MWs - PASP-1 (MW: 5517), PASP-2 (MW: 6934), and PASP-3 (MW: 7568) - on nitrogen leaching, lettuce growth, and wheat cultivation. The results revealed that PASP favored plant growth and nitrogen accumulation in the soil, independent of crop species. PASP with a higher MW improved yields and the agronomic characteristics of lettuce and wheat. Furthermore, apparent amelioration of nitrogen use efficiency for lettuce (7.6%, 12.8%, and 15.0%) and wheat (4.6%, 8.1%, and 9.2%) was observed in the treatments with PASP addition. The effects and merits of PASPs on preventing ammonium nitrogen leaching and improving lettuce and wheat productivity were as follows: PASP-3 > PASP-2 > PASP-1.

CONCLUSION

The MW of PASP is an essential factor affecting inorganic nitrogen leaching and crop productivity, and PASP with a higher MW (7568) is recommended for application in agriculture. © 2022 Society of Chemical Industry.

Comparison of Synthetic vs. Biogenic Polymeric Process-Directing Agents for Intrafibrillar Mineralization of Collagen

With the aging population, there is a growing need for mineralized tissue restoration and synthetic bone substitutes. Previous studies have shown that a polymer-induced liquid-precursor (PILP) process can successfully mineralize collagen substrates to achieve compositions found in native bone and dentin. This process also leads to intrafibrillar apatitic crystals with their [001] axes aligned roughly parallel to the long axis of the collagen fibril, emulating the nanostructural organization found in native bone and dentin. When demineralized bovine bone was remineralized via the PILP process using osteopontin (OPN), the samples were able to activate mouse marrow-derived osteoclasts to similar levels to those of native bone, suggesting a means for fabricating bioactive bone substitutes that could trigger remodeling through the native bone multicellular unit (BMU). In order to determine if OPN derived from bovine milk could be a cost-effective process-directing agent, the mineralization of type I collagen scaffolds using this protein was compared to the benchmark polypeptide of polyaspartic acid (sodium salt; pAsp). In this set of experiments, we found that OPN led to much faster and more uniform mineralization when compared with pAsp, making it a cheaper and commercially attractive alternative for mineralized tissue restorations.

A novel polyaspartic acid derivative with multifunctional groups for scale inhibition application

Polyaspartic acid is a green biodegradable antiscalant and widely applied in water treatment field. However, its scale inhibition efficiency is not prominent, especially for calcium orthophosphate. So we introduced acylamino and hydroxyl groups simultaneously to prepare a novel polyaspartic-acid derivative (PASPTU) with multifunctional groups by the reaction of polysuccinimide with threonine and urea. The graft copolymer was analyzed by using nuclear magnetic resonance, gel permeation chromatography, thermogravimetric analyzer and Fourier transform infrared spectroscopy. Its scale inhibition performance for calcium orthophosphate, calcium sulfate and calcium carbonate was evaluated. The findings showed that the scale inhibition rates of the graft copolymer reached up to 100% for calcium orthophosphate, 100% for calcium sulfate and 91% for calcium carbonate at certain dosages. The findings above showed that the copolymer had excellent scale inhibition efficiency for calcium salts in water treatment processes.

Polyaspartic acid-anchored mesoporous silica nanoparticles for pH-responsive doxorubicin release

Background

Nanotechnology-based drug delivery systems exhibit promising therapeutic efficacy in cancer chemotherapy. However, ideal nano drug carriers are supposed to be sufficiently internalized into cancer cells and then release therapeutic cargoes in response to certain intracellular stimuli, which has never been an easy task to achieve.

Objective

This study is to design mesoporous silica nanoparticles (MSNs)-based pH-responsive nano drug delivery system that is effectively internalized into cancer cells and then release drug in response to lysosomal/endosomal acidified environment.

Methods

We synthesized MSNs by sol-gel method. Doxorubicin (DOX) was encapsulated into the pores as a model drug. Polyaspartic acid (PAsA) was anchored on the surface of mesoporous MSNs (P-MSNs) as a gatekeeper via amide linkage and endowed MSNs with positive charge.

Results

In vitro release analysis demonstrated enhanced DOX release from DOX-loaded PAsA-anchored MSNs (DOX@P-MSNs) under endosomal/lysosomal acidic pH condition. Moreover, more DOX@P-MSNs were internalized into HepG2 cells than DOX-loaded MSNs (DOX@MSNs) and free DOX revealed by flow cytometry. Likewise, confocal microscopic images revealed that DOX@P-MSNs effectively released DOX and translocated to the nucleus. Much stronger cytotoxicity of DOX@P-MSNs against HepG2 cells was observed compared with DOX@MSNs and free DOX.

Conclusion

DOX@P-MSNs were successfully fabricated and achieved pH-responsive DOX release. We anticipated this nanotherapeutics might be suitable contenders for future in vivo cancer chemotherapeutic applications.

[Enhanced Electrokinetic Remediation of Heavy Metals Contaminated Soils by Stainless Steel Electrodes as well as the Phenomenon and Mechanism of Electrode Corrosion and Crystallization]

Electrode corrosion and salt crystallization are important challenges that restrict the engineering application of electrokinetic technology. In the present study, using stainless steel as an electrode, and deionized water (DW), citric acid (CA) and polyaspartic acid (PASP) as electrolytes, Pb/Cu-contaminated soil was remediated by electrokinetic. All of the EK experiments were conducted in a 2 L soil cell reactor with a moisture level of about 35% blended with 1000 mg·g^-1 of Pb and 778 mg·g^-1 of Cu under a constant voltage gradient (1 V·cm^-1, 2 V·cm^-1) for 150 h. The removal efficiency of heavy metals and influencing factors, as well as the phenomenon and mechanism of electrode corrosion and salt crystallization were explored. The experimental results showed under the action of electric field, the Ca in the test soil would move to the cathode, and the crystal was formed in the alkaline condition. Additionally, the conductivity of the electrode was reduced. During the EK process, water at the anode was primarily oxidized, undergoing a reduction reaction at the cathode. Because H⁺ and OH^- were transported through the soil by electromigration and electro-osmotic flow (EOF), changes in soil pH could occur. The concentrations distribution of Pb-Cu appeared to be related to the distribution of soil pH in the cell, which might be associated with the desorption and hydroxide precipitation of Pb-Cu. PASP resulted in obvious inhibitory effect on the corrosion of stainless steel electrode, CA and PASP could clearly destroy the formation of CaCO₃ crystal, while barely effectively disrupted the formation of Ca (OH)₂ crystal. Both CA and PASP could promote the removal of Pb, but the influence of PASP on the removal of Cu was not obvious, and the effect of CA was very significant. Combined with different corrosion inhibitor and reinforcing agent, stainless steel can be chosen as the engineering application electrode in electrokinetic remediation.

Synthesis and characterization of an injectable hyaluronic acid-polyaspartylhydrazide hydrogel

The hydrogel produced by the reaction between a hyaluronic acid derivative (HAALD) and α,β-polyaspartylhydrazide (PAHy) hydrogel was used for lacrimal duct studies. In order to improve the mechanical properties of HAALD-PAHy hydrogel, glutaraldehyde (GA) was used as a candidate to increase the mechanical properties of the hydrogel. The optimum mass ratio of the GA and PAHy was 1:50. HAALD-PAHy and HAALD-PAHy-GA50 were both synthesized in PBSA solution and characterized by different methods including gel content and swelling, rheological analysis, in vitro degradation and in vivo degradation via rheological analysis. The storage modulus (G') of the HAALD-PAHy-GA50 hydrogel reached 3800 Pa, i.e. (2.9±0.3 times higher than for HAALD-PAHy). The in vitro cytotoxicity test revealed that HAALD-PAHy-GA50 have a good biocompatibility and in vivo animal testing concluded that HAALD-PAHy-GA50 remains in the rabbit's lacrimal duct for 28 days.

Tumor-targeting, pH-sensitive nanoparticles for docetaxel delivery to drug-resistant cancer cells

The attachment of polyethylene glycol (PEG) increases the circulation time of drug-containing nanoparticles; however, this also negatively affects cellular uptake. To overcome this problem, unique lipid polymer hybrid (LPH) nanoparticles were developed with a pH-responsive PEG layer that detached prior to cell uptake. Docetaxel (DTX) was incorporated into the lipid core of the nanoparticles, which was then shielded with the pH-responsive block co-polymer polyethylene glycol-b-polyaspartic acid (PEG-b-PAsp) using a modified emulsion method. The optimized LPH nanoparticles were ~200 nm and had a narrow size distribution. Drug release from DTX-loaded LPH (DTX-LPH) nanoparticles was pH-sensitive, which is beneficial for tumor targeting. More importantly, DTX-LPH nanoparticles were able to effectively induce apoptosis in cancer cells. The negative surface charge and PEG shell of vehicle remarkably enhanced the blood circulation and physiological activity of DTX-LPH nanoparticles compared with that of free DTX. The nanoparticles were also found to reduce the size of tumors in tumor-bearing xenograft mice. The in vivo anticancer effect of DTX-LPH nanoparticles was further confirmed by the elevated levels of caspase-3 and poly ADP ribose polymerase found in the tumors after treatment. Thus, the results suggest that this novel LPH system could be an effective new treatment for cancer.