Γ-glutamic Acid Research Articles

An injectable bioactive poly(γ-glutamic acid) modified magnesium phosphate bone cement for bone regeneration.

As potential alternatives for calcium phosphate bone cements, magnesium phosphate bone cements (MPC) have attracted considerable attention in recent years. However, their several defects, such as rapid setting times, highly hydration temperature and alkaline pH due to the part of the unreacted phosphate, restricted their applications in human body. With aim to overcome these defects, a novel polypeptite poly(γ-glutamic acid) (γ-PGA) modified MPC were developed. Effect of γ-PGA content on the injectability, anti-washout ability, setting times, hydration temperature, mechanical compressive strength, in vitro bioactivity and degradation were investigated. Moreover, in vitro cyto-compatibility was evaluated using MC3T3-E1 cells by CCK-8 and Live/Dead staining. All these results indicated that the 10%PGA-MPC with an improved handling performances, low hydration temperature, high mechanical compressive strength, and good cyto-compatibility hold a great potential for bone repair and regeneration.

Net-Neutral Nanoparticles-Extruded Microcapsules for Oral Delivery of Insulin.

Oral delivery of insulin could widely improve the quality of life of diabetic patients but still requires further exploration. Commonly utilized oral delivery vehicles hardly penetrate the intestinal mucus barrier, thus greatly hurdling their therapeutic efficacy. State-of-the-art technology shows that coating particles with neutral surface charge could reduce adsorption of mucins and improved the transport of particles within mucus. However, the synthesis of net-neutral particles (NNs) usually need complex purification and processing procedure. Herein, the NNs were conveniently constructed by simply adjusting the ratio of positive (chitosan) and negative (γ-glutamic acid) materials. To further achieve the optimal bioavailability of NNs, NNs formed materials were package in to wild chrysanthemum pollens, obtaining pH-triggered nanoparticles-extruding microcapsules (PNMs@insulin). At the small intestine pH value (∼6.0), the amino groups of CS deprotonate gradually and trigger the swelling, followed by the rapid extrusion of NNs through nano-orifices on the pollens' surface. After oral administration of the microcapsules, plasma insulin levels were enhanced significantly with a high oral bioavailability of >40%, leading to a remarkable and longer-sustained blood glucose-reducing effect. Moreover, we discovered that the empty pollen shells could act as a potential saccharide-adsorbing agent, which helps to manage sugar intake. This oral strategy of insulin will provide a vast potential for daily and facile diabetes treatment.

Synthesis of a novel pH-sensitive hydrogel based on poly(γ-glutamic acid) crosslinked with urea

Synthesis of a novel pH-sensitive hydrogel based on poly(γ-glutamic acid) crosslinked with urea

Nano-encapsulation of a combination of clove oil and thymol and their application in fresh-cut apples and raw minced beef

This study aimed to improve the antimicrobial activity of natural antimicrobials by combination and nanoencapsulation technology and to confirm the effect of combination and nanoencapsulation on their antimicrobial activity in fresh-cut apples and raw minced beef. The combinations of clove oil and thymol (CoTh), and clove oil and α-tocopherol (CoTo) were selected as primary synergistic antimicrobial combinations against two gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes) and two gram-negative bacteria (Escherichia coli and Salmonella typhimurium) using minimum inhibitory concentrations and fractional inhibitory concentration indices. CoTh-loaded and CoTo-loaded nanoparticles (NPs) were obtained by ionic gelation of chitosan (CS) with poly γ-glutamic acid (γ-PGA). CoTh was selected as the final combination based on the synergistic antimicrobial activity identified against all bacteria tested in this study using a time-kill assay. The CoTh-loaded CS/γ-PGA NPs more effectively inhibited the growth of gram-positive and gram-negative bacteria than free CoTh for an elongated period in the time-kill assay and fresh-cut apple and minced beef samples. Therefore, CS/γ-PGA nanoencapsulation could be a promising technique for improving and maintaining the inhibitory effects of CoTh against pathogenic bacteria, even in the presence of other ingredients, such as sugar, fat, and protein, in food.

Calcium-based polymers for suppression of soil acidification by improving acid-buffering capacity and inhibiting nitrification

Soil acidification is a major threat to agricultural sustainability in tropical and subtropical regions. Biodegradable and environmentally friendly materials, such as calcium lignosulfonate (CaLS), calcium poly(aspartic acid) (PASP-Ca), and calcium poly γ-glutamic acid (γ-PGA-Ca), are known to effectively ameliorate soil acidity. However, their effectiveness in inhibiting soil acidification has not been studied. This study aimed to evaluate the effect of CaLS, PASP-Ca, and γ-PGA-Ca on the resistance of soil toward acidification as directly and indirectly (i.e., via nitrification) caused by the application of HNO3 and urea, respectively. For comparison, Ca(OH)2 and lignin were used as the inorganic and organic controls, respectively. Among the materials, γ-PGA-Ca drove the substantial improvements in the pH buffering capacity (pHBC) of the soil and exhibited the greatest potential in inhibiting HNO3-induced soil acidification via protonation of carboxyl, complexing with Al3+, and cation exchange processes. Under acidification induced by urea, CaLS was the optimal one in inhibiting acidification and increasing exchangeable acidity during incubation. Furthermore, the sharp reduction in the population sizes of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) confirmed the inhibition of nitrification via CaLS application. Therefore, compared to improving soil pHBC, CaLS may play a more important role in suppressing indirect acidification. Overall, γ-PGA-Ca was superior to PASP-Ca and CaLS in enhancing the soil pHBC and the its resistance to acidification induced by HNO3 addition, whereas CaLS was the best at suppressing urea-driven soil acidification by inhibiting nitrification. In conclusion, these results provide a reference for inhibiting soil re-acidification in intensive agricultural systems.

Hydrophobic Modification of Poly(γ-glutamic acid) by Grafting 4-Phenyl-butyl Side Groups for the Encapsulation and Release of Doxorubicin.

The delivery of drugs is a great challenge, since most of active pharmaceutical ingredients developed today are hydrophobic and poorly water soluble. From this perspective, drug encapsulation on biodegradable and biocompatible polymers can surpass this problem. Poly(γ-glutamic acid) (PGGA), a bioedible and biocompatible polymer has been chosen for this purpose. Carboxylic side groups of PGGA have been partially esterified with 4-phenyl-butyl bromide, producing a series of aliphatic-aromatic ester derivatives with different hydrophilic-lipophilic balances. Using nanoprecipitation or emulsion/evaporation methods, these copolymers were self-assembled in a water solution, forming nanoparticles with average diameters between 89 and 374 nm and zeta potential values between -13.1 and -49.5 mV. The hydrophobic core containing 4-phenyl-butyl side groups was used for the encapsulation of an anticancer drug, such as Doxorubicin (DOX). The highest encapsulation efficiency was reached for a copolymer derived from PGGA, with a 46 mol% degree of esterification. Drug release studies carried out for 5 days at different pHs (4.2 and 7.4) indicated that DOX was released faster at pH 4.2, revealing the potential of these nanoparticles as chemotherapy agents.

Biochemical reprogramming of active-targeting and redox responsive nanoparticles for enhancing selective internalization

Selective internalization is urgently needed in accelerating drug release. Herein, the synergistic DOX@PBA-COS/γ-PGA nanoparticles with GGT/SA activate-targeting and pH-H2O2 sensitivities were successively synthetized through the entanglement of chitosan oligosaccharide (COS) chains with phenylboronic acid (PBA) and poly (γ-glutamic acid) (γ-PGA). DOX@PBA-COS/γ-PGA was highly susceptible to gamma-glutamyl transpeptidase (GGT)-targeting than sialic acid (SA)-targeting in HepG2 cells. The selective internalization of DOX@PBA-COS/γ-PGA in the order of HepG2＞HeLa＞MCF-7, due to the clathrin-mediated endocytosis and microtubule polymerization/vesicular transport in HepG2 cells. The innovative strategies to augment selective internalization through the synergistic γ-PGA shielding and redox homeostasis interference provide enlightenment in the hepatocellular carcinoma therapy.

Chronic toxicity of broflanilide in Daphnia magna: changes in molting, behavior, and gene expression.

Broflanilide is a novel pesticide used in agriculture that binds to unique receptors on pests; however, the widespread use of broflanilide has led to toxicity in Daphnia magna. At present, little information on the potential threats broflanilide imposes on D. magna is available. Therefore, the present study examined the chronic toxicity of broflanilide in D. magna by comparing changes in molting, neurotransmitter function, and behavior. The results showed that broflanilide caused chronic toxicity in D. magna at a concentration of 8.45μg/L, and growth, development, reproduction, and the development of offspring were affected. In addition, broflanilide affected the molting of D. magna by significantly inhibiting the expression of chitinase, ecdysteroid, and related genes. Broflanilide also affected the expression of γ-glutamic acid, glutamine, gamma-aminobutyric acid, 5-hydroxytryptamine, 5-hydroxytryptophan, dopa, and dopamine. Furthermore, the swimming distance and speed of D. magna were reduced. Taken together, the results demonstrate the chronic toxicity and exposure risk of broflanilide in D. magna.

Poly-γ-glutamic acid-producing Bacillus velezensis fermentation can improve the feed properties of soybean meal

Soybean meal (SBM), a high-protein animal feed, contains several anti-nutritional factors, which limit its utilization. Poly-γ-glutamic acid (γ-PGA), a biological macromolecule, can significantly improve the health and growth benefits of animal feed. However, there are rare reports about SBM fermentation with γ-PGA-producing bacteria to improve its nutritional quality. In this study, we isolated a glutamic acid-independent poly γ-glutamic acid (γ-PGA) producing Bacillus velezensis SCP024–S-4 bacterial strain and used it for solid fermentation of SBM. The results showed that the maximum γ-PGA yield in fermented soybean meal (FSBM) reached up to 89.64 g/kg without adding glutamic acid. Meanwhile, the content of proteins, free amino acids and small peptides increased by 12.83%, 347.96 μg/g and 108.11 mg/g, respectively. Soy globulin, β-conglutinin and trypsin inhibitor all decreased below 3 mg/g. Mice were fed with CK (control diet), SBM and FSBM respectively. The average daily food intake in the FSBM, SBM, and CK groups were 7.68, 5.25, and 6.36 g, respectively. Compared with the CK group, the mice weight growth rate was significantly higher in the FSBM group. Mice blood and spleen tests showed no negative effect of FSBM. The high-throughput sequencing of mice intestinal microflora indicated that FSBM increased the richness of intestinal microbiota; especially, the types and quantities of Lactobacillus were significantly increased. This study provides a feasible strategy to improve the nutritional quality of SBM as an animal feed.

β-Alanine enhancing the crosslink of chitosan/poly-(γ-glutamic acid) hydrogel for a potential alkaline-adapted wound dressing

Tiny crosslink in chitosan (CS)/poly-(γ-glutamic acid) (γ-PGA) hydrogel leads to some disadvantages including low mechanical strength and high swelling. To enhance the crosslink of CS/γ-PGA hydrogel, amino acid (AA) was introduced to remove the drawbacks. The results indicated that AA can dramatically increase the crosslink and mechanical properties of CS/γ-PGA hydrogel, and AA chain length and concentration have a drastic effect on them. Particularly, 0.5 % β-Alanine (β-Ala) decreased the hydrogel by 70 % in porosity, 52 % in water solubility, and 30 % in swelling, but increased by 2.2-fold in elastic modulus, 2.08-fold in stress, and 1.53-fold in water retention. The porosity of the hydrogel correlates positively with the elastic modulus but negatively with the crosslinking degree. The effect of pH on CS/β-Ala/γ-PGA hydrogel was investigated in the load and release of benzalkonium chlorides (BAC). β-Ala strengthened pH response of the hydrogel in BAC load and release. The loading capacity increased with pH value, and 0.5 % β-Ala increased the hydrogel by 1.25-fold in the release capacity in alkaline environment, suggesting a good buffering effect of β-Ala on pH variation to accelerate the transportation of BAC. CS/β-Ala/γ-PGA hydrogel will be competently applied as a potential material for wound dressing in alkaline environment.

A novel PGA/TiO2 nanocomposite prepared with poly(γ-glutamic acid) from the newly isolated Bacillus subtilis 17B strain

Poly(?-glutamic acid) (PGA), naturally produced by Bacillus species, is a biodegradable, non-toxic, biocompatible and non-immunogenic negatively charged polymer. Due to its properties, it has found various applications in the food, cosmetic and pharmaceutical industries. In this work, Bacillus subtilis 17B was selected as the best PGA producer among fifty wild-types Bacillus strains tested and characterized as a glutamate-independent producer. The production of PGA by the newly identified strain was optimized and increased tenfold using the Box?Behnken experimental design. The purity of PGA after recovery and purification from the fermentation broth was confirmed by SDS- -PAGE followed by methylene blue staining. PGA was characterized by ESI MS and used for the preparation of a new nanocomposite with TiO2. The synthesis of PGA/TiO2 nanocomposite, its structural analysis, and cytotoxic effect on the cervical cancer cell line (HeLa cell) was investigated to determine the potential anti-cancer usage of this newly prepared material. It is encouraging that PGA/TiO2 nanocomposite showed an increased cytotoxic effect compared to TiO2 alone.

Synthesis of Hydrophobic Poly(γ-Glutamic Acid) Derivatives by Enzymatic Grafting of Partially 2-Deoxygenated Amyloses

We have previously found that a partially 2-deoxygenated (P2D)-amylose, produced by glucan phosphorylase (GP)-catalyzed enzymatic copolymerization, shows hydrophobic nature. Based on this finding, the present study demonstrates hydrophobization of a strong hydrophilic polypeptide, i.e., poly(γ-glutamic acid) (PGA), by grafting of the P2D-amylose chains via GP-catalyzed enzymatic approach. After maltooligosaccharide primers for the enzymatic reaction were modified on the PGA chain, we performed GP-catalyzed copolymerization of d-glucan with α-d-glucose 1-phosphate as comonomers in different feed ratios from the primers to produce P2D-amylose-grafted PGAs. We analyzed the structures (chemical and crystalline) of the products, precipitated from reaction mixtures, by 1H NMR and powder X-ray diffraction measurements, respectively. The values of the water contact angle of the cast films, prepared from DMSO solutions of the products with different 2-deoxyglucose/glucose unit ratios, were greater than 100°, indicating efficient hydrophobization of the hydrophilic polypeptide by the present approach.

Engineering of a newly isolated Bacillus tequilensis BL01 for poly-γ-glutamic acid production from citric acid

BackgroundPoly γ-glutamic acid (γ-PGA) is a promising biopolymer for various applications. For glutamic acid-independent strains, the titer of γ-PGA is too low to meet the industrial demand. In this study, we isolated a novel γ-PGA-producing strain, Bacillus tequilensis BL01, and multiple genetic engineering strategies were implemented to improve γ-PGA production.ResultsFirst, the one-factor-at-a-time method was used to investigate the influence of carbon and nitrogen sources and temperature on γ-PGA production. The optimal sources of carbon and nitrogen were sucrose and (NH4)2SO4 at 37 °C, respectively. Second, the sucA, gudB, pgdS, and ggt genes were knocked out simultaneously, which increased the titer of γ-PGA by 1.75 times. Then, the titer of γ-PGA increased to 18.0 ± 0.3 g/L by co-overexpression of the citZ and pyk genes in the mutant strain. Furthermore, the γ-PGA titer reached 25.3 ± 0.8 g/L with a productivity of 0.84 g/L/h and a yield of 1.50 g of γ-PGA/g of citric acid in fed-batch fermentation. It should be noted that this study enables the synthesis of low (1.84 × 105 Da) and high (2.06 × 106 Da) molecular weight of γ-PGA by BL01 and the engineering strain.ConclusionThe application of recently published strategies to successfully improve γ-PGA production for the new strain B. tequilensis BL01 is reported. The titer of γ-PGA increased 2.17-fold and 1.32-fold compared with that of the wild type strain in the flask and 5 L fermenter. The strain shows excellent promise as a γ-PGA producer compared with previous studies. Meanwhile, different molecular weights of γ-PGA were obtained, enhancing the scope of application in industry.

Programmed cyclodextrin-based core–shell nanoparticles for cooperative TGF-β blockade to reverse immunosuppression post photodynamic therapy

Photodynamic therapy (PDT), as a clinical method of tumor treatment, has an advantage of immune activation, making it become an ideal adjuvant strategy for tumor immunotherapy. However, research data showed that the anti-tumor immune response of PDT was not lasting though existing, and would induce immunosuppression at the late stage. Our back-to-back previous research has just confirmed that TGF-β1 upregulation accounts for tumor immunosuppression aggravating post PDT and TGF-β blockade is a potential strategy to reverse this effect. How to realize the efficient coordination between PDT and TGF-β blockade becomes a burning question. Nanomedicine fully utilizing PDT principles could be a promising solution. In this study, a cyclodextrin-based core–shell nanoparticles (LC@HCDFC NPs) were designed to co-deliver LY2109761 (LY, a TGF-β1 inhibitor) and chlorin e6 for enhanced PDT combined with TGF-β blockade immunotherapy. Through utilizing PDT induced upregulation of CD44 and ROS, the inclusion complex shells of hyaluronic acid (HA) modified β-CD and ferrocene could realize incremental HA-CD44 mediated tumor targeting and ROS responsive drug release, and the cores of benzyl-modified poly (γ-glutamic acid) (BzPGA) improved the encapsulation efficiency of LY. Ultimately, through programmed delivery of TGF-β1 inhibitors, LC@HCDFC NPs not only enhanced the antitumor effect in situ, but reversed tumor immunosuppression and metastasis under the reshaped tumor microenvironment. This study provided enlightenment for programmed PDT in coordinate with TGF-β blockade immunotherapy and shed light on the efficient encapsulation and controlled release of TGF-β1 inhibitors.

Engineering the dynamics of biophysical cues in supramolecular hydrogels to facile control stem cell chondrogenesis for cartilage regeneration

Hydrogel systems have been widely used to engineer biomimetic niches that capture microenvironments cues to steer cell fate; however, challenges remain in inducing mesenchymal stromal cells (MSCs)'s differentiation into chondrocytes remains a challenge due to natural extracellular matrix (ECM)'s complex composition. Herein, we designed double network (DN) hydrogels with tunable viscoelastic properties that recapitulated the biophysical cues of ECM to guide MSCs chondrogenesis. DN hydrogels were formed through the combination of supramolecular guest-host (GH) hyaluronic acid (HA) and poly (γ-glutamic acid) (γ-PGA) networks with covalent networks by the crosslinking of thiolated γ-PGA and PEG diacrylate. By adjusting GH concentration, the biophysical properties (e.g., viscoelasticity) of DN hydrogel could be tailored on-demand to investigate the effect of viscoelasticity in three dimensions (3D). The DN hydrogel with increased GH concentration showed viscoelastic matrices, enhanced ECM secretion, and chondrogenesis of encapsulated MSCs, as evidenced by upregulated expression of key biomarkers (e.g., aggrecans, collagen II). We further showed that DN hydrogel with viscoelastic behavior promoted cartilage-specific matrix deposition and regeneration of articular cartilage through in vivo studies. Our results have provided valuable insights into the design of viscoelastic DN hydrogel with an ECM-mimicking 3D microenvironment for efficient chondrogenesis for cartilage regeneration therapies.

N-Doped Two-Dimensional Carbon Nanosheets with Micropore-Dominant Porosity for High-Performance Supercapacitors

N-doped two-dimensional (2D) porous carbon nanosheets (PCNs) have been developed for high-performance supercapacitors (SCs) through chemical crosslinking of biomass shell and γ-glutamic acid followed by pyrolysis and activation. The C and N recomposition and pore formation processes occur within the shell/γ-glutamic acid composite during pyrolysis. The enormous specific surface area of 2393 m2 g–1, unique 2D nanosheet, and rich microporous structure are only a few of the benefits of an optimized PCNs material. The rich oxygen/nitrogen functional groups and 2D nanosheet structure endow the materials with super hydrophilicity, and also provide extra pseudocapacitance. With these added structural advantages and the component synergy, the PCNs show superior performance for which the specific capacitance is 321 F g–1, and only with a 7% capacitance loss after 13,000 cycles in a three-electrode system. Furthermore, a PCNs-based symmetric SC displays a high specific energy of 9.7 W h kg–1.

Improved biocompatibility and antibacterial property of zinc alloy fabricated with γ-polyglutamic acid-g-dopamine/copper coatings for orthopedic implants

Zinc-lithium (Zn-Li) alloys have attracted considerable attention as potential biodegradable orthopedic implant materials. However, the biocompatibility and antibacterial property need further improvement to meet the clinical requirements. In this study, poly(γ-glutamic acid)-g-dopamine/copper (γ-PGA-g-DA/Cu) hybrid coatings were fabricated on a Zn alloy to improve its biocompatibility and antibacterial performance. Corrosion analysis in simulated body fluid indicated that the γ-PGA-g-DA/Cu coatings afforded tunable degradation rates of Zn alloys. The cytotoxicity evaluation revealed that the presence of copper ions in the coatings could reduce the cytotoxicity problem caused by zinc ions and enhance the biocompatibility of Zn alloy. In vitro antibacterial tests exhibited that the antibacterial activity of Zn alloy enhanced due to the γ-PGA-g-DA/Cu coatings and the antibacterial performance of γ-PGA-g-DA/Cu coated samples increased with increasing copper content of the coatings. In summary, γ-PGA-g-DA/Cu coatings provide a feasible strategy to design Zn alloy implant materials with improved functional performance.

Single Gold Nanostars Achieve Inherent Cascade Catalytic and Near-Infrared Photothermal Activities for Efficient Tumor Therapy.

Gold nanoparticles (Au NPs) used as photosensitizers for photothermal therapy (PTT) have attracted extensive attention. However, limited tissue penetration of light seriously hinders the practical application, causing Au NPs to be combined with multiple theranostic agents to improve the treatment effect. Herein, we fabricate one potent gold nanostars (GNS) that can unify the dual nanozyme activities and photothermal property, achieving effective synergistic cascade catalytic and photothermal therapy. Notably, GNS is prepared by a green and facile one-step synthesis method using biodegradable poly(γ-glutamic acid) as a medium. The single GNS exhibits inherent dual nanozyme activities, glucose oxidase- and peroxidase-like activities, which not only convert glucose of tumor tissue into hydrogen peroxide (H2O2) but also catalyze H2O2 to produce the amount of toxic hydroxyl radicals (•OH), leading to an amplified cascade catalytic therapy. Moreover, the cascade catalytic activity of GNS is enhanced 1.4-fold in the photothermal effect. Finally, the GNS can achieve photoacoustic imaging-guided efficient synergistic cascade catalytic and photothermal therapy with a high antitumor rate of 97.0%. This simple but multifunctional GNS could provide a new strategy facilitating the practical treatment application of single Au NPs.

Integrated and dual-responsive lipopeptide nanovector with parallel effect to tumor and micro-environment regulation by efficient gene and drug co-delivery

The integrated lipopeptide (RVA)/gene complexes are fabricated with bi-directional regulation on tumor cells and micro-environment. After self-assembling and target coating modification, the poly(γ-glutamic acid) (γ-PGA)/RVA nano-vectors can sequentially respond to pH & redox stimuli, and guarantee efficient therapeutic gene delivery and control release of all-trans retinoic acid. The design provides a facile but promising strategy to treat refractory cancers.

Effects of Amendments and Indigenous Microorganisms on the Growth and Cd and Pb Uptake of Coriander (Coriandrum sativum L.) in Heavy Metal-Contaminated Soils.

Heavy metal (HM) contamination of soils is a worldwide problem with adverse consequences to the environment and human health. For the safe production of vegetables in contaminated soil, efficient soil amendments need to be applied such as nano-hydroxyapatite (n-HAP) and poly γ-glutamic acid (γ-PGA), which can mitigate heavy metal uptake and enhance crop yield. However, the combined effects of soil amendments and indigenous microorganisms (IMOs) on HMs immobilisation and accumulation by crops have received little attention. We established a pot experiment to investigate the effects of IMOs combined with n-HAP and γ-PGA on coriander (Coriandrum sativum L.) growth and its Cd and Pb uptake in two acidic soils contaminated with HMs. The study demonstrated that applying n-HAP, with and without IMOs, significantly increased shoot dry biomass and reduced plant Cd and Pb uptake and diethylenetriaminepentaacetic acid (DTPA) extractable Cd and Pb concentrations in most cases. However, γ-PGA, with and without IMOs, only reduced soil DTPA-extractable Pb concentrations in slightly contaminated soil with 0.29 mg/kg Cd and 50.9 mg/kg Pb. Regardless of amendments, IMOs independently increased shoot dry biomass and soil DTPA-extractable Cd concentrations in moderately contaminated soil with 1.08 mg/kg Cd and 100.0 mg/kg Pb. A synergistic effect was observed with a combined IMOs and n-HAP treatment, where DTPA-extractable Cd and Pb concentrations decreased in slightly contaminated soil compared with the independent IMOs and n-HAP treatments. The combined treatment of γ-PGA and IMOs substantially increased shoot dry biomass in moderately contaminated soil. These results indicate that solo n-HAP enhanced plant growth and soil Cd and Pb immobilisation, and mitigated Cd and Pb accumulation in shoots. However, the combination of n-HAP and IMOs was optimal for stabilising and reducing HMs’ uptake and promoting plant growth in contaminated soil, suggesting its potential for safe crop production.