Macromolecular Agent Research Articles

An In-Vitro Study on Photochemical Internalization of Methylene Blue with Gold Nanoparticles Coated By Thio-Glucose

Objectives: Photochemical internalization (PCI) is a novel PDT-based technology for intracellular delivery of hydrophilic macromolecular therapeutic agents and other drugs with limited ability to penetrate cellular membranes with intracellular targets. One of the approaches is the use of nanoparticles along with photosensitizing agents. In this study, the presence of thioglucose-coated gold nanoparticles in the efficiency of the photodynamic effect of methylene blue due to photochemical internalization phenomenon was investigatedMaterials and Methods: This study was performed on the MCF-7 cell line derived from tumor cells of breast adenocarcinoma. First, GNPs-Tio was synthesized. Next, the toxicity of GNPs-Tio and MB were determined to achieve their optimal concentrations. Then, their photodynamic effects of GNPs-Tio combined with MB by Luma-Care source light at different doses were evaluated by using MTT assay and colony assay (12 days after treatment). Results: According to MTT assay, the photodynamic effect in the GNPs-Tio receiving group did not show a significant efficacy, whereas the ability of colony forming for all groups decreased with an optical dose of 15.6 J / cm2 compared with similar group without light exposure (P-Value  0.05). Conclusion: The photodynamic efficiency of MB with GNPs-Tio group was reduced compared to the free MB group at 15.6 J / cm2. This reduction in efficiency can be due to various reasons such as photochemical bleaching of free MB due to ROS and 1O2 produced by the plasmonic photodynamic phenomenon of GNPs-Tio or changing of optophysical properties of surface plasmon resonance of final product (MB+ GNPs-Tio) due to the possible electrostatic bonding of the drug and the nanoparticles to each other. More studies are needed to understand the more precise mechanism of this event.

A nitroxides-based macromolecular MRI contrast agent with an extraordinary longitudinal relaxivity for tumor imaging via clinical T1WI SE sequence

BackgroundMacromoleculization of nitroxides has been an effective strategy to improve low relaxivities and poor in vivo stability, however, nitroxides-based metal-free magnetic resonance imaging (MRI) macromolecular contrast agents (mCAs) are still under-performed. These mCAs do not possess a high nitroxides content sufficient for a cumulative effect. Amphiphilic nanostructures in these mCAs are not stable enough for highly efficient protection of nitroxides and do not have adequate molecular flexibility for full contact of the paramagnetic center with the peripheral water molecules. In addition, these mCAs still raise the concerns over biocompatibility and biodegradability due to the presence of macromolecules in these mCAs.ResultsHerein, a water-soluble biodegradable nitroxides-based mCA (Linear pDHPMA-mPEG-Ppa-PROXYL) was prepared via covalent conjugation of a nitroxides (2,2,5,5-tetramethyl-1-pyrrolidinyl-N-oxyl, PROXYL) onto an enzyme-sensitive linear di-block poly[N-(1, 3-dihydroxypropyl) methacrylamide] (pDHPMA). A high content of PROXYL up to 0.111 mmol/g in Linear pDHPMA-mPEG-Ppa-PROXYL was achieved and a stable nano-sized self-assembled aggregate in an aqueous environment (ca. 23 nm) was formed. Its longitudinal relaxivity (r1 = 0.93 mM− 1 s− 1) was the highest compared to reported nitroxides-based mCAs. The blood retention time of PROXYL from the prepared mCA in vivo was up to ca. 8 h and great accumulation of the mCA was realized in the tumor site due to its passive targeting ability to tumors. Thus, Linear pDHPMA-mPEG-Ppa-PROXYL could provide a clearly detectable MRI enhancement at the tumor site of mice via the T1WI SE sequence conventionally used in clinical Gd3+-based contrast agents, although it cannot be compared with DTPA-Gd in the longitudinal relaxivity and the continuous enhancement time at the tumor site of mice. Additionally, it was demonstrated to have great biosafety, hemocompatibility and biocompatibility.ConclusionsTherefore, Linear pDHPMA-mPEG-Ppa-PROXYL could be a potential candidate as a substitute of metal-based MRI CAs for clinical application.Graphic

The Enhanced Permeability and Retention (EPR) Effect: The Significance of the Concept and Methods to Enhance Its Application

Chemotherapy for human solid tumors in clinical practice is far from satisfactory. Despite the discovery and synthesis of hundreds of thousands of anticancer compounds targeting various crucial units in cancer cell proliferation and metabolism, the fundamental problem is the lack of targeting delivery of these compounds selectively into solid tumor tissue to maintain an effective concentration level for a certain length of time for drug-tumor interaction to execute anticancer activities. The enhanced permeability and retention effect (EPR effect) describes a universal pathophysiological phenomenon and mechanism in which macromolecular compounds such as albumin and other polymer-conjugated drugs beyond certain sizes (above 40 kDa) can progressively accumulate in the tumor vascularized area and thus achieve targeting delivery and retention of anticancer compounds into solid tumor tissue. Targeting therapy via the EPR effect in clinical practice is not always successful since the strength of the EPR effect varies depending on the type and location of tumors, status of blood perfusion in tumors, and the physical-chemical properties of macromolecular anticancer agents. This review highlights the significance of the concept and mechanism of the EPR effect and discusses methods for better utilizing the EPR effect in developing smarter macromolecular nanomedicine to achieve a satisfactory outcome in clinical applications.

Intestinal Transcytosis of a Protein Cargo and Nanoparticles Mediated by a Non-Toxic Form of Pseudomonas aeruginosa Exotoxin A.

The low permeability of nanoparticles (NPs) across the intestinal epithelium remains a major challenge for their application of delivering macromolecular therapeutic agents via the oral route. Previous studies have demonstrated the epithelial transcytosis capacity of a non-toxic version of Pseudomonas aeruginosa exotoxin A (ntPE). Here, we show that ntPE can be used to deliver the protein cargo green fluorescent protein (GFP) or human growth hormone (hGH), as genetic fusions, across intact rat jejunum in a model where the material is administered by direct intra-luminal injection (ILI) in vivo in a transcytosis process that required less than 15 min. Next, ntPE chemically coupled onto biodegradable alginate/chitosan condensate nanoparticles (AC NPs-ntPE) were shown to transport similarly to ntPE-GFP and ntPE-hGH across rat jejunum. Finally, AC NPs-ntPE loaded with GFP as a model cargo were demonstrated to undergo a similar transcytosis process that resulted in GFP being colocalized with CD11c+ cells in the lamina propria after 30 min. Control NP preparations, not decorated with ntPE, were not observed within polarized epithelial cells or within the cells of the lamina propria. These studies demonstrate the capacity of ntPE to facilitate the transcytosis of a covalently associated protein cargo as well as a biodegradable NP that can undergo transcytosis across the intestinal epithelium to deliver a noncovalently associated protein cargo. In sum, these studies support the potential applications of ntPE to facilitate the oral delivery of macromolecular therapeutics under conditions of covalent or non-covalent association.

Soft, tough, and fast polyacrylate dielectric elastomer for non-magnetic motor

Dielectric elastomer actuators (DEAs) with large electrically-actuated strain can build light-weight and flexible non-magnetic motors. However, dielectric elastomers commonly used in the field of soft actuation suffer from high stiffness, low strength, and high driving field, severely limiting the DEA’s actuating performance. Here we design a new polyacrylate dielectric elastomer with optimized crosslinking network by rationally employing the difunctional macromolecular crosslinking agent. The proposed elastomer simultaneously possesses desirable modulus (~0.073 MPa), high toughness (elongation ~2400%), low mechanical loss (tan δm = 0.21@1 Hz, 20 °C), and satisfactory dielectric properties ({varepsilon }_{{{{{{rm{r}}}}}}} = 5.75, tan δe = 0.0019 @1 kHz), and accordingly, large actuation strain (118% @ 70 MV m−1), high energy density (0.24 MJ m−3 @ 70 MV m−1), and rapid response (bandwidth above 100 Hz). Compared with VHBTM 4910, the non-magnetic motor made of our elastomer presents 15 times higher rotation speed. These findings offer a strategy to fabricate high-performance dielectric elastomers for soft actuators.

A low molecular weight Zr(IV) metallogel for protein delivery

With an exceptional portfolio of properties such as high water content and cross-linked nature, hydrogels can provide an ideal and compatible environment not only to encapsulate but also to control the delivery of biological therapeutics. However, uncontrollable degradation, release and especially swelling impose limitations on our ability to engineer these gels. Herein a zirconium metallogel is proposed that utilizes zirconyl tetramers as the metal component in conjunction with a nucleic acid (adenine). The variable gel-formation temperature as a simple step of gel formation allows the tuning of gel formation and properties by controlling the adenine-nucleobase interactions. Reconstitution, entrapment, degradation, cytotoxicity, and release of bovine serum albumin (BSA) as a negatively charged macromolecular therapeutic agent were investigated. The controllable and sustained release of BSA, offers a route to new tailorable protein delivery applications.

Investigating plasma volume expanders as novel macromolecular MRI-CEST contrast agents for tumor contrast-enhanced imaging.

The aim of this study was to investigate two clinically approved plasma volume expanders (dextran 70 and voluven) as macromolecular MRI-chemical exchange saturation transfer (CEST) contrast agents to assess tumor vascular properties. CEST contrast efficiency of both molecules (6% w/v) was measured in vitro at various irradiation saturation powers (1-6 μT for 5 s) and pH values (range, 5.5-7.9) and the exchange rate of hydroxyl protons was calculated. In vivo studies in a murine adenocarcinoma model (n = 4 mice for each contrast agent) upon i.v. injection provided CEST-derived perfusion tumor properties that were compared with those obtained with a gadolinium-based blood-pool agent (Gd-AAZTA-Madec). In vitro measurements showed a marked CEST contrast dependency to pH, with higher CEST contrast at lower pH values for both molecules. The measured prototropic exchange rates confirmed a base-catalyzed exchange rate that was faster for dextran 70 in comparison to voluven. Both molecules showed a similar CEST contrast increase (ΔST% > 3%) in the tumor tissue up to 30 min postinjection, with heterogeneous accumulation. In tumors receiving both CEST and T1 -weighted agents, a voxel-by-voxel analysis indicated moderate spatial correlation of perfusion properties between voluven/dextran 70 and Gd-AAZTA-Madec, suggesting different distribution patterns according to their molecular size. The obtained results showed that both voluven and dextran 70 can be exploited as MRI-CEST contrast agents for evaluating tumor enhancement properties. Their increased accumulation in tumors and prolonged contrast enhancement promote their use as blood-pool MRI-CEST agents to examine tumor vascularization.

High thermal stability and low flammability for Ethylene‐Vinyl acetate Monomer/Ethylene‐Propylene‐Diene Monomer by incorporating macromolecular charring agent

The intumescent flame retardant (IFR) compounded with triazine charcoal‐forming agent (CFA) and ammonium polyphosphate (APP) was applied to the flame‐retardant modification of EVM/EPDM. The effect of APP‐CFA on the flame‐retardant performance of the composite was studied. The results showed that APP‐CFA effectively enhanced the flame‐retardant performance of EVM/EPDM. Compared with the control sample, when the APP–CFA ratio was 4:1, the limit oxygen index of EVM/EPDM with APP–CFA was up to 27.1%, which was increased by about 40%, and the average heat release rate was 110.1 kW/m2, which was reduced by about 29%. Moreover, it passed the UL‐94 V‐0 test. TGA results showed that after the addition of APP/CFA, the amount of residue significantly increased. SEM test showed that the char layer formed by the composite containing APP/CFA during combustion was denser and more uniform. In addition, compared with the traditional intumescent flame‐retardant ammonium polyphosphate–dipentaerythritol–melamine (APP‐DPER‐MN), the new flame‐retardant APP–CFA has better flame‐retardant and comprehensive performances.

Cadmium uptake and transfer by Sedum plumbizincicola using EDTA, tea saponin, and citric acid as activators

Sedum plumbizincicola (S. plumbizincicola) is known as a sufficient plant for phytoremediation of cadmium (Cd) polluted soils. This study aimed to investigate the effects of ethylene diamine tetraacetic acid (EDTA), tea saponin (TS), and citric acid (CA) on Cd uptake and translocation by S. plumbizincicola. To do so, using a pot experiment, we set four concentration levels of activators (1, 3, 5, and 10 mmol L−1) and a control (CK). Results showed that none of the applied activators had significant impact on soil pH. Except for CA-10, the concentration of available Cd in Cd polluted soils increased by 65.8–72.9% compared with CK. The EDTA-1, CA-1, and TS-5 treatments caused significant increases of 52.3, 67.2, and 38.4%, respectively, in the biomass of aerial parts of S. plumbizincicola (p < 0.05) compared with CK. Except for CA-3, activators increased Cd accumulation in the aerial parts of plants by 47–124% compared with CK. Of all activators, EDTA-3 caused the highest Cd accumulation of 6.64 g pot−1 in the aerial plant tissues followed by CA-10 (6.25 g pot−1) and TS-1 (5.48 g pot−1). Finally, our results suggested that the application of S. plumbizincicola together with different activators sufficiently reduced soil total Cd by 4.64–48.4% compared with CK. These findings suggest that appropriate application of EDTA, TS, and CA can promote phytoremediation of Cd contaminated soils by hyper-accumulators. In particular, the combined use of EDTA and S. plumbizincicola is an affordable and promising strategy for remediation of Cd contaminated soil. Novelty statement: Sedum plumbizincicola (S. plumbizincicola) is a well-known hyper-accumulator plant for remediation of cadmium (Cd) and zinc (Zn) contaminated soils. In addition, low molecular rganic acids and macromolecular chelating agents can improve the solubility and leaching of soil heavy metals. In the present work, we examined the combined effects of three activators (EDTA, tea saponin, and citric acid) with S. plumbizincicola to remediate a Cd contaminated soil in Anhui Province, East China. Our results indicated the effectiveness of these activators to increase soil available Cd, as well as improving the biomass of S. plumbizincicola and its Cd uptake. We believe that this study provides an efficient approach to increase the uptake of Cd by S. plumbizincicola, restoring Cd contaminated soils. Nevertheless, excessive activators may have adverse effects on soil aggregates and soil microorganisms. Therefore, it is necessary to control the amount of chelating agents and subsequently the deterioration of soil quality.

Targeting drug delivery with light: A highly focused approach.

Light is a uniquely powerful tool for controlling molecular events in biology. No other external input (e.g., heat, ultrasound, magnetic field) can be so tightly focused or so highly regulated as a clinical laser. Drug delivery vehicles that can be photonically activated have been developed across many platforms, from the simplest "caging" of therapeutics in a prodrug form, to more complex micelles and circulating liposomes that improve drug uptake and efficacy, to large-scale hydrogel platforms that can be used to protect and deliver macromolecular agents including full-length proteins. In this Review, we discuss recent innovations in photosensitive drug delivery and highlight future opportunities to engineer and exploit such light-responsive technologies in the clinical setting.

Efficacy and safety of scleral crosslinking using poly(ethylene glycol)ether tetrasuccinimidyl glutarate for form-deprivation myopia progression in rabbits.

Myopia is becoming increasingly prevalent worldwide at an alarming rate. However, no effective treatment is available for inhibiting myopia progression. Materials chemistry advancements have made it possible to regulate mechanical properties and rate of degradation with good compatibility by developing newly crosslinking systems such as the branched polyethylene glycol (PEG) systems. Herein, we presented a PEG molecule with N-hydroxysuccinimide (NHS) ester functional groups at the chain ends as a macromolecular crosslinking agent for the treatment of myopia. We found that the scleral collagen crosslinked with the four-armed star-shaped PEG molecule with NHS ester functional group (4S-PEG) showed better biomechanical properties, increased thermal stability and higher resistance to degradation. 4S-PEG exhibited relatively low cytotoxicity for human fetal scleral fibroblasts. The retrobulbar injection of 4S-PEG at a relatively low concentration (2.5 mM) showed good effective control of the progression of form-deprivation myopia in rabbits. There were no signs of adverse effect or damage by repeated injections with 4S-PEG in rabbits. The results of this work demonstrate that 4S-PEG can serve as a robust macromolecular crosslinking agent and is expected to have promise for application in the treatment of the progression of myopia.

Approaches for the inhibition and elimination of microbial biofilms using macromolecular agents.

Biofilms are complex three-dimensional structures formed at interfaces by the vast majority of bacteria and fungi. These robust communities have an important detrimental impact on a wide range of industries and other facets of our daily lives, yet their removal is challenging owing to the high tolerance of biofilms towards conventional antimicrobial agents. This key issue has driven an urgent search for new innovative antibiofilm materials. Amongst these emerging approaches are highly promising materials that employ aqueous-soluble macromolecules, including peptides, proteins, synthetic polymers, and nanomaterials thereof, which exhibit a range of functionalities that can inhibit biofilm formation or detach and destroy organisms residing within established biofilms. In this Review, we outline the progress made in inhibiting and removing biofilms using macromolecular approaches, including a spotlight on cutting-edge materials that respond to environmental stimuli for "on-demand" antibiofilm activity, as well as synergistic multi-action antibiofilm materials. We also highlight materials that imitate and harness naturally derived species to achieve new and improved biomimetic and biohybrid antibiofilm materials. Finally, we share some speculative insights into possible future directions for this exciting and highly significant field of research.

Polymerizable Gd(iii) building blocks for the synthesis of high relaxivity macromolecular MRI contrast agents.

A new synthetic strategy for the preparation of macromolecular MRI contrast agents (CAs) is reported. Four gadolinium(iii) complexes bearing either one or two polymerizable methacrylamide groups were synthesized, serving as monomers or crosslinkers for the preparation of water-soluble, polymeric CAs using Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization. Using this approach, macromolecular CAs were synthesized with different architectures, including linear, hyperbranched polymers and gels. The relaxivities of the polymeric CAs were determined by NMR relaxometry, revealing an up to 5-fold increase in relaxivity (60 MHz, 310 K) for the linear polymers compared with the clinically used CA, Gd-DOTA. Moreover, hyperbranched polymers obtained from Gd(iii) crosslinkers, displayed even higher relaxivities up to 22.8 mM−1 s−1, approximately 8 times higher than that of Gd-DOTA (60 MHz, 310 K). A detailed NMRD study revealed that the enhanced relaxivities of the hyperbranched polymers were obtained by limiting the local motion of the crosslinked Gd(iii) chelate. The versatility of RAFT polymerization of Gd(iii) monomers and crosslinkers opens the doors to more advanced polymeric CAs capable of multimodal, bioresponsive or targeting properties.

Preparation of Novel High-Efficiency Macromolecular Carbon-Forming Agent Modified by Silica and its Application in Halogen-Free Flame Retardant Tpee

Preparation of Novel High-Efficiency Macromolecular Carbon-Forming Agent Modified by Silica and its Application in Halogen-Free Flame Retardant Tpee

Liposomes Derived from Macrocyclic Polyamine as a Versatile Macromolecule Delivery System

Macromolecular therapeutic agents such as nucleic acids and proteins have attracted increased attention due to the satisfactory specificity and potent therapeutic effect, holding great significance...

Synthesis and properties of styrenic triblock copolymers with dual structural asymmetry via RAFT emulsion polymerization

The polystyrene-block-poly(n-butyl acrylate)-block-polystyrene (PSt-b-PBA-b-PSt, SBAS) triblock copolymers (TBCPs) with dual structural asymmetry were synthesized via a reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization. The dual structural asymmetry contained two asymmetric outer PSt blocks and a single short ionic block on one chain end while the SBAS TBCPs had the almost same molecular weight (~100 kDa) and composition (~70 wt% of PSt and ~30 wt% of PBA) excluding the short ionic block. The dual structural asymmetry with a synergistic effect was designed by locating the long PSt block near the short ionic block that was derived from ionic macromolecular RAFT agent. With the SBAS TBCPs having microphase separation structure, the structural asymmetry of two outer PSt blocks tailored the interaction of PSt and PBA blocks, further leading to the change of static tensile and dynamic mechanical properties, and rheology. Structural asymmetry will provide an alternative to tailor-made properties of TBCPs.

Polycarbonate-block-polycycloalkenes via epoxide/carbon dioxide copolymerization and ring-opening metathesis polymerization

Aliphatic polycarbonate (APC) macromolecular chain-transfer agents (macro-CTAs) with an allyl end group were successfully synthesized by cobalt-catalyzed epoxide/carbon dioxide copolymerization in the presence of allyl alcohol as a chain-transfer agent. The ring-opening metathesis polymerization of cycloalkene monomers using the obtained APC macro-CTAs yielded the corresponding APC-block-polycycloalkene copolymers. Thermal degradation temperatures of the APC blocks were found to be slightly higher (≈20 oC) than those of the block copolymers containing APC and vinyl-polymer blocks we have previously reported. Aliphatic polycarbonate (APC) macromolecular chain-transfer agents (macro-CTAs) with an allyl end group were successfully synthesized by cobalt-catalyzed epoxide/carbon dioxide copolymerization in the presence of allyl alcohol as a chain-transfer agent. The ring-opening metathesis polymerization of cycloalkene monomers using the obtained APC macro-CTAs yielded the corresponding APC-block-polycycloalkene copolymers.

Structural Optimization and Enhanced Prodrug-Mediated Delivery Overcomes Camptothecin Resistance in High-Risk Solid Tumors.

Camptothecins are potent topoisomerase I inhibitors used to treat high-risk pediatric solid tumors, but they often show poor efficacy due to intrinsic or acquired chemoresistance. Here, we developed a multivalent, polymer-based prodrug of a structurally optimized camptothecin (SN22) designed to overcome key chemoresistance mechanisms. The ability of SN22 vs. SN38 (the active form of irinotecan/CPT-11) to overcome efflux pump-driven drug resistance was tested. Tumor uptake and biodistribution of SN22 as a polymer-based prodrug (PEG-[SN22]4) compared with SN38 was determined. The therapeutic efficacy of PEG-[SN22]4 to CPT-11 was compared in: (i) spontaneous neuroblastomas (NB) in transgenic TH-MYCN mice; (ii) orthotopic xenografts of a drug-resistant NB line SK-N-BE(2)C (mutated TP53); (iii) flank xenografts of a drug-resistant NB-PDX; and (iv) xenografts of Ewing sarcoma and rhabdomyosarcoma. Unlike SN38, SN22 inhibited NB cell growth regardless of ABCG2 expression levels. SN22 prodrug delivery resulted in sustained intratumoral drug concentrations, dramatically higher than those of SN38 at all time points. CPT-11/SN38 treatment had only marginal effects on tumors in transgenic mice, but PEG-[SN22]4 treatment caused complete tumor regression lasting over 6 months (tumor free at necropsy). PEG-[SN22]4 also markedly extended survival of mice with drug-resistant, orthotopic NB and it caused long-term (6+ months) remissions in 80% to 100% of NB and sarcoma xenografts. SN22 administered as a multivalent polymeric prodrug resulted in increased and protracted tumor drug exposure compared with CPT-11, leading to long-term "cures" in NB models of intrinsic or acquired drug resistance, and models of high-risk sarcomas, warranting its further development for clinical trials. SIGNIFICANCE: SN22 is an effective and curative multivalent macromolecular agent in multiple solid tumor mouse models, overcoming common mechanisms of drug resistance with the potential to elicit fewer toxicities than most cancer therapeutics.

Optimization of Ultrasound-Assisted Extraction of Functional Food Fiber from Canadian Horseweed (Erigeron canadensis L.)

Much attention has been recently paid to the design of sustainable processes for the production of functional food additives based on renewable resources. Thus, methods for incorporation of green techniques in treatment of undeveloped biomass, resulting in value-added bioproducts, are in great demand. We focus here on the biological activity and chemical properties of Erigeron canadensis (horseweed) functional food fiber, which can be strongly affected by the extraction procedure employed. In the present contribution, we report on an attempt to introduce a sustainable and energy-efficient ultrasound-assisted extraction process, followed by a multistep purification procedure, resulting in a macromolecular plant-derived anticoagulant agent. The most efficient ultrasound-assisted process was determined by optimization through the response surface methodology I-optimal design (24). A comparison with the conventional procedure for retrieval of horseweed biomacromolecules revealed that the optimized ultrasound-assisted extraction was more sustainable, with the cumulative energy demand being 38% lower (12.2 MJ), 6.6 times reduced water consumption (3.5 L), and 1.2 times shorter (41 h) total processing time. Moreover, the optimal ultrasound-assisted extraction process-purified food fiber turned out to be a better anticoagulant agent by 57%, compared to a conventional product, and was a more selective indirect inhibitor of the human Xa coagulation factor.

Synthesis of a triazine-based macromolecular hybrid charring agent containing zinc borate and its flame retardancy and thermal properties in polypropylene

A triazine-based macromolecular hybrid charring agent containing zinc borate (MCA-K-ZB) was synthesized and combined with ammonium polyphosphate (APP) to improve the flame retardancy of polypropylene (PP). The flame retardancy and thermal properties of PP composites were investigated using limited oxygen index, vertical burning test, and thermogravimetric analysis. The results showed APP/MCA-K-ZB can improve the flame retardancy of PP compared with APP/MCA-K/ZB. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The SEM result shows that MCA-K-ZB can improve the compactness and continuity of char residue compared with MCA-K/ZB, therefore improving the flame retardancy of PP composites.