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PubMed2006

Three-dimensional microchannels in biodegradable polymeric films for control orientation and phenotype of vascular smooth muscle cells.

The poor mechanical strength and vasoactivity of current small-diameter tissue engineered blood vessels (TEBVs) remain unsolved problems. Given the plasticity of smooth muscle cells (SMCs), 1 of the main limitations of current scaffolding techniques is the difficulty in controlling SMC phenotype shifts in vitro. A synthetic phenotype allows the cells to rapidly proliferate and produce extracellular matrix (ECM), whereas a shift to contractile phenotype with organized ECM ultimately provides a functional blood vessel. In this study, 3D deep (65 microm) and wide microchannels separated by high-aspect ratio (8) microwalls were successfully ultraviolet (UV) microembossed using a liquid UV polymerizable biodegradable macromer (poly(epsilon-caprolactone-r-L-lactide-r-glycolide) diacrylate) and the in vitro guidance effects of varying channel width (40-160 microm) on SMCs were verified. The results show that SMCs cultured in the wider microchannels (80-160 microm wide) switch from fibroblast morphology and random orientation to spindle-shaped morphology, and align along the direction of the microchannel nearing confluence achieved with similar cell density to unpatterned film. Further, an enhanced expression of smooth muscle alpha-actin of SMCs grown on micropatterns was found nearing confluence, which demonstrates a phenotype shift to a more contractile phenotype. These films are flexible and can be folded into tubular and lamellar structures for tissue engineering of small-diameter TEBVs as well as other organs such as esophagus or intestine. These results suggest that these micropatterned synthetic biodegradable scaffolds may be useful for guiding SMCs to grow into functional, small-diameter vascular grafts.

Animals↗
PubMed2003

BSD: the Biodegradative Strain Database.

The Biodegradative Strain Database (BSD) is a freely-accessible, web-based database providing detailed information on degradative bacteria and the hazardous substances that they degrade, including corresponding literature citations, relevant patents and links to additional web-based biological and chemical data. The BSD (http://bsd.cme.msu.edu) is being developed within the phylogenetic framework of the Ribosomal Database Project II (RDPII: http://rdp.cme.msu.edu/html) to provide a biological complement to the chemical and degradative pathway data of the University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD: http://umbbd.ahc.umn.edu). Data is accessible through a series of strain, chemical and reference lists or by keyword search. The web site also includes on-line data submission and user survey forms to solicit user contributions and suggestions. The current release contains information on over 250 degradative bacterial strains and 150 hazardous substances. The transformation of xenobiotics and other environmentally toxic compounds by microorganisms is central to strategies for biocatalysis and the bioremediation of contaminated environments. However, practical, comprehensive, strain-level information on biocatalytic/biodegradative microbes is not readily available and is often difficult to compile. Similarly, for any given environmental contaminant, there is no single resource that can provide comparative information on the array of identified microbes capable of degrading the chemical. A web site that consolidates and cross-references strain, chemical and reference data related to biocatalysis, biotransformation, biodegradation and bioremediation would be an invaluable tool for academic and industrial researchers and environmental engineers.

Bacteria↗
PubMed1999

The use of poultry litter as co-substrate and source of inorganic nutrients and microorganisms for the ex situ biodegradation of petroleum compounds.

The purpose of this investigation was to determine the feasibility of utilizing poultry litter as a source of microorganisms, C co-substrate, N, and P to enhance the biodegradation of petroleum compounds in contaminated soil. An initial laboratory-scale study utilized soil contaminated with approximately 3,000 mg/kg (ppm) total petroleum hydrocarbons (TPHC) as diesel fuel. Biotreatment units, each containing 10 L of contaminated soil, were supplemented (0, 1, 10, and 20%, total weight basis) with broiler litter containing 3.65% N and 1.89% P. Petroleum-degrading microorganisms previously enriched from broiler and turkey litter were also inoculated into the litter-treated units. A significant first order rate of TPHC biodegradation was measured for all treatment units containing broiler litter (P < 0.05). Based on these results, a subsequent study was conducted at the site of a commercial facility permitted to treat soil (ex situ) contaminated with hazardous compounds. Soil treatment plots, each containing approximately 1 ton of soil contaminated with approximately 1,200 to 1,600 mg/kg diesel fuel were established. Each plot was replicated four times and the experiment was conducted for 35 d. Treatments were as follows: control, soil only; soil + commercial blend of bioremediation nutrients; soil + commercial fertilizer; soil + poultry litter (1% by volume); soil + poultry litter (10% by volume); soil + pelleted poultry litter (10% by volume). The results showed that the remediation of soil contaminated with petroleum compounds is significantly (P < 0.05) enhanced when supplemented with poultry litter (pelleted or nonpelleted) in concentrations of 10% soil volume. These results demonstrate the potential for a specialized market for the use of poultry litter.

Animals↗
PubMed1995

Prolongation of epidural anesthesia in the rabbit with the use of a biodegradable copolymer paste containing lidocaine.

Prolongation of the drug effect using a drug-delivery system has recently been introduced in local anesthesia. In this study, we investigated the prolonging effect of an epidurally injected biodegradable copolymer paste containing 10% lidocaine (Lid-CoPol). Twenty-nine rabbits were studied. A catheter was placed in the epidural space at the level of L6-7 in each animal. A solution of 10% lidocaine (Group I, n = 12), or a copolymer containing 10% lidocaine (Lid-CoPol), (Group II, n = 12) or copolymer paste only (Group III, n = 5) was injected epidurally at a dose of 0.15 mL/kg. The effect of each drug was assessed by evaluation of response to pain stimulation and of the degree of motor block produced. The plasma lidocaine concentration was also measured consecutively in five animals of both Groups I and II. The duration of sensory and motor block of Lid-CoPol was 800% and 975% longer, respectively, than that of plain lidocaine solution. Plasma lidocaine concentration reached a maximum 5 min after injection (5.5 +/- 0.5 micrograms/mL) in Group I. In Group II, the level reached a maximum 30 min after injection (3.7 +/- 1.5 micrograms/mL). The findings are attributed in part to the slow release of lidocaine from the biodegradable copolymer paste, which is suggested as a new drug-delivery system for local anesthetics.

Anesthesia, Epidural↗
PubMed1996

Prolonged regional nerve blockade. Injectable biodegradable bupivacaine/polyester microspheres.

BACKGROUND: Biodegradable microspheres are a useful method of drug delivery because they are both injectable and biodegradable, eliminating the need for surgical implantation or removal. Previous work has characterized implantable preparations of local anesthetics in polymer pellets for prolonged regional anesthesia. In this article, the authors characterize injectable suspensions of bupivacaine-polymer microspheres and examine whether they can produce prolonged blockade of the sciatic nerve in rats. METHODS: Microspheres were prepared using polylactic-co-glycolic acid polymers loaded with 75% w/w bupivacaine by a solvent evaporation method. Bupivacaine release from microspheres was determined in vitro by ultraviolet spectroscopy and scintillation counting. Sensory and motor blockade of the rat sciatic nerve were assessed in vivo after injection of microsphere suspensions. RESULTS: Depending on the type of microspheres, the dose, and the additive used, mean duration of sciatic nerve block ranged from 10 h to 5.5 days. Incorporation of 0.05% w/w dexamethasone into the microspheres resulted in significant prolongation of block (up to 13-fold), and only preparations that contained dexamethasone produced blocks lasting beyond 1 day. Bupivacaine was released in a controlled manner in vitro. Dexamethasone does not substantially slow bupivacaine release from microspheres in vitro. CONCLUSIONS: Prolonged percutaneous blockade of peripheral nerves is feasible. The recovery from blockade is complete, and plasma bupivacaine levels are far below the range associated with systemic toxicity. The mechanisms underlying the dexamethasone block-prolonging effect are under investigation.

Anesthetics, Local↗
PubMed1997

Biodegradable and titanium plating in experimental craniotomies: a radiographic follow-up study.

Plain film radiography and computed tomography (CT) were evaluated in assessing the consolidation of experimental craniotomy lines covered with titanium miniplates or biodegradable self-reinforced poly-L-lactide (SR-PLLA) plates. Two sagittal (2.3-2.5 mm wide and 22 mm long) symmetrical craniotomy lines were made in the skulls of eight young sheep. One craniotomy line was covered with a biodegradable SR-PLLA plate and the other with a titanium miniplate. Both plates were fixed with four titanium miniscrews. Consolidation of the osteotomies was studied using plain film radiography and CT 6, 12, 20, and 52 weeks postoperatively. Microradiography and histology were used for reference. Plain film was not reliable in assessing osseous consolidation because false-positive results were obtained in three osteotomies. Osseous consolidation was more reliably assessed by CT, which showed consolidation on the SR-PLLA side within 20 weeks, whereas none of the titanium-plated lines was consolidated by 52 weeks. Superior consolidation under the resorbable plate was confirmed in histology and microradiography. The radiolucent SR-PLLA plates did not interfere with CT, whereas the titanium plates caused minor CT artifacts.

Animals↗
PubMed1997

MR imaging of biodegradable polylevolactide osteosynthesis devices in the ankle.

OBJECTIVE: To assess the feasibility of magnetic resonance (MR) imaging in the postoperative follow-up after internal fracture fixation using biodegradable polylevolactide (PLLA) plugs and to investigate the MR characteristics of these devices. STUDY DESIGN AND METHODS: MR findings in ten patients with displaced malleolar fractures treated by internal fixation using absorbable PLLA plugs were evaluated after three different postoperative periods. The average postoperative follow-up time was thirty months for four patients, forty-two months for another four patients, and fifty-one months for the remaining two patients. RESULTS: On T1-weighted coronal images, the geometry of the PLLA plug was clearly visible in all cases, without signs of fatigue failure or absorption. The host-to-tissue area between the deployed two fins of the plug showed higher signal intensity than the surrounding cancellous bone on fat-saturated proton density (PD) and turbo inversion recovery (tIR) images. This area had signal intensity similar to articular cartilage on T1-weighted coronal images. In none of the cases could any fluid accumulation be seen around the plug. In all ten cases, a thin rim with signal intensity similar to the area between the deployed fins was detected around the PLLA plug on fat-saturated axial PD images. On fat-saturated T2 and tIR sequences, this rim was less clearly detectable in all cases. No differences in the signal intensity or geometry of the PLLA plug on the MR images emerged between the three patient groups with mean follow-ups of thirty, forty-two, and fifty-one months. No artifacts produced by the implants were seen on any of the MR images. A biopsy specimen obtained at a reoperation necessary seventeen months postoperatively showed no signs of degradation of the PLLA plug. CONCLUSIONS: MR imaging can visualize PLLA implants within bone. It also shows, without artifacts, the tissue interaction between the artificial biodegradable material and bone tissue in humans.

Absorption↗
PubMed2002

Tissue-engineered cartilage on biodegradable macroporous scaffolds: cell shape and phenotypic expression.

OBJECTIVE: The purpose of the study was to establish in vitro culture of chondrocytes on biodegradable, poly(D,L-lactic-co-glycolic acid) [PLGA] scaffolds. STUDY DESIGN: Laboratory experiment using cartilage of rat rib and biodegradable scaffolds. METHODS: Chondrocytes were cultured on a poly-hydroxyethyl methacrylate (poly-HEMA)-coated dish, proliferated, and transferred into the PLGA scaffolds. Phenotypic expression of cells was examined according to the condition of poly-HEMA coating. Morphological, biochemical, and immunohistochemical characteristics of cells cultured within PLGA scaffolds were also examined. RESULTS: Chondrocytes cultured on a poly-HEMA-coated dish aggregated into distinct nodules containing large clusters of spherical cells and showed cartilage-specific phenotype, collagen type II. The results of immunostaining andreverse transcriptase-polymerase chain reaction of cells cultured within PLGA scaffolds showed cartilage-specific morphological appearance and structural characteristics such as lacunae and expression of collagen type II. CONCLUSION: The chondrocytes cultured on a poly-HEMA-coated dish and PLGA scaffolds showed chondrocyte-specific phenotypes and morphological appearance.

Animals↗
PubMed2005

Novel strategy for treatment of inner ears using a biodegradable gel.

OBJECTIVE: The present study aimed to evaluate the efficacy of a biodegradable hydrogel as a drug-delivery medium for the inner ear. Brain-derived neurotrophic factor (BDNF) was chosen as the agent to be administered. METHOD: First, we used an enzyme-linked immunosorbent assay to measure BDNF concentrations in the cochlear fluid after placing a hydrogel containing this agent onto the round-window membrane of the ear. Second, the functional and histologic protection of the auditory primary neurons (spiral ganglion neurons [SGNs]) by BDNF applied through the hydrogel was examined using an animal model of SGN degeneration. RESULTS: The results revealed sustained delivery of BDNF into the cochlear fluid by way of the hydrogel. Second, the functional and histologic protection of the auditory primary neurons (SGNs) by BDNF applied through the hydrogel was examined using an animal model of SGN degeneration. The measurement of electrically evoked auditory-brainstem responses demonstrated that BDNF delivered by way of the hydrogel significantly reduced the threshold elevation. Immunohistochemistry for neurofilament 200 kD demonstrated increased survival of SGNs because of BDNF application through the hydrogel. CONCLUSION: These findings indicate that biodegradable hydrogels can be used for drug delivery to the inner ear.

Animals↗
PubMed2006

Cochlear protection by local insulin-like growth factor-1 application using biodegradable hydrogel.

OBJECTIVE: The aim of this experimental study was to examine the potential of local recombinant human insulin-like growth factor-1 (rhIGF-1) application through a biodegradable hydrogel for the treatment of cochleae. METHODS: A hydrogel immersed with rhIGF-1 was placed on the round window membrane of Sprague-Dawley rats while a hydrogel immersed with physiological saline was applied to control animals. On day 3 after drug application, the animals were exposed to white noise at 120 dB sound pressure level (SPL) for 2 hours. Cochlear function was monitored using measurements of auditory brain stem responses (ABRs) at frequencies of 8, 16, and 32 kHz. The temporal bones were collected 7 or 30 days after noise exposure and the loss of hair cells was quantitatively analyzed. RESULTS: Local rhIGF-1 treatment significantly reduced the elevation of ABR thresholds on days 7 and 30 after noise exposure. Histologic analysis revealed that local rhIGF-1 treatment significantly prohibited the loss of outer hair cells. CONCLUSIONS: These findings demonstrate that local IGF-1 application through the biodegradable hydrogel has the potential for protection of cochleae from noise trauma.

Administration, Topical↗
PubMedDate not supplied

Internal fixation with biodegradable rods in pediatric fractures: one-year follow-up of fifty patients.

Fifty children with transphyseal or osteochondral fractures were treated with biodegradable osteosynthesis material and followed for at least 1 year. All 50 fractures healed, and there were no major complications; 11 of them were fractures of the radial humeral condyle. In a prospective randomized study, they were compared with metal pin fixation of the same fracture (eight cases). No major differences were noted. After the study was completed, we observed two cases of nonunion of intraarticular fractures of the radial head, probably related to foreign body reaction to the resorbable implant material. Biodegradable osteosynthesis material is advantageous in treatment of children's fractures because it makes a removal operation unnecessary. It is ideal in cases of osteochondral fractures. Further experience with this material is necessary, however, before it can be safely recommended.

Adolescent↗
PubMed1986

Metabolite production during the biodegradation of the surfactant sodium dodecyltriethoxy sulphate under mixed-culture die-away conditions.

Sodium dodecyltriethoxy sulphate (SDTES), either pure or as a component of commercial surfactant mixtures, underwent rapid primary biodegradation by mixed bacterial cultures in OECD screen and river-water die-away tests. Inoculation of [35S]SDTES-containing solutions with OECD screen test media acclimatized to surfactants or their degradation products led to production of various 35S-labelled glycol sulphates and their oxidation products, all known to occur during degradation of [35S]SDTES by pure bacterial isolates. Triethylene glycol monosulphate was the major catabolite together with smaller amounts of di- and monoethylene glycol monosulphates implying, by analogy with pure cultures, that ether-cleavage was the major primary biodegradation step. The oxidation product (carboxylate derivative) of each glycol sulphate was also detected together with metabolites tentatively identified as omega-/beta-oxidation products of the dodecyl chain. Relatively little SO2-4 was liberated directly from SDTES but mixed cultures derived from sewage could metabolize the sulphated glycols to SO2-4. The environmental relevance of these degradation routes was established by following metabolite production from [35S]SDTES in full-scale river-water die-away tests. Triethylene glycol sulphate was formed first, then rapidly oxidized to acetic acid 2-(diethoxy sulphate) which persisted as the major metabolite for 2-3 weeks. Small amounts of sulphated derivatives of di- and monoethylene glycols were also detected during the same period. Very little SO2-4 was formed directly from SDTES but large amounts accompanied the eventual disappearance of glycol sulphate derivatives. None of the 35S-labelled organic metabolites was persistent and, whenever [35S]SDTES was a component of a commercial mixture, all ester sulphate was completely mineralized to 35SO4(2-) within 28 d.

Biodegradation, Environmental↗
PubMed2003

Site-directed mutagenesis of an extradiol dioxygenase involved in tetralin biodegradation identifies residues important for activity or substrate specificity.

The sequence of the extradiol dioxygenase ThnC, involved in tetralin biodegradation, was aligned with other extradiol dioxygenases involved in biodegradation of polycyclic compounds, and a three-dimensional model of ThnC, based on the structure of the previously crystallized 2,3-dihydroxybiphenyl dioxygenase from Burkholderia fungorum LB400, was built. In order to assess the functional importance of some non-active-site residues whose relevance could not be established by structural information, a number of positions surrounding the substrate-binding site were mutated in ThnC. Ten mutant proteins were purified and their activity towards 1,2-dihydroxytetralin, 1,2-dihydroxynaphthalene and 2,3-dihydroxybiphenyl was characterized. N213H, Q198H, G206M, A282R and A282G mutants increased k(cat)/K(m) at least twofold using 1,2-dihydroxytetralin as the substrate, thus showing that activity of ThnC is not maximized for this substrate. N213H and Q198H mutants increased k(cat)/K(m) using any of the substrates tested, thus showing the relevance for activity of these two histidines, which are highly conserved in dihydroxybiphenyl dioxygenases, but not present in dihydroxynaphthalene dioxygenases. Different substitutions in position 282 had different effects on general activity or substrate specificity, thus showing the functional importance of the most C-terminal beta-sheet of the protein. A251M and G206M mutants showed increased activity specifically for a particular substrate. N213H, G206M, A282R, A282G and Y177I substitutions resulted in enzymes more tolerant to acidic pH, the most striking effect being observed in mutant Y177I, which showed maximal activity at pH 5.5. In addition, Q198D and V175D mutants, which had altered K(m), also showed altered sensitivity to substrate inhibition, thus indicating that inhibition is exerted through the same binding site. This mutational analysis, therefore, identified conserved residues important for activity or substrate specificity, and also shed some light on the mechanism of substrate inhibition exhibited by extradiol dioxygenases.

Amino Acid Sequence↗
PubMed2004

Allergen-loaded biodegradable poly(D,L-lactic-co-glycolic) acid nanoparticles down-regulate an ongoing Th2 response in the BALB/c mouse model.

BACKGROUND AND OBJECTIVE: Biocompatible and biodegradable microparticles have gained interest as antigen delivery systems during the recent years. We investigated whether biodegradable poly(d,l-lactic-co-glycolic) acid (PLGA) nanospheres could be used as allergen vehicles for few-shot therapy of type I allergy. METHODS: The major birch pollen allergen Bet v 1 was encapsulated in PLGA nanospheres (PLGA-Bet v 1). We examined the antigenicity and the immune response to PLGA-Bet v 1 in a BALB/c mouse model. RESULTS: The antigenicity of Bet v 1 was largely unaffected by PLGA entrapment. When BALB/c mice were immunized subcutaneously with PLGA-Bet v 1, they formed allergen-specific IgG antibodies, but did not develop hypersensitivity to Bet v 1, as shown by type I skin tests. To evaluate their therapeutic potential, PLGA-Bet v 1 with or without Al(OH)3 or non-entrapped Bet v 1 with Al(OH)3 were used for single-shot treatment of sensitized mice. Both groups treated with PLGA-Bet v 1 developed high levels of Bet v 1-specific IgG2a antibodies (P<0.01), whereas IgG1 levels decreased significantly (P<0.01). Moreover, T cells from mice treated with PLGA-Bet v 1 showed IFN-gamma and IL-10 production. The synthesis of these cytokines was enhanced in the groups where Al(OH)3 had been added to the vaccine formulation. CONCLUSION: Allergen-loaded PLGA nanoparticles modulate an ongoing Th2 response in the BALB/c mouse model, as demonstrated by down-regulation of IgG1 and production of IFN-gamma and IL-10. Our data strongly suggest that PLGA nanospheres can advantageously be used for formulations of allergen extracts or allergen derivatives for the few-shot treatment of type I allergy.

Allergens↗
PubMed2006

Enhanced biodegradation of diesel oil by a newly identified Rhodococcus baikonurensis EN3 in the presence of mycolic acid.

AIMS: The aim of the present study was to isolate and characterize a bacterium, strain EN3, capable of using diesel oil as a major carbon and energy source, and to analyse the enhancement of diesel oil degradation by this organism using synthetic mycolic acid (2-hexyl-3-hydroxyldecanoic acid). METHOD AND RESULTS: An actinomycete with the ability to degrade diesel oil was isolated from oil contaminated soil and characterized. The strain had phenotypic properties consistent with its classification in the genus Rhodococcus showing a 16S rRNA gene similarity of 99.7% with Rhodococcus baikonurensis DSM 44587(T). The ability of the characterized strain to degrade diesel oil at various concentrations (1000, 5000, 10 000 and 20 000 mg l(-1)) was determined. The effect of synthetic mycolic acid on the biodegradation of diesel oil was investigated at the 20 000 mg l(-1) concentration; the surfactant was added to the flask cultures at three different concentrations (10, 50 and 100 mg l(-1)) and degradation followed over 7 days. Enhanced degradation was found at all three concentrations of the surfactant. In addition, the enhancement of diesel oil degradation by other surfactants was observed. CONCLUSIONS: The synthetic mycolic acid has potential for the remediation of petroleum-contaminated sites from both an economic and applied perspective as it can stimulate biodegradation at low concentrations. SIGNIFICANCE AND IMPACT OF THE STUDY: This study showed that the synthesized mycolic acid can be used for potential applications in the bioremediation industries, for example, in oil spill clean-up, diesel fuel remediation and biostimulation.

Biodegradation, Environmental↗
PubMed2006

Carbazole biodegradation in gas oil/water biphasic media by a new isolated bacterium Burkholderia sp. strain IMP5GC.

AIM: To select carbazole-degrading bacteria able to survive and metabolize carbazole in biphasic organic-water media and to study the factors affecting carbazole degradation in such conditions. METHODS AND RESULTS: In this research a new carbazole-degrading strain was isolated from hot springs in Mexico. This bacterium was preliminary identified as Burkholderia sp. IMP5GC and was able to grow using carbazole as sole carbon and nitrogen source. Genetic analysis showed that this bacterium carries carA genes identical to those reported in Pseudomonas resinovorans CA10. Burkholderia IMP5GC efficiently degraded carbazole in aqueous media as well as in biphasic media with n-hexadecane. Furthermore, the strain IMPGC5 efficiently reduced the concentration of carbazole and monomethyl carbazole species in gas oil-water biphasic media. CONCLUSIONS: This study demonstrates the biodegradation of carbazole in biphasic gas oil/water media (1 : 1), regardless of the highly toxic effects of this petroleum distillate. SIGNIFICANCE AND IMPACT OF THE STUDY: Biodegradation of carbazole in biphasic media contributes to the understanding and design of bioprocesses for carbazole removal from petroleum-upgrading fractions and other carbazole-rich organic mixtures.

Alkanes↗
PubMed2006

Effect of iron(III), humic acids and anthraquinone-2,6-disulfonate on biodegradation of cyclic nitramines by Clostridium sp. EDB2.

AIMS: To determine the biodegradation of cyclic nitramines by an anaerobic marine bacterium, Clostridium sp. EDB2, in the presence of Fe(III), humic acids (HA) and anthraquinone-2,6-disulfonate (AQDS). METHODS AND RESULTS: An obligate anaerobic bacterium, Clostridium sp. EDB2, degraded RDX and HMX, and produced similar product distribution including nitrite, methylenedinitramine, nitrous oxide, ammonium, formaldehyde, formic acid and carbon dioxide. Carbon (C) and nitrogen (N) mass balance for RDX products were 87% and 82%, respectively, and for HMX were 88% and 74%, respectively. Bacterial growth and biodegradation of RDX and HMX were stimulated in the presence of Fe(III), HA and AQDS suggesting that strain EDB2 utilized Fe(III), HA and AQDS as redox mediators to transfer electrons to cyclic nitramines. CONCLUSIONS: Strain EDB2 demonstrated a multidimensional approach to degrade RDX and HMX: first, direct degradation of the chemicals; second, indirect degradation by reducing Fe(III) to produce reactive-Fe(II); third, indirect degradation by reducing HA and AQDS which act as electron shuttles to transfer electrons to the cyclic nitramines. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study could be helpful in determining the fate of cyclic nitramine energetic chemicals in the environments rich in Fe(III) and HA.

Anthraquinones↗