Exposure to low doses of pesticides induces an immune response and the production of nitric oxide in honeybees

Pesticide immunotoxicity on insects - Are agroecosystems at risk?

Recent years have witnessed heightened scrutiny of the non-target sublethal effects of pesticides on behavioural and physiological traits of insects. Traditionally, attention has focused on investigating pesticides' primary modes of action, often overlooking the potential secondary mechanisms. This review brings forth the nuanced impacts of sublethal pesticide exposure on the immune system of target and non-target insect species. Pesticides, such as for example neonicotinoids, suppress immune response, while others, like certain organophosphates and some insect growth regulators (IGRs), appear to bolster immunocompetence under certain circumstances. Beyond their individual impacts, the synergic effects of pesticide mixtures on insect immunity are garnering increasing interest. This review thus summarizes recent advances in the immunomodulatory effects of pesticides, detailing both mechanisms and consequences of such interactions. The implications of these effects for ecosystem preservation and viability of beneficial organisms, such as pollinators and natural enemies of pests, are discussed. The review also considers further research directions on pesticide secondary modes of action and explores potential implications for integrated pest management (IPM) programs, as several model organisms studied are crop pest species. While current data provide an expansive overview of how insect innate immunity is modulated, concrete endpoints remain elusive requiring further research into pesticide secondary modes of actions.

The neonicotinoid acetamiprid reduces larval and adult survival in honeybees (Apis mellifera) and interacts with a fungicide mixture

Plant protection products (PPPs), which are frequently used in agriculture, can be major stressors for honeybees. They have been found abundantly in the beehive, particularly in pollen. Few studies have analysed effects on honeybee larvae, and little is known about effects of insecticide-fungicide-mixtures, although this is a highly realistic exposure scenario. We asked whether the combination of a frequently used insecticide and fungicides would affect developing bees. Honeybee larvae (Apis mellifera carnica) were reared in vitro on larval diets containing different PPPs at two concentrations, derived from residues found in pollen. We used the neonicotinoid acetamiprid, the combined fungicides boscalid/dimoxystrobin and the mixture of all three substances. Mortality was assessed at larval, pupal, and adult stages, and the size and weight of newly emerged bees were measured. The insecticide treatment in higher concentrations significantly reduced larval and adult survival. Interestingly, survival was not affected by the high concentrated insecticide-fungicides-mixture. However, negative synergistic effects on adult survival were caused by the low concentrated insecticide-fungicides-mixture, which had no effect when applied alone. The lower concentrated combined fungicides led to significantly lighter adult bees, although the survival was unaffected. Our results suggest that environmental relevant concentrations can be harmful to honeybees. To fully understand the interaction of different PPPs, more combinations and concentrations should be studied in social and solitary bees with possibly different sensitivities.

Physiological responses of the stingless bee Partamona helleri to oral exposure to three agrochemicals: impact on antioxidant enzymes and hemocyte count

Agrochemicals pose significant threats to the survival of bees, yet the physiological impacts of sublethal doses on stingless bees remain poorly understood. This study investigated the effects of acute oral exposure to three commercial formulations of agrochemicals [CuSO4 (leaf fertilizer), glyphosate (herbicide), and spinosad (bioinsecticide)] on antioxidant enzymes, malondialdehyde content (MDA), nitric oxide (NO) levels, and total hemocyte count (THC) in the stingless bee Partamona helleri. Foragers were exposed to lethal concentrations aimed to kill 5% (LC5) of CuSO4 (120 μg mL-1) or spinosad (0.85 μg mL-1) over a 24-h period. Glyphosate-exposed bees received the recommended label concentration (7400 μg mL-1), as they exhibited 100% survival after exposure. Ingestion of CuSO4 or glyphosate-treated diets by bees was reduced. Levels of NO and catalase (CAT) remained unaffected at 0 h or 24 h post-exposure. Superoxide dismutase (SOD) activity was higher at 0 h compared to 24 h, although insignificantly so when compared to the control. Exposure to CuSO4 reduced glutathione S-transferase (GST) activity at 0 h but increased it after 24 h, for both CuSO4 and glyphosate. MDA levels decreased after 0 h exposure to CuSO4 or spinosad but increased after 24 h exposure to all tested agrochemicals. THC showed no difference among glyphosate or spinosad compared to the control or across time. However, CuSO4 exposure significantly increased THC. These findings shed light on the physiological responses of stingless bees to agrochemicals, crucial for understanding their overall health.

Cytotoxic and genotoxic effects of a pendimethalin-based herbicide in Apis mellifera

Public concern about the effects of pesticides on non-target organisms has increased in the recent years. Nevertheless, there is a limited number of studies that address the actual toxic effects of herbicides on insects. This study investigated the side effects of herbicides on non-target organisms inhabiting agroecosystems and performing essential ecological and economic functions such as crop pollination. We analysed morphological alterations in the gut, Malpighian tubules and circulating haemocytes of Apis mellifera workers as markers of exposure effects. A commercial formulation of a pendimethalin-based herbicide (PND) was administered orally under laboratory conditions at a realistic concentration admitted in the field (330gL-1 of active ingredient., 4 L ha-1 for cereal and vegetable crops). The worker bees were exposed to a single application of PND for a period of one week, to simulate the exposure that can occur when foraging bees accidentally drink drops of contaminated water upon treatments. Histopathological analyses of the midgut, ileum and Malpighian tubules showed alterations over time (from 24 to 72 h after the beginning of exposure) such as loss of epithelial organisation, cellular vacuolisation and altered pyknotic nuclei as well as disruption of the peritrophic membrane over time. Semiquantitative analyses of the midgut showed a significant increase in the organ injury index 24 and 72 h after the initial exposure in PND-exposed bees compared to control bees. In addition, a change in positivity to Gram staining was observed in the midgut histological sections. A recovery of cytotoxic effects was observed one week after the initial exposure, which was favoured by the periodic renewal of the intestinal epithelium and the herbicide dissipation time. Cytochemical staining with Giemsa of haemocytes from PND-treated workers over 24 and 72 h showed significant nuclear alterations such as lobed or polymorphic nuclei and micronuclei compared to bees in the control group. These results show that the dose of PND used to protect crops from weeds can lead to significant cytotoxic and genotoxic effects in non-target organisms such as honey bees. In croplands, the sublethal effects on cell morphology can impair vital physiological processes such as nutrition, osmoregulation, and resistance to pathogens, contributing to the decline in biodiversity and abundance of species that play a prominent ecological role, such as pollinators.

Sublethal acetamiprid exposure induces immunity, suppresses pathways linked to juvenile hormone synthesis in queens and affects cycle-related signaling in emerging bees

Acetamiprid is the only neonicotinoid registered in the European Union because the risks of neonicotinoids to honey bees and other pollinators are strictly regulated. Herein, we orally exposed honey bee colonies to sublethal concentrations of acetamiprid (20 μg/L) under isolated conditions. After one month of continuous exposure, the emerging bees and queens were collected and analyzed via high-throughput label-free quantitative proteomics using a data-independent acquisition strategy. Six and 34 significantly differentially expressed proteins (DEPs) were identified in the emerging bees and queens, respectively. Mrjp3 was the only DEP found in both sample types/castes, and its opposite regulation illustrated a differential response. The DEPs in the emerging bees (H/ACA RNP, Rap1GAP, Mrjp3, and JHE) suggested that sublethal exposure to acetamiprid affected cell cycle-related signaling, which may affect the life history of workers in the colony. The DEPs with increased levels in queens, such as Mrjps 1-4 and 6-7, hymenoptaecin, and apidaecin 22, indicated an activated immune response. Additionally, the level of farnesyl pyrophosphate synthase (FPPS), which is essential for the mevalonate pathway and juvenile hormone biosynthesis, was significantly decreased in queens. The impaired utilization of juvenile hormone in queens supported the identification of additional DEPs. Furthermore, the proteome changes suggested the existence of increased neonicotinoid detoxification by UDP-glucuronosyltransferase and increased amino acid metabolism. The results suggest that the continuous exposure of bee colonies to acetamiprid at low doses (nanograms per gram in feed) may pose a threat to the colonies. The different exposure routes and durations for the emerging bees and queens in our experiment must be considered, i.e., the emerging bees were exposed as larvae via feeding royal jelly and beebread provided by workers (nurse bees), whereas the queens were fed royal jelly throughout the experiment. The biological consequences of the proteomic changes resulting from sublethal/chronic exposure require future determination.

Route of exposure to veterinary products in bees: Unraveling pasture's impact on avermectin exposure and tolerance in stingless bees

Deforestation rapidly increases in tropical regions, primarily driven by converting natural habitats into pastures for extensive cattle ranching. This landscape transformation, coupled with pesticide use, are key drivers of bee population decline. Here, we investigate the impact of pasture-dominated landscapes on colony performance, pesticide exposure, and insecticide sensitivity of the stingless bee Tetragonisca angustula. We monitored 16 colonies located in landscapes with varying proportions of pasture. We collected bee bread for pesticide and palynological analysis. We found a positive correlation between pollen diversity and colony growth, with no effect of the proportion of pasture in the landscape. In contrast, we detected prevalent and hazardous concentrations of the insecticide abamectin (9.6-1,856 µg/kg) in bee bread, which significantly increased with a higher proportion of pasture. Despite the abamectin exposure, the bee colonies displayed no adverse effects on their growth, indicating a potential tolerance response. Further investigations revealed that bees from sites with higher proportions of pasture showed significantly reduced mortality when exposed to a lethal concentration of abamectin (0.021 µg/µL) after 48 h. Since abamectin is scarcely used in the study area, we designed an experiment to track ivermectin, a closely related antiparasitic drug used in cattle. Our findings uncovered a new exposure route of bees to pesticides, wherein ivermectin excreted by cattle is absorbed and biotransformed into abamectin within flowering plants in the pastures. These results highlight that unexplained exposure routes of bees to pesticides remain to be described while also revealing that bees adapt to changing landscapes.

Investigating the effects of mesotrione/atrazine-based herbicide on honey bee foragers

A mixture of the herbicides mesotrione and atrazine (Calaris®) is a widely used herbicide in agriculture in several countries. However, the possible toxicological effects of this formulation on non-target organisms require investigation. In this study, the effects of acute oral exposure to Calaris® were evaluated in Apis mellifera foragers. The effect of seven different concentrations of Calaris® on survival and sucrose consumption was studied, while the recommended concentration for field use (FC) and its 10× dilution (0.1 FC) were used to assess overall locomotor activity, respiratory rate, flight, midgut morphology, oxidative and nitrosative stresses, and hemocyte counting. The exposure to FC or 0.1 FC decreased locomotor activity and induced damage to the midgut epithelium. Additionally, the two tested concentrations reduced superoxide dismutase activity, nitric oxide levels, and total hemocyte count. FC also increased malondialdehyde content and 0.1 FC increased respiratory rate and decreased the proportion of prohemocytes. Overall, our findings evidenced significant harmful effects on A. mellifera foragers resulting from the ingestion of the Calaris® herbicide.

Midgut Cell Damage and Oxidative Stress in Partamona helleri (Hymenoptera: Apidae) Workers Caused by the Insecticide Lambda-Cyhalothrin

The stingless bee Partamona helleri plays a role in pollinating both native and cultivated plants in the Neotropics. However, its populations can be reduced by the pyrethroid insecticide lambda-cyhalothrin. This compound may cross the intestinal barrier and circulate through the hemolymph, affecting various non-target bee organs. The aim of the present study was to assess the extent of cellular damage in the midgut and the resulting oxidative stress caused by lambda-cyhalothrin in P. helleri workers. Bees were orally exposed to lambda-cyhalothrin. The lethal concentration at which 50% of the bees died (LC50) was 0.043 mg a.i. L-1. The P. helleri workers were fed this concentration of lambda-cyhalothrin and their midguts were evaluated. The results revealed signs of damage in the midgut epithelium, including pyknotic nuclei, cytoplasm vacuolization, changes in the striated border, and the release of cell fragments, indicating that the midgut was compromised. Furthermore, the ingestion of lambda-cyhalothrin led to an increase in the activity of the detoxification enzyme superoxide dismutase and the levels of the NO2/NO3 markers, indicating oxidative stress. Conversely, the activities of the catalase and glutathione S-transferase enzymes decreased, supporting the occurrence of oxidative stress. In conclusion, the ingestion of lambda-cyhalothrin by P. helleri workers resulted in damage to their midguts and induced oxidative stress.

Ecotoxicological effects of common fungicides on the eastern honeybee Apis cerana cerana (Hymenoptera)

The widespread use of fungicides for plant protection has increased the potential for pollinator exposure. This study therefore aimed at assessing the acute and chronic effects of fungicides on pollinators. For this purpose, the acute oral toxicity of the common fungicides azoxystrobin, pyraclostrobin, and boscalid to Eastern honeybee Apis cerana cerena was first evaluated, and the chronic effects on multiple aspects were investigated after exposure to a one-tenth medium lethal dose (LD₅₀) for 10 days. This study revealed that the LD₅₀ values of azoxystrobin, pyraclostrobin and boscalid for adult Eastern honeybees were 12.7 μg/bee, 36.6 μg/bee, and >119 μg/bee, respectively. Midgut epithelial cells revealed that fungicide exposure caused increased intercellular spaces and varying degrees of vacuolization. Exposure to these three fungicides and their binary mixtures significantly affected glycerophospholipid, alanine, aspartate, and glutamate metabolism in Eastern honeybee midguts. Additionally, the relative composition of Lactobacillus, the dominant functional genus in Eastern honeybee guts decreased and microbial balance was disrupted. All fungicides and their mixtures induced strong transcriptional upregulation of genes associated with the immune response and encoding enzymes related to oxidative phosphorylation and metabolism, including abaecin, apidaecin, hymenotaecin, cyp4c3, cyp6a2 and hbg3. Our study provides important insight for understanding the effects of commonly used fungicides on nontarget pollinator and contributes to a more comprehensive assessment of fungicide effects on ecological and environmental safety.

Exposure of chlorothalonil and acetamiprid reduce the survival and cause multiple internal disturbances in Apis mellifera larvae reared in vitro

Background: Chlorothalonil and acetamiprid are chemical pesticides commonly used in agricultural production and have been shown to have negative effects on bee's fitness. Despite many studies have revealed that honey bee (Apis mellifera L.) larvae are posting a high risk on exposure to pesticides, but the toxicology information of chlorothalonil and acetamiprid on bee larvae remain limited. Results: The no observed adverse effect concentration (NOAEC) of chlorothalonil and acetamiprid for honey bee larvae were 4 μg/mL and 2 μg/mL, respectively. Except for CarE, the enzymic activities of GST and P450 were not influenced by chlorothalonil at NOAEC, while chronic exposure to acetamiprid slightly increased the activities of the three tested enzymes at NOAEC. Further, the exposed larvae showed significantly higher expression of genes involved in a series of different toxicologically relevant process following, including caste development (Tor (GB44905), InR-2 (GB55425), Hr4 (GB47037), Ac3 (GB11637) and ILP-2 (GB10174)), immune system response (abaecin (GB18323), defensin-1 (GB19392), toll-X4 (GB50418)), and oxidative stress response (P450, GSH, GST, CarE). Conclusion: Our results suggest that the exposure to chlorothalonil and acetamiprid, even at concentrations below the NOAEC, showed potentially effects on bee larvae's fitness, and more important synergistic and behavioral effects that can affect larvae fitness should be explored in the further.

Differential Production of Nitric Oxide and Hydrogen Peroxide among Drosophila melanogaster, Apis mellifera, and Mamestra brassicae Immune-Activated Hemocytes after Exposure to Imidacloprid and Amitraz

Invertebrates have a diverse immune system that responds differently to stressors such as pesticides and pathogens, which leads to different degrees of susceptibility. Honeybees are facing a phenomenon called colony collapse disorder which is attributed to several factors including pesticides and pathogens. We applied an in vitro approach to assess the response of immune-activated hemocytes from Apis mellifera, Drosophila melanogaster and Mamestra brassicae after exposure to imidacloprid and amitraz. Hemocytes were exposed to the pesticides in single and co-exposures using zymosan A for immune activation. We measured the effect of these exposures on cell viability, nitric oxide (NO) production from 15 to 120 min and on extracellular hydrogen peroxide (H2O2) production after 3 h to assess potential alterations in the oxidative response. Our results indicate that NO and H2O2 production is more altered in honeybee hemocytes compared to D. melanogaster and M. brassicae cell lines. There is also a differential production at different time points after pesticide exposure between these insect species as contrasting effects were evident with the oxidative responses in hemocytes. The results imply that imidacloprid and amitraz act differently on the immune response among insect orders and may render honeybee colonies more susceptible to infection and pests.

A matter of the beehive sound: Can honey bees alert the pollution out of their hives?

Honey bees (Apis spp.) are often used as biological indicators of environmental changes. Recently, bees have been explored to monitor air contaminants by listening to the beehive sound. The beehive sound is believed to encode information on bee responses to chemicals outside their hives. Here we conducted an experiment to address this. First, we randomly fed colonies with pure syrup (PS), acetone-laced syrup (AS), or ethyl acetate-laced syrup (ES) in front of the beehives and collect the beehive sound. Based on the audio data, we build machine learning (ML) models to identify the types of syrup. The result shows that ML models achieved over 90% accuracy for identifying syrup types, indicating that the bees inside their hives emitted the sound associated with the chemicals outside their hives. Then, we sequentially fed the colonies in the order of PS, ES, and AS (the first session) and again in the reverse order (the second session), but did not remove the accumulated ES or AS in the alternative feeding experiment. Based on the audio data, the identification accuracy of both ES and AS by the ML model built on the randomly feeding experiment was different, indicating that the accumulated chemical residuals could confuse the ML models. Therefore, the beehive sound-based environmental monitoring should simultaneously consider the responses of bees to the chemicals outside their hives and their responses to those accumulated inside their hives, which may act simultaneously.

Are fungicides a driver of European foulbrood disease in honey bee colonies pollinating blueberries?

Introduction

Blueberry producers in Canada depend heavily on pollination services provided by honey bees (Apis mellifera L.). Anecdotal reports indicate an increased incidence of European foulbrood (EFB), a bacterial disease caused by Melissococcus plutonius, is compromising pollination services and colony health. Fungicidal products are commonly used in blueberry production to prevent fungal diseases such as anthracnose and botrytis fruit rot. Pesticide exposure has been implicated in honey bee immunosuppression; however, the effects of commercial fungicidal products, commonly used during blueberry pollination, on honey bee larval susceptibility to EFB have not been investigated.

Methods

Using an in vitro infection model of EFB, we infected first instar honey bee larvae with M. plutonius 2019 BC1, a strain isolated from an EFB outbreak in British Columbia, Canada, and chronically exposed larvae to environmentally relevant concentrations of fungicide products over 6 days. Survival was monitored until pupation or eclosion.

Results

We found that larvae chronically exposed to one, two, or three fungicidal products [Supra® Captan 80WDG (Captan), low concentration of Kenja™ 400SC (Kenja), Luna® Tranquility (Luna), and/or Switch® 62.5 WG (Switch)], did not significantly reduce survival from EFB relative to infected controls. When larvae were exposed to four fungicide products concurrently, we observed a significant 24.2% decrease in survival from M. plutonius infection (p = 0.0038). Similarly, higher concentrations of Kenja significantly reduced larval survival by 24.7–33.0% from EFB (p < 0.0001).

Discussion

These in vitro results suggest that fungicides may contribute to larval susceptibility and response to M. plutonius infections. Further testing of other pesticide combinations is warranted as well as continued surveillance of pesticide residues in blueberry-pollinating colonies.

Effect of amide protoporphyrin derivatives on immune response in Apis mellifera

The intracellular microsporidian parasite Nosema ceranae is known to compromise bee health by induction of energetic stress and downregulation of the immune system. Porphyrins are candidate therapeutic agents for controlling Nosema infection without adverse effects on honeybees. In the present work, the impact of two protoporphyrin IX derivatives, i.e. PP[Asp]2 and PP[Lys]2, on Apis mellifera humoral immune response has been investigated in laboratory conditions in non-infected and N. ceranae-infected honeybees. Fluorescence spectroscopy analysis of hemolymph showed for the first time that porphyrin molecules penetrate into the hemocoel of honeybees. Phenoloxidase (PO) activity and the expression of genes encoding antimicrobial peptides (AMPs: abaecin, defensin, and hymenoptaecin) were assessed. Porphyrins significantly increased the phenoloxidase activity in healthy honeybees but did not increase the expression of AMP genes. Compared with the control bees, the hemolymph of non-infected bees treated with porphyrins had an 11.3- and 6.1-fold higher level of PO activity after the 24- and 48-h porphyrin administration, respectively. Notably, there was a significant inverse correlation between the PO activity and the AMP gene expression level (r =  - 0.61696, p = 0.0143). The PO activity profile in the infected bees was completely opposite to that in the healthy bees (r =  - 0.5118, p = 0.000), which was related to the changing load of N. ceranae spores in the porphyrin treated-bees. On day 12 post-infection, the spore loads in the infected porphyrin-fed individuals significantly decreased by 74%, compared with the control bees. Our findings show involvement of the honeybee immune system in the porphyrin-based control of Nosema infection. This allows the infected bees to improve their lifespan considerably by choosing an optimal PO activity/AMP expression variant to cope with the varying level of N. ceranae infection.

Characterization of Insecticide Response-Associated Transcripts in the Colorado Potato Beetle: Relevance of Selected Cytochrome P450s and Clothianidin

Simple Summary

The Colorado potato beetle is an insect pest that can significantly harm potato crops. Various approaches are available to mitigate its damages including the use of insecticides. Unfortunately, its ability to develop resistance towards these compounds is substantial, and understanding the basis of this process is of utmost importance to design strategies to limit the impact of this insect. This work thus aims at quantifying the expression of key transcripts coding for proteins associated with insecticide resistance in Colorado potato beetles exposed to four insecticides. Significant variations were observed, notably in insects exposed to the insecticide clothianidin. Interestingly, subsequent reduction of endogenous levels of selected targets modulated by clothianidin was associated with increased insect susceptibility to this neonicotinoid. These results further highlight molecular players with potential relevance for insecticide resistance, and introduce novel targets that underlie clothianidin resistance in the Colorado potato beetle.

Abstract

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) is known for its capacity to cause significant damages to potato crops worldwide. Multiple approaches have been considered to limit its spread including the use of a diverse arsenal of insecticides. Unfortunately, this insect frequently develops resistance towards these compounds. Investigating the molecular bases underlying the response of L. decemlineata against insecticides is of strong interest to ultimately devise novel and targeted approaches aimed at this pest. This work aimed to characterize, via qRT-PCR, the expression status of targets with relevance to insecticide response, including ones coding for cytochrome P450s, glutathione s-transferases, and cuticular proteins, in L. decemlineata exposed to four insecticides; chlorantraniliprole, clothianidin, imidacloprid, and spinosad. Modulation of levels associated with transcripts coding for selected cytochrome P450s was reported in insects treated with three of the four insecticides studied. Clothianidin treatment yielded the most variations in transcript levels, leading to significant changes in transcripts coding for CYP4c1, CYP4g15, CYP6a13, CYP9e2, GST, and GST-1-Like. Injection of dsRNA targeting CYP4c1 and CYP9e2 was associated with a substantial decrease in expression levels and was, in the case of the latter target, linked to a greater susceptibility of L. decemlineata towards this neonicotinoid, supporting a potential role for this target in clothianidin response. Overall, this data further highlights the differential expression of transcripts with potential relevance in insecticide response, as well as generating specific targets that warrant investigation as novel dsRNA-based approaches are developed against this insect pest.

Midgut and Head Transcriptomic Analysis of Silkworms Reveals the Physiological Effects of Artificial Diets

Silkworms, a model lepidopteran insect, have a very simple diet. Artificial diets as an alternative nutrient source for silkworms are gradually being developed. To understand the effects of various nutrients on the growth and development of silkworms, we studied the transcriptomic differences in the midgut and head tissues of male and female silkworms fed either fresh mulberry leaves or artificial diets. In the artificial diet group, compared with the control group (fed mulberry leaves), 923 and 619 differentially expressed genes (DEGs) were identified from the midgut, and 2969 and 3427 DEGs were identified from the head, in female and male silkworms. According to our analysis, the DEGs were mainly involved in the digestion and absorption of nutrients and silkworm innate immunity. These experimental results provide insights into the effects of different foods, such as artificial diets or fresh mulberry leaves, on silkworms.

Lactobacillus amylovorus derived lipase-mediated silver derivatization over poly(ε-caprolactone) towards antimicrobial coatings

Owing to the probiotic origin, lipases-derived from the Lactobacilli sp. are considered to be promising biomaterials for in vivo applications. On a different note, poly(ε-caprolactone) (PCL)-an FDA-approved polymer for implantable applications-lacks inherent antimicrobial property, because of which suitable modifications are required to render it with bactericidal activity. Here, we employ Lactobacillus amylovorous derived lipase to surface derivatize the PCL films with silver that is a highly efficient inorganic broad-spectrum antimicrobial substance. Two different surface functionalization strategies have been employed over the alkaline hydrolyzed PCL films towards this purpose: In the first strategy, lipase-capped silver nanoparticles (Ag NPs) have been synthesized in a first step, which have been covalently immobilized over the activated carboxylic groups on the PCL film surface in a subsequent step. In the second strategy, the lipase was covalently immobilized over the activated carboxylic groups of the PCL film surface in the first step, over which silver was deposited in the second step using the dip-coating method. While the characterization study using X-ray photoelectron spectroscopy (XPS) has revealed the successful derivatization of silver over the PCL film, the surface characterization using field-emission scanning electron microscopy (FE-SEM) study has shown a distinct morphological change with higher silver loading in both strategies. The antimicrobial studies employing E. coli have revealed 100 % inhibition in the bacterial growth in 4-6 h with the Ag NPs-immobilized PCL films as opposed to >8 h with those prepared through the dip-coating method. Additionally, the cytotoxicity assay using mouse fibroblast cells has shown that the PCL films immobilized with lipase-capped Ag NPs exhibit high cell compatibility, similar to that of pristine PCL film, and thereby making it suitable for in vivo applications.