Easy and versatile cellulosic support inhibiting broad spectrum strains: synergy between photodynamic antimicrobial therapy and polymyxin B.

Despite advances achieved in the health field over the last decade, infections caused by resistant bacterial strains are an increasingly important societal issue that needs to be addressed. New approaches have already been developed to overcome this problem. Photodynamic antimicrobial chemotherapy (PACT) could provide a promising alternative method to eradicate microbes. This approach has already inspired the development of innovative surfaces. Interesting results were achieved against Gram-positive bacteria, but it also appeared that Gram-negative strains, especially Pseudomonas aeruginosa, were less sensitive to PACT. However, materials coated with cationic porphyrins have already proven their wide-spectrum activity, but these materials were not suitable for industrial-scale production. The main aim of this work was the design of a large-scale evolutionary material based on PACT and antibiotic prophylaxis. Transparent regenerated cellulose has been simply impregnated with a usual cationic porphyrin (N-methylpyridyl) and an antimicrobial peptide (polymyxin B). In addition to its photophysical properties, this film exhibited a wide-spectrum bactericidal activity over 4 days despite daily application of fresh bacterial inoculums. The efficiency of PACT and polymyxin B combination could help to reduce the emergence of bacterial multi-resistant strains and we believe that this kind of material would provide an excellent opportunity to prevent bacterial contamination of bandages or packaging.

A Review of Phototoxic Plants, Their Phototoxic Metabolites, and Possible Developments as Photosensitizers.

This study provides a comprehensive overview of the current knowledge regarding phototoxic terrestrial plants and their phototoxic and photosensitizing metabolites. Within the 435,000 land plant species, only around 250 vascular plants have been documented as phototoxic or implicated in phototoxic occurrences in humans and animals. This work compiles a comprehensive catalog of these phototoxic plant species, organized alphabetically based on their taxonomic family. The dataset encompasses meticulous details including taxonomy, geographical distribution, vernacular names, and information on the nature and structure of their phototoxic and photosensitizing molecule(s). Subsequently, this study undertook an in-depth investigation into phototoxic molecules, resulting in the compilation of a comprehensive and up-to-date list of phytochemicals exhibiting phototoxic or photosensitizing activity synthesized by terrestrial plants. For each identified molecule, an extensive review was conducted, encompassing discussions on its phototoxic activity, chemical family, occurrence in plant families or species, distribution within different plant tissues and organs, as well as the biogeographical locations of the producer species worldwide. The analysis also includes a thorough discussion on the potential use of these molecules for the development of new photosensitizers that could be used in topical or injectable formulations for antimicrobial and anticancer phototherapy as well as manufacturing of photoactive devices.

Optimized Single-Step Recovery of Lipophilic and Hydrophilic Compounds from Raspberry, Strawberry and Blackberry Pomaces Using a Simultaneous Ultrasound-Enzyme-Assisted Extraction (UEAE).

An ultrasound-enzyme-assisted extraction (UEAE) was optimized to extract, simultaneously, the hydrophilic and lipophilic compounds from three berry pomaces (raspberry, strawberry and blackberry). First, an enzyme screening designated a thermostable alkaline protease as the most suitable enzyme to recover, in an aqueous medium, the highest yields of polyphenols and oil in the most efficient way. Secondly, the selected enzyme was coupled to ultrasounds (US) in sequential and simultaneous combinations. The simultaneous US-alkaline enzyme combination was selected as a one-single-step process and was then optimized by definitive screening design (DSD). The optimized parameters were: US amplitude, 20% (raspberry pomace) or 70% (strawberry and blackberry pomaces); pH, 8; E/S ratio, 1% (w/w); S/L ratio, 6% (w/v); extraction time, 30 min; temperature, 60 °C. Compared to conventional extractions using organic solvents, the UEAE extracted all the polyphenols, with around 75% of the active polyphenols (measured by the DPPH● method) and up to 75% of the initial oil from the berry pomaces. Characterized lipophilic compounds were rich in polyunsaturated fatty acids (PUFAs), tocols and phytosterols. The polyphenolics were analyzed by UPLC-MS/MS; characteristic ellagitannins of the Rosaceae family (sanguiin H-6 or agrimoniin, sanguiin H-10, …) and ellagic acid conjugates were found as the major components.

In vitro antitumor activity, molecular dynamics simulation, DFT study, ADME prediction, and Eg5 binding of enastron analogues.

The objective of this study is to evaluate a series of molecules based on cyclosulfamide as potential anticancer agents. Additionally, the study aims to analyze the obtained results through in silico studies; by conducting experiments and utilizing theoretical methods. In this context, we investigated the cytotoxic activity of enastron analogues on three human cell lines PRI (lymphoblastic cell line) derived from B-cell lymphoma. JURKAT (ATCC TIB-152) acute T cell leukaemia and K562 (ATCC CLL-243) is a chronic myelogenous leukaemia. Most of the tested compounds showed good inhibitory activity compared with the reference ligand (chlorambucil). The 5a derivative demonstrated the strongest effect against all cancer cells used. Furthermore, molecular docking simulations of the Eg5-enastron analogue complex revealed that studied molecules have the ability to inhibit the Eg5 enzyme, as evidenced by their calculated docking score. Following the promising results from the molecular docking study, the complex Eg5-4a underwent a 100 ns molecular dynamics simulation using Desmond. During the simulation, the receptor-ligand pairing demonstrated substantial stability after the initial 70 ns. In addition, we used DFT calculations to analyze the electronic and geometric characteristics of the studied compounds. The HOMO and LUMO band gap energies, and the molecular electrostatic potential surface were also deducted for the stable structure of each compound. Also, we studied the prediction of absorption, distribution, metabolism and excretion (ADME) of the compounds.

Xylan-Porphyrin Hydrogels as Light-Triggered Gram-Positive Antibacterial Agents.

In the present work, we report on the synthesis of light-triggered antibacterial hydrogels, based on xylan chains covalently bound to meso-tetra(4-carboxyphenyl)porphyrin (TCPP). Not only does TCPP act as a photosensitizer efficient against Gram-positive bacteria, but it also serves as a cross-linking gelator, enabling the simple and easy building of xylan conjugate hydrogels. The hydrogels were characterized by infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), along with swelling and rheological tests. The antimicrobial activity of the hydrogels was tested under visible light irradiation against two Gram-positive bacterial strains, Staphylococcus aureus and Bacillus cereus. The preliminary results showed an interesting activity on these bacteria, indicating that these hydrogels could be of great potential in the treatment of skin bacterial infections with this species by photodynamic antimicrobial chemotherapy (PACT).

Efficient synthesis and antitumor activity of novel oxazaphosphinane derivatives: X-ray crystallography, DFT study and molecular docking.

A novel potentially biologically active oxazaphosphinane derivatives was synthesized by facile synthetic approaches from the combination of hydroxyaniline, aldehyde, and triethylphosphite. The crystal structure of compound 1b has been determined. Single crystals belong to the triclinic system with p - 1 space. The relative in vitro antitumor activity against human cell lines (PRI, K562, and JURKAT) of these derivatives in comparison to chlorombucil is reported. All synthesized compound showed excellent activity with IC50 value of 0.014-0.035 mM. The binding energy of the Epidermal growth factor receptor (EGFR)-oxazaphosphinane complex and the calculated inhibition constant using docking simulation showed that all molecules has the ability to inhibit EGFR therapeutic target. In addition, DFT calculation has been used to analyze the electronic and geometric characteristics.Communicated by Ramaswamy H. Sarma.

Antibacterial Photodynamic Therapy in the Near-Infrared Region with a Targeting Antimicrobial Peptide Connected to a π-Extended Porphyrin.

The increase of antimicrobial resistance to conventional antibiotics is worldwide a major health problem that requires the development of new bactericidal strategies. Antimicrobial photodynamic therapy (a-PDT) that generates reactive oxygen species acting on multiple cellular targets is unlikely to induce bacterial resistance. This localized treatment requires, for safe and efficient treatment of nonsuperficial infections, a targeting photosensitizer excited in the near IR. To this end, a new conjugate consisting of an antimicrobial peptide linked to a π-extended porphyrin photosensitizer was designed for a-PDT. Upon irradiation at 720 nm, the conjugate has shown at micromolar concentration strong bactericidal action on both Gram-positive and Gram-negative bacteria. Moreover, this conjugate allows one to reach a low minimum bactericidal concentration with near IR excitation without inducing toxicity to skin cells.

Latest trends on photodynamic disinfection of Gram-negative bacteria: photosensitizer's structure and delivery systems.

Antimicrobial resistance is threatening to overshadow last century's medical advances. Etiological agents of previously eradicated infectious diseases are now resurgent as multidrug-resistant strains, especially for Gram-negative strains. Finding new therapeutic solutions is a real challenge for our society. In this framework, Photodynamic Antimicrobial ChemoTherapy relies on the generation of toxic reactive oxygen species in the presence of light, oxygen, and a photosensitizer molecule. The use of reactive oxygen species is common for disinfection processes, using chemical agents, such as chlorine and hydrogen peroxide, and as they do not have a specific molecular target, it decreases the potential of tolerance to the antimicrobial treatment. However, light-driven generated reactive species result in an interesting alternative, as reactive species generation can be easily tuned with light irradiation and several PSs are known for their low environmental impact. Over the past few years, this topic has been thoroughly studied, exploring strategies based on single-molecule PSs (tetrapyrrolic compounds, dipyrrinate derivatives, metal complexes, etc.) or on conjunction with delivery systems. The present work describes some of the most relevant advances of the last 6 years, focusing on photosensitizers design, formulation, and potentiation, aiming for the disinfection of Gram-negative bacteria.

Development of Phenalenone-Triazolium Salt Derivatives for aPDT: Synthesis and Antibacterial Screening.

The increasing number of hospital-acquired infections demand the development of innovative antimicrobial treatments. Antimicrobial photodynamic therapy (aPDT) is a versatile technique which relies on the production of reactive oxygen species (ROS) generated by light-irradiated photosensitizers (PS) in the presence of oxygen (O2). 1H-Phenalen-1-one is a very efficient photosensitizer known for its high singlet oxygen quantum yield and its antimicrobial potential in aPDT when covalently bound to quaternary ammonium groups. Triazolium salts are stable aromatic quaternary ammonium salts that recently appeared as interesting moieties endowed with antimicrobial activities. The coupling between phenalenone and triazolium groups bearing various substituents was realized by copper-catalyzed azide-alkyne cycloaddition followed by alkylation with methyl iodide or 2-(bromomethyl)-1H-phenalen-1-one. As expected, most of the compounds retained the initial singlet oxygen quantum yield, close to unity. Minimum inhibitory concentrations (MIC) of 14 new phenalenone-triazolium salt derivatives and 2 phenalenone-triazole derivatives were determined against 6 bacterial strains (Gram-negatives and Gram-positives species). Most of these PS showed significant photoinactivation activities, the strongest effects being observed against Gram-positive strains with as low as submicromolar MIC values.

Photophysical and Antibacterial Properties of Porphyrins Encapsulated inside Acetylated Lignin Nanoparticles.

Lignin has recently attracted the attention of the scientific community, as a suitable raw material for biomedical applications. In this work, acetylated lignin was used to encapsulate five different porphyrins, aiming to preserve their photophysical properties, and for further use as antibacterial treatment. The obtained nanoparticles were physically characterized, through dynamic light scattering size measurement, polydispersity index and zeta potential values. Additionally, the photophysical properties of the nanoparticles, namely UV-vis absorption, fluorescence emission, singlet oxygen production and photobleaching, were compared with those of the free porphyrins. It was found that all the porphyrins were susceptible to encapsulation, with an observed decrease in their fluorescence quantum yield and singlet oxygen production. These nanoparticles were able to exert an effective photodynamic bactericide effect (blue-LED light, 450-460 nm, 15 J/cm2) on Staphylococcus aureus and Escherichia coli. Furthermore, it was achieved a photodynamic bactericidal activity on an encapsulated lipophillic porphyrin, where the free porphyrin failed to diminish the bacterial survival. In this work it was demonstrated that acetylated lignin encapsulation works as a universal, cheap and green material for the delivery of porphyrins, while preserving their photophysical properties.

Photophysical and Bactericidal Properties of Pyridinium and Imidazolium Porphyrins for Photodynamic Antimicrobial Chemotherapy.

Despite advances achieved over the last decade, infections caused by multi-drug-resistant bacterial strains are increasingly becoming important societal issues that need to be addressed. New approaches have already been developed in order to overcome this problem. Photodynamic antimicrobial chemotherapy (PACT) could provide an alternative to fight infectious bacteria. Many studies have highlighted the value of cationic photosensitizers in order to improve this approach. This study reports the synthesis and the characterization of cationic porphyrins derived from methylimidazolium and phenylimidazolium porphyrins, along with a comparison of their photophysical properties with the well-known N-methylpyridyl (pyridinium) porphyrin family. PACT tests conducted with the tetracationic porphyrins of these three families showed that these new photosensitizers may offer a good alternative to the classical pyridinium porphyrins, especially against S.aureus and E.coli. In addition, they pave the way to new cationic photosensitizers by the means of derivatization through amide bond formation.

Xylan-Based Cross-Linked Hydrogel for Photodynamic Antimicrobial Chemotherapy.

Photodynamic antimicrobial chemotherapy or PACT has been shown to be a promising antibacterial treatment that could overcome the challenge of multidrug-resistant bacteria. However, the use of most existing photosensitizers has been severely hampered by their significant self-quenching effect, poor water solubility, lack of selectivity against bacterial cells, and possible damage to the surrounding tissues. The use of hydrogels may overcome some of these limitations. We herein report a simple strategy to synthesize a cross-linked hydrogel from beech xylan. The hydrogel showed a high swelling ratio, up to 62, an interconnected porous structure, and good mechanical integrity, and 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetraiodide (TMPyP) was chosen as a model of hydrophilic photosensitizer (PS) and was encapsulated inside the xylan-based hydrogel. TMPyP-loaded hydrogel prolonged release of PS up to 24 h with a cumulative amount that could reach 100%. TMPyP-loaded hydrogel showed a photocytotoxic effect against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus strains, and Bacillus cereus, while no cytotoxicity was observed in the dark.

Porphyrin-Loaded Lignin Nanoparticles Against Bacteria: A Photodynamic Antimicrobial Chemotherapy Application.

The need for alternative strategies to fight bacteria is evident from the emergence of antimicrobial resistance. To that respect, photodynamic antimicrobial chemotherapy steadily rises in bacterial eradication by using light, a photosensitizer and oxygen, which generates reactive oxygen species that may kill bacteria. Herein, we report the encapsulation of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin into acetylated lignin water-dispersible nanoparticles (THPP@AcLi), with characterization of those systems by standard spectroscopic and microscopic techniques. We observed that THPP@AcLi retained porphyrin's photophysical/photochemical properties, including singlet oxygen generation and fluorescence. Besides, the nanoparticles demonstrated enhanced stability on storage and light bleaching. THPP@AcLi were evaluated as photosensitizers against two Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, and against three Gram-positive bacteria, Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus faecalis. THPP@AcLi were able to diminish Gram-positive bacterial survival to 0.1% when exposed to low white LED light doses (4.16 J/cm2), requiring concentrations below 5 µM. Nevertheless, the obtained nanoparticles were unable to diminish the survival of Gram-negative bacteria. Through transmission electron microscopy observations, we could demonstrate that nanoparticles did not penetrate inside the bacterial cell, exerting their destructive effect on the bacterial wall; also, a high affinity between acetylated lignin nanoparticles and bacteria was observed, leading to bacterial flocculation. Altogether, these findings allow to establish a photodynamic antimicrobial chemotherapy alternative that can be used effectively against Gram-positive topic infections using the widely available natural polymeric lignin as a drug carrier. Further research, aimed to inhibit the growth and survival of Gram-negative bacteria, is likely to enhance the wideness of acetylated lignin nanoparticle applications.

Encapsulation of a Ru(II) Polypyridyl Complex into Polylactide Nanoparticles for Antimicrobial Photodynamic Therapy.

Antimicrobial photodynamic therapy (aPDT) also known as photodynamic inactivation (PDI) is a promising strategy to eradicate pathogenic microorganisms such as Gram-positive and Gram-negative bacteria. This therapy relies on the use of a molecule called photosensitizer capable of generating, from molecular oxygen, reactive oxygen species including singlet oxygen under light irradiation to induce bacteria inactivation. Ru(II) polypyridyl complexes can be considered as potential photosensitizers for aPDT/PDI. However, to allow efficient treatment, they must be able to penetrate bacteria. This can be promoted by using nanoparticles. In this work, ruthenium-polylactide (RuPLA) nanoconjugates with different tacticities and molecular weights were prepared from a Ru(II) polypyridyl complex, RuOH. Narrowly-dispersed nanoparticles with high ruthenium loadings (up to 53%) and an intensity-average diameter < 300 nm were obtained by nanoprecipitation, as characterized by dynamic light scattering (DLS). Their phototoxicity effect was evaluated on four bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa) and compared to the parent compound RuOH. RuOH and the nanoparticles were found to be non-active towards Gram-negative bacterial strains. However, depending on the tacticity and molecular weight of the RuPLA nanoconjugates, differences in photobactericidal activity on Gram-positive bacterial strains have been evidenced whereas RuOH remained non active.

Conjugating biomaterials with photosensitizers: advances and perspectives for photodynamic antimicrobial chemotherapy.

Antimicrobial resistance is threatening to overshadow last century's medical advances. Previously eradicated infectious diseases are now resurgent as multi-drug resistant strains, leading to expensive, toxic and, in some cases, ineffective antimicrobial treatments. Given this outlook, researchers are willing to investigate novel antimicrobial treatments that may be able to deal with antimicrobial resistance, namely photodynamic therapy (PDT). PDT relies on the generation of toxic reactive oxygen species (ROS) in the presence of light and a photosensitizer (PS) molecule. PDT has been known for almost a century, but most of its applications have been directed towards the treatment of cancer and topical diseases. Unlike classical antimicrobial chemotherapy treatments, photodynamic antimicrobial chemotherapy (PACT) has a non-target specific mechanism of action, based on the generation of ROS, working against cellular membranes, walls, proteins, lipids and nucleic acids. This non-specific mechanism diminishes the chances of bacteria developing resistance. However, PSs usually are large molecules, prone to aggregation, diminishing their efficiency. This review will report the development of materials obtained from natural sources, as delivery systems for photosensitizing molecules against microorganisms. The present work emphasizes on the biological results rather than on the synthesis routes to prepare the conjugates. Also, it discusses the current state of the art, providing our perspective on the field.

Does low hydroxyl group surface density explain less bacterial adhesion on porous alumina?

BACKGROUND: Bacterial adhesion depends on surface materials. Recently it was suggested that ceramic-on-ceramic bearings could be less prone to infection than other bearings. We examined the possibility that porous alumina ceramic could be less susceptible to bacterial adhesion. HYPOTHESIS: As hydroxyl groups (OH) on material surface are a major factor governing the surface properties (for example: adsorption, first non-specific step of bacterial adhesion), we hypothesized that alumina had lower OH group density than other material. Thus, we asked (i) if bacterial adhesion was lower on alumina than on titanium alloy, stainless steel and polyethylene and (ii) if OH group density was also lower on alumina. MATERIAL AND METHODS: We performed (i) in vitro bacterial cultures on porous alumina, titanium, stainless steel and polyethylene using Staphylococcus aureus and Pseudomonas aeruginosa, known to adhere to surfaces. Bacterial cultures were done 3 times in duplicate for each material and each strain. Colony Forming Units (CFU) per cm2 were measured; (ii) Neutral red reagent helped obtaining OH density estimates using spacer arms. UV-visible spectrophotometry method with Neutral red test, reproduced twice for each surface, provided µg/cm2 measurements of OH density. RESULTS: There was significantly less P. aeruginosa adherent on porous alumina (2.25×104 CFU/cm2) than on titanium (4.27×105 CFU/cm2, p=0.01), on stainless steel (2.44×105 CFU/cm2, p=0.02) and on polyethylene (7.29×105 CFU/cm2, p<0.001). S. aureus was significantly less adherent on porous alumina (3.22×105 CFU/cm2) than on polyethylene (5.23×106 CFU/cm2, p=0.01), but there was no difference with titanium (1.64×106 CFU/cm2, p=0.08) and stainless steel (1.79×106 CFU/cm2, p=0.1). There was significantly lower Neutral red grafted on porous alumina (0.09µg/cm2) than on titanium (8.88µg/cm2, p<0.0001), on stainless steel (39.8µg/cm2, p=0.002) and on polyethylene (4.5µg/cm2, p<0.01). However, no correlation was found between bacterial adherence and OH group density. DISCUSSION: Bacterial adherence on porous alumina was lower than on other bearings. Although there were less surface OH groups on porous alumina, we failed establishing a statistical correlation between bacterial adherence and OH group density. LEVEL OF EVIDENCE: IV, in vitro study.

Antibacterial activity of a photosensitive hybrid cellulose fabric.

We report the preparation of a cellulose fabric bearing derivative protoporphyrin IX units covalently attached to the cellulose backbone of a fabric. Ce(IV) redox system radical polymerization was used to polymerize methacrylic acid (MAA) onto a cotton material and to obtain cotton-g-polyMAA. Attachment of the photosensitizer, a protoporphyrin IX (PpIX) amino derivative, on cotton-g-polyMAA was realized successfully by a classical peptidic covalent link. The modified surfaces were characterized by ATR-FTIR, DRUV, TGA, and SEM methods. Under visible light irradiation, protoporphyrinic cotton showed antibacterial activity against Staphyloccoccus aureus. This concept is very promising in the field of bacterial decontamination (sterile area, hospital equipment, etc.).

Lysine Analogue of Polymyxin B as a Significant Opportunity for Photodynamic Antimicrobial Chemotherapy.

In order to highlight the potential of photodynamic antimicrobial chemotherapy in case of infections by antibiotic resistant-strains, a new antimicrobial peptide conjugate has been synthesized, consisting of a derivative of polymyxin B and a cationic porphyrin covalently attached together to a spacer. A polymyxin-derived moiety was subjected to a primary structural modification in the replacement of four diaminobutyrate residues with lysine ones. This modification was done in order to strongly reduce bactericidal activity, with the aim to eliminate the potential rise of polymyxin-resistant strains. Despite this modification, this new conjugate displayed a strong photobactericidal activity against Gram-positive as well as Gram-negative bacteria. It was further shown that this conjugate was able to strongly stick to the cell walls of either kind of strain, thus helping to inactivate bacteria through the production of reactive oxygen species under light irradiation.

Enhanced Photobactericidal and Targeting Properties of a Cationic Porphyrin following the Attachment of Polymyxin B.

A novel compound consisting of a cationic porphyrin covalently attached to a derivative of polymyxin B has been synthesized and presents enhanced activity and targeting properties compared to the usual cationic porphyrins recognized as efficient photosensitizers in photodynamic antimicrobial chemotherapy (PACT). A synthesis pathway was established to preserve the bactericidal activity of the peptide. Accordingly, the N-terminal amino acid (l-2,4-diaminobutyric acid) of polymyxin B (PMB) was switched for a cysteine residue. Then, the resulting derivative of PMB was covalently bound to 5-(4-aminophenyl)-10,15,20-tri(4-N-methylpyridyl)-21H,23H-porphyrin using a thiol-maleimide "click" coupling. The peptide-coupled photosensitizer has demonstrated an improved PACT efficiency compared to the cationic porphyrin alone. This enhancement has been observed against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli in particular. Flow cytometry analyses and confocal imaging microscopy demonstrated that the porphyrin-peptide conjugate selectively adhered to the cell walls of either Gram-positive or Gram-negative bacteria, thus justifying the damages induced by singlet oxygen production.

Enhancement of photobactericidal activity of chlorin-e6-cellulose nanocrystals by covalent attachment of polymyxin B.

Despite the advances made over the last decade, infections caused by multi-drug resistant bacterial strains are increasingly important societal issues that need to be addressed. New approaches have already been developed in order to overcome this problem. Photodynamic antimicrobial chemotherapy (PACT) could provide an alternative to fight infectious bacteria. This approach has already inspired the development of innovative materials. Interesting results have been obtained against Gram-positive bacteria, but it also appeared that Gram-negative strains, especially Pseudomonas aeruginosa, were less sensitive to PACT. Enhanced efficacy against Gram-negative bacteria had been previously obtained with photosensitizers bound to antimicrobial peptides. In this work, we designed a photobactericidal organic material, CNCsc6-PMB, consisting of cellulose nanocrystals to which the photosensitizer chlorin-e6 and the antimicrobial polypeptide polymyxin B (PMB) were covalently attached. These modified nanocrystals were characterized by IR spectroscopy, zeta potential measurements and elemental analyses, after which antibacterial assays were carried out. Following light irradiation, CNCsc6-PMB demonstrated efficiency against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) by inhibition of bacterial growth. An amplifying effect of chlorin-e6 has been highlighted against these Gram-negative strains, based on membrane weakening and a potential docking effect from the polymyxin moiety. Such results confirmed the importance of using an antimicrobial peptide in order to broaden the spectrum of PACT.