Glycomimetic-Conjugated Photosensitizer for Specific Pseudomonas aeruginosa Recognition and Targeted Photodynamic Therapy

Photochemical Strategies toward Precision Targeting against Multidrug-Resistant Bacterial Infections

Infectious diseases pose a serious threat and a substantial economic burden on global human and public health security, especially with the frequent emergence of multidrug-resistant (MDR) bacteria in clinical settings. In response to this urgent need, various photobased anti-infectious therapies have been reported lately. This Review explores and discusses several photochemical targeted antibacterial therapeutic strategies for addressing bacterial infections regardless of their antibiotic susceptibility. In contrast to conventional photobased therapies, these approaches facilitate precise targeting of pathogenic bacteria and/or infectious microenvironments, effectively minimizing toxicity to mammalian cells and surrounding healthy tissues. The highlighted therapies include photodynamic therapy, photocatalytic therapy, photothermal therapy, endogenous pigments-based photobleaching therapy, and polyphenols-based photo-oxidation therapy. This comprehensive exploration aims to offer updated information to facilitate the development of effective, convenient, safe, and alternative strategies to counter the growing threat of MDR bacteria in the future.

Antimicrobial efficacy of aloe-emodin mediated photodynamic therapy against antibiotic-resistant Pseudomonas aeruginosa in vitro

Multidrug-resistant Pseudomonas aeruginosa is a common pathogen that causes topical infections following burn injuries. Antimicrobial photodynamic therapy (aPDT) has emerged as a promising approach for treating antibiotic-resistant bacterial infections. The objective of this study was to evaluate the aPDT efficacy of aloe-emodin (AE), which is a photosensitizer extracted from traditional Chinese herbs, on antibiotic-sensitive and antibiotic-resistant P. aeruginosa in vitro. In this study, we confirmed the effectiveness of AE-mediated aPDT against both standard and MDR P. aeruginosa, explored the effects of irradiation time and AE concentration on bacterial survival in AE-mediated aPDT, and observed the structural damage of P. aeruginosa by using transmission electron microscope. Our results showed that neither AE nor light irradiation alone caused cytotoxic effects on P. aeruginosa. However, AE-mediated aPDT effectively inactivated both antibiotic-sensitive and antibiotic-resistant P. aeruginosa. The transmission electron microscope investigation showed that aPDT mediated by AE primarily caused damage to the cytoplasm and cell membrane. Our findings suggest that AE is a photosensitizer in the aPDT of MDR P. aeruginosa-caused topical infections following burn injuries. Future investigations will concentrate on the safety and efficacy of AE-mediated aPDT in animal models and clinical trials.

Recent advances in engineered polymeric materials for efficient photodynamic inactivation of bacterial pathogens

Nowadays, infectious diseases persist as a global crisis by causing significant destruction to public health and the economic stability of countries worldwide. Especially bacterial infections remain a most severe concern due to the prevalence and emergence of multi-drug resistance (MDR) and limitations with existing therapeutic options. Antibacterial photodynamic therapy (APDT) is a potential therapeutic modality that involves the systematic administration of photosensitizers (PSs), light, and molecular oxygen (O₂) for coping with bacterial infections. Although the existing porphyrin and non-porphyrin PSs were effective in APDT, the poor solubility, limited efficacy against Gram-negative bacteria, and non-specific distribution hinder their clinical applications. Accordingly, to promote the efficiency of conventional PSs, various polymer-driven modification and functionalization strategies have been adopted to engineer multifunctional hybrid phototherapeutics. This review assesses recent advancements and state-of-the-art research in polymer-PSs hybrid materials developed for APDT applications. Further, the key research findings of the following aspects are considered in-depth with constructive discussions: i) PSs-integrated/functionalized polymeric composites through various molecular interactions; ii) PSs-deposited coatings on different substrates and devices to eliminate healthcare-associated infections; and iii) PSs-embedded films, scaffolds, and hydrogels for regenerative medicine applications.

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Synthetic strategies of engineered polymer-based hybrid materials integrated with photosensitizers for APDT.

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Utilization of photosensitizer-incorporated polymeric materials in health care applications.

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Challenges and opportunities in the future development of polymeric biomaterials with improved photo-bactericidal properties.

Bromo- and glycosyl-substituted BODIPYs for application in photodynamic therapy and imaging

The introduction of heavy atoms into the BODIPY-core structure has proven to be a straightforward strategy for optimizing the design of such dyes towards enhanced generation of singlet oxygen rendering them suitable as photosensitizers for photodynamic therapy (PDT). In this work, BODIPYs are presented by combining the concept of bromination with nucleophilic aromatic substitution (S_NAr) of a pentafluorophenyl or a 4-fluoro-3-nitrophenyl moiety to introduce functional groups, thus improving the phototoxic effect of the BODIPYs as well as their solubility in the biological environment. The nucleophilic substitution enabled functionalization with various amines and alcohols as well as unprotected thiocarbohydrates. The phototoxic activity of these more than 50 BODIPYs has been assessed in cellular assays against four cancer cell lines in order to more broadly evaluate their PDT potential, thus accounting for the known variability between cell lines with respect to PDT activity. In these investigations, dibrominated polar-substituted BODIPYs, particularly dibrominated glyco-substituted compounds, showed promising potential as photomedicine candidates. Furthermore, the cellular uptake of the glycosylated BODIPYs has been confirmed via fluorescence microscopy.

Degradable Glycopolyester-like Nanoparticles by Radical Ring-Opening Polymerization

A small library of degradable polyester-like glycopolymers was successfully prepared by the combination of radical ring-opening copolymerization of 2-methylene-1,3-dioxepane as a cyclic ketene acetal (CKA) with vinyl ether (VE) derivatives and a Pd-catalyzed thioglycoconjugation. The resulting thioglycopolymers were formulated into self-stabilized thioglyconanoparticles, which were stable up to 4 months and were enzymatically degraded. Nanoparticles and their degradation products exhibited a good cytocompatibility on two healthy cell lines. Interactions between thioglyconanoparticles and lectins were investigated and highlighted the presence of both specific carbohydrate/lectin interactions and nonspecific hydrophobic interactions. Fluorescent thioglyconanoparticles were also prepared either by encapsulation of Nile red or by the functionalization of the polymer backbone with rhodamine B. Such nanoparticles were used to prove the cell internalization of the thioglyconanoparticles by lung adenocarcinoma (A549) cells, which underlined the great potential of P(CKA-co-VE) copolymers for biomedical applications.

NIR-activated nanosystems with self-modulated bacteria targeting for enhanced biofilm eradication and caries prevention

The efficacious delivery of antimicrobial drugs to intractable oral biofilms remains a challenge due to inadequate biofilm penetration and lack of pathogen targeting. Herein, we have developed a microenvironment-activated poly(ethylene glycol) (PEG)-sheddable nanoplatform to mediate targeted delivery of drugs into oral biofilms for the efficient prevention of dental caries. The PEGylated nanoplatform with enhanced biofilm penetration is capable of deshielding the PEG layer under slightly acidic conditions in a PEG chain length-dependent manner to re-expose the bacteria-targeting ligands, thereby facilitating targeted codelivery of ciprofloxacin (CIP) and IR780 to the bacteria after accumulation within biofilms. The nanoplatform tends to induce bacterial agglomeration and suffers from degradation in the acidic oral biofilm microenvironment, triggering rapid drug release on demand around bacterial cells. The self-modulating nanoplatform under near-infrared (NIR) irradiation accordingly displays greatly augmented potency in oral biofilm penetration and disruption compared with drugs alone. Topical oral treatment with nanoplatforms involving synergetic pharmacological and photothermal/photodynamic trinary therapy results in robust biofilm dispersion and efficacious suppression of severe tooth decay in rats. This versatile nanoplatform can promote local accumulation and specific drug transport into biofilms and represents a new paradigm for targeted drug delivery for the management of oral biofilm-associated infections.

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A targeted drug delivery system was developed to scavenge oral biofilms and prevent dental caries.

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The system is activated by pH gradient to modulate biofilm penetration, bacterial anchorage and drug release.

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The system demonstrated significant efficacy in preventing dental caries under a multimodal treatment regimen.

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This strategy is expected to be applied to control a range of oral biofilm-associated infections.

Searching for antimicrobial photosensitizers among a panel of BODIPYs

In recent years, antimicrobial Photodynamic Therapy (aPDT) gained increasing attention for its potential to inhibit the growth and spread of microorganisms, both as free-living cells and/or embedded in biofilm communities. In this scenario, compounds belonging to the family of boron-dipyrromethenes (BODIPYs) represent a very promising class of photosensitizers for applications in antimicrobial field. In this study, twelve non-ionic and three cationic BODIPYs were assayed for the inactivation of Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. As expected, S. aureus showed to be very sensitive to BODIPYs and mild conditions were sufficient to reach good rates of photoinactivation with both neutral and monocationic ones. Surprisingly, one neutral compound (named B9 in this study) resulted the best BODIPY to photoinactivate P. aeruginosa PAO1. The photoinactivation of C. albicans was reached with both neutral and mono-cationic BODIPYs. Furthermore, biofilms of the three model microorganisms were challenged with BODIPYs in light-based antimicrobial technique. S. aureus biofilms were successfully inhibited with milder conditions than those applied to P. aeruginosa and C. albicans. Notably, it was possible to eradicate 24-h-old biofilms of both S. aureus and P. aeruginosa. In conclusion, this study supports the potential of neutral BODIPYs as pan-antimicrobial PSs.

Phototherapy and optical waveguides for the treatment of infection

With rapid emergence of multi-drug resistant microbes, it is imperative to seek alternative means for infection control. Optical waveguides are an auspicious delivery method for precise administration of phototherapy. Studies have shown that phototherapy is promising in fighting against a myriad of infectious pathogens (i.e. viruses, bacteria, fungi, and protozoa) including biofilm-forming species and drug-resistant strains while evading treatment resistance. When administered via optical waveguides, phototherapy can treat both superficial and deep-tissue infections while minimizing off-site effects that afflict conventional phototherapy and pharmacotherapy. Despite great therapeutic potential, exact mechanisms, materials, and fabrication designs to optimize this promising treatment option are underexplored. This review outlines principles and applications of phototherapy and optical waveguides for infection control. Research advances, challenges, and outlook regarding this delivery system are rigorously discussed in a hope to inspire future developments of optical waveguide-mediated phototherapy for the management of infection and beyond.

Cross-dehydrogenative Coupling of N-Aryl Tetrahydroisoquinolines Catalyzed by an Anthraquinone-containing Polymeric Photosensitizer

This work reports the photocatalytic application of an anthraquinone-containing polymeric photosensitizer (AQ-PHEMA) in the visible light-induced cross-dehydrogenative-coupling of N-aryl tetrahydroisoquinolines with several nucleophiles, including nitromethane, 1-methyl-2-alkyl ketone and dialkyl (aryl) phosphine oxide. The results revealed that the reaction could be catalyzed by AQ-PHEMA efficiently to afford a series of 1-substituted-2-aryl-1,2,3,4-tetrahydroisoquinolines in good to excellent yields with nice substrate tolerance under aerobic conditions at room temperature. The practical application potential was also showcased by a gram-scale synthesis. More importantly, the utilization of AQ-PHEMA as a heterogeneous photosensitizer also showed nice recyclability and reusability of the catalyst, whereas AQ-PHEMA can be easily separated and reused for at least 8 times without significant loss of photocatalytic activity.

A Targeted Photosensitizer Mediated by Visible Light for Efficient Therapy of Bacterial Keratitis

Bacterial keratitis is a serious bacterial infection of the cornea that can cause sight loss in severe cases because of the sharp decline of efficacious antibiotics. Herein, a targeted photosensitizer based on BODIPY severing as a photobactericidal agent was developed for treating bacterial keratitis. The water solubility of the material was as high as 10 mg/mL, which was attributable to the introduction of pathogen-targeting galactose and fucose. The photosensitizer was able to preferentially bind Pseudomonas aeruginosa instead of mammalian cells and trigger the aggregation of bacteria, which ultimately facilitated effective pathogen ablation upon the generation of reactive oxygen species (ROS) via laser irradiation. Photoexcited targeted photosensitizers can promote wound healing by eradicating P. aeruginosa in rat eyes and reducing the inflammatory response, thus exhibiting the significant therapeutic effect on bacterial keratitis. We also performed molecular level mechanistic studies using the unique field-induced droplet ionization mass spectrometry methodology and confirmed that the generated ROS were mainly singlet oxygen that caused lipid peroxidation (Type II mechanism). We anticipate that the targeted photosensitizer will have great potential in the application of clinical photodynamic therapy to ocular infection.

Oxygen Self-Supplying Nanotherapeutic for Mitigation of Tissue Hypoxia and Enhanced Photodynamic Therapy of Bacterial Keratitis

Hypoxia, a common characteristic of bacterial infections, is known to be closely associated with the emergence of multidrug-resistant bacteria, which hastens the need to develop advanced microbicides and antibacterial techniques. Photodynamic therapy is a promising strategy to reduce bacterial antibiotic resistance and employs photosensitizers, excitation light sources, and sufficient oxygen to generate toxic reactive oxygen species (ROS). The inherent limitation of PDT is that the generation of ROS is restricted by the hypoxic microenvironment in infection sites. Here, an oxygen self-supplying nanotherapeutic is developed to enhance antibacterial activity against multidrug-resistant bacteria on the basis of fluorinated boron dipyrromethene (BODIPY)-based glycomimetics. The nanotherapeutic not only could capture the bacteria efficiently but also was able to act as an oxygen carrier to relieve the hypoxic microenvironment of bacterial infections, thus achieving enhanced PDT efficacy. In a Pseudomonas aeruginosa infection of a rat cornea, typical administration of the nanotherapeutic decreased the infiltrate and showed a faster healing capacity in comparison with BODIPY-based glycomimetics. Self-supplying oxygen nanotherapeutics that relieve the hypoxic microenvironment and interfere with bacterial colonization have been shown to be a promising candidate for the management of drug-resistant microbial keratitis.

Nanoparticles as therapeutic options for treating multidrug-resistant bacteria: research progress, challenges, and prospects

Resistance to antimicrobial agents has been alarming in recent years and poses a huge public health threat globally according to the WHO. The increase in morbidity and mortality resulting from microbial infections has been attributed to the emergence of multidrug-resistant microbes. Associated with the increase in multidrug resistance is the lack of new and effective antimicrobials. This has led to global initiatives to identify novel and more effective antimicrobial agents in addition to discovering novel and effective drug delivery and targeting methods. The use of nanoparticles as novel biomaterials to fully achieve this feat is currently gaining global attention. Nanoparticles could become an indispensable viable therapeutic option for treating drug-resistant infections. Of all the nanoparticles, the metals and metal oxide nanoparticles appear to offer the most promise and have attracted tremendous interest from many researchers. Moreover, the use of nanomaterials in photothermal therapy has received considerable attention over the years. This review provides current insight on antimicrobial resistance as well as the mechanisms of nanoparticle antibacterial activity. It offers an in-depth review of all the recent findings in the use of nanomaterials as agents against multi-resistant pathogenic bacteria. Also, nanomaterials that can respond to light stimuli (photothermal therapy) to kill microbes and facilitate enhanced drug delivery and release are discussed. Moreover, the synergistic interactions of nanoparticles with antibiotics and other nanomaterials, microbial adaptation strategies to nanoparticles, current challenges, and future prospects were extensively discussed.

BODIPY-attached zinc(II) complexes of curcumin drug for visible light assisted photo-sensitization, cellular imaging and targeted PDT

Boron-dipyrromethene (BODIPY) based photosensitizers as porphyrinoids and curcumin as natural product possess exciting photophysical features suitable for theranostic applications, namely, imaging and photodynamic therapy (PDT). Limited aqueous solubility and insufficient physiological stability, however, reduce their efficacy significantly. We have designed a novel strategy to deliver these two unusable cytotoxins simultaneously in cancer cells and herein, report the synthesis, characterization and imaging-assisted photocytotoxicity of three zinc(II) complexes containing N³-donor dipicolylamine (dpa) ligands (L^1-3) and O,O-donor curcumin (Hcur) viz. [Zn(L¹)(cur)]Cl (1), [Zn(L²)(cur)]Cl (2) and [Zn(L³)(cur)]Cl (3), where L² and L³ have pendant fluorescent BODIPY and non-emissive di-iodo-BODIPY moieties. Metal chelation imparted remarkable biological stability (pH ∼7.4) to the respective ligands and induces significant aqueous solubility. These ternary complexes could act as replacements of the existing metalloporphyrin-based PDT photosensitizers as their visible-light photosensitizing ability is reinforced by the dual presence of blue light absorbing curcumin and green light harvesting BODIPY units. Complex 2 having emissive BODIPY unit L² and curcumin, showed mitochondria selective localization in HeLa, MCF-7 cancer cells and complex 3, the di-iodinated analogue of complex 2, exhibited type-I/II PDT activity via inducing apoptosis through mitochondrial membrane disruption in cancer cells while being significantly nontoxic in dark and to the healthy cells.

Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa is an opportunistic human pathogen causing devastating acute and chronic infections in individuals with compromised immune systems. Its highly notorious persistence in clinical settings is attributed to its ability to form antibiotic-resistant biofilms. Biofilm is an architecture built mostly by autogenic extracellular polymeric substances which function as a scaffold to encase the bacteria together on surfaces, and to protect them from environmental stresses, impedes phagocytosis and thereby conferring the capacity for colonization and long-term persistence. Here we review the current knowledge on P. aeruginosa biofilms, its development stages, and molecular mechanisms of invasion and persistence conferred by biofilms. Explosive cell lysis within bacterial biofilm to produce essential communal materials, and interspecies biofilms of P. aeruginosa and commensal Streptococcus which impedes P. aeruginosa virulence and possibly improves disease conditions will also be discussed. Recent research on diagnostics of P. aeruginosa infections will be investigated. Finally, therapeutic strategies for the treatment of P. aeruginosa biofilms along with their advantages and limitations will be compiled.

The main strategies for tuning BODIPY fluorophores into photosensitizers

Photodynamic therapy (PDT) is a minimally invasive technique for the treatment of target malignant tumors via the generation of highly reactive singlet oxygen species. PDT treatment of cancer/tumor tissues greatly relies on the development of suitable stable, highly specific and efficient photosensitizers. BODIPY (Boron dipyrromethene) derivatives, as a class of well-developed, versatile fluorescent dyes, has emerged as a new class of PDT agents over the past decade. Many elegant strategies have been developed to enhance the singlet oxygen generation efficiency and the cancer/tumor cell selectivity of BODIPY-based photosensitizers to improve the therapeutic outcomes as well as to minimize the side effects. Many of the currently reported BODIPY-based photosensitizers are valuable dual imaging and therapeutic agents, which can efficiently generate singlet oxygen for PDT and emit fluorescence for in vivo imaging. Although the currently approved PDT agents used for clinical trials do not feature BODIPYs, this situation is expected to change. In this review, we provide an overview of the various strategies that have been used to improve the singlet oxygen generation efficiency for tuning BODIPY fluorophores into photosensitizers and dual imaging/therapeutic agents. Their photophysical properties and photocytotoxic activity including the absorption/emission wavelengths, the singlet oxygen generation efficiency ([Formula: see text] and the half maximal inhibitory concentration [Formula: see text] of these currently reported photosensitizers are summarized. We believe these newly developed BODIPY-based photosensitizers will broaden current concepts of strategies for PDT agent design, and promise to make an important contribution to the diagnosis and therapeutics for the treatment of cancer.

Exploring the relationship between structure and activity in BODIPYs designed for antimicrobial phototherapy

A synthetic strategy to BODIPY dyes is presented giving access to a range of new compounds relevant in the context of antimicrobial photodynamic therapy (aPDT). BODIPYs with the 8-(4-fluoro-3-nitrophenyl) and the 8-pentafluorophenyl substituents were used for the synthesis of new mono- and dibrominated BODIPYs. The para-fluorine atoms in these electron-withdrawing groups facilitate functional modification via nucleophilic aromatic substitution (SNAr) with a number of amines and thio-carbohydrates. Subsequently, the antibacterial phototoxic activity of these BODIPYs has been assessed in bacterial assays against the Gram-positive germ S. aureus and also against the Gram-negative germ P. aeruginosa. The bacterial assays allowed to identify substitution patterns which ensured antibacterial activity not only in phosphate-buffered saline (PBS) but also in the presence of serum, hereby more realistically modelling the complex biological environment that is present in clinical applications.

Concanavalin A-Rose Bengal bioconjugate for targeted Gram-negative antimicrobial photodynamic therapy

Photodynamic therapy (PDT) is considered a very promising therapeutic modality for antimicrobial therapy. Although several studies have demonstrated that Gram-positive bacteria are very sensitive to PDT, Gram-negative bacteria are more resistant to photodynamic action. This difference is due to a different cell wall structure. Gram-negative bacteria have an outer cell membrane containing lipopolysaccharides (LPS) that hinder the binding of photosensitizer molecules, protecting the bacterial cells from chemical attacks. Combination of the lipopolysaccharides-binding activity of Concanavalin A (ConA) with the photodynamic properties of Rose Bengal (RB) holds the potential of an innovative protein platform for targeted photodynamic therapy against Gram-negative bacteria. A ConA-RB bioconjugate was synthesized and characterized. Approximately 2.4 RB molecules were conjugated per ConA monomer. The conjugation of RB to ConA determines a decrease of the singlet oxygen generation and an increase of superoxide and peroxide production. The photokilling efficacy of the ConA-RB bioconjugate was demonstrated in a planktonic culture of E. coli. Irradiation with white light from a LED lamp produced a dose-dependent photokilling of bacteria. ConA-RB conjugates exhibited a consistent improvement over RB (up to 117-fold). The improved uptake of the photosensitizer explains the enhanced PDT effect accompanying increased membrane damages induced by the ConA-RB conjugate. The approach can be readily generalized (i) using different photo/sonosensitizers, (ii) to target other pathogens characterized by cell membranes containing lipopolysaccharides (LPS).

Synthesis of an anthraquinone-containing polymeric photosensitizer and its application in aerobic photooxidation of thioethers

Work on the synthesis of a polymeric photosensitizer and its application in the photooxidation of thioethers is reported herein. Firstly, the polymeric photosensitizer was designed and synthesized by the reaction of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly(2-hydroxyethyl methacrylate) (PHEMA). Then, the visible light-induced photooxidation of thioethers under aerobic conditions was investigated. The results revealed that the reaction yielded sulfoxides highly chemoselectively in excellent yields with good substrate tolerance. Importantly, AQ-PHEMA could be easily recovered and reused more than 20 times without significant loss of the catalytic activity.

Work on the synthesis of a polymeric photosensitizer and its application in the photooxidation of thioethers is reported herein.

Considerations and Caveats in Combating ESKAPE Pathogens against Nosocomial Infections

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are among the most common opportunistic pathogens in nosocomial infections. ESKAPE pathogens distinguish themselves from normal ones by developing a high level of antibiotic resistance that involves multiple mechanisms. Contemporary therapeutic strategies which are potential options in combating ESKAPE bacteria need further investigation. Herein, a broad overview of the antimicrobial research on ESKAPE pathogens over the past five years is provided with prospective clinical applications.

Rejuvenated Photodynamic Therapy for Bacterial Infections

The emergence of multidrug resistant bacterial strains has hastened the exploration of advanced microbicides and antibacterial techniques. Photodynamic antibacterial therapy (PDAT), an old-fashioned technique, has been rejuvenated to combat "superbugs" and biofilm-associated infections owing to its excellent characteristics of noninvasiveness and broad antibacterial spectrum. More importantly, bacteria are less likely to produce drug resistance to PDAT because it does not require specific targeting interaction between photosensitizers (PSs) and bacteria. This review mainly focuses on recent developments and future prospects of PDAT. The mechanisms of PDAT against bacteria and biofilms are briefly introduced. In addition to classical macrocyclic PSs, several innovative PSs, including non-self-quenching PSs, conjugated polymer-based PSs, and nano-PSs, are summarized in detail. Numerous multifunctional PDAT systems such as in situ light-activated PDAT, stimuli-responsive PDAT, oxygen self-enriching enhanced PDAT, and PDAT-based multimodal therapy are highlighted to overcome the inherent defects of PDAT in vivo (e.g., limited penetration depth of light and hypoxic environment of infectious sites).

Emerging Strategies to Combat ESKAPE Pathogens in the Era of Antimicrobial Resistance: A Review

The acronym ESKAPE includes six nosocomial pathogens that exhibit multidrug resistance and virulence: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. Persistent use of antibiotics has provoked the emergence of multidrug resistant (MDR) and extensively drug resistant (XDR) bacteria, which render even the most effective drugs ineffective. Extended spectrum β-lactamase (ESBL) and carbapenemase producing Gram negative bacteria have emerged as an important therapeutic challenge. Development of novel therapeutics to treat drug resistant infections, especially those caused by ESKAPE pathogens is the need of the hour. Alternative therapies such as use of antibiotics in combination or with adjuvants, bacteriophages, antimicrobial peptides, nanoparticles, and photodynamic light therapy are widely reported. Many reviews published till date describe these therapies with respect to the various agents used, their dosage details and mechanism of action against MDR pathogens but very few have focused specifically on ESKAPE. The objective of this review is to describe the alternative therapies reported to treat ESKAPE infections, their advantages and limitations, potential application in vivo, and status in clinical trials. The review further highlights the importance of a combinatorial approach, wherein two or more therapies are used in combination in order to overcome their individual limitations, additional studies on which are warranted, before translating them into clinical practice. These advances could possibly give an alternate solution or extend the lifetime of current antimicrobials.