45 research outputs found
Fatty Acid Comprising Lysine Conjugates: Anti-MRSA Agents That Display In Vivo Efficacy by Disrupting Biofilms with No Resistance Development
Methicillin-resistant Staphylococcus aureus (MRSA) has developed resistance
to antibiotics of last resort such
as vancomycin, linezolid, and daptomycin. Additionally, their biofilm
forming capability has set an alarming situation in the treatment
of bacterial infections. Herein we report the potency of fatty acid
comprising lysine conjugates as novel anti-MRSA agents, which were
not only capable of killing growing planktonic MRSA at low concentration
(MIC = 3.1–6.3 μg/mL), but also displayed potent activity
against nondividing stationary phase cells. Furthermore, the conjugates
eradicated established biofilms of MRSA. The bactericidal activity
of d-lysine conjugated tetradecanoyl analogue (D-LANA-14)
is attributed to its membrane disruption against these metabolically
distinct cells. In a mouse model of superficial skin infection, D-LANA-14
displayed potent in vivo anti-MRSA activity (2.7 and 3.9 Log reduction
at 20 mg/kg and 40 mg/kg, respectively) without showing any skin toxicity
even at 200 mg/kg of the compound exposure. Additionally, MRSA could
not develop resistance against D-LANA-14 even after 18 subsequent
passages, whereas the topical anti-MRSA antibiotic fusidic acid succumbed
to rapid resistance development. Collectively, the results suggested
that this new class of membrane targeting conjugates bear immense
potential to treat MRSA infections over conventional antibiotic therapy
Lysine-Based Small Molecules That Disrupt Biofilms and Kill both Actively Growing Planktonic and Nondividing Stationary Phase Bacteria
The
emergence of bacterial resistance is a major threat to global health.
Alongside this issue, formation of bacterial biofilms is another cause
of concern because most antibiotics are ineffective against these
recalcitrant microbial communities. Ideal future antibacterial therapeutics
should possess both antibacterial and anti-biofilm activities. In
this study we engineered lysine-based small molecules, which showed
not only commendable broad-spectrum antibacterial activity but also
potent biofilm-disrupting properties. Synthesis of these lipophilic
lysine–norspermidine conjugates was achieved in three simple
reaction steps, and the resultant molecules displayed potent antibacterial
activity against various Gram-positive (Staphylococcus
aureus, Enterococcus faecium) and Gram-negative bacteria (Escherichia coli) including drug-resistant superbugs MRSA (methicillin-resistant <i>S. aureus</i>), VRE (vancomycin-resistant <i>E. faecium</i>), and β-lactam-resistant Klebsiella pneumoniae. An optimized compound in the series showed activity against planktonic
bacteria in the concentration range of 3–10 μg/mL, and
bactericidal activity against stationary phase <i>S. aureus</i> was observed within an hour. The compound also displayed about 120-fold
selectivity toward both classes of bacteria (<i>S. aureus</i> and <i>E. coli</i>) over human erythrocytes. This rapidly
bactericidal compound primarily acts on bacteria by causing significant
membrane depolarization and K<sup>+</sup> leakage. Most importantly,
the compound disrupted preformed biofilms of <i>S. aureus</i> and did not trigger bacterial resistance. Therefore, this class
of compounds has high potential to be developed as future antibacterial
drugs for treating infections caused by planktonic bacteria as well
as bacterial biofilms
Versatile and User-Friendly Anti-infective Hydrogel for Effective Wound Healing
Wound dressings play a crucial role
in facilitating optimal
wound
healing and protecting against microbial infections. However, existing
commercial options often fall short in addressing chronic infections
due to antibiotic resistance and the limited spectrum of activity
against both Gram-positive and Gram-negative bacteria frequently encountered
at wound sites. Additionally, complex fabrication processes and cumbersome
administration strategies pose challenges for cost-effective wound
dressing development. Consequently, there is a pressing need to explore
easily engineered biocompatible biomaterials as alternative solutions
to combat these challenging wound infections. In this study, we present
the development of an anti-infective hydrogel, P-BAC (polymeric bactericidal
hydrogel), which exhibits simple administration and promotes efficient
wound healing. P-BAC is synthesized via a one-step fabrication method
that involves the noncovalent cross-linking of poly(vinyl alcohol), N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride-AgCl
nanocomposite, and proline. Remarkably, P-BAC demonstrates broad-spectrum
antibacterial activity against both planktonic and stationary cells
of clinically isolated Gram-positive and Gram-negative bacteria, resulting
in a significant reduction of bacterial load (5–7 log reduction).
Moreover, P-BAC exhibits excellent efficacy in eradicating bacterial
cells within biofilm matrices (>95% reduction). In vivo experiments
reveal that P-BAC accelerates wound healing by stimulating rapid collagen
deposition at the wound site and effectively inactivates ∼95%
of Pseudomonas aeruginosa cells. Importantly,
the shear-thinning property of P-BAC simplifies the administration
process, enhancing its practicality and usability. Taken together,
our findings demonstrate the potential of this easily administrable
hydrogel as a versatile solution for effective wound healing with
potent anti-infective properties. The developed hydrogel holds promise
for applications in diverse healthcare settings, addressing the critical
need for improved wound dressing materials
Lipopolysaccharide Neutralization by Cationic-Amphiphilic Polymers through Pseudoaggregate Formation
Synthetic
polymers incorporating the cationic charge and hydrophobicity
to mimic the function of antimicrobial peptides (AMPs) have been developed.
These cationic-amphiphilic polymers bind to bacterial membranes that
generally contain negatively charged phospholipids and cause membrane
disintegration resulting in cell death; however, cationic-amphiphilic
antibacterial polymers with endotoxin neutralization properties, to
the best of our knowledge, have not been reported. Bacterial endotoxins
such as lipopolysaccharide (LPS) cause sepsis that is responsible
for a great amount of mortality worldwide. These cationic-amphiphilic
polymers can also bind to negatively charged and hydrophobic LPS and
cause detoxification. Hence, we envisaged that cationic-amphiphilic
polymers can have both antibacterial as well as LPS binding properties.
Here we report synthetic amphiphilic polymers with both antibacterial
as well as endotoxin neutralizing properties. Levels of proinflammatory
cytokines in human monocytes caused by LPS stimulation were inhibited
by >80% when coincubated with these polymers. These reductions
were
found to be dependent on concentration and, more importantly, on the
side-chain chemical structure due to variations in the hydrophobicity
profiles of these polymers. These cationic-amphiphilic polymers bind
and cause LPS neutralization and detoxification. Investigations of
polymer interaction with LPS using fluorescence spectroscopy and dynamic
light scattering (DLS) showed that these polymers bind but neither
dissociate nor promote LPS aggregation. We show that polymer binding
to LPS leads to sort of a pseudoaggregate formation resulting in LPS
neutralization/detoxification. These findings provide an unusual mechanism
of LPS neutralization using novel synthetic cationic-amphiphilic polymers
Membrane Active Vancomycin Analogues: A Strategy to Combat Bacterial Resistance
The
alarming growth of antibiotic resistant superbugs such as vancomycin-resistant
Enterococci and Staphylococci has become a major global health hazard.
To address this issue, we report the development of lipophilic cationic
vancomycin analogues possessing excellent antibacterial activity against
several drug-resistant strains. Compared to vancomycin, efficacy greater
than 1000-fold was demonstrated against vancomycin-resistant Enterococci
(VRE). Significantly, unlike vancomycin, these compounds were shown
to be bactericidal at low concentrations and did not induce bacterial
resistance. An optimized compound in the series, compared to vancomycin,
showed higher activity in methicillin-resistant Staphylococcus
aureus (MRSA) infected mouse model and exhibited superior
antibacterial activity in whole blood with no observed toxicity. The
remarkable activity of these compounds is attributed to the incorporation
of a new membrane disruption mechanism into vancomycin and opens up
a great opportunity for the development of novel antibiotics
Membrane Active Phenylalanine Conjugated Lipophilic Norspermidine Derivatives with Selective Antibacterial Activity
Natural and synthetic membrane active
antibacterial agents offer
hope as potential solutions to the problem of bacterial resistance
as the membrane-active nature imparts low propensity for the development
of resistance. In this report norspermidine based antibacterial molecules
were developed that displayed excellent antibacterial activity against
various wild-type bacteria (Gram-positive and Gram-negative) and drug-resistant
bacteria (methicillin-resistant <i>Staphylococcus aureus</i>, vancomycin-resistant <i>Enterococcus faecium</i>, and
β-lactam-resistant <i>Klebsiella pneumoniae</i>).
In a novel structure–activity relationship study it has been
shown how incorporation of an aromatic amino acid drastically improves
selective antibacterial activity. Additionally, the effect of stereochemistry
on activity, toxicity, and plasma stability has also been studied.
These rapidly bactericidal, membrane active antibacterial compounds
do not trigger development of resistance in bacteria and hence bear
immense potential as therapeutic agents to tackle multidrug resistant
bacterial infections
Cleavable Amphiphilic Biocides with Ester-Bearing Moieties: Aggregation Properties and Antibacterial Activity
The rise of multidrug-resistant bacterial
infections
and the dwindling
supply of newly approved antibiotics have emerged as a grave threat
to public health. Toward the ever-growing necessity of the development
of novel antimicrobial agents, herein, we synthesized a series of
cationic amphiphilic biocides featuring two cationic headgroups separated
by different hydrophobic spacers, accompanied by the inclusion of
two lipophilic tails through cleavable ester functionality. The detailed
aggregation properties offered by these biocides were investigated
by small-angle neutron scattering (SANS) and conductivity. The critical
micellar concentration of the biocides and the size and shape of the
micellar aggregates differed with variation of pendant and spacer
hydrophobicity. Furthermore, the aggregation number and size of the
micelles were found to vary with changing concentration and temperature.
These easily synthesized biocides exhibited potent antibacterial properties
against various multidrug-resistant bacteria. The optimized biocides
with minimum hematotoxicity and potent antibacterial activity against
methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii exhibited
rapid killing kinetics against planktonic bacteria. Also, these membrane-active
agents were able to eradicate preformed biofilms. The enzymatic and
acidic degradation profile further offered proof of gradual degradation.
Collectively, these cleavable amphiphilic biocides demonstrated excellent
potency for combating the multidrug-resistant bacterial infection
Structure–Activity Relationship of Amino Acid Tunable Lipidated Norspermidine Conjugates: Disrupting Biofilms with Potent Activity against Bacterial Persisters
The emergence of bacterial resistance
and biofilm associated infections
has created a challenging situation in global health. In this present
state of affairs where conventional antibiotics are falling short
of being able to provide a solution to these problems, development
of novel antibacterial compounds possessing the twin prowess of antibacterial
and antibiofilm efficacy is imperative. Herein, we report a library
of amino acid tunable lipidated norspermidine conjugates that were
prepared by conjugating both amino acids and fatty acids with the
amine functionalities of norspermidine through amide bond formation.
These lipidated conjugates displayed potent antibacterial activity
against various planktonic Gram-positive and Gram-negative bacteria
including drug-resistant superbugs such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium, and β-lactam-resistant Klebsiella pneumoniae. This class of nontoxic and
fast-acting antibacterial molecules (capable of killing bacteria within
15 min) did not allow bacteria to develop resistance against them
after several passages. Most importantly, an optimized compound in
the series was also capable of killing metabolically inactive persisters
and stationary phase bacteria. Additionally, this compound was capable
of disrupting the preformed biofilms of S. aureus and E. coli. Therefore, this class
of antibacterial conjugates have potential in tackling the challenging
situation posed by both bacterial resistance as well as drug tolerance
due to biofilm formation
Dual Function Injectable Hydrogel for Controlled Release of Antibiotic and Local Antibacterial Therapy
We
present vancomycin-loaded dual-function injectable hydrogel
that delivers antibiotic locally suitable for treatment of infections
in avascular or necrotic tissues. The syringe-deliverable gels were
developed using polydextran aldehyde and an inherently antibacterial
polymer <i>N</i>-(2-hydroxypropyl)-3-trimethylammonium chitosan
chloride along with vancomycin. The antibiotic was primarily encapsulated
via reversible imine bonds formed between vancomycin and polydextran
aldehyde in the hydrogel which allowed sustained release of vancomycin
over an extended period of time in a pH-dependent manner. Being inherently
antibacterial, the gels displayed excellent efficacy against bacteria
due to dual mode of action (killing bacteria upon contact as well
as by releasing antibiotics into surroundings). Upon subcutaneous
implantation, the gel was shown to kill methicillin-resistant Staphylococcus aureus (>99.999%) when bacteria
were
introduced directly into the gel as well as at distal site from the
gel in a mice model. These materials thus represent as novel noninvasive
drug-delivery device suitable for local antibiotic therapy
Dual-Function Polymer–Silver Nanocomposites for Rapid Killing of Microbes and Inhibiting Biofilms
Polymer–silver
nanocomposites have emerged as an integral
weapon to combat device-related infections. However, synthesis of
the nanocomposites still remains a major challenge that often involves
two-step process in which silver nanoparticles are synthesized ex
situ. Additionally, polymers used in the nanocomposites are commonly
not antimicrobial and biodegradable thus often lack bioactivity and
biocompatibility. Herein we report highly active dual-function polymer-silver
nanocomposites consisting of an inherently antimicrobial and biodegradable
polymer in one-pot. A simple method of in situ reduction of a silver
salt was employed to synthesize the silver nanoparticles (5–15
nm) from silver <i>para</i>-toluenesulfonate in which the
intrinsically biodegradable and antimicrobial polymer <i>N</i>,<i>N</i>-dimethyl-<i>N</i>-hexadecyl ammonium
chitin tosylate acted as reducing as well as stabilizing agent. The
nanocomposite with the water-insoluble and organo-soluble polymer
was simply painted onto surfaces via facile noncovalent immobilization.
Notably, composite-coated surfaces inactivated both drug-sensitive
and drug-resistant bacteria including pathogenic fungi at a much faster
rate than polymer alone. The composites released active silver ions
over an extended period of time and displayed remarkably long-lasting
activity. In addition, surfaces coated with composites effectively
inhibited both bacterial and fungal biofilm formation. Further, upon
coating on catheter, the nanocomposites reduced methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) burden both on catheter (>99.99%
reduction) and in tissues surrounding the catheter (>99.999% reduction)
in a mice model. These novel nanomaterials that showed negligible
hemolysis toward human erythrocytes might be used as safe and effective
antimicrobial coatings in biomedical device applications