User:Stephenwinston/sandbox/Final Draft Project 2

Article Evaluation

Week 2 Assignment https://en.wikipedia.org/wiki/Ixodes_scapularis

Is everything in the article relevant to the article topic? Is there anything that distracted you? The article is entirely relevant to the topic: the common deer tick Ixodes scapularis. They discuss its lifecycle, role in the ecosystem, and their role as a vector for disease. These all comprise the different topics encompassed by this article. The article is entirely neutral and doesn't appear biased. The article bluntly states facts regarding the organism, not appearing to sway the reader in any direction.

I think they underrepresented the magnitude of the prevalence of the organism by merely citing data regarding a New Jersey study. From my own research, I easily found data published by the CDC showcasing national statistics about tick spread illnesses. There is also plenty of relevant data regarding contraction of the disease, and the incessant migration of the organism which was not discussed in the article at all.

Many of the sources were surprisingly book sources. However, the links to online sources were all still valid and I was able to verify the author's source. These sources all appear neutral, trying to inform the reader Citations are regularly interspersed within the article, and it is very clear where all of the information comes from, on a sentence to sentence basis.

On the talk page, it appears editors have addressed concerns regarding some outdated information. They don't believe the maps listed in the source outline the full geography inhabited by the tick. They are citing papers from 2007, which is very outdated. I believe this could be improved. There were also discussions regarding the external links used in the source. It appears some of them were previously invalid, and one of the authors corrected the issue.Stephenwinston (talk) 21:20, 18 May 2018 (UTC)

Two Articles For Improvement Week 3

https://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier

This article provides an in depth account of the structure of the blood brain barrier. But the article could be improved by providing more details in the diseases section. The descriptions are very generic, and brief. Some of the descriptions are only 1-2 sentences long with minimal sources. More details on the diseases, and their properties which enable them to bypass this defense mechanism would improve this article.

https://en.wikipedia.org/wiki/PLGA

“Information that would improve this article would be detailed explanations and descriptions of the metabolic pathways in which PLGA is broken down, and how it gets eliminated in the body. This would support the claims of biocompatibility and the safe nature of PLGA.” Stephenwinston (talk) 00:20, 25 May 2018 (UTC)

Topic:PLGA and Antibiotic Resistance + Sources

Topic: PLGA and Antibiotic Resistance

We are planning on writing an article from scratch describing PLGA and its potential application to antibiotic resistance. Many traditional antibiotics have been unable to cross the blood brain barrier, so if the infection reaches the bloodstream it becomes difficult to treat. There have been recent advancements combining nanoparticle technology with antibiotics to attempt to solve this problem.

Sources

Poly (DL‐lactide‐co‐glycolide) (PLGA) Nanoparticles with Entrapped trans‐Cinnamaldehyde and Eugenol for Antimicrobial Delivery Applications

Fabrication of Biodegradable Electrospun Poly(L-lactide-co-glycolide) Fibers with Antimicrobial Nanosilver Particles

Antimicrobial PLGA ultrafine fibers: Interaction with wound bacteria

Bioburden-responsive antimicrobial PLGA ultrafine fibers for wound healing

Study of antimicrobial activity of anethole and carvone loaded PLGA nanoparticles

Antimicrobial Efficacy of Poly (DL‐lactide‐co‐glycolide) (PLGA) Nanoparticles with Entrapped Cinnamon Bark Extract against Listeria monocytogenes and Salmonella typhimurium

Multifunctional PLGA particles containing poly(L-glutamic acid)-capped silver nanoparticles and ascorbic acid with simultaneous antioxidative and prolonged antimicrobial activity — Preceding unsigned comment added by Stephenwinston (talk • contribs) 00:33, 25 May 2018 (UTC)

Lead Section: Assignment 2

PLGA or poly(D,L-lactide-co-glycolide) is a matrix of aliphatic polyester nanofibers which can be used to generate spherical structures capable of encapsulating various therapeutics. These dense fibrous structures have been characterized by Scanning Electron Microscopy (SEM). The small size, and hydrophilic nature enables these particles to penetrate environments, the hydrophobic drug they carry, could not otherwise. These nanofibers can also be woven into larger matrices in hydrogels for dressing wounds. Depending on the application they can be generated to meet variety of criteria including size, polydisperity index (PDI), medicinal saturation and release rates of encapsulated product. Varying synthesis methodologies has been shown in the literature to manipulate these attributes to optimize therapeutic outcomes. The use of this PLGA microsphere technology has been widely approved for use by the Food and Drug Administration (FDA).

Multiple methods exist for their generation including emulsion methods as well as nanoprecipitation methods. Emulsion methods generally require dissolved PLGA in an organic solvent, which is then introduced to the aqueous phase with a homogenizer on ice. The resulting particles are centrifuged, washed, and collected for use. PLGA degrades slowly by hydrolysis in aqueous environments. Other than emulsion, a common method for formulating PLGA nanoparticles is nanoprecipitation. Like emulsion, it involves dissolved PLGA in an organic solvent such as DMSO, DMF, THF. The organic phase is then introduced dropwise to an aqueous solution being stirred at least 12,000 rpm. The size of the needle used as well as the stir-plate speed influence the size of the resulting PLGA particles.

These vehicles can be synthesized with a multitude of modifications depending on the desired function. These include Mg micromotors and trimethylated chitosan which enhance the delivery capabilities of these nanoparticles in particular in vivo environments like the stomach which is highly acidic, or facilitating transport across the Blood Brain Barrier (BBB) via absorptive-mediated transcytosis (AMT). While some modifications facilitate transportation, others can modulate particle release efficiency. The literature demonstrates that coating PLGA microspheres surface with a combination bioactive wallastonite and Poly(3-hydroxybutyric acid-co-3-hydroxyvalerate) or PHBV you can modulate particle release time to generate a slow release therapeutic. In addition, chitosan could be conjugated with PLGA particles containing nucleic acids such as siRNA, to give the conjugation a positive charge, thus facilitating the transport over the blood brain barrier.

In vivo studies demonstrate capabilities to enable a targeted release of the drug, correlated to bacterial proliferation and severity of symptoms. For instance, naturally occurring antimicrobials like Cinnamon Bark Extract (CBE) have been used for bacterial infections. However, alone, the drug is not stable in physiological conditions. By encapsulating this natural antimicrobial in PLGA particles, it stays stable in physiological conditions, and its more hydrophobic nature allows it to bind more easily and bypass the microbial membranes. Therefore, it allows for specific targeting and delivery of the drug in interest, with no side effects. — Preceding unsigned comment added by Stephenwinston (talk • contribs) 16:57, 1 June 2018 (UTC)

Draft Project 2

PLGA nanoparticles as carriers in antimicrobial drug delivery

Poly(lactic-co-glycolic acid) or PLGA, is a copolymer consisting of lactic acid and glycolic acid. These monomers are then polymerized via ester linkages to form PLGA, resulting in a linear product with aliphatic properties, a desired trait for nanoparticle carriers. PLGA is also biocompatible and degrades easily into non-toxic compounds (lactic acid, glycolic acid), and is approved by the Food and Drug Administration for use in many therapeutic products.

While PLGA has been shown to degrade by metabolism of lactic acid and glycolic acid in the tricarboxylic acid cycle (in the presence of water), different compositions of PLGA has been shown to demonstrate different stabilities and time taken for degradation. The different compositions utilize different ratios of lactic acid and glycolic acid (PLGA 50:50 refers to 50% lactic acid and 50% glycolic acid), and higher ratios of lactic acid has been shown to be more stable and degrade slower than other ratios.

Multiple methods exist for the formulation of PLGA including emulsion methods as well as nanoprecipitation methods. Emulsion methods generally require dissolved PLGA in an organic solvent, which is then introduced to the aqueous phase with a homogenizer on ice. The resulting particles are centrifuged, washed, and collected for use. Other than emulsion, a common method for formulating PLGA nanoparticles is nanoprecipitation. Like emulsion, it involves dissolved PLGA in an organic solvent such as Dimethyl Sulfoxide (DMSO), Dimethyl formamide (DMF), and tetrahydrofuran (THF). The organic phase is then introduced dropwise to an aqueous solution being stirred at least 12,000 rpm. The size of the needle used as well as the stir-plate speed influence the size of the resulting PLGA particles.

The resulting size of the particles could be as small as 10 nanometers in diameter, depending on the method and solvent used. The small size of the nanoparticle makes them permeable to many membranes in the body such as the Blood-Brain Barrier, making PLGA an excellent drug-delivery system. Countless studies have conjugated therapeutic drugs, peptides, siRNA, etc. into PLGA nanoparticles to transport them across the Blood-Brain Barrier. For example, one study highlights the potential of Trimethylated chitosan conjugated PLGA molecules to pass the Blood Brain Barrier. This modification uses charge interactions to bypass the BBB using absorptive mediated transcytosis (AMT). These interactions are non-specific, but the majority of potent hydrophobic drugs have still been unable to pass through the BBB. Using PLGA to encapsulate these drugs, they detail a mechanism to transport and slowly release medicines into afflicted regions, which have not been accessible before this technology. These hypotheses are supported by in vivo findings in mice, using fluorescent imaging to detect PLGA presence in brain tissue. In addition to membrane permeability, the known stability of PLGA in physiological conditions allow for the drugs to be protected and circulate longer without facing elimination through excretion, degradation by hydrolysis, etc.

These desirable characteristics of PLGA led to the development of new antimicrobial treatments to treat infections and wounds, using PLGA as the carrier. For instance, one study describes the capabilities of using PLGA as a therapeutic during wound healing. It demonstrates that during microbial aggression, ultrafibrous (UF) PLGA matrices trigger a correlated release of encapsulated antimicrobial drugs. In addition. the entrapped molecules in these nanoparticles maintain functionality and upon release, greatly reduce biofilm formation. This finding was termed a “bioburden-triggered drug release”. These findings were sustained in both in vitro and vivo assays.

Aside from antimicrobial drugs, encapsulating certain natural oils in PLGA has shown effective against bacteria as well. One study details the encapsulation of carvone and anethole, also demonstrating the different preparation methods, resulting sizes, and burst-release or sustained-release properties. It suggests that the ability control these properties in PLGA could be tailored towards specific applications in the food industry, as well as the pharmaceutical industry. More importantly, it demonstrates the effects of PLGA encapsulated oils like carvone and anethole on bacterial strains such as S. Aureus (gram-positive), and E. Coli (gram-negative).

As mentioned above, PLGA has many potential uses in the food industry as well, aside from therapeutic and pharmaceutical purposes. One article highlights the potential for the use of PLGA incorporation in the food industry to prevent the growth of harmful bacteria like Salmonella typhimurium and L. monocytogenes. Both of these bacteria are notorious for frequent outbreaks in food supplies. The use of naturally occurring antimicrobials like Cinnamon Bark Extract (CBE) have been explored to appease the consumer, which would prevent the inclusion of synthetic antibiotics. These natural compounds are hydrophobic which limits their effectivity in this setting by restricting the compounds potential to interact with the growing bacterium. However, once delivered by PLGA, their amphipathic nature increases their affinity to microbial membranes, thereby increasing their propensity to bypass its membrane. Alone, these molecules may just coalesce in an arbitrary location, but PLGA also provides a vehicle and delivery mechanism to transport these compounds to microbial populations where they can be effective. This article shows that encapsulating naturally occurring hydrophobic antibiotics in PLGA is an effective means of delivery for applications in the food industry. — Preceding unsigned comment added by Stephenwinston (talk • contribs) 23:06, 10 June 2018 (UTC)

Updated Draft Project #2

PLGA nanoparticles as carriers in antimicrobial drug delivery

Introduction

Poly(lactic-co-glycolic acid) or PLGA, is a copolymer consisting of lactic acid and glycolic acid. These monomers are polymerized via ester linkages to form PLGA, resulting in a linear product with aliphatic properties, a desired trait for nanoparticle carriers. PLGA is also biocompatible and degrades easily into its original non-toxic building blocks (lactic acid, glycolic acid). The nanoparticle is approved by the Food and Drug Administration (FDA) for use in many therapeutic products. PLGA has seen a variety of uses, and repeated testing in medicinal and agricultural products has shown no side effects specific to this carrier molecule.

Tailoring PLGA Nanoparticle Generation for Antibacterial and Release Properties

Multiple methods exist for the formulation of PLGA including emulsion methods as well as nanoprecipitation methods. Emulsion methods generally require dissolved PLGA in an organic solvent, which is then introduced to the aqueous phase with a homogenizer on ice. The resulting particles are centrifuged, washed, and collected for use. Other than emulsion, a common method for formulating PLGA nanoparticles is nanoprecipitation. Like emulsion, it involves dissolved PLGA in an organic solvent such as Dimethyl Sulfoxide (DMSO), Dimethyl formamide (DMF), and tetrahydrofuran (THF). The organic phase is then introduced dropwise to an aqueous solution being stirred at least 12,000 rpm. The size of the needle used as well as the stir-plate speed influence the size of the resulting PLGA particles. The resulting size of the particles could be as small as 10 nanometers in diameter, depending on the method and solvent used.

While PLGA has been shown to degrade by metabolism of lactic acid and glycolic acid in the tricarboxylic acid cycle (in the presence of water), different compositions of PLGA has been shown to demonstrate different stabilities and time taken for degradation. The different compositions utilize different ratios of lactic acid and glycolic acid (PLGA 50:50 refers to 50% lactic acid and 50% glycolic acid), and higher ratios of lactic acid has been shown to be more stable and degrade slower than other ratios. Additionally, varying the ratio of encapsulated antibiotic to PLGA varies release. Increasing the concentration of antibiotic during emulsification results in a larger proportion of antibiotic along the outer layer of PLGA, thereby facilitating diffusion out of the microsphere.

A group at the University of Belgrade in Serbia incorporated silver and ascorbic acid (PLGA/AgNpPGA/ascorbic acid) to enhance the slow release and antimicrobial properties of PLGA. In in vitro degradation studies using physiologically relevant solutions they tracked ascorbic acid release by pH drop. The modification enhanced the slow release such that they were detecting ascorbic acid 80 days after mock treatment. The enhanced antibacterial activity is likely due to the reactive oxygen species (ROS) produced by AgNp interactions. These have been detailed in previous literature. This group modified the approach by coating these ROS producing groups with an organic polymer layer, and incorporating ascorbic acid, an antioxidant, to reduce off target cytotoxicity. Viability assays performed in vitro using HepG2 liver cells showed no significant cell death associated with a range of concentrations of PLGA/AgNpPGA/ascorbic acid. This cell line has been noted in alternative literature to accurately replicate in vivo results.

PLGA use in Agricultural Settings

Aside from antimicrobial drugs, encapsulating certain natural oils in PLGA has shown effective against bacteria as well. One study details the encapsulation of carvone and anethole, also demonstrating the different preparation methods, resulting sizes, and burst-release or sustained-release properties. It suggests that the ability control these properties in PLGA could be tailored towards specific applications in the food industry, as well as the pharmaceutical industry. More importantly, it demonstrates the effects of PLGA encapsulated oils like carvone and anethole on bacterial strains such as S. Aureus (gram-positive), and E. Coli (gram-negative).

As mentioned above, PLGA has many potential uses in the food industry as well, aside from therapeutic and pharmaceutical purposes. One article highlights the potential for the use of PLGA incorporation in the food industry to prevent the growth of harmful bacteria like Salmonella typhimurium and L. monocytogenes. Both of these bacteria are notorious for frequent outbreaks in food supplies. The use of naturally occurring antimicrobials like Cinnamon Bark Extract (CBE) have been explored to appease the consumer, which would prevent the inclusion of synthetic antibiotics. These natural compounds are hydrophobic which limits their effectivity in this setting by restricting the compounds potential to interact with the growing bacterium. However, once delivered by PLGA, their amphipathic nature increases their affinity to microbial membranes, thereby increasing their propensity to bypass its membrane. Alone, these molecules may just coalesce in an arbitrary location, but PLGA also provides a vehicle and delivery mechanism to transport these compounds to microbial populations where they can be effective. This article shows that encapsulating naturally occurring hydrophobic antibiotics in PLGA is an effective means of delivery for applications in the food industry.

Modification of PLGA to Pass the Blood Brain Barrier

The small size of the nanoparticle makes them permeable to many membranes in the body such as the Blood-Brain Barrier, making PLGA an excellent drug-delivery system. Countless studies have conjugated therapeutic drugs, peptides, siRNA, etc. into PLGA nanoparticles to transport them across the Blood-Brain Barrier.In addition to membrane permeability, the known stability of PLGA in physiological conditions allow for the drugs to be protected and circulate longer without facing elimination through excretion, degradation by hydrolysis, etc. For example, one study highlights the potential of covalently linking Trimethylated chitosan (TMC) to PLGA molecules in order to pass the Blood Brain Barrier (BBB). This modification uses charge interactions to bypass the BBB using absorptive mediated transcytosis (AMT). The trimethylation on the surface provides the positive charge necessary to interact with the negatively charged membrane. This attraction results in electrostatic interactions between the TMC PLGA and the anionic membrane native to brain capillaries. These electrostatic interactions are believed to be what enables the microspheres passage through the BBB. The covalently linked TMC also increases the hydrophilicity of the surface, thereby making the microspheres less likely to be removed via phagocytosis, and increasing the resulting half life of the therapeutic.

Interactions associated with AMT are non-specific, but the majority of potent hydrophobic drugs have still been unable to pass through the BBB. However, even if they were able to pass, the unregulated release is hypothesized to result in inflammation at the sites of aggregation leading to serious potentially fatal side effects. Using PLGA to encapsulate these drugs, they detail a mechanism to transport and slowly release medicines into afflicted regions, which have not been accessible before this technology. These hypotheses are supported by in vivo findings in transgenic mice, using fluorescent microscopy to detect TMC PLGA presence in brain sections.While TMC PLGA was found to penetrate the BBB, the unmodified PLGA was unable to do so. To assess whether or not these modified microspheres could be harmful, they used an MTT assay. This investigated the potential cytotoxicity of novel external modifications, and found that at low concentrations (used in vivo experiments) there was no discernable difference in viability between TMC PLGA and their negative control PLGA-NP. They concluded that while TMC PLGA modifications enhance delivery capabilities, they have no statistical implications on resulting cell viability.

PLGA Ultra Fibrous Mats Facilitate Wound Healing

These desirable characteristics of PLGA led to the development of new antimicrobial treatments to treat infections and wounds, using PLGA as the carrier. For instance, one study describes the capabilities of using PLGA as a therapeutic during wound healing. It demonstrates that during microbial aggression, ultrafibrous (UF) PLGA matrices trigger a correlated release of encapsulated antimicrobial drugs. In addition. the entrapped molecules in these nanoparticles maintain functionality and upon release, greatly reduce biofilm formation. This finding was termed a “bioburden-triggered drug release”. As bacteria grow, their secretions and waste products reduce the pH of the environment facilitating the degradation of the PLGA. These findings were sustained in both in vitro and vivo assays.They lowered the pH of the aqueous environment in the absence of bacteria and observed similar results. To improve in vivo results, they structurally modified the PLGA molecules such that a larger portion of the drug molecules were on near the surface, increasing the initial release of the drug. The study also demonstrated that by exposing the UF mats to UV light before treatment facilitated the release of entrapped antimicrobial agents. The exposure to UV light for an hour results in sharp reductions to PLGA molecular weight as well as textile strength. The observation of cracking and micropore formation correlates with enhanced initial drug release. These efforts were intended to combat the exponential burst phase well characterized in bacterial growth.

In vivo studies indicated that bacteria such as Methicillin-resistant Staphylococcus aureus (MRSA) adhere to the UF mats, and enhancing the initial release stunts bacterial growth tremendously. The dense network of nanofibers mimic that of extracellular matrix which is hypothesized why bacteria latch on to the fibers. In addition to bacterial cells, mammalian tissue has shown to use the UF fibers as a scaffolding in regenerating lost tissue reducing the time for wound healing. Visual analysis of mice tissue showed that wounds treated with PLGA encapsulated antibiotics closed faster and were less likely to develop infections than the controls, and those treated with traditional topical antibiotics. This data is corroborated by bacterial culture results. They measured number of viable S. aureus colonies a week into the of the study and found that the PLGA treated infection had 10% of the number of viable colonies relative to the untreated sample, and significantly fewer colonies than the traditionally treated sample.

PLGA Based Micromotors Targeting H. Pylori

The diverse range of applications of this new technologies has led to clinical exploration in treating Helicobacter pylori, the bacteria linked to the formation of stomach ulcers. This unique species of bacterium is neither gram negative, or gram positive ruling out treatment using several classes of antibiotics targeting the rebuilding of bacterial cell walls. Treatment of H. pylori generally requires a cocktail of antibiotics over a several month duration. The stomach is a highly acidic environment which degrades unencapsulated antibiotics. To facilitate delivery and stability of the antibiotic, they are prescribed with a proton pump inhibitor (PPI) which reduces the acidity of stomach enabling antibiotic function. These PPIs are believed to be responsible for the majority of symptoms generally associated with stomach ulcer treatment.

To circumvent the need for this treatment methodology, a group of UCSD devised a PLGA based magnesium micromotor to safely deliver Clarithromycin (CLR) to the infection. They emulsified the PLGA using Chitosan to reinforce the outer 100 nm membrane. The inner membrane was layered with titanium dioxide (TiO2) and magnesium. These layers were coated using atomic layer deposition (ALD) to ensure uniform coating of the PLGA. The underneath of the TiO2 which acts as as a scaffold for the layers, ensure the structure is maintained during treatment. The inside of the TiO2 was layered with magnesium using the same technology. This ALD methodology of nanoparticle formation enabled the maintenance of microscopic pores that are critical for propulsion. The pores enable the magnesium to react the stomach acid generating hydrogen microbubbles which drive the propulsion of the nanoparticle. The increased motility ensures the drug reaches the mucosal layer of the stomach, and the root of the H. pylori infection. The group used Scanning Electron Microscopy (SEM) to verify these structural modifications didn’t impede uniform loading of CLR, the antibiotic, during emulsification. Their micromotors maintained bactericidal efficacy during in vitro studies. Once verified, they carried out in vivo studies in mice using controls to monitor for effective treatment and potential toxicity of the therapeutic. After inoculating the mice with H. pylori over two weeks, they orally ingested the PLGA based treatment. After the final treatment, the mice were killed and the stomach was excised to enable recovery of viable H. pylori from gastric tissues. Statistical analysis of bacterial burden post mortem revealed magnesium based propulsion of PLGA encapsulated therapeutics significantly reduced the quantity of viable bacteria at the end of the study. Stephenwinston (talk) 23:12, 19 June 2018 (UTC)

Final Draft Project 2

PLGA Nanoparticles as Carriers in Anti-Microbial Drug Delivery

Introduction

Poly(lactic-co-glycolic acid) or PLGA, is a copolymer consisting of lactic acid and glycolic acid. These monomers are polymerized via ester linkages to form PLGA, resulting in a linear product with aliphatic properties, a desired trait for nanoparticle carriers. PLGA is also biocompatible and degrades easily into its original non-toxic building blocks (lactic acid, glycolic acid). The nanoparticle is approved by the Food and Drug Administration (FDA) for use in many therapeutic products. PLGA has seen a variety of uses, and repeated testing in medicinal and agricultural products has shown no side effects specific to this carrier molecule. 6

Tailoring PLGA Nanoparticle Generation for Antibacterial and Release Properties

Multiple methods exist for the formulation of PLGA including emulsion methods as well as nanoprecipitation methods. Emulsion methods generally require dissolved PLGA in an organic solvent, which is then introduced to the aqueous phase with a homogenizer on ice. The resulting particles are centrifuged, washed, and collected for use. Other than emulsion, a common method for formulating PLGA nanoparticles is nanoprecipitation. Like emulsion, it involves dissolved PLGA in an organic solvent such as Dimethyl Sulfoxide (DMSO), Dimethyl formamide (DMF), and tetrahydrofuran (THF). The organic phase is then introduced dropwise to an aqueous solution being stirred at least 12,000 rpm. The size of the needle used as well as the stir-plate speed influence the size of the resulting PLGA particles. The resulting size of the particles could be as small as 10 nanometers in diameter, depending on the method and solvent used. 2,6

While PLGA has been shown to degrade by metabolism of lactic acid and glycolic acid in the tricarboxylic acid cycle (in the presence of water), different compositions of PLGA has been shown to demonstrate different stabilities and time of degradation. The different compositions utilize different ratios of lactic acid and glycolic acid (PLGA 50:50 refers to 50% lactic acid and 50% glycolic acid), and higher ratios of lactic acid has been shown to be more stable and degrade slower than other ratios. Additionally, varying the ratio of encapsulated antibiotics in the PLGA carrier varies release. Increasing the concentration of antibiotic during emulsification results in a larger proportion of antibiotics along the outer layer of PLGA, thereby facilitating diffusion out of the microsphere. 2,6

A group at the University of Belgrade in Serbia incorporated silver and ascorbic acid (PLGA/AgNpPGA/ascorbic acid) to enhance the slow/sustained release and antimicrobial properties of PLGA. In in vitro degradation studies using physiologically relevant solutions they tracked ascorbic acid release by pH drop. The modification enhanced the slow release such that they were detecting ascorbic acid 80 days after mock treatment. The enhanced antibacterial activity is likely due to the reactive oxygen species (ROS) produced by AgNp interactions. These have been detailed in previous literature. This group modified the approach by coating these ROS producing groups with an organic polymer layer, and incorporating ascorbic acid, an antioxidant, to reduce off target cytotoxicity. Viability assays performed in vitro using HepG2 liver cells showed no significant cell death associated with a range of concentrations of PLGA/AgNpPGA/ascorbic acid. This cell line has been noted in alternative literature to accurately replicate in vivo results. 8

PLGA Use in Agricultural Settings

Aside from antimicrobial drugs, encapsulating certain natural oils in PLGA has shown to be effective against bacteria as well. One study details the encapsulation of carvone and anethole, also demonstrating the different preparation methods, resulting sizes, and burst-release or sustained-release properties. It suggests that the ability to control for these properties in PLGA could be tailored towards specific applications in the food industry, as well as the pharmaceutical industry. More importantly, it demonstrates the effects of PLGA encapsulated oils like carvone and anethole on bacterial strains such as S. Aureus (gram-positive), and E. Coli (gram-negative). 3

As mentioned above, PLGA has many potential uses in the food industry as well, aside from therapeutic and pharmaceutical purposes. One article highlights the potential for the use of PLGA incorporation in the food industry to prevent the growth of harmful bacteria like Salmonella typhimurium and L. monocytogenes. Both of these bacteria are notorious for frequent outbreaks in food supplies. The use of naturally occurring antimicrobials like Cinnamon Bark Extract (CBE) have been explored to appease the consumer, which would prevent the inclusion of synthetic antibiotics. These natural compounds are hydrophobic which limits their effectivity in this setting by restricting the compounds potential to interact with the growing bacterium. However, once delivered by PLGA, their amphipathic nature increases their affinity to microbial membranes, thereby increasing their propensity to bypass its membrane. Alone, these molecules may just coalesce in an arbitrary location, but PLGA also provides a vehicle and delivery mechanism to transport these compounds to microbial populations where they can be effective. This article shows that encapsulating naturally occurring hydrophobic antibiotics in PLGA is an effective means of delivery for applications in the food industry.2

Modification of PLGA to Pass the Blood-Brain Barrier

The small size of the nanoparticle makes them permeable to many membranes in the body such as the Blood-Brain Barrier, making PLGA an excellent drug-delivery system. Countless studies have conjugated therapeutic drugs, peptides, siRNA, etc. into PLGA nanoparticles to transport them across the Blood-Brain Barrier. In addition to membrane permeability, the known stability of PLGA in physiological conditions allow for the drugs to be protected and circulate longer without facing elimination through excretion, degradation by hydrolysis, etc. For example, one study highlights the potential of covalently linking Trimethylated chitosan (TMC) to PLGA molecules in order to pass the Blood Brain Barrier (BBB). This modification uses charge interactions to bypass the BBB using Absorptive Mediated Transcytosis (AMT). The trimethylation on the surface provides the positive charge necessary to interact with the negatively charged membrane. This attraction results in electrostatic interactions between the TMC PLGA and the anionic membrane native to brain capillaries. These electrostatic interactions are believed to be what enables the microspheres passage through the BBB. The covalently linked TMC also increases the hydrophilicity of the surface, thereby making the microspheres less likely to be removed via phagocytosis, and increasing the resulting half life of the therapeutic. 4

Interactions associated with AMT are non-specific, but the majority of potent hydrophobic drugs have still been unable to pass through the BBB. However, even if they were able to pass, the unregulated release is hypothesized to result in inflammation at the sites of aggregation leading to serious potentially fatal side effects. Using PLGA to encapsulate these drugs, they detail a mechanism to transport and slowly release medicines into afflicted regions, which have not been accessible before this technology. These hypotheses are supported by in vivo findings in transgenic mice, using fluorescent microscopy to detect TMC PLGA presence in brain sections. While TMC PLGA was found to penetrate the BBB, the unmodified PLGA was unable to do so. To assess whether or not these modified microspheres could be harmful, they used an MTT assay. This investigated the potential cytotoxicity of novel external modifications, and found that at low concentrations (used in vivo experiments) there was no discernable difference in viability between TMC PLGA and their negative control PLGA-NP. They concluded that while TMC PLGA modifications enhance delivery capabilities, they have no statistical implications on resulting cell viability.4

PLGA Ultra Fibrous Mats Facilitate Wound Healing

These desirable characteristics of PLGA led to the development of new antimicrobial treatments to treat infections and wounds, using PLGA as the carrier. For instance, one study describes the capabilities of using PLGA as a therapeutic during wound healing. It demonstrates that during microbial aggression, ultra fibrous (UF) PLGA matrices trigger a correlated release of encapsulated antimicrobial drugs. In addition. the entrapped molecules in these nanoparticles maintain functionality and upon release, greatly reduce biofilm formation. This finding was termed a “bioburden-triggered drug release”. As bacteria grow, their secretions and waste products reduce the pH of the environment facilitating the degradation of the PLGA. These findings were sustained in both in vitro and vivo assays.They lowered the pH of the aqueous environment in the absence of bacteria and observed similar results. To improve in vivo results, they structurally modified the PLGA molecules such that a larger portion of the drug molecules were on near the surface, increasing the initial release of the drug. The study also demonstrated that by exposing the UF mats to UV light before treatment facilitated the release of entrapped antimicrobial agents. The exposure to UV light for an hour results in sharp reductions to PLGA molecular weight as well as textile strength. The observation of cracking and micropore formation correlates with enhanced initial drug release. These efforts were intended to combat the exponential burst phase well characterized in bacterial growth. 1

In vivo studies indicated that bacteria such as Methicillin-resistant Staphylococcus aureus (MRSA) adhere to the UF mats, and enhancing the initial release stunts bacterial growth tremendously. The dense network of nanofibers mimic that of extracellular matrix which is hypothesized why bacteria latch on to the fibers. In addition to bacterial cells, mammalian tissue has shown to use the UF fibers as a scaffolding in regenerating lost tissue reducing the time for wound healing. Visual analysis of mice tissue showed that wounds treated with PLGA encapsulated antibiotics closed faster and were less likely to develop infections than the controls, and those treated with traditional topical antibiotics. This data is corroborated by bacterial culture results. They measured number of viable S. aureus colonies a week into the of the study and found that the PLGA treated infection had 10% of the number of viable colonies relative to the untreated sample, and significantly fewer colonies than the traditionally treated sample. 1

PLGA Based Micromotors Targeting H. Pylori

The diverse range of applications of this new technologies has led to clinical exploration in treating Helicobacter pylori, the bacteria linked to the formation of stomach ulcers. This unique species of bacterium is neither gram negative, or gram positive ruling out treatment using several classes of antibiotics targeting the rebuilding of bacterial cell walls. Treatment of H. pylori generally requires a cocktail of antibiotics over a several month duration. The stomach is a highly acidic environment which degrades unencapsulated antibiotics. To facilitate delivery and stability of the antibiotic, they are prescribed with a proton pump inhibitor (PPI) which reduces the acidity of stomach enabling antibiotic function. These PPIs are believed to be responsible for the majority of symptoms generally associated with stomach ulcer treatment. 5

To circumvent the need for this treatment methodology, a group of UCSD devised a PLGA based magnesium micromotor to safely deliver Clarithromycin (CLR) to the infection. They emulsified the PLGA using Chitosan to reinforce the outer 100 nm membrane. The inner membrane was layered with titanium dioxide (TiO2) and magnesium. These layers were coated using atomic layer deposition (ALD) to ensure uniform coating of the PLGA. The underneath of the TiO2 which acts as as a scaffold for the layers, ensure the structure is maintained during treatment. The inside of the TiO2 was layered with magnesium using the same technology. This ALD methodology of nanoparticle formation enabled the maintenance of microscopic pores that are critical for propulsion. The pores enable the magnesium to react the stomach acid generating hydrogen microbubbles which drive the propulsion of the nanoparticle. The increased motility ensures the drug reaches the mucosal layer of the stomach, and the root of the H. pylori infection. The group used Scanning Electron Microscopy (SEM) to verify these structural modifications didn’t impede uniform loading of CLR, the antibiotic, during emulsification. Their micromotors maintained bactericidal efficacy during in vitro studies. Once verified, they carried out in vivo studies in mice using controls to monitor for effective treatment and potential toxicity of the therapeutic. After inoculating the mice with H. pylori over two weeks, they orally ingested the PLGA based treatment. After the final treatment, the mice were killed and the stomach was excised to enable recovery of viable H. pylori from gastric tissues. Statistical analysis of bacterial burden post mortem revealed magnesium based propulsion of PLGA encapsulated therapeutics significantly reduced the quantity of viable bacteria at the end of the study. 5

Works Cited

1Said, Somiraa S., et al. "Antimicrobial PLGA ultrafine fibers: Interaction with wound bacteria." European Journal of Pharmaceutics and Biopharmaceutics 79.1 (2011): 108-118. 2Hill, Laura E., T. Matthew Taylor, and Carmen Gomes. "Antimicrobial Efficacy of Poly (DL‐lactide‐co‐glycolide)(PLGA) Nanoparticles with Entrapped Cinnamon Bark Extract against Listeria monocytogenes and Salmonella typhimurium." Journal of food science 78.4 (2013). 3Esfandyari-Manesh, Mehdi, et al. "Study of antimicrobial activity of anethole and carvone loaded PLGA nanoparticles." Journal of Pharmacy Research 7.4 (2013): 290-295. 4Wang, Zhao H., et al. "Trimethylated chitosan-conjugated PLGA nanoparticles for the delivery of drugs to the brain." Biomaterials 31.5 (2010): 908-915. 5de Ávila, Berta Esteban-Fernández, et al. "Micromotor-enabled active drug delivery for in vivo treatment of stomach infection." Nature communications 8.1 (2017): 272. 6Gao, Ping, et al. "Recent advances in materials for extended-release antibiotic delivery system." The Journal of antibiotics64.9 (2011): 625.

7Said, Somiraa S., et al. "Antimicrobial PLGA ultrafine fibers: Interaction with wound bacteria." European Journal of Pharmaceutics and Biopharmaceutics 79.1 (2011): 108-118.

8Stevanović, Magdalena, et al. "Multifunctional PLGA particles containing poly (l-glutamic acid)-capped silver nanoparticles and ascorbic acid with simultaneous antioxidative and prolonged antimicrobial activity." Acta biomaterialia 10.1 (2014): 151-162.

Stephenwinston (talk) 21:48, 23 June 2018 (UTC)