Browsing by Author "McHugh, Kevin"

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    Developing Supramolecular Peptide Hydrogels for Immunomodulation and Drug Delivery
    (2024-03-20) Pogostin, Brett Harris; McHugh, Kevin; Hartgerink, Jeffrey
    Supramolecular peptide hydrogels are promising materials for a wide variety of biomedical applications. Since they are composed of the same 20 natural amino acid building blocks that comprise all human proteins, they have the potential for enhanced biocompatibility and modular bioactivity. Their supramolecular nature endows them with shear-thinning and self-healing materials properties that enables their minimally invasive administration through small-bore needles. These viscoelastic materials can be over 99% water by mass. Their high-water content mimics the natural extracellular matrix and facilitates the facile loading of hydrophilic drugs and proteins while avoiding denaturation from organic solvents. Due to these promising properties, many groups have focused on developing these materials as tissue engineering scaffolds, drug delivery platforms, vaccine adjuvants, materials for cancer immunotherapy, hemostatic agents, antimicrobial wound dressings, etc. Multidomain peptide (MDP) hydrogels, developed in the Hartgerink lab, are a class of self-assembling peptides that form hydrogels under physiologically relevant conditions. These peptide sequences follow a general ABA structural pattern. The “A” motifs contain a charged amino acid selected from arginine, lysine, aspartic acid, and glutamic acid. The B domain is an amphiphilic region that promotes self-assembly into β-sheets. This region of the sequence typically contains repeating serine-leucine residues. For over a decade, these materials have been investigated for use in a plethora of different biomedical applications. In this thesis, I describe my investigations into using MDP hydrogels as vaccine adjuvants and drug delivery vehicles. I additionally explore designing novel peptide hydrogels with non-canonical motifs to improve their adjutancy and capacity to control the release of small and macromolecular payloads. Chapter 1 serves as an introduction to adjuvants and immunomodulatory materials. While each chapter relating to vaccine adjuvants contains a targeted introduction, this chapter particularly provides critical context for the importance of these materials in today’s world for pandemic preparedness. In Chapter 2, I investigate the use of differently charged MDPs to adjuvant the model antigen ovalbumin. I found that lysine containing MDPs are the best suited MDPs for vaccine adjuvant applications and that, interestingly, MDPs strongly bias a humoral immune response. I build on this work in Chapter 3 where, by modifying MDPs with a toll-like receptor 7 agonist, we further enhance the adjuvant potential of these peptide hydrogels. Further, we illicit a more balanced cellular and humoral immune response, which could be useful for a wide variety of infectious disease vaccines and cancer immunotherapies. Chapter 4 is a bridge chapter that links my work in immunomodulation to drug delivery leveraging dynamic covalent interactions. In this chapter, I aimed to control the release of the carbohydrate adjuvant mannan by forming dynamic imine bonds between the oxidized carbohydrate that the primary amines on a lysine containing MDP. I found that imine bonds can delay the release of oxidized mannan in vitro, but in vivo reduced and oxidized mannan is cleared much more rapidly than reduced mannan. The release of this oxidized carbohydrate can be reduced to the same rate as the reduced carbohydrate through imine bonding the MDP. The differences in reduced and oxidized mannan have been underappreciated in the literature, and I describe how MDPs may be useful for investigating the biological consequences of the different behaviors of these two materials in vivo. Chapter 5 focuses on peptide-based hydrogels that leverage boronic acid dynamic covalent chemistry for drug delivery. A thorough review of related drug delivery literature is included in the introduction of Chapter 5. In this part of my thesis, I describe my work developing new MDPs capable of forming dynamic covalent interactions with boronic acids (BAs). I found that these modified MDPs can significantly delay the release of BA-containing small molecules and BA-labeled proteins in vitro and in vivo. These materials can be used for both the local systemic delivery of therapeutics and improve the pharmacokinetic profiles of the drugs tested. I evaluate the potential application of this system by delivering basal insulin to diabetic mice. After a single injection of BA-modified insulin in this drug delivery platform, diabetic mice remain normoglycemic for 144 h. In comparison, a single injection of the maximum safe dose of insulin without hydrogel only maintained healthy blood glucose levels for 4 h. The work I present in this thesis aims to motivate the development of the next generation of peptide materials that leverage non-canonical modifications to improve upon the 20 amino acids nature provides. I show that including these modifications can alter both the immunological activity and drug delivery capabilities of MDPs and enhance their performance in in vivo models beyond what is possible with unmodified MDPs. This work shows the potential for next-generation MDPs that include non-canonical motifs to build on the past success of these materials and further their development towards clinical translation.
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    Development and Characterization of Novel Biomaterials-Based Platforms to Enhance Vaccine Efficacy
    (2024-04-10) Euliano, Erin Marie; McHugh, Kevin
    Vaccination is an effective strategy for reducing the spread of infectious diseases, yet potent vaccines against some of the most widespread pathogens remain elusive. Some of the most common innovations to improve vaccine immunogenicity include carrier-based mechanisms to target lymphoid tissues and the inclusion of novel adjuvants, additives that help activate the immune response. This thesis describes the development and characterization of two vaccination platforms, both of which improve immunogenicity of the model protein antigen ovalbumin (OVA) over controls. First, the development of a novel platform is presented in which two complementary multi-arm poly(ethylene glycol) (PEG) polymers—one of which is covalently bound to OVA—are injected subcutaneously into two distinct sites that drain to the same lymph node (LN) through different lymphatic vessels. Upon meeting in the LN, the two materials rapidly crosslink. This system improves OVA delivery to, and residence time within, the draining LN compared to all control groups. The crosslinking of the two PEG components improves humoral immunity over controls without the need for any immunostimulatory adjuvants, while also increasing the activation of dendritic cells in the LN above alum, the most common clinical adjuvant. Second, the immune response generated against OVA when co-delivered with a novel multidomain peptide (MDP) hydrogel adjuvant is described. The toll-like receptor 7 (TLR7) agonist 1V209 was conjugated to an MDP, K2, which was previously shown to act as an adjuvant by promoting humoral immunity. When co-delivered with OVA, 1V209-functionalized K2 produces antigen-specific IgG titers statistically comparable to alum. Further, the ratio of the antibody subclasses IgG1 and IgG2a suggests a more balanced cellular and humoral response than alum, expanding the repertoire of applicable diseases to those requiring both major arms of adaptive immunity. Together, the results of this thesis show two promising methods that leverage different mechanisms to improve the immune response to vaccines, allowing for the tunability of the immune response for different disease targets.
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    Development of a Methacrylated Poly(Glycerol Sebacate) Platform for the Sustained Release of Small Molecule Therapeutics
    (2024-07-29) Laracuente, Mei-Li; McHugh, Kevin
    Pharmaceutical drugs are an important part of the global healthcare system, yet their impact is diminished by many factors, including unwanted side effects and poor patient adherence. Many drugs require daily dosing in which drug levels rapidly rise and then fall over time as the drug is cleared from the body. Drug formulations that maintain effective drug concentrations over a prolonged period could reduce the need for daily oral administration and thereby improve adherence; however, traditional controlled-release systems yield first-order release kinetics which release drug at progressively slower rates over time, limiting the duration over which they can be used safely and effectively. One promising solution is sustained delivery via surface-eroding polymeric microparticles. These polymers are hydrophobic, thus limiting water penetration, but are also degraded via hydrolysis, resulting in erosion exclusively at the particle surface. As a result, degradation and the associated release of encapsulated drug occur at a rate proportional to the polymeric particle’s exposed surface area at that time. We plan to leverage this property to precisely control drug release. Until recently, this strategy was hindered by traditional fabrication methods that limited microparticles to spherical shapes, which decrease in surface area as the particle degrades. However, recent advances in fabrication and materials science have enabled the unprecedented customization of microstructures, enabling the production of particles that can exploit geometry dependent degradation to achieve a consistent rate of drug release over time. This thesis describes the development and characterization of methacrylated poly(glycerol sebacate) (PGS-M) as a drug delivery platform. First, we examined the factors affecting the in vitro and in vivo degradation rates of PGS-M, evaluated PGS-M biocompatibility, and examined the drug release profiles (from disks) that can be obtained. The results indicate that PGS-M releases drug in a relatively linear fashion and that the rate of drug release can be altered by changing the polymer’s DM and drug loading. Overall, PGS-M’s rate of degradation was substantially slower than reported for conventionally prepared PGS in vitro and in vivo. These features highlight the potential of PGS-M to be used for long-term drug delivery and tissue engineering applications on the order of months to years, overcoming a limitation of traditional PGS. Furthermore, PGS-M is photocurable, providing the potential to create complex scaffold structures through 3D photolithographic techniques and directly incorporate thermosensitive drug molecules into the polymer scaffold with post-curing loading. Finally, PGS-M was shown to cause only a minimal inflammatory response, another key factor in determining clinical relevance. Taken together, these results establish the in vivo compatibility of PGS-M and highlights its potential utility for both tissue engineering and drug delivery applications. Second, we examined the influence of microparticle geometry on the rates of drug release. We first established a method to successfully synthesize large arrays of microparticles via the use of photomasks. We then leveraged the inherent swelling properties of PGS-M to develop a method of loading drugs into the particles without exposing them to heat, vacuum, and UV light. Microparticles with different surface area/volume ratios were loaded with different therapeutics and the resulting release was examined. We found that daunorubicin hydrochloride released from micro-cylinders and micro-disks comprised of a higher methacrylated PGS-M achieved sustained release over the period tested (28 days). Hollow cylinders and rings released a higher proportion of their encapsulated drug within the first 8 days and a smaller amount for the next 10 days, similar to a first-order release profile. The results of this study indicate that particles with a higher surface area to volume ratio (hollow cylinders and rings) release drug at a faster rate compared to particles with lower surface area to volume ratios (cylinders and disks). Taken together, the results of this thesis suggest that PGS-M can be fabricated into non-spherical microparticles that are biocompatible, injectable through a standard needle, and release drug in a sustained release fashion.