A modern approach to the treatment of localized disease involves the use of advanced polymeric or ceramic implant materials for controlled-rate drug delivery. These implants are dynamic systems that maintain drug concentrations within the optimal therapeutic window via complex hydration, swelling, and degradation processes. To optimize the performance of these materials, however, requires a fundamental understanding of the mechanisms that govern drug release. Magnetic resonance imaging (MRI) provides a means of non-invasively characterizing the microstructure and transport properties in this type of material, and has proven to be an invaluable tool for their advancement. Calcium polyphosphate (CPP) is a biomaterial that has shown promise as a degradable matrix for drug delivery and bone defect repair. Release rates are potentially governed by hydrogelation, swelling, and polymer chain scission. CPP bioceramics have previously been studied using models for drug elution, but these tend to be simplistic and unable to explain the many interrelated mechanisms. Structural analysis techniques have also been applied, but these tend to be inherently destructive and unable to characterize the material in situ. With the aim of characterizing degradation/drug release mechanisms, a non-invasive approach based on MRI was developed and optimized for imaging two existing types of CPP device. Techniques included mapping of the T1 and T2 relaxation times and the apparent diffusion coefficient (ADC), which together provide sensitivity to local fluid transport parameters. The non-destructive nature of MRI permitted longitudinal observation, and structural degradation effects were investigated by correlation with concurrent drug elution measurements. Temporal variation in the release mechanisms was treated by analyzing elution in stages. Large variation between samples was found, but on average, drug elution that was controlled by a structural-relaxation mechanism appeared correlated with the gradual formation of a highly-mobile ``free'' water component within the disk. Other characteristics, such as swelling rate, did not appear to correlate with drug release at all. While the data did not implicate a singular, governing scheme for drug release from CPP bioceramics, the approach did yield an assessment of the relative importance of the various contributing mechanisms.

Currently, therapeutic proteins and peptides are delivered subcutaneously, as they are readily denatured in the acidic, protease rich environment of the stomach or gastrointestinal track and low bioavailability results from poor intestinal absorption through the paracellular route. Encapsulation of therapeutic peptides and proteins into polymeric micro- and nano- particle systems has been proposed as a possible strategy to overcome limitations to oral protein administration. Furthermore, it was shown that nanoparticles having diameters less than 5µm are able to be taken up by the M cells of Peyer’s patches found in intestinal mucosa . However, the current methodologies to produce particles within desired range involves organic solvents and several steps. In this study, spray drying was investigated as a microencapsulation alternative, as it offers the potential for single step operation, producing dry particles, with the potential for extending the microparticle size into the nano-range. The particles were produced by spray drying of alginate/protein solutions. The effect of spray drying operational parameters on particle properties such as recovery, residual activity and particle size was studied. Particle recovery depended on the inlet temperature of the drying air, whereas the particle size was affected by the feed rate and the alginate concentration of the feed solution. Increase in alginate:protein ratio increased protein stability during the process and shelf live experiments. Presence of 0.2 g trehalose/g particle increased the residual activity up to 90%. The resulting spherical micro and nanoparticles had smooth surfaces. Stable glycol-chitosan-ca-alginate particles were produced with single step operation. The resulting particles had mean diameter around 3.5μm and released 35% of the initial protein content to the simulated stomach environment within 2 hours. The protein distribution within the particle was studied by confocal laser scanning microscope with florescent labeled protein. The image showed protein deposition toward the surface of the particles. Total drying time and Peclet number was calculated for the particles and found to be 8.5 ms and 240, which indicates that particle formation was governed mainly by convection, which resulted in a hollow central region and protein distribution toward the particle surface. This study shows that stable alginate particles containing proteins can be produced in a single step by spray drying, where the particles had a mean size lower than the critical diameter necessary to be orally absorbed by M cell’s of the Peyer’s patches in the gastrointestinal tract and thus can be considered as a promising technology for oral peptide and protein delivery. / Thesis (Master, Chemical Engineering) -- Queen's University, 2007-10-30 12:20:47.728

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In this work, transparent and rigid organogels suitable for intravitreal drug delivery applications were produced with pharmaceutical/food grade polar and amphiphilic solvents with HLB values ranging from 0-19. Maximum sterol solubility was obtained with solvents with approximately HLB=6. Solvents with high sterol solubility also required higher sterol concentrations to produce a gel. However, the strength of all the organogels increased with increasing sterol concentration. Furthermore, DSC and SAXS data suggest that the structure of all the organogels was similar. An in vitro release of dexamethasone was performed over a 5.5 month period using novel organogel- dexamethasone implants. The release of dexamethasone varied from 2 to 5.5 months (or more) depending on the organogel used for the implant. These multiple-month release in vitro profiles are comparable and/or exceed the release of commercially available and FDA approved dexamethasone delivery system Ozurdex (~2 month dexamethasone release).

In this work, transparent and rigid organogels suitable for intravitreal drug delivery applications were produced with pharmaceutical/food grade polar and amphiphilic solvents with HLB values ranging from 0-19. Maximum sterol solubility was obtained with solvents with approximately HLB=6. Solvents with high sterol solubility also required higher sterol concentrations to produce a gel. However, the strength of all the organogels increased with increasing sterol concentration. Furthermore, DSC and SAXS data suggest that the structure of all the organogels was similar. An in vitro release of dexamethasone was performed over a 5.5 month period using novel organogel- dexamethasone implants. The release of dexamethasone varied from 2 to 5.5 months (or more) depending on the organogel used for the implant. These multiple-month release in vitro profiles are comparable and/or exceed the release of commercially available and FDA approved dexamethasone delivery system Ozurdex (~2 month dexamethasone release).

Biodegradable polymer materials, specifically poly(lactic-co-glycolide) (PLGA) can be used as bone replacements for bone regeneration. Scaffolds can be prepared to be porous to induce bone growth into a scaffold so that it is replaced with natural tissue as the polymer degrades. However, simply using PLGA will result in formation of scar tissue rather than regeneration of natural bone. Therefore focus has turned to attaching growth factors to the PLGA molecules to elicit a specific cellular response when the implant is placed in the body. Site-directed immobilization utilizes specific groups on both the biomaterial and biomolecule so that growth factors can be oriented in a specific manner for increased cellular response. In this research, exposed carboxyl groups on a non end-capped PLGA were modified with bishydrazide spacer molecules of varying length for the eventual attachment of a biomolecule via carbodiimide chemistry. The number of hydrazide groups attached to the surface could be controlled to investigate the effects of the spacer length on protein immobilization. Both vascular endothelial growth factor (VEGF) and parathyroid hormone (PTH) were used in these studies. These two molecules have different target cells and actions, although both can play a role in bone formation. Both molecules have carbohydrate residues that were oxidized with periodate to form aldehyde moieties that were able to react with the hydrazide spacers to form a stable bond between the spacer and protein. The use of a spacer enhanced the binding accessibility of the protein as compared to randomly adsorbed protein. The shortest and longest of the spacers resulted in the highest amount of protein, with corresponding results for antibody binding. The modification of PLGA functional groups with a spacer molecule indicates that this material could be used for site-directed immobilization for any application, simply by tailoring the reaction between the biomaterial and biomolecule.

Ellipticine (EPT), a natural plant polyphenolic compound, has long been known for its significant anticancer and anti-HIV activities. Recent study on its photophysical properties has revealed that ellipticine has three molecular states: protonated, neutral and crystalline. Further in vitro cytotoxicity tests indicated that protonated ellipticine exhibited much higher anticancer activity than the other two states. To maximize drug therapeutic effect, a small library of ariginine-rich ionic complementary peptides derived from EAK, including EAR8-II, EAR8-a, ELR8-a, and EAR16-II, were investigated as a potential carrier to deliver prescribed protonated ellipticine for treatment of cancer. Fluorescence study demonstrated that all four peptides were able to solubilize and stabilize protonated ellipticine in aqueous solution at 5:1 mass ratio of peptide-to-ellipticine (0.5: 0.1 mg/mL) even upon 4000 times dilution. Physicochemical characteristics of peptides self-assemblies and peptide-ellipticine complexes such as particle size, surface charge, secondary structure and morphology were determined by dynamic light scattering (DLS), zeta potential, circular dichroism (CD) , atomic force microscopy (AFM) and transmission electron microscopy (TEM), respectively. Then the ellipticine maximum suspension was determined by ellipticine UV-absorption. With the help of the peptides and mechanical stirring overtime, up to 100% ellipticine could be uptaken and stabilized in the solution as protonated ellipticine. In vitro cytotoxicity tests indicated that the peptides were demonstrating significant biocompatibility without affecting the survival of two cancer cell lines, human lung carcinoma cell line A549 and breast cancer cell line MCF-7, whereas the complexes with protonated ellipticine were found to show great anticancer activity to the two cancer cell lines. The IC50 values were obtained for each of four different peptide-ellipticine complexes ranged from 0.36±0.12 to 18.90±0.46 μM. It is worth noting that the IC50 value of EAR16-ellipticine complex to MCF-7 was over 50 times higher than that one to A549, which presented that EAR16-ellipticine complex has a selective targeting activity to A549, with the lowest IC50 value of 0.36±0.12 μM among all four complexes. Such a result indicated that this library of novel arginine-rich ionic complementary peptides had a great potential to encapsulate prescribed protonated ellipticine and exhibited an excellent anticancer activity upon serial dilution in aqueous solution. Overall, the charge distribution and increased hydrophobicity of the short (8 amino acids length) peptides seemed not to affect the complex formation and its therapeutic efficacy in vitro; however, the increase in length of the peptides significantly altered the nanostructure of peptides and its complexation with ellipticine, increased the therapeutic efficacy of EAR16-EPT to A549. This work provides essential information for peptide sequence design in the development of self-assembling peptide-based delivery of hydrophobic anticancer drugs.

The skin forms an attractive and accessible route for systemic delivery of drugs as alternative to other methods of administration, such as the oral and parental methods because of the problems associated with last mentioned methods. The lipophilic character of the stratum corneum, coupled with its intrinsic tortuosity, ensures that it almost always provides the principal barrier to the entry of drug molecules into the skin. Due to the fact that methotrexate (MTX) and acyclovir (ACV) have poor penetration properties through the skin, the aim of this study was to enhance the permeation of methotrexate and acyclovir with the use of two lamellar gel phase systems (LPGS) (Physiogel® NT and Physiogel® Dermaquadrille) and with Emzaloid® as transdermal drug delivery systems. Three different sets of experiments were done in this study: 1) the viscosity of the two Physiogel® creams was measured as an indication of stability and to determine whether the internal structure of the Physiogel® creams were affected by the investigated drugs; 2) the drug release rate from the three drug delivery vehicles was measured with a Vankel ® dissolution apparatus; 3) in vitro permeation studies were preformed using vertical Franz diffusion cells with human epidermal skin clamped between the donor and receptor compartments. The skin was hydrated with PBS buffer for one hour before 1% mixtures of the drugs in both the Physiogel® creams and Emzaloid® were applied to the donor chamber. Samples were taken at 2, 4, 6, 8, 10, 12 and 24 hours. It was then analysed by HPLC for methotrexate and acyclovir. The fluxes of drug permeation were determined. The viscosity measurements confirmed that the internal structure of the two Physiogel® creams was not influenced by the drugs. Acyclovir and methotrexate were both released from the delivery vehicles. There was an enhancement of acyclovir through the skin from one of the Physiogel® creams. The permeability of methotrexate in the presence of the two Physiogel® vehicles was not significantly enhanced. Emzaloid® as delivery vehicle increased the penetration of both drugs through the skin significantly. The lamellar gel phase system mimics the structure of the stratum corneum, but does not improve the drug permeation through the stratum corneum significantly. The utilisation of Emzaloid® as a drug delivery system could be advocated from these findings. As could be seen from the penetration profiles Emzaloid® was a superior delivery system for methotrexate and acyclovir compared to the lamellar gel phase systems. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.

Micromachined needles have been shown to successfully transport biological molecules into the body with minimal invasiveness and pain, following the insertion of needles into the skin. The aim of this research is to demonstrate that micromachined hollow polymer needle arrays fabricated using UV lithography into micromolds, a potential batch-manufacturable process, can exhibit comparable insertion and injection performance to conventional hypodermic needles for drug delivery into skin. A dual-exposure-and-single-development process flow is proposed for the above-mentioned UV lithography into micromolds approach to construct a pyramidal-tip hollow microneedle array with an integral baseplate and fluidic manifold. The developed process ultimately resulted in the ability to fabricate a 10×10 array of hollow SU-8 microneedles measuring 825 μm in height, 400 μm in width, and possessing a lumen of 120 μm in diameter. The tip diameter of the microneedles ranges from 15 μm to 25 μm. The insertion force of single needles characterized using excised porcine skin as a substrate is 2.4±1.2 N. Nevertheless, the high insertion force of 2.4 N per needle may cause a significant concern when a large number of needles are required to insert into skin for drug delivery. Conventional hypodermic needles have two key structural characteristics: a sharp beveled tip and a large side-terminated lumen. Integration of these two key characteristics of hypodermic needles into microneedle design can potentially enhance microneedle performance. To reduce the insertion force and to incorporate the two key characteristics of hypodermic needles into the design of microneedles, a new needle tip design, namely the hypodermic-needle-like design, is presented. A 6×6 array of hypodermic-needle-like microneedles of 1 mm in height, approximate 350 μm in width, and with a lumen of 150 μm in diameter is demonstrated with successful insertion of the needle array into skin and an 85% lumen openness yield. The insertion force is significantly reduced by an order of magnitude with the new needle tip design and is 0.275±0.113 N per needle, comparable to that of hypodermic needles, i.e., 0.284±0.059 N. The hypodermic-needle-like microneedles exhibit a margin of safety of 180 for successful needle insertion into skin prior to needle fracture. A successful manual fluid injection into skin using single microneedle is demonstrated. The micromachined hypodermic-needle-like polymer needle arrays presented in this dissertation are fabricated using UV lithography into micromolds, a potentially batch-manufacturable process, and exhibit comparable insertion performance to conventional hypodermic needles. Injection capability into skin is also demonstrated with a hypodermic-needle-like microneedle, illustrating the utility of these devices.

Type-1 diabetes and influenza cause significant illness and unnecessary medical costs despite the existence of insulin for maintenance of diabetes and a vaccine for prevention of influenza. This dissertation describes three studies on the development and clinical translation of microneedles to improve the administration of these biopharmaceuticals. The first study reports on a sharp-tipped hollow metal microneedle designed to reduce manufacturing costs, improve insertion into skin, and improve fluid flow compared to other hollow microneedles used for drug delivery. The results showed sharp-tipped metal microneedles could be fabricated using an inexpensive electroplating and sacrificial micromolding process. Single-microneedle devices made by this method achieved high flow rates and delivered model drugs into tissue. The second study reports on insulin delivery using microneedles in children with type-1 diabetes. The results showed microneedle insertion was less painful, which is a promising result for improving injection compliance in children. Additionally, microneedle delivery showed rapid onset of insulin action compared to subcutaneous catheter delivery, which may enable automatic closed-loop insulin therapy. This was the first study of drug delivery to children using microneedles. The last study reports on microneedle patches for self-vaccination against influenza. Human subjects were recruited from greater Atlanta, were asked to self-administer placebo microneedle patches, and were then given a dynamic questionnaire to determine their views and preferences regarding influenza vaccination using microneedles compared to conventional intramuscular injection. The results showed that microneedles were usable by the participants, the introduction of microneedles may improve vaccination coverage by approximately 20%, and self-administration of vaccines may significantly reduce vaccination costs for a healthcare payer. This was the first study to assess the ability of human subjects to self- administer a microneedle patch and the first study to determine the potential impact of self-vaccination against influenza using a microneedle patch on vaccination coverage and vaccination cost. Overall, the fabrication advances and positive findings from human subjects research support additional translation of microneedles for insulin delivery and self-vaccination toward clinical use.