Epigenetic modifications, including changes in DNA methylation, lead to altered gene expression and thus may underlie epileptogenesis via induction of permanent changes in neuronal excitability. Therapies that could inhibit or reverse these changes may be highly effective in halting disease progression. Here we identify an epigenetic function of the brain's endogenous anticonvulsant adenosine, showing that this compound induces hypomethylation of DNA via biochemical interference with the transmethylation pathway. We show that inhibition of DNA methylation inhibited epileptogenesis in multiple seizure models. Using a rat model of temporal lobe epilepsy, we identified an increase in hippocampal DNA methylation, which correlates with increased DNA methyltransferase activity, disruption of adenosine homeostasis, and spontaneous recurrent seizures. Finally, we used bioengineered silk implants to deliver a defined dose of adenosine over 10 days to the brains of epileptic rats. This transient therapeutic intervention reversed the DNA hypermethylation seen in the epileptic brain, inhibited sprouting of mossy fibers in the hippocampus, and prevented the progression of epilepsy for at least 3 months. These data demonstrate that pathological changes in DNA methylation homeostasis may underlie epileptogenesis and reversal of these epigenetic changes with adenosine augmentation therapy may halt disease progression.

Microneedles are emerging as a minimally invasive drug delivery alternative to hypodermic needles. Current material systems utilized in microneedles impose constraints hindering the further development of this technology. In particular, it is difficult to preserve sensitive biochemical compounds (such as pharmaceuticals) during processing in a single microneedle system and subsequently achieve their controlled release. A possible solution involves fabricating microneedles systems from the biomaterial silk fibroin. Silk fibroin combines excellent mechanical properties, biocompatibility, biodegradability, benign processing conditions, and the ability to preserve and maintain the activity of biological compounds entrained in its material matrix. The degradation rate of silk fibroin and the diffusion rate of the entrained molecules can be controlled simply by adjusting post‐processing conditions. This combination of properties makes silk an ideal choice to improve on existing issues associated with other microneedle‐based drug delivery system. In this study, a fabrication method to produce silk biopolymer microstructures with the high aspect ratios and mechanical properties required to manufacture microneedle systems is reported. Room temperature and aqueous‐based micromolding allows for the bulk loading of these microneedles with labile drugs. The drug release rate is decreased 5.6‐fold by adjusting the post‐processing conditions of the microneedles, mainly by controlling the silk protein secondary structure. The release kinetics are quantified in an in vitro collagen hydrogel model, which allows tracking of the model drug. Antibiotic loaded silk microneedles are manufactured and used to demonstrate a 10‐fold reduction of bacterial density after their application. The processing strategies developed in this study can be expanded to other silk‐based structural formats for drug delivery and biologicals storage applications.

Owing to its unique material properties, stabilization effects and tight controllability, silk fibroin is a promising biomaterial for implantable and injectable drug delivery applications. Many promising control points have been identified, and characterization of the relationships between silk processing and/or material properties and the resulting drug loading and release kinetics will ultimately enhance the overall utility of this unique biomaterial. The ever-expanding biomaterial 'tool kit' that silk provides will eventually allow the simultaneous optimization of implant structure, material properties and drug release behavior that is needed to maximize the cost-efficiency, convenience, efficacy and safety of many new and existing therapeutics, especially those that cannot be delivered by means of traditional administration approaches.

The challenge of stabilization of small molecules and proteins has received considerable interest. The biological activity of small molecules can be lost as a consequence of chemical modifications, while protein activity may be lost due to chemical or structural degradation, such as a change in macromolecular conformation or aggregation. In these cases stabilization is required to preserve therapeutic and bioactivity efficacy and safety. In addition to use in therapeutic applications, strategies to stabilize small molecules and proteins also have applications in industrial processes, diagnostics, and consumer products like food and cosmetics. Traditionally, therapeutic drug formulation efforts have focused on maintaining stability during product preparation and storage. However, with growing interest in the fields of encapsulation, tissue engineering and controlled release drug delivery systems, new stabilization challenges are being addressed; the compounds or protein of interest must be stabilized during: (1) fabrication of the protein or small molecule loaded carrier, (2) device storage, and (3) for the duration of intended release needs in vitro or in vivo. We review common mechanisms of compound degradation for small molecules and proteins during biomaterial preparation (including tissue engineering scaffolds and drug delivery systems), storage and in vivo implantation. We also review the physical and chemical aspects of polymer-based stabilization approaches, with a particular focus on the stabilizing properties of silk fibroin biomaterials.

Sensitive biological compounds, such as vaccines and antibiotics, traditionally require a time-dependent “cold chain” to maximize therapeutic activity. This flawed process results in billions of dollars worth of viable drug loss during shipping and storage, and severely limits distribution to developing nations with limited infrastructure. To address these major limitations, we demonstrate self-standing silk protein biomaterial matrices capable of stabilizing labile vaccines and antibiotics, even at temperatures up to 60 °C over more than 6 months. Initial insight into the mechanistic basis for these findings is provided. Importantly, these findings suggest a transformative approach to the cold chain to revolutionize the way many labile therapeutic drugs are stored and utilized throughout the world.

Standard care for early stage breast cancer includes tumor resection and local radiotherapy to achieve long-term remission. Systemic chemotherapy provides only low locoregional control of the disease; therefore, we describe self-assembling silk hydrogels that can retain and then deliver doxorubicin locally. Self-assembling silk hydrogels show no swelling, are readily loaded with doxorubicin under aqueous conditions and release drug over 4 weeks in amounts that can be fine-tuned by varying the silk content. Following successful in vitro studies, locally injected silk hydrogels loaded with doxorubicin show excellent antitumor response in mice, outperforming the equivalent amount of doxorubicin delivered intravenously. In addition to reducing primary tumor growth, doxorubicin-loaded silk hydrogels reduce metastatic spread and are well tolerated in vivo. Thus, silk hydrogels are well suited for the local delivery of chemotherapy and provide a promising approach to improve locoregional control of breast cancer.

Effective treatment of infections in avascular and necrotic tissues can be challenging due to limited penetration into the target tissue and systemic toxicities. Controlled release polymer implants have the potential to achieve the high local concentrations needed while also minimizing systemic exposure. Silk biomaterials possess unique characteristics for antibiotic delivery including biocompatibility, tunable biodegradation, stabilizing effects, water-based processing and diverse material formats. We report on functional release of antibiotics spanning a range of chemical properties from different material formats of silk (films, microspheres, hydrogels, coatings). The release of penicillin and ampicillin from bulk-loaded silk films, drug-loaded silk microspheres suspended in silk hydrogels and bulk-loaded silk hydrogels was investigated and in vivo efficacy of ampicillin-releasing silk hydrogels was demonstrated in a murine infected wound model. Silk sponges with nanofilm coatings were loaded with gentamicin and cefazolin and release was sustained for 5 and 3 days, respectively. The capability of silk antibiotic carriers to sequester, stabilize and then release bioactive antibiotics represents a major advantage over implants and pumps based on liquid drug reservoirs where instability at room or body temperature is limiting. The present studies demonstrate that silk biomaterials represent a novel, customizable antibiotic platform for focal delivery of antibiotics using a range of material formats (injectable to implantable).

Adenosine augmentation therapies (AAT) make rational use of the brain's own adenosine-based seizure control system and hold promise for the therapy of refractory epilepsy. In an effort to develop an AAT compatible with future clinical application, we developed a novel silk protein-based release system for adenosine. Adenosine releasing brain implants with target release doses of 0, 40, 200, and 1,000 ng adenosine/day were prepared by embedding adenosine-containing microspheres into nanofilm-coated silk fibroin scaffolds. In vitro, the respective polymers released 0, 33.4, 170.5, and 819.0 ng adenosine/day over 14 days. The therapeutic potential of the implants was validated in a dose-response study in the rat model of kindling epileptogenesis. Four days prior to the onset of kindling, adenosine-releasing polymers were implanted into the infrahippocampal cleft and progressive acquisition of kindled seizures was monitored over a total of 48 stimulations. We document a dose-dependent retardation of seizure acquisition. In recipients of polymers releasing 819 ng adenosine/day, kindling epileptogenesis was delayed by one week corresponding to 18 kindling stimulations. Histological analysis of brain samples confirmed correct location of implants and electrodes. We conclude that silk-based delivery of around 1,000 ng adenosine/day is a safe and efficient strategy to suppress seizures.