Investigation of Liquid Collagen Ink for Three-Dimensional Printing.

Three-dimensional printing provides more versatility in the fabrication of scaffold materials for hard and soft tissue replacement, but a critical component is the ink. The ink solution should be biocompatible, stable, and able to maintain scaffold shape, size, and function once printed. This paper describes the development of a collagen ink that remains in a liquid pre-fibrillized state prior to printing. The liquid stability occurs due to the incorporation of ethylenediaminetetraacetic acid (EDTA) during dialysis of the collagen. Collagen inks were 3D-printed using two different printers. The resulting scaffolds were further processed using two different chemical crosslinkers, 1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride)/N-hydroxysuccinimide (EDC/NHS) and genipin; gold nanoparticles were conjugated to the scaffolds. The 3D-printed scaffolds were characterized to determine their extrudability, stability, amount of AuNP conjugated, and overall biocompatibility via cell culture studies using fibroblast cells and stroma cells. The results demonstrated that the liquid collagen ink was amendable to 3D printing and was able to maintain its 3D shape. The scaffolds could be conjugated with gold nanoparticles and demonstrated enhanced biocompatibility. It was concluded that the liquid collagen ink is a good candidate material for the 3D printing of tissue scaffolds.

Development and Characterization of a AuNP-Genipin-Viscoelastic Collagen Material.

Lower back pain is one of the leading causes of disability, affecting 11.9% of the population worldwide and studies have shown that intervertebral disc degeneration is a common cause for chronic lower back pain. We have explored the combination of three components, viscoelastic collagen, genipin, and gold nanoparticles to determine its potential to promote regeneration of the intervertebral disc, specifically for nucleus pulposus regeneration. The goal of this study was to develop, fabricate and characterize different formulations of viscoelastic collagen conjugated with gold nanoparticles and genipin to assess the feasibility as a tissue template. Results demonstrated the successful attachment of gold nanoparticles to the viscoelastic collagen utilizing the genipin crosslinker. For each of the viscoelastic collagen compositions examined, cell biocompatibility was achieved. The results also demonstrated an increase in stiffness of the material with different sizes and concentrations of AuNPs. Results from the TEM and STEM also demonstrated that the viscoelastic collagen that was developed did not display the characteristic D banding pattern of polymerized collagen. The findings from this study could lead to the development of a more efficient and cost-effective treatment for patients with chronic back pain caused by IVD degeneration.

Investigation of an injectable gold nanoparticle extracellular matrix.

Post-traumatic osteoarthritis (PTOA) is a progressive articular degenerative disease that degrades articular cartilage and stimulates apoptosis in chondrocyte cells. An injectable decellularized, extracellular matrix (ECM) scaffold, that might be able to combat the effects of PTOA, was developed where the ECM was conjugated with 20 nm gold nanoparticles (AuNP) and supplemented with curcumin and hyaluronic acid (HA). Porcine diaphragm ECM was decellularized and homogenized; AuNPs were conjugated using chemical crosslinking followed by mixing with curcumin and/or HA. Injection force testing and scanning electron microscopy with energy-dispersive X-ray spectroscopy were utilized to characterize the ECM scaffolds. In vitro testing with L929 murine fibroblasts, equine synovial fibroblasts, and Human Chondrocytes were used to determine biocompatibility, reactive oxygen species (ROS) reduction, and chondroprotective ability. The results demonstrated that conjugation of 20 nm AuNPs to the ECM was successful without significantly altering the physical properties as noted in the low injection force. In vitro work provided evidence of biocompatibility with a propensity to reduce intracellular ROS and an ability to mitigate apoptosis of chondrocyte cells stimulated with IL-1ß, a known apoptosis inducing cytokine. It was concluded that an injectable AuNP-ECM may have the ability to mitigate inflammation and apoptosis.

The use of gold nanoparticles in improving ACL graft performance in an ovine model.

Surgical repair of the anterior cruciate ligament (ACL) can involve autograft or allograft materials. Allografts are typically chosen to avoid donor site morbidity associated with autografts harvest, but they can also result in a prolonged inflammatory period and delayed graft remodeling when compared to autografts. The aim of this study was to investigate the use of gold nanoparticles (AuNPs) conjugated to allografts to determine if AuNPs can reduce inflammation and enhance graft remodeling in an ovine model. Six sheep had their ACL surgically removed and replaced with a decellularized human gracilis tendon. Three of the sheep received grafts conjugated with 20 nm gold nanoparticles, while three of the sheep received grafts without the gold nanoparticles. The sheep were sacrificed 8 weeks after ACL reconstruction. Immediately following sacrifice, joint fluid was collected for cytology. Semi-quantitative histological scoring of the bone tunnel portion and the intra-articular portion of the grafts were performed independently along with descriptive analysis of histologic changes and quantitative analysis of revascularization. The results demonstrated that AuNP experimental grafts had an overall better histological scores than the non-AuNPs graft. The AuNPs grafts exhibited decreased inflammation in the bone tunnel portion of the graft, the intra-articular portion of the graft, and in the synovial fluid cell count. Overall, the results demonstrated that the grafts conjugated with nanoparticles have the potential to be influence inflammation and overall remodeling response.

Electrospun PCL, gold nanoparticles, and soy lecithin composite material for tissue engineering applications.

Soy lecithin has been shown to play a critical role in cell signaling and cellular membrane structure. In addition, it has been shown to increase biocompatibility, hydrophilicity, and decrease cytotoxicity. Gold nanoparticles have also shown to improve cellularity. Lecithin, gold nanoparticles, and polycaprolactone (PCL) solutions were electrospun in order to develop unique mesh materials for the treatment of osteoarthritis. The electrospinning parameters were optimized to achieve different solution ratios for fiber optimization. The amount of lecithin mixed with PCL varied from 30 wt.% to 50 wt.% . Gold nanoparticles (1% to 10% concentrations) were also added to lecithin-PCL mixture. The mechanical and chemical properties of the fiber mesh were analyzed via contact angle test, tensile mechanical tests, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Cell viability was measured using a WST-1 Assay. Scanning electron microscopy confirmed the successful formation of fiber mesh. The compositions of 40% soy lecithin with PCL in 40% solvent (40:40) resulted in the most well-formed fiber mesh. DSC melt temperatures were statically insignificant; uniaxial stresses and the moduli resulted in no significant difference between the test composition and pristine PCL compositions. WST-1 assay revealed all compositions were non-cytotoxic. Overall, the addition of lecithin increased hydrophilicity while maintaining cell viability and the mechanical and chemical properties of PCL. This study demonstrated that it is possible to successfully electrospin a lecithin, gold nanoparticle, and polycaprolactone scaffold for tissue engineering applications.

Gold Nanoparticle-Collagen Gels for Soft Tissue Augmentation.

Collagen soft tissue fillers suffer from fast reabsorption, which minimizes their use as a tissue-engineered construct. Extensive cross-linking can be utilized to extend longevity, but changes in microstructure and biomechanics can have deleterious effects. To enhance longevity while still achieving a natural microstructure, gold nanoparticles (AuNPs) were conjugated to fibrilized collagen and homogenized into an injectable form for use as a soft tissue filler. A long-term animal study in Yucatan swine was conducted to assess biocompatibility and longevity. Two formulations of the AuNP-collagen were compared to porcine cross-linked collagen and commercially available hyaluronic acid (HA). The results of the study demonstrated that the AuNPs may provide enhanced longevity over 6 months compared to HA and cross-linked collagen. Irritation scores indicated that the AuNP-collagen construct (AuNP-CC) demonstrated low irritation compared to the cross-linked collagen and HA while histology scores demonstrated good biocompatibility. Overall, it may be possible to utilize AuNPs to stabilize and increase the longevity of CC while still achieving biocompatibility.

Controlled Ion Release from Novel Polyester/Ceramic Composites Enhances Osteoinductivity.

Due to the growing number of patients suffering from musculoskeletal defects and the limited supply of and sub-optimal outcomes associated with biological graft materials, novel biomaterials must be created that can function as graft substitutes. For bone regeneration, composite materials that mimic the organic and inorganic phases of natural bone can provide cues which expedite and enhance endogenous repair. Specifically, recent research has shown that calcium and phosphate ions are inherently osteoinductive, so controllably delivering their release holds significant promise for this field. In this study, unique aliphatic polyesters were synthesized and complexed with a rapidly decomposing ceramic (monobasic calcium phosphate, MCP) yielding novel polymer/ceramic composite biomaterials. It was discovered that the fast dissolution and rapid burst release of ions from MCP could be modulated depending on polymer length and chemistry. Also, controlled ion release was found to moderate solution pH associated with polyester degradation. When composite biomaterials were incubated with mesenchymal stems cells (MSCs) they were found to better facilitate osteogenic differentiation than the individual components as evidenced by increased alkaline phosphate expression and more rapid mineralization. These results indicate that controlling calcium and phosphate ion release via a polyester matrix is a promising approach for bone regenerative engineering.

In vivo bone tunnel evaluation of nanoparticle-grafts using an ACL reconstruction rabbit model.

Acellular human gracilis tendons conjugated with gold nanoparticles (AuNP) and hydroxyapatite nanoparticles (nano-HAp) were used as a graft in an anterior cruciate ligament (ACL) reconstruction rabbit model. The ACLs of 11 New Zealand rabbits were reconstructed using grafts conjugated without nanoparticles, with AuNP only, and with both AuNP and nano-HAp. Semi-quantitative histological scoring of bone tunnel portion of grafts was performed after 14 weeks. Bone tunnels were scored for graft degeneration, graft remodeling, percentage of new host fibrous connective, collateral connection, head-to-head connection, graft collagen fiber organization, new host fibrous connective tissue organization, and graft and interface vascularity. All grafts were intact at 14 weeks. Results of bone tunnel scoring indicate remodeling in all graft types with new organized host fibrous connective tissue, head-to-head connection to bone and mild inflammation associated with remodeling. Components of the 20 nm AuNP grafts have significantly more graft degeneration, more new host fibrous connective tissue, and more vascularity compared to crosslinked grafts. Comparison between femoral and tibial tunnel scores indicate more degeneration in femoral tunnels compared to tibial tunnels. Overall results indicated potentially enhanced remodeling from the use of 20 nm AuNP grafts. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1071-1082, 2017.

Integrating Nanostructured Artificial Receptors with Whispering Gallery Mode Optical Microresonators via Inorganic Molecular Imprinting Techniques.

The creation of label-free biosensors capable of accurately detecting trace contaminants, particularly small organic molecules, is of significant interest for applications in environmental monitoring. This is achieved by pairing a high-sensitivity signal transducer with a biorecognition element that imparts selectivity towards the compound of interest. However, many environmental pollutants do not have corresponding biorecognition elements. Fortunately, biomimetic chemistries, such as molecular imprinting, allow for the design of artificial receptors with very high selectivity for the target. Here, we perform a proof-of-concept study to show how artificial receptors may be created from inorganic silanes using the molecular imprinting technique and paired with high-sensitivity transducers without loss of device performance. Silica microsphere Whispering Gallery Mode optical microresonators are coated with a silica thin film templated by a small fluorescent dye, fluorescein isothiocyanate, which serves as our model target. Oxygen plasma degradation and solvent extraction of the template are compared. Extracted optical devices are interacted with the template molecule to confirm successful sorption of the template. Surface characterization is accomplished via fluorescence and optical microscopy, ellipsometry, optical profilometry, and contact angle measurements. The quality factors of the devices are measured to evaluate the impact of the coating on device sensitivity. The resulting devices show uniform surface coating with no microstructural damage with Q factors above 106. This is the first report demonstrating the integration of these devices with molecular imprinting techniques, and could lead to new routes to biosensor creation for environmental monitoring.

Feasibility of a nanomaterial-tissue patch for vascular and cardiac reconstruction.

Vascular and cardiac reconstruction involves the use of biological patches to treat trauma and defects. An in vivo study was performed to determine the remodeling and biologic effects of novel nanostructured vascular patches with and without gold nanoparticles. Porcine vascular tissue was decellularized and conjugated with gold nanoparticles to evaluate if integration would occur while avoiding rupture and stenosis. Swine underwent a bilateral patch angioplasty of the carotid arteries with experimental patches on the right and control patches of bovine pericardium on the left. Animals were sacrificed after surgery and at 3 and 9 weeks. Ultrasound was performed during surgery, every 3 weeks, and before euthanasia. Endothelial regeneration was examined using Evans Blue dye and histology using Trichrome and H&E. There was a 100% success rate of implantation with 0% mortality. All patches were patent on ultrasound. At 3 weeks, experimental patches had regenerating endothelial cell growth and normal healing responses. At 9 weeks, the experimental patches demonstrated excellent integration. Histology demonstrated cellular in-growth into the experimental patches and no major immune reactions. This is one of the first studies to demonstrate the feasibility of nanomaterial-tissue patches for vascular and cardiac reconstruction.

Development and characterization of a rapid polymerizing collagen for soft tissue augmentation.

A liquid collagen has been developed that fibrilizes upon injection. Rapid polymerizing collagen (RPC) is a type I porcine collagen that undergoes fibrillization upon interaction with ionic solutions, such as physiological solutions. The ability to inject liquid collagen would be beneficial for many soft tissue augmentation applications. In this study, RPC was synthesized and characterized as a possible dermal filler. Transmission electron microscopy, ion induced RPC fibrillogenesis tests, collagenase resistance assay, and injection force studies were performed to assess RPC's physicochemical properties. An in vivo study was performed which consisted of a 1-, 3-, and 6-month study where RPC was injected into the ears of miniature swine. The results demonstrated that the liquid RPC requires low injection force (<7 N); fibrillogenesis and banding of collagen occurs when RPC is injected into ionic solutions, and RPC has enhanced resistance to collagenase breakdown. The in vivo study demonstrated long-term biocompatibility with low irritation scores. In conclusion RPC possesses many of the desirable properties of a soft tissue augmentation material. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 758-767, 2016.

Materials characterization of explanted polypropylene hernia mesh: Patient factor correlation.

This study quantitatively assessed polypropylene (PP) hernia mesh degradation and its correlation with patient factors including body mass index, tobacco use, and diabetes status with the goal of improving hernia repair outcomes through patient-matched mesh. Thirty PP hernia mesh explants were subjected to a tissue removal process followed by assessment of their in vivo degradation using Fourier transform infrared, differential scanning calorimetry, and thermogravimetric analysis analyses. Results were then analyzed with respect to patient factors (body mass index, tobacco use, and diabetes status) to determine their influence on in vivo hernia mesh oxidation and degradation. Twenty of the explants show significant surface oxidation. Tobacco use exhibits a positive correlation with modulated differential scanning calorimetry melt temperature and exhibits significantly lower TGA decomposition temperatures than non-/past users. Chemical and thermal characterization of the explanted meshes indicate measurable degradation while in vivo regardless of the patient population; however, tobacco use is correlated with less oxidation and degradation of the polymeric mesh possibly due to a reduced inflammatory response.

Fluorescence imaging preparation methods for tissue scaffolds implanted into a green fluorescent protein porcine model.

Green fluorescent protein (GFP) animal models have become increasingly popular due to their potential to enhance in vivo imaging and their application to many fields of study. We have developed a technique to observe host tissue integration into scaffolds using GFP expressing swine and fluorescence imaging. Current fluorescence imaging preparation methods cannot be translated to a full GFP animal model due to several challenges and limitations that are investigated here. We have implanted tissue scaffolds into GFP expressing swine and have prepared explanted scaffolds for fluorescence imaging using four different methods including formalin fixation and paraffin embedding, vapor fixation, freshly prepared paraformaldehyde fixation, and fresh frozen tissue. Explanted scaffolds and tissue were imaged using confocal microscopy with spectral separation to evaluate the GFP animal model for visualization of host tissue integration into explanted scaffolds. All methods except fresh frozen tissue induced autofluorescence of the scaffold, preventing visualization of detail between host tissue and scaffold fibers. Fresh frozen tissue preparation allowed for the most reliable visualization of fluorescent host tissue integration into non-fluorescent scaffolds. It was concluded that fresh frozen tissue preparation is the best method for fluorescence imaging preparation when using scaffolds implanted into GFP whole animal models.

In vitro electromagnetic stimulation to enhance cell proliferation in extracellular matrix constructs with and without metallic nanoparticles.

Extremely low frequency electromagnetic fields (ELF-EMFs) can induce beneficial effects including enhanced protein synthesis and cell proliferation on healing bone and skin wounds. This study investigated the effects of ELF-EMFs on acellular tissue constructs with and without gold nanoparticles (AuNPs) to determine if cell proliferation could be increase and thus provide an enhanced mechanism for in vitro cell seeding on tissue engineered constructs. Different sized AuNPs, 20 and 100 nm, were conjugated to acellular porcine tissue, seeded with L929 murine fibroblasts and exposed to a continuous 12 gauss, 60 Hz electromagnetic field for 2 hours each day up to 10 days. Scanning electron microscopy and cell culture assays were performed to ascertain cell proliferation and viability before and after exposure. Results indicate the ELF-EMF stimulation significantly increased cell proliferation. The presence of AuNPs did not boost the stimulatory effects, but they did demonstrated higher rates of proliferation from day 3 to day 10. In addition, unstimulated 100 nm AuNPs constructs resulted in significant increases in proliferation as compared to unstimulated crosslinked constructs. In conclusion, ELF-EMF stimulation enhanced cellular proliferation and while the presence of AuNPs did not significantly enhance this effect, AuNPs resulted in increased proliferation rates from day 3 to day 10.

Assessment of the biocompatibility and stability of a gold nanoparticle collagen bioscaffold.

Collagen has been utilized as a scaffold for tissue engineering applications due to its many advantageous properties. However, collagen in its purified state is mechanically weak and prone to rapid degradation. To mitigate these effects, collagen can be crosslinked. Although enhanced mechanical properties and stability can be achieved by crosslinking, collagen can be rendered less biocompatible either due to changes in the overall microstructure or due to the cytotoxicity of the crosslinkers. We have investigated crosslinking collagen using gold nanoparticles (AuNPs) to enhance mechanical properties and resistance to degradation while also maintaining its natural microstructure and biocompatibility. Rat tail type I collagen was crosslinked with AuNPs using a zero-length crosslinker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Several characterization studies were performed including electron microscopy, collagenase assays, ROS assays, and biocompatibility assays. The results demonstrated that AuNP-collagen scaffolds had increased resistance to degradation as compared to non-AuNP-collagen while still maintaining an open microstructure. Although the biocompatibility assays showed that the collagen and AuNP-collagen scaffolds are biocompatible, the AuNP-collagen demonstrated enhanced cellularity and glycoaminoglycans (GAG) production over the collagen scaffolds. Additionally, the Reactive Oxygen Species (ROS) assays indicated the ability of the AuNP-collagen to reduce oxidation. Overall, the AuNP-collagen scaffolds demonstrated enhanced biocompatibility and stability over non-AuNP scaffolds.

Electrospinning collagen and hyaluronic acid nanofiber meshes.

Collagen and hyaluronic acid (HA) are main components of the extracellular matrix and have been utilized in electrospinning; a technique that creates nanosized fibers for tissue scaffolds. A collagen/HA polymer solution was electrospun into a scaffold material for osteoporosis patients who have reduced bone strength. To synthesize nanofibers, a high voltage was applied to the polymer solution to draw out nanofibers that were collected on a ground plate as a uniform mesh. The meshes were then crosslinked to render them insoluble and conjugated with gold nanoparticles to promote biocompatibility. Characterization of the mesh was performed using scanning electron microscope, electron dispersive spectroscopy and fourier transform infrared spectroscopy. A WST-1 assay determined the potential biocompatibility. The results show that collagen/HA scaffolds were developed that were insoluble in aqueous solutions and promoted cellular attachment that could be used as a tissue engineered scaffold to promote cell growth.

Differentiation of biologic scaffold materials through physicomechanical, thermal, and enzymatic degradation techniques.

OBJECTIVE: The objective of this study was to characterize the physicomechanical, thermal, and degradation properties of several types of biologic scaffold materials to differentiate between the various materials. BACKGROUND: As more biologic scaffold materials arrive on the market, it is critical that surgeons understand the properties of each material and are provided with resources to determine the suitability of these products for specific applications such as hernia repair. METHODS: Twelve biologic scaffold materials were evaluated, including crosslinked and non-crosslinked; those of bovine, human, and porcine origin; and derivatives of pericardium, dermis, and small intestine submucosa. Physicomechanical, thermal, and degradation properties were evaluated through biomechanical testing, modulated differential scanning calorimetry, and collagenase digestion assays, respectively. Biomechanical testing included suture retention, tear strength, uniaxial tensile, and ball burst techniques. RESULTS: All scaffolds exhibited suture retention strengths greater than 20 N, but only half of the scaffolds exhibited tear resistance greater than 20 N, indicating that some scaffolds may not provide adequate resistance to tearing. A wide range of burst strengths were observed ranging from 66.2 ± 10.8 N/cm for Permacol to 1,028.0 ± 199.1 N/cm for X-Thick AlloDerm, and all scaffolds except SurgiMend, Strattice, and CollaMend exhibited strains in the physiological range of 10% to 30% (at a stress of 16 N/cm). Thermal analysis revealed differences between crosslinked and non-crosslinked materials with crosslinked bovine pericardium and porcine dermis materials exhibiting a higher melting temperature than their non-crosslinked counterparts. Similarly, the collagenase digestion assay revealed that crosslinked bovine pericardium materials resisted enzymatic degradation significantly longer than non-crosslinked bovine pericardium. CONCLUSIONS: Although differences were observed because of cross-linking, some crosslinked and non-crosslinked materials exhibited very similar properties. Variables other than cross-linking, such as decellularization/sterilization treatments or species/tissue type also contribute to the properties of the scaffolds.

Characterization of bionanocomposite scaffolds comprised of mercaptoethylamine-functionalized gold nanoparticles crosslinked to acellular porcine tissue.

Bionanocomposite scaffolds comprised of nanomaterials and the extracellular matrix (ECM) of porcine diaphragm tissue capitalizes on the benefits of utilizing a natural ECM material, while also potentially enhancing physicomechanical properties and biocompatibility through nanomaterials. Gold nanoparticle (AuNP) bionanocomposite scaffolds were subjected to a number of characterization techniques to determine whether the fabrication process negatively impacted the properties of the porcine diaphragm tissue and whether the AuNP improved the properties of the tissue. Tensile testing and differential scanning calorimetry demonstrated that the bionanocomposite possessed improved tensile strength and thermal stability relative to natural tissue. The collagenase assay and Fourier transform infrared spectroscopy additionally confirmed that denaturation of the collagen of the ECM did not occur. The novel bionanocomposite scaffold possessed properties similar to commercially available scaffolds and will be further developed for soft tissue applications such as hernia repair through in vivo studies in an animal model.

Assessment of decellularized porcine diaphragm conjugated with gold nanomaterials as a tissue scaffold for wound healing.

One million Americans suffer from chronic wounds every year with diabetics and older populations representing the majority. Mechanisms that may be responsible for the reduced healing response in these patients include reduction in growth factors or vascularization and an increase in free radical levels. The focus of this study was to develop a biocompatible gold/porcine diaphragm scaffold capable of sustaining fibroblast attachment and proliferation which was measured using viability and dsDNA assays. The free radical scavenging properties, as measured by ROS assays, were also investigated as a mechanism for improving the wound environment. Results indicated 69-89% viability for gold nanoparticle (AuNP) scaffolds and 51-74% for gold nanorod (AuNR) scaffolds as compared to 100% for decellularized scaffolds and 77% for crosslinked scaffolds. All scaffolds exhibited good cell attachment while AuNP-1X scaffolds showed the greatest cell proliferation with a 74% increase in dsDNA content from Day 3 to 7. AuNP-2X and AuNP-4X scaffolds generated higher levels of free radicals with AuNP-4X generating over twice as much as decellularized scaffolds. This study suggests the capability for gold/porcine diaphragm scaffolds to enhance cell proliferation while the modification of free radical generation appears to be dependent on nanomaterial shape and concentration.

Comparison of molecular imprinted particles prepared using precipitation polymerization in water and chloroform for fluorescent detection of nitroaromatics.

A comparative study was conducted to study the effects that two different polymerization solvents would have on the properties of imprinted polymer microparticles prepared using precipitation polymerization. Microparticles prepared in chloroform, which previous results indicated was the optimal solvent for molecular imprinting of nitroaromatic explosive compounds, were compared to water, which was hypothesized to decrease water swelling of the polymer and allow enhanced rebinding of aqueous template. The microparticles were characterized and were integrated into a fluorescence sensing mechanism for detection of nitroaromatic explosive compounds. The performance of the sensing mechanisms was compared to illustrate which polymerization solvent produced optimal imprinted polymer microparticles for detection of nitroaromatic molecules. Results indicated that the structures of microparticles synthesized in chloroform versus water varied greatly. Sensor performance studies showed that the microparticles prepared in chloroform had greater imprinting efficiency and higher template rebinding than those prepared in water. For detection of 2,4,6-trinitrotoluene, the chloroform-based fluorescent microparticles achieved a lower limit of detection of 0.1 µM, as compared to 100 µM for the water-based fluorescent microparticles. Detection limits for 2,4-dinitrotoluene, as well as time response studies, also demonstrated that the chloroform-based particles are more effective for detection of nitroaromatic compounds than water-based particles. These results illustrate that the enhanced chemical properties of using the experimentally determined optimal polymerization solvent overcome deformation of imprinted binding sites by water swelling and benefits of using the polymerization solvent for rebinding of the template.