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We review our recent efforts utilizing poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgels and their assemblies for the removal of an azo-dye molecule, 4-(2-Hyrodxy-1-napthylazo) benzenesulfonic acid sodium salt (Orange II), from aqueous solutions. First, the ability of dispersed, single microgels to remove Orange II from aqueous solutions at room temperature is discussed. Uptake efficiency (i.e., the amount of Orange II removed from water) increased with AAc composition in the microgels, yielding a maximum uptake efficiency of 29.5% for pNIPAm microgels with 10% AAc. Assemblies of microgels (aggregates) were also investigated for their removal efficiency, which yielded a maximum uptake efficiency of 44.1% at room temperature. Removal efficiencies for the microgels and their aggregates were also monitored at elevated temperatures, and a maximum of 56.6% removal efficiency was achieved for unaggregated microgels, while aggregates were able to remove 73.1% Orange II. To further explore the impact of the microgel system's structure on function, we investigated the role microgel size in the aggregates plays on the uptake efficiency. Initial observations showed that the aggregates composed of microgels with large diameter yielded improved uptake efficiency over the aggregates composed of small diameter microgels. Langmuir sorption isotherms were fit to the data for the dye removal by the unaggregated and aggregated microgels, which showed good fits in all cases.

Thermally responsive poly(N-isopropylacrylamide) (pNIPAm)-based hydrogel particles (microgels) have been extensively studied over past few decades. We, and others, have found that assemblies of these microgels exhibit unique properties that make them useful such as nonfouling surface coatings, drug release/delivery vehicles, and sensors. In this submission, we review our efforts to develop novel water remediation systems and optical devices from pNIPAm-based microgels.

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55-year-old woman with poorly controlled diabetes mellitus presented with three days of anorexia and coffeeground emesis in the context of noncompliance to insulin therapy. She denied caustic ingestion and was hemodynamically stable on presentation. Blood tests showed hyperglycemia (glucose 25.4 mmol/L), anion-gap metabolic acidosis (pH 7.21) and ketosis (β-hydroxybutyric acid 12.99 mmol/L). Diabetic ketoacidosis was managed in a medical step-up unit with potassium supplementation, intravenous fluid resuscitation and intravenous insulin infusion, followed by transition to subcutaneous insulin. For suspected upper gastrointestinal bleed, she received an intravenous proton pump inhibitor (PPI) infusion and was given nothing by mouth. Subsequent esophagogastroduodenoscopy showed circumferential black mucosa in the distal esophagus, immediately proximal to the gastroesophageal junction (Figure 1, A and B), sparing the gastric and duodenal mucosae. This endoscopic appearance is consistent with acute esophageal necrosis. After achievement of good glycemic control and six days of PPI therapy, repeat endoscopy showed substantial resolution of the mucosal necrosis, with residual inflammation and patchy ulcers (Figure 1, C and D). Following discharge, gastric acid suppression with an oral PPI was continued; however, the patient was subsequently lost to follow-up. Acute esophageal necrosis, or "black esophagus," is a rare clinical entity that may complicate acute hyperglycemic states, such as diabetic ketoacidosis, and has also been reported in association with critical illness, shock, sepsis, ischemia and malignancy. 1 Preceding caustic ingestion must be excluded. The hallmark image on endoscopy is diffuse, friable, dark mucosal discoloration of the distal esophagus, terminating sharply before the gastroesophageal junction, and sparing the stomach, duodenum and proximal esophagus. 1 Acute esophageal necrosis may arise from hypoperfusion, corrosive injury and decreased mucosal repair secondary to physiologic stress. 1 Treatment is supportive, with esophageal rest, gastric acid suppression and correction of any reversible underlying conditions. 2 Underlying illness severity portends poor prognosis. 3 Potential complications include esophageal perforation, superinfection and strictures. 1