Role of Oligoethylene Glycol Side Chain Length in Responsive Polymeric Nanoassemblies.

An oft-desired feature of a responsive nanomaterial is that it should undergo disassembly or morphological change upon application of a specific stimulus. The extent of response has been found to depend on factors such as the nature and the number of responsive functionalities incorporated into these particles. In this work, the length of oligoethylene glycol (OEG) side chains associated with the polymers has been shown to greatly influence the responsive behavior of polymeric nanoparticles. The integrity of these OEG-based polymeric assemblies was found to depend not only on the chemical cross-links but also on the physical cross-links in these aggregates in cases where the polymer chains bear long OEG side chains. The physical cross-linking in longer OEG side chain containing polymeric nanogels is present in the form of crystalline domains. Our results here highlight that these ethylene glycol-based hydrophilic units are not to be ignored as spectator units with water-solubilization characteristics but must be analyzed in the context of assembly stabilization and triggerability with the targeted stimulus.

Oligomers as Triggers for Responsive Liquid Crystals.

We report an investigation of the influence of aqueous solutions of amphiphilic oligomers on the ordering of micrometer-thick films of thermotropic liquid crystals (LCs), thus addressing the gap in knowledge arising from previous studies of the interactions of monomeric and polymeric amphiphiles with LCs. Specifically, we synthesized amphiphilic oligomers (with decyl hydrophobic and pentaethylene glycol hydrophilic domains) in monomer, dimer, and trimer forms, and incubated aqueous solutions of the oligomers against nematic films of 4'-pentyl-4-biphenylcarbonitrile (5CB). All amphiphilic oligomers caused sequential surface-driven orientational (planar to homeotropic) and then bulk phase transitions (nematic to isotropic) with dynamics depending strongly on the degree of oligomerization. The dynamics of the orientational transitions accelerated from monomer to trimer, consistent with the effects of an increase in adsorption free energy. The mechanism underlying the orientational transition, however, involved a decrease in anchoring energy and not change in the easy axis of the LC. In contrast, the rate of the phase transition induced by absorption of oligomers into the LC decreased from monomer to trimer, suggesting that constraints on configurational degrees of freedom influence the absorption free energies of the oligomers. Interestingly, the oligomer-induced transition from the nematic to isotropic phase of 5CB was observed to nucleate at the aqueous-5CB interface, consistent with surface-induced disorder underlying the above-reported decrease in anchoring energy caused by the oligomers. Finally, we provided proof-of-concept experiments of the triggering of LCs using a trimeric amphiphile that is photocleaved by UV illumination into monomeric fragments. Overall, our results provide insight into the rational design of oligomers that can be used as triggers to create responsive LCs.

Influence of backbone conformational rigidity in temperature-sensitive amphiphilic supramolecular assemblies.

Molecular design features that endow amphiphilic supramolecular assemblies with a unique temperature-sensitive transition have been investigated. We find that conformational rigidity in the backbone is an important feature for eliciting this feature. We also find that intramolecular hydrogen-bonding can induce such rigidity in amphiphile backbone. Guest encapsulation stability of these assemblies was found to be significantly altered within a narrow temperature window, which correlates with the temperature-sensitive size transition of the molecular assembly. Molecular design principles demonstrated here could have broad implications in developing future temperature-responsive systems.

Autologous serum eye drops in dry eye disease: Preferred practice pattern guidelines.

Autologous serum eye drops provide lubrication and promote epithelial healing. They have been successfully used in the management of ocular surface disorders such as dry eye disease, persistent epithelial defects and neurotrophic keratopathy for many decades. A great deal of variation in the methods of preparation of autologous serum eye drops, the end concentration and the duration of use exists in published literature. In this review, simplified recommendations for preparation, transport, storage and use of autologous serum are described. Evidence for the use of this modality in aqueous deficient dry eye disease is summarized, along with expertise-based rationale.

A novel biodegradable polymer scaffold for in vitro growth of corneal epithelial cells.

The shortage of donor corneal tissue worldwide has led to extensive research for alternate corneal equivalents utilizing tissue engineering methods. We conducted experiments using Poly D, L lactic acid polymer along with a copolymer (Eudragit) in varying concentrations to create a biodegradable scaffold suitable for in vitro growth of corneal epithelial stem cells. It was found that stable, spherical, and porous microparticles can be prepared by combining PDLLA and Eudragit RL100 polymers in the ratio of 90:10 and 70:30. The microparticles can then be fused to form scaffold membranes with porous architecture and good water retention capacity at room temperature using methanol, which can withstand handling during transplantation procedures. The scaffolds made using a 70:30 ratio were found to be suitable for the promotion of growth of laboratory corneal epithelial stem cell lines (SIRC cell lines). This innovation can pave way for further developments in corneal stem cell research and growth, thus providing for viable laboratory-derived corneal substitutes.

Repeated phototherapeutic keratectomy (PTK) followed by PTK with photorefractive keratectomy for anterior granular corneal dystrophy.

Two preteen siblings with the anterior-stromal variant of granular corneal dystrophy type 1 underwent multiple phototherapeutic keratectomies (PTK) (due to recurrences of the dystrophy) with progressively increasing hyperopia after each procedure. The last procedure performed was an additional photorefractive keratectomy along with the PTK which led to a decrease in the hyperopia with better refractive outcomes. The addition of mitomycin C may have led to a delay in the recurrence of the dystrophy.

A New Strategy for Reporting Specific Protein Binding Events at Aqueous-Liquid Crystal Interfaces in the Presence of Non-Specific Proteins.

Aqueous-liquid crystal (LC) interfaces offer promise as responsive interfaces at which biomolecular recognition events can be amplified into macroscopic signals. However, the design of LC interfaces that distinguish between specific and non-specific protein interactions remains an unresolved challenge. Herein, we report the synthesis of amphiphilic monomers, dimers, and trimers conjugated to sulfonamide ligands via triazole rings, their assembly at aqueous-LC interfaces, and the orientational response of LCs to the interactions of carbonic anhydrase II (CAII) and serum albumin with the oligomer-decorated LC interfaces. Of six oligomers synthesized, only dimers without amide methylation were found to assemble at aqueous interfaces of nematic 4-cyano-4'-pentylbiphenyl (5CB) to induce perpendicular LC orientations. At dimer-decorated LC interfaces, we found that concentrations of CAII less than 4 µM did not measurably perturb the LC but prevented non-specific adsorption and penetration of serum albumin into the dimer-decorated interface that otherwise triggered bright, globular LC optical domains. These experiments and others (including competitive adsorption of CAII, BSA, and lysozyme) support our hypothesis that specific binding of CAII to the dimer prevents LC anchoring transitions triggered by non-specific adsorption of serum albumin. We illustrate the utility of the approach by reporting (i) the relative activity of two small-molecule inhibitors (6-ethoxy-2-benzothiazolesulfonamide and benzenesulfonamide) of CAII to sulfonamide and (ii) proteolytic digestion of a protein (CAII) by thermolysin. Overall, the results in this paper provide new insight into the interactions of proteins at aqueous-LC interfaces and fresh ideas for either blocking non-specific interactions of proteins at surfaces or reporting specific binding events at LC interfaces in the presence of non-specific proteins.

Panscleritis masquerading as an attack of primary acute angle closure glaucoma.

Purpose: To report a female who presented with acute angle closure glaucoma and was found to have panscleritis on further evaluation. Method: Case report. Case description: A 50-year-old female was referred to us as a case of primary acute angle closure attack in the right eye and for laser peripheral iridotomy. She had severe pain, redness, a very shallow anterior chamber, and an intraocular pressure of 38 mmHg in the right eye. However, the fellow eye had a deep anterior chamber and the right eye also had severe chemosis, lid edema, scleral tenderness, choroidal folds, and pain during ocular movements which was limited. Ultrasound biomicroscopy showed a ciliochoroidal effusion with anterior rotation of the ciliary body. The ultrasound of the eye revealed an increased thickness of the ocular coats and subtenon fluid. A diagnosis of panscleritis causing secondary angle closure glaucoma was made. She responded well to topical atropine, and topical with systemic steroids. Conclusions: Secondary angle closure glaucoma due to panscleritis may mimic primary acute angle closure attack in a clinical setting. It is important to differentiate the two as treatment is opposite and may worsen the condition if misdiagnosed.

Amniotic membrane transplant with superficial keratectomy in superficial corneal degenerations: efficacy in a rural population of north India.

AIM: To evaluate the applicability and efficacy of superficial keratectomy with transplantation of preserved amniotic membrane in superficial corneal degenerations in a rural population of Northern India in terms of visual improvement and surface regularization. SETTINGS: Peripheral referral center in rural north India. MATERIALS AND METHODS: This was a prospective non-comparative interventional case series where 24 eyes of 20 farmers from peripheral rural areas (M:F = 19:1) with visually significant superficial degenerative disorders (15 eyes with climatic droplet keratopathy one of which was associated with Salzmann nodular degeneration and nine eyes with band-shaped keratopathy) were subjected to amniotic membrane transplantation (single or multiple layer) combined with superficial keratectomy. Subjective and objective outcomes after surgery were evaluated and analyzed and statistical significance of the outcomes in various disorders was evaluated. RESULTS: Eighty-eight per cent (21 eyes) had symptomatic relief from distressing preoperative symptoms while postoperative visual improvement by two or more lines was achieved in 23 eyes (96%) over a mean follow-up period of 26.8 +/- 10.2 months. The surface irregularity present preoperatively was relieved in 23 cases while postoperative decline of vision with visually significant scarring was seen in one case (4%), which was labeled as failure. CONCLUSIONS: Amniotic membrane transplant with superficial keratectomy helped achieve subjective comfort, visual rehabilitation and clinical regularization of the corneal surface in superficial corneal degenerations during the mean followup of 26.8 +/- 10.2 months in rural setups.