Photonic porous silicon as a pH sensor

Chronic wounds do not heal within 3 months, and during the lengthy healing process, the wound is invariably exposed to bacteria, which can colonize the wound bed and form biofilms. This alters the wound metabolism and brings about a change of pH. In this work, porous silicon photonic films were coated with the pH-responsive polymer poly(2-diethylaminoethyl acrylate). We demonstrated that the pH-responsive polymer deposited on the surface of the photonic film acts as a barrier to prevent water from penetrating inside the porous matrix at neutral pH. Moreover, the device demonstrated optical pH sensing capability visible by the unaided eye

Stimulus-responsive antibiotic releasing systems for the treatment of wound infections

There remains an unmet need for innovative treatments for chronic wound infections as they continue to be a financial and social burden on society. Because of the dynamic nature of wounds, this study investigated the utilization of stimulus-responsive plasma polymers for the development of pH-and thermoresponsive antibiotic delivery systems for the treatment of wound infections. Porous silicon films were loaded with the antibiotic levofloxacin (LVX) and subsequently coated with plasma polymer layers: first, poly(1,7-octadiene) (pOCT) for stability, followed by either the temperature-responsive polymer poly N,N-diethylacrylamide (pDEA) or the pH-responsive polymer poly 2-(diethylamino)ethyl methacrylate (pDEAEMA), to fabricate two delivery systems. The delivery systems were thoroughly characterized chemically and physically and tested in vitro through drug release and bacterial zone of inhibition studies. After a 16 h time point, the system containing pDEA achieved 3.2-fold greater release at 45 °C compared to 22 °C, whereas the system containing pDEAEMA achieved a 2.2-fold greater release when exposed to pH 8.5 media compared to pH 6.2 media. Furthermore, both systems retained their antimicrobial activity and demonstrated stimulus-responsive release to form zones of inhibition on relevant wound pathogens, Pseudomonas aeruginosa, Staphylococcus epidermidis and Staphylococcus aureus. Therefore, this proof-of-principle study confirms that stimulus-responsive porous silicon films can be utilized to deliver antibiotic when exposed to physiologically relevant stimuli such as pH and temperature with the potential to be applied to other pharmaceutics

Polymerization-Amplified Optical DNA Detection on Porous Silicon Templates

A porous silicon-based optical DNA sensor is described herein, which enables rapid DNA detection. The DNA sensor relies on the specificity of the DNA base pairing in conjunction with an interferometric optical signal amplification step based on polymer formation within the porous silicon layer to detect the DNA targets in a highly selective fashion. We demonstrate that it is possible to discriminate between DNA strands exhibiting even a single nucleotide mismatch using this sensor

Fabrication and characterization of a porous silicon drug delivery system with an initiated chemical vapor deposition temperature-responsive coating

This paper reports on the fabrication of a pSi-based drug delivery system, functionalized with an initiated chemical vapor deposition (iCVD) polymer film, for the sustainable and temperature-dependent delivery of drugs. The devices were prepared by loading biodegradable porous silicon (pSi) with a fluorescent anticancer drug camptothecin (CPT) and coating the surface with temperature-responsive poly(N-isopropylacrylamide-co-diethylene glycol divinyl ether) (pNIPAM-co-DEGDVE) or non-stimulus-responsive poly(aminostyrene) (pAS) via iCVD. CPT released from the uncoated oxidized pSi control with a burst release fashion (similar to 21 nmol/(cm(2) h)), and this was almost identical at temperatures both above (37 degrees C) and below (25 degrees C) the lower critical solution temperature (LCST) of the switchable polymer used, pNIPAM-co-DEGDVE (28.5 degrees C). In comparison, the burst release rate from the pSi-pNIPAM-co-DEGDVE sample was substantially slower at 6.12 and 9.19 nmol/(cm(2) h) at 25 and 37 degrees C, respectively. The final amount of CPT released over 16 h was 10% higher at 37 degrees C compared to 25 degrees C for pSi coated with pNIPAM-co-DEGDVE (46.29% vs 35.67%), indicating that this material can be used to deliver drugs on-demand at elevated temperatures. pSi coated with pAS also displayed sustainable drug delivery profiles, but these were independent of the release temperature. These data show that sustainable and temperature-responsive delivery systems can be produced by functionalization of pSi with iCVD polymer films. Benefits of the iCVD approach include the application of the iCVD coating after drug loading without causing degradation of the drug commonly caused by exposure to factors such as solvents or high temperatures. Importantly, the iCVD process is applicable to a wide array of surfaces as the process is independent of the surface chemistry and pore size of the nanoporous matrix being coated

Microwave Heating of Poly(<i>N</i>‑isopropylacrylamide)-Conjugated Gold Nanoparticles for Temperature-Controlled Display of Concanavalin A

We demonstrate microwave-induced heating of gold nanoparticles and nanorods. An appreciably higher and concentration-dependent microwave-induced heating rate was observed with aqueous dispersions of the nanomaterials as opposed to pure water and other controls. Grafted with the thermoresponsive polymer poly­(<i>N</i>-isopropylacrylamide), these gold nanomaterials react to microwave-induced heating with a conformational change in the polymer shell, leading to particle aggregation. We subsequently covalently immobilize concanavalin A (Con A) on the thermoresponsive gold nanoparticles. Con A is a bioreceptor commonly used in bacterial sensors because of its affinity for carbohydrates on bacterial cell surfaces. The microwave-induced thermal transitions of the polymer reversibly switch on and off the display of Con A on the particle surface and hence the interactions of the nanomaterials with carbohydrate-functionalized surfaces. This effect was determined using linear sweep voltammetry on a methyl-α-d-mannopyranoside-functionalized electrode