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Conventional mass spectrometry (MS)-based analytical methods for small carbohydrate fragments (oligosaccharides, degree of polymerization 2–12) are time-consuming due to the need for offline sample pretreatment such as desalting. Herein, we report a new paper spray ionization method, named desalting paper spray (DPS), which employs a piece of triangular filter paper for both sample desalting and ionization. Unlike regular paper spray ionization (PSI) and nano electrospray ionization (nanoESI), DPS-MS allows fast and sensitive detection of oligosaccharides in biological samples having complex matrices (e.g., Tris, PBS, HEPES buffers or urine). When oligosaccharide sample is loaded onto the filter paper substrate (10 mm × 5 mm, height × base) made mostly of cellulose, oligosaccharides adsorb on the paper via hydrophilic interactions between oligosaccharides and cellulose. Salts and buffers can be washed away using an ACN/H(2)O (90/10 v/v) solution, While oligosaccharides can be eluted from the paper using a solution of ACN/H(2)O/formic acid (FA) (10/90/1 v/v/v) and directly spray-ionized from the tip of the paper. Various saccharides at trace levels (e.g., 50 fmol) in nonvolatile buffer can be quickly analyzed by DPS-MS (< 5 min per sample). DPS-MS is also applicable for direct detection of oligosaccharides from glycosyltransferase (GT) reactions, a challenging task which typically requires radioactive assay. Quantitative analysis of acceptor and product oligosaccharides shows increased product with increased GT enzymes used for the reaction, a result in line with radioactivity assay. This work suggests that DPS-MS has potential for rapid oligosaccharides analysis from biological samples.

Paper-based cultures are an emerging platform for preparing 3D tissue-like structures. Chemical gradients can be imposed upon these cultures, generating microenvironments similar to those found in poorly vascularized tumors. There is increasing evidence that the tumor microenvironment is responsible for promoting drug resistance and increased invasiveness. Acidosis, or the acidification of the extracellular space, is particularly important in promoting these aggressive cancer phenotypes. To better understand how cells respond to acidosis there is a need for 3D culture platforms that not only model relevant disease states but also contain sensors capable of quantifying small molecules in the extracellular environment. In this work, we describe pH-sensing optodes that are capable of generating high spatial and temporal resolution maps of pH gradients in paper-based cultures. This sensor was fabricated by suspending microparticles containing pH-sensitive (fluorescein) and pH-insensitive (diphenylanthracene) dyes in a polyurethane hydrogel, which was then coated onto a transparent film. The pH-sensing films have a fast response time, are reversible, stable in long-term culture environments, have minimal photobleaching, and are not cytotoxic. These films have a pKa of 7.61 ± 0.04 and are sensitive in the pH range corresponding to normal and tumorigenic tissues. With these optodes, we measured the spatiotemporal evolution of pH gradients in paper-based tumor models.

Carbohydrate analysis is an important source of the information required for understanding and control of pulp and paper processes. The behavior of cellulose and hemicelluloses in the process, carbohydrate–lignin interactions, and the enzymatic treatment of fibers are examples of situations for which reliable, fast, qualitative, and quantitative methods are required. New uses of lignocellulosic material have further increased the need for carbohydrate analysis. This review collates and summarizes the most important findings and approaches in the analysis of wood-based carbohydrates by use of capillary zone electrophoresis and provides an analysis of the effect of different conditions on the separation, showing the advantages and limitations of the methods used. It provides guidelines for achieving higher quality and improved separation efficiency in carbohydrate analysis.

The cellulases of Streptomyces thermodiastaticus (strain 2Sts) and thermomonospora fusca (strain 190Th) were produced with carboxymethyl-cellulose (CMC) serving as the carbon source during growth. Both cellulases act by random internal hydrolysis of the CMC chain, producing cellobiose, glucose, and intermediate length oligosaccharides. Cellobiase was not detected in culture filtrates produced under these conditions.