Poly­(lactic acid), also abbreviated as PLA, is a promising biopolymer for food packaging owing to its environmental-friendly characteristic and desirable physical properties. Electrospinning technology makes the production of PLA-based nanomaterials available with expected structures and enhanced barrier, mechanical, and thermal properties; especially, the facile process produces a high encapsulation efficiency and controlled release of bioactive agents for the purpose of extending the shelf life and promoting the quality of foodstuffs. In this study, different types of electrospinning techniques used for the preparation of PLA-based nanofibers are summarized, and the enhanced properties of which are also described. Moreover, its application in active and intelligent packaging materials by introducing different components into nanofibers is highlighted. In all, the review establishes the promising prospects of PLA-based nanocomposites for food packaging application.

Acrylamide is toxic aliphatic amide formed via the Maillard reaction between asparagine and reducing sugars during thermal processing of food. Herein, a specific nanobody termed Nb-7E against the acrylamide derivative xanthyl acrylamide (XAA) was isolated from an immunized phage display library and confirmed to be able to detect acrylamide. First, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was established for acrylamide with a limit of detection (LOD) of 0.089 μg/mL and working range from 0.23 to 5.6 μg/mL. Furthermore, an enhanced electrochemical immunoassay (ECIA) was developed based on the optimized reaction conditions. The LOD was as low as 0.033 μg/mL, threefold improved compared to that of ic-ELISA, and a wider linear detection range from 0.39 to 50.0 μg/mL was achieved. The average recoveries ranged from 88.29 to 111.76% in spiked baked biscuits and potato crisps. Finally, the analytical performance of the ECIA was validated by standard ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS).

A simple and sensitive fluoroimmunoassay (FIA) based on a heavy-chain antibody (VHH) for rapid detection of fenitrothion was developed. A VHH library was constructed from an immunized alpaca, and one clone recognizing fenitrothion (namely, VHHjd8) was achieved after careful biopanning. It was biotinylated by fusing with the Avi tag and biotin ligase to obtain a fusion protein (VHHjd8-BT), showing both binding capacity to fenitrothion and the streptavidin poly-horseradish peroxidase conjugate (SA-polyHRP). Based on a competitive assay format, the absorbance spectrum of oxidized 3,3′,5,5′-tetramethylbenzidine generated by SA-polyHRP overlapped the emission spectrum of carbon dots, which resulted in quenching of signals due to the inner-filter effect. The developed FIA showed an IC50 value of 1.4 ng/mL and a limit of detection of 0.03 ng/mL, which exhibited 15-fold improvement compared with conventional enzyme-linked immunosorbent assay. The recovery test of FIA was validated by standard GC–MS/MS, and the results showed good consistency, indicating that the assay is an ideal tool for rapid screening of fenitrothion in bulk food samples.

Nanobodies (Nbs) have great potential in immunoassays due to their exceptional physicochemical properties. With the immortal nature of Nbs and the ability to manipulate their structures using protein engineering, it will become increasingly valuable to understand what structural features of Nbs drive high stability, affinity, and selectivity. Here, we employed an anti-quinalphos Nb as a model to illustrate the structural basis of Nbs’ distinctive physicochemical properties and the recognition mechanism. The results indicated that the Nb-11A-ligand complexes exhibit a “tunnel” binding mode formed by CDR1, CDR2, and FR3. The orientation and hydrophobicity of small ligands are the primary determinants of their diverse affinities to Nb-11A. In addition, the primary factors contributing to Nb-11A’s limited stability at high temperatures and in organic solvents are the rearrangement of the hydrogen bonding network and the enlargement of the binding cavity. Importantly, Ala 97 and Ala 34 at the active cavity’s bottom and Arg 29 and Leu 73 at its entrance play vital roles in hapten recognition, which were further confirmed by mutant Nb-F3. Thus, our findings contribute to a deeper understanding of the recognition and stability mechanisms of anti-hapten Nbs and shed new light on the rational design of novel haptens and directed evolution to produce high-performance antibodies.