**4. Conclusions**

In conclusion, this report describes a technological advancement in the field of electrospinning. While retaining all the benefits of the electrospinning process, a sodium chloride-based pellet (sacrificial core) has been introduced to act as a rotating collector, placed directly in front of a grounded plate. Subsequently, the dissolution of the salt pellet results in a hollow core containing capsule. With this technique, we have developed nylon (PA66)-based devices with varying macroscale features such as size (2 × 4, 1 × 2 and 0.5 × 1 cm), shape (rectangular, triangular and circular) and thickness (1, 1.5 and 2 mm). Additionally, it was possible to control the morphological properties of the capsule, such as fiber diameter by altering the conventional electrospinning parameters, including solvent type, polymer concentration, voltage, distance, voltage–to–distance ratio and flow rate. The results from the ATR-FTIR and TG/DTA studies performed suggest that the use of the sodium chloride pellet as the sacrificial core had no influence on the bulk properties of the polymer. Protein diffusion studies revealed that the capsules allowed free diffusion of biomolecules such as insulin, albumin and Ig G. Cell encapsulation studies with HDF and Jurkat cells revealed that the optimized capsules could be used to support the viability of encapsulated cells, whilst the walls of the capsules would restrict the ingress of immune cells. Further studies to unravel the potential of this system in various cell and tissue encapsulation applications are in progress.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2079-4991/8/10/863/s1, Figure S1: Physical state of the sacrificial core electrospun device without a supporting framework; Figure S2: A representative image of a 3D-printed supporting framework; Figure S3: Electrospinning onto 3D printed framework without inclusion of a NaCl pellet; Figure S4: Pore area calculations.

**Author Contributions:** Conceptualization, N.K., H.Y. and Z.C.; Methodology, N.K. and J.G.; Data Curation, N.K., J.G. and H.Y.; Writing-Original Draft Preparation, N.K.; Writing-Review & Editing, H.Y. and Z.C.

**Funding:** This research was funded by China Regenerative Medicine International Limited, Hong Kong.

**Acknowledgments:** We extend our thanks to our colleague *Dr. Nguyen T.B. Linh* for assistance with ATR-FTIR studies, *Dr. Colin Johnston* (Department of Materials) for assistance with TG/DTA analysis and *Dr. Michelle Kümin* for critical reading of the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, and in the decision to publish the results.
