Preparation and Formation Mechanism of l-Valine Spherulites via Evaporation Crystallization

Current Trends in API Co-Processing: Spherical Crystallization and Co-Precipitation Techniques

Active Pharmaceutical Ingredients (APIs) do not always exhibit processable physical properties, which makes their processing in an industrial setup very demanding. These issues often lead to poor robustness and higher cost of the drug product. The issue can be mitigated by co-processing the APIs using suitable solvent media-based techniques to streamline pharmaceutical manufacturing operations. Some of the co-processing methods are the amalgamation of API purification and granulation steps. These techniques also exhibit adequate robustness for successful adoption by the pharmaceutical industry to manufacture high quality drug products. Spherical crystallization and co-precipitation are solvent media-based co-processing approaches that enhances the micromeritic and dissolution characteristics of problematic APIs. These methods not only improve API characteristics but also enable direct compression into tablets. These methods are economical and time-saving as they have the potential for effectively circumventing the granulation step, which can be a major source of variability in the product. This review highlights the recent advancements pertaining to these techniques to aid researchers in adopting the right co-processing method. Similarly, the possibility of scaling up the production of co-processed APIs by these techniques is discussed. The continuous manufacturability by co-processing is outlined with a short note on Process Analytical Technology (PAT) applicability in monitoring and improving the process.

Rational Design of Biological Crystals with Enhanced Physical Properties by Hydrogen Bonding Interactions

Hydrogen bonds are non-covalent interactions and essential for assembling supermolecules into ordered structures in biological systems, endowing crystals with fascinating physical properties, and inspiring the construction of eco-friendly electromechanical devices. However, the interplay between hydrogen bonding and the physical properties is not fully understood at the molecular level. Herein, we demonstrate that the physical property of biological crystals with double-layer structures could be enhanced by rationally controlling hydrogen bonding interactions between amino and carboxyl groups. Different hydrogen bonding interactions result in various thermal, mechanical, electronic, and piezoelectric properties. In particular, the weak interaction between O and H atoms contributes to low mechanical strength that permits important ion displacement under stress, giving rise to a strong piezoelectric response. This study not only reveals the correlation between the hydrogen bonding and physical properties in double-layer structures of biological crystals but also demonstrates the potential of these crystals as functional biomaterials for high-performance energy-harvesting devices. Theoretical calculations and experimental verifications in this work provide new insights into the rational design of biomaterials with desirable physical properties for bioelectrical devices by modulating intermolecular interactions.

Modified Stranski-Krastanov Growth of Amino Acid Arrays toward Piezoelectric Energy Harvesting

Biomolecule-based piezoelectric nanostructures emerged as a new class of energy-converse materials, and designing tailored piezoelectric amino acid arrays is essential to achieve efficient electrical-mechanical coupling and fulfill their application potential. However, the controlled growth of amino acid nanostructures is still challenging due to the limited understanding of their growth mechanism. Herein, we base on the Stranski-Krastanov (S-K) growth mode and propose a mechanism for the growth of ordered amino acid array structures via physical vapor deposition. The growth of vertical valine sheet arrays is examined by changing the substrate temperature, chamber pressure, and source-substrate distance, and a "layer-plus-sheet" growth process is revealed. The modified S-K growth mode is applied to fabricate other amino acid nanostructures like leucine and isoleucine. The growth mode not only explains the formation of uniform and controllable morphology of amino acid structures but also leads to the significant enhancement of their piezoelectric properties. The maximal effective piezoelectric constant of valine sheets is 11.4 pm V^-1, which approaches its highest predicted value. The output voltage of the valine array-based nanogenerator is ∼4.6 times the output voltage of the valine powder-based nanogenerator. This work provides new insights into the growth mechanism of ordered piezoelectric amino acid arrays, making them promising candidates for applications in wearable or implantable electronic devices.

Reversed crystal growth of metal organic framework MIL-68(In)

A reversed crystal growth mechanism of MIL-68(In) is revealed. Nanorods of MIL-68 aggregate in parallel into microrods, followed by surface recrystallisation into a single crystal hexagonal shell and extension of crystallisation from surface to core.