Efficient strategies for controlled release of nanoencapsulated phytohormones to improve plant stress tolerance

Table 2 Different encapsulation techniques used in agriculture to form capsule-core samples

Encapsulation techniques
Process	Chemical			Physico-Chemical
	Ionic gelation	In-situ polymerization	Liposome entrapment	Coacervation	Sol–gel encapsulation	Solvent evaporation
Diagram
Advantages	• Simple process •High encapsulation efficiency	• Inexpensive materials • Simple manufacturing	• Stable	• Versatile operation • High encapsulation capacity	• Good thermal stability • Good encapsulation efficiency	• Simple procedure • Low cost
Disadvantages	• Limited polymers • Produced always in aqueous dispersion	• Complex procedure • Use a toxic precursor	• Difficult to scale	• Expensive process • Agglomeration • Difficult to scale up	• Long process time • Use of toxic organic solutions	• Low efficiency encapsulation • Restricted process
PHs encapsulated	SA, IAA, GAs	SA, ABA, GAs	SA, CKs	JAs	ABA	JAs
Particle size range	0.5–1000 μm	0.05–1100 μm	2–1200 nm	2–1200 μm	0.2–20 μm	0.5–1000 μm
Shelf life	Short	Short	Short	Short	Medium	Poor
Reliability	Poor	Poor	Poor	Poor	Good	Poor
References	[129, 132, 133]	[129, 132, 134]	[129, 132, 135]	[129, 132, 136]	[129, 132, 137]	[129, 132, 138]

Process	Physical–Mechanical
	Spray drying	Multi-orifice centrifugation	Pan coating	Co-extrusion	Fluidized bed	Air suspension coating
Diagram
Advantages	• Simple process • Easy to scale up • Adjustable cost	• Can use solid and liquid core materials	• Low cost	• Stability • High retention	• Extensive capsule materials	• Low cost
Disadvantages	• Limited capsule materials • High energy consumption	• High temperatures required	• Inconsistent encapsulation efficiency • Difficult to control • Time-consuming	• Limited capsules materials	• Restricted to solid particle coating • Agglomeration	• Restricted to solid cores • Complex process
PHs encapsulated	SA, ABA	ABA	SA	JAs, IAA	ABA	SA
Particle size range	5–5000 μm	5–1500 μm	600–5000 μm	500–3000 μm	20–1500 μm	0.1–1000 μm
Shelf life*	Large	Medium	Short	Medium	Medium	Medium
Reliability**	Good	Good	Poor	Good	Good	Poor
References	[129, 132, 139]	[129, 132, 140]	[129, 132, 141]	[129, 132, 142]	[129, 132, 143]	[129, 132, 144]

^*Shell life: large (30–60 weeks), medium (10–30 weeks) and Short (< 10 weeks)
^**Reliability refers to degradation of encapsulated at temperature gradient (Thermogravimetric analysis): poor (> 50% of mass lost) and good (< 50% of mass lost)

ISSN: 1746-4811