Define ion-radio as required

Good evening,

I'm building a dynamic form using ionic2, but the multiple-choice components do not accept the required property how would I do this in ionic? The component that I'm trying to put the required property on is the ion-radio already tried with ion-checkbox .

  

Example of the code used.

<ion-list radio-group>
<ion-item *ngFor="‪#‎option‬ of pergunta.lista">
<ion-label>{{option.label}}</ion-label>
<ion-radio value="{{option.label}}" required></ion-radio>
</ion-item>
</ion-template>
</ion-list>

What could be happening?