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  <xsd:element abstract="true" id="clsn_statement-statement-note-10-stockbased-compensation-tables" name="statement-statement-note-10-stockbased-compensation-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-11-earnout-milestone-liability-schedule-of-milestone-riskadjustment-assessment-details" name="statement-statement-note-11-earnout-milestone-liability-schedule-of-milestone-riskadjustment-assessment-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-11-earnout-milestone-liability-summary-of-the-changes-in-the-earnout-milestone-liability-details" name="statement-statement-note-11-earnout-milestone-liability-summary-of-the-changes-in-the-earnout-milestone-liability-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-11-earnout-milestone-liability-tables" name="statement-statement-note-11-earnout-milestone-liability-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-12-warrants-summary-of-warrant-activity-details" name="statement-statement-note-12-warrants-summary-of-warrant-activity-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-12-warrants-tables" name="statement-statement-note-12-warrants-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-6-fair-value-of-measurements-assets-and-liabilities-at-fair-value-on-a-recurring-basis-details" name="statement-statement-note-6-fair-value-of-measurements-assets-and-liabilities-at-fair-value-on-a-recurring-basis-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-6-fair-value-of-measurements-tables" name="statement-statement-note-6-fair-value-of-measurements-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-7-accrued-liabilities-other-accrued-liabilities-details" name="statement-statement-note-7-accrued-liabilities-other-accrued-liabilities-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="clsn_statement-statement-note-7-accrued-liabilities-tables" name="statement-statement-note-7-accrued-liabilities-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
</xsd:schema>
